amazon rainforest case study water and carbon cycle

Tropical rainforest case study

Case study of a tropical rainforest setting to illustrate and analyse key themes in water and carbon cycles and their relationship to environmental change and human activity.

Amazon Forest The Amazon is the largest tropical rainforest on Earth. It sits within the Amazon River basin, covers some 40% of the South American continent and as you can see on the map below includes parts of eight South American countries: Brazil, Bolivia, Peru, Ecuador, Colombia, Venezuela, Guyana, and Suriname. The actual word “Amazon” comes from river. Amazing Amazon facts; • It is home to 1000 species of bird and 60,000 species of plants • 10 million species of insects live in the Amazon • It is home to 20 million people, who use the wood, cut down trees for farms and for cattle. • It covers 2.1 million square miles of land • The Amazon is home to almost 20% of species on Earth • The UK and Ireland would fit into the Amazon 17 times! The Amazon caught the public’s attention in the 1980s when a series of shocking news reports said that an area of rainforest the size of Belgium was being cut down and subsequently burnt every year. This deforestation has continued to the present day according to the Sao Paulo Space Research Centre. Current statistics suggest that we have lost 20% of Amazon rainforest. Their satellite data is also showing increased deforestation in parts of the Amazon.

Water The water cycle is very active within the Amazon rainforest and it interlinks the lithosphere, atmosphere and biosphere.  The basin is drained by the Amazon River and its tributaries.  The average discharge of water into the Atlantic Ocean by the Amazon is approximately 175,000 m 3 per second, or between 1/5th and 1/6th of the total discharge into the oceans of all of the world's rivers. 3 The Rio Negro, a tributary of the Amazon, is the second largest river in the world in terms of water flow, and is 100 meters deep and 14 kilometers wide near its mouth at Manaus, Brazil. Rainfall across the Amazon is very high.  Average rainfall across the whole Amazon basin is approximately 2300 mm annually. In some areas of the northwest portion of the Amazon basin, yearly rainfall can exceed 6000 mm. 3 Only around 1/3 of the rain that falls in the Amazon basin is discharged into the Atlantic Ocean. It is thought that; 1. Up to half of the rainfall in some areas may never reach the ground, being intercepted by the forest and re-evaporated into the atmosphere. 2. Additional evaporation occurs from ground and river surfaces, or is released into the atmosphere by transpiration from plant leaves (in which plants release water from their leaves during photosynthesis) 3. This moisture contributes to the formation of rain clouds, which release the water back onto the rainforest. In the Amazon, 50-80 percent of moisture remains in the ecosystem’s water cycle. 4

This means that much of the rainfall re-enters the water cycling system of the Amazon, and a given molecule of water may be "re-cycled" many times between the time that it leaves the surface of the Atlantic Ocean and is carried by the prevailing westerly winds into the Amazon basin, to the time that it is carried back to the ocean by the Amazon River. 4 It is thought that the water cycle of the Amazon has global effects.  The moisture created by rainforests travels around the world. Moisture created in the Amazon ends up falling as rain as far away as Texas, and forests in Southeast Asia influence rain patterns in south eastern Europe and China. 4 When forests are cut down, less moisture goes into the atmosphere and rainfall declines, sometimes leading to drought. These have been made worse by deforestation. 4 Change to the water and carbon cycles in the Amazon The main change to the Amazon rainforest is deforestation.  Deforestation in the Amazon is generally the result of land clearances for; 1. Agriculture (to grow crops like Soya or Palm oil) or for pasture land for cattle grazing 2. Logging – This involves cutting down trees for sale as timber or pulp.  The timber is used to build homes, furniture, etc. and the pulp is used to make paper and paper products.  Logging can be either selective or clear cutting. Selective logging is selective because loggers choose only wood that is highly valued, such as mahogany. Clear-cutting is not selective.  Loggers are interested in all types of wood and therefore cut all of the trees down, thus clearing the forest, hence the name- clear-cutting. 3. Road building – trees are also clear for roads.  Roads are an essential way for the Brazilian government to allow development of the Amazon rainforest.  However, unless they are paved many of the roads are unusable during the wettest periods of the year.  The Trans Amazonian Highway has already opened up large parts of the forest and now a new road is going to be paved, the BR163 is a road that runs 1700km from Cuiaba to Santarem. The government planned to tarmac it making it a superhighway. This would make the untouched forest along the route more accessible and under threat from development. 4. Mineral extraction – forests are also cleared to make way for huge mines. The Brazilian part of the Amazon has mines that extract iron, manganese, nickel, tin, bauxite, beryllium, copper, lead, tungsten, zinc and gold! 5. Energy developmen t – This has focussed mainly on using Hydro Electric Power, and there are 150 new dams planned for the Amazon alone.  The dams create electricity as water is passed through huge pipes within them, where it turns a turbine which helps to generate the electricity.  The power in the Amazon is often used for mining.  Dams displace many people and the reservoirs they create flood large area of land, which would previously have been forest.  They also alter the hydrological cycle and trap huge quantities of sediment behind them. The huge Belo Monte dam started operating in April 2016 and will generate over 11,000 Mw of power.  A new scheme the 8,000-megawatt São Luiz do Tapajós dam has been held up because of the concerns over the impacts on the local Munduruku people. 6. Settlement & population growth – populations are growing within the Amazon forest and along with them settlements.  Many people are migrating to the forest looking for work associated with the natural wealth of this environment. Settlements like Parauapebas, an iron ore mining town, have grown rapidly, destroying forest and replacing it with a swath of shanty towns. The population has grown from 154,000 in 2010 to 220,000 in 2012. The Brazilian Amazon’s population grew by a massive 23% between 2000 and 2010, 11% above the national average.

The WWF estimates that 27 per cent, more than a quarter, of the Amazon biome will be without trees by 2030 if the current rate of deforestation continues. They also state that Forest losses in the Amazon biome averaged 1.4 million hectares per year between 2001 and 2012, resulting in a total loss of 17.7 million hectares, mostly in Brazil, Peru and Bolivia.  12

The impacts of deforestation Atmospheric impacts Deforestation causes important changes in the energy and water balance of the Amazon. Pasturelands and croplands (e.g. soya beans and corn) have a higher albedo and decreased water demand, evapotranspiration and canopy interception compared with the forests they replace. 9 Lathuillière et al. 10 found that forests in the state of Mato Grosso; • Contributed about 50 km 3 per year of evapotranspiration to the atmosphere in the year 2000. • Deforestation reduced that forest flux rate by approximately 1 km 3 per year throughout the decade. • As a result, by 2009, forests were contributing about 40 km 3 per year of evapotranspiration in Mato Grosso.

Differences such as these can affect atmospheric circulation and rainfall in proportion to the scale of deforestation The agriculture that replaces forest cover also decreases precipitation. In Rondônia, Brazil, one of the most heavily deforested areas of Brazil, daily rainfall data suggest that deforestation since the 1970s has caused an 18-day delay in the onset of the rainy season. 11 SSE Amazon also has many wild fires, which are closely associated with deforestation, forest fragmentation and drought intensity. According to Coe et al (2015) “ the increased atmospheric aerosol loads produced by fires have been shown to decrease droplet size, increase cloud height and cloud lifetime and inhibit rainfall, particularly in the dry season in the SSE Amazon. Thus, fires and drought may create a positive feedback in the SSE Amazon such that drought is more severe with continued deforestation and climate change .” 9

The impacts of climate change on the Amazon According to the WWF: • Some Amazon species capable of moving fast enough will attempt to find a more suitable environment. Many other species will either be unable to move or will have nowhere to go. • Higher temperatures will impact temperature-dependent species like fish, causing their distribution to change. • Reduced rainfall and increased temperatures may also reduce suitable habitat during dry, warm months and potentially lead to an increase in invasive, exotic species, which then can out-compete native species. • Less rainfall during the dry months could seriously affect many Amazon rivers and other freshwater systems. • The impact of reduced rainfall is a change in nutrient input into streams and rivers, which can greatly affect aquatic organisms. • A more variable climate and more extreme events will also likely mean that Amazon fish populations will more often experience hot temperatures and potentially lethal environmental conditions. • Flooding associated with sea-level rise will have substantial impacts on lowland areas such as the Amazon River delta. The rate of sea-level rise over the last 100 years has been 1.0-2.5 mm per year, and this rate could rise to 5 mm per year. • Sea-level rise, increased temperature, changes in rainfall and runoff will likely cause major changes in species habitats such as mangrove ecosystems. 15 Impacts of deforestation on soils Removing trees deprives the forest of portions of its canopy, which blocks the sun’s rays during the day, and holds in heat at night. This disruption leads to more extreme temperature swings that can be harmful to plants and animals. 8 Without protection from sun-blocking tree cover, moist tropical soils quickly dry out. In terms of Carbon, Tropical soils contain a lot of carbon.  The top meter holds 66.9 PgC with around 52% of this carbon pool held in the top 0.3 m of the soil, the layer which is most prone to changes upon land use conversion and deforestation. 14 Deforestation releases much of this carbon through clearance and burning.  For the carbon that remains in the soil, when it rains soil erosion will wash much of the carbon away into rivers after initial deforestation and some will be lost to the atmosphere via decomposition too. 

Impacts of deforestation on Rivers Trees also help continue the water cycle by returning water vapor to the atmosphere. When trees are removed this cycle is severely disrupted and areas can suffer more droughts. There are many consequences of deforestation and climate change for the water cycle in forests; 1. There is increased soil erosion and weathering of rainforest soils as water acts immediately upon them rather than being intercepted. 2. Flash floods are more likely to happen as there is less interception and absorption by the forest cover. 3. Conversely, the interruption of normal water cycling has resulted in more droughts in the forest, increasing the risk of wild fires 4. More soil and silt is being washed into rivers, resulting in changes to waterways and transport 5. Disrupt water supplies to many people in Brazil

References 1 - Malhi, Y. et al. The regional variation of aboveground live biomass in old-growth Amazonian forests. Glob. Chang. Biol. 12, 1107–1138 (2006). 2 - Fernando D.B. Espírito-Santo  et al.  Size and frequency of natural forest disturbances and the Amazon forest carbon balance. Nature Communications volume 5, Article number: 3434 (2014) Accessed 3rd of January 2019 retrieved from https://www.nature.com/articles/ncomms4434#ref4 3 - Project Amazonas. Accessed 3rd of January 2019 retrieved from https://www.projectamazonas.org/amazon-facts  4 - Rhett Butler, 2012. IMPACT OF DEFORESTATION: LOCAL AND NATIONAL CONSEQUENCES.  Accessed 3rd of January 2019 retrieved from https://rainforests.mongabay.com/0902.htm 5 – Mark Kinver. Amazon: 1% of tree species store 50% of region's carbon. 2015. BBC. Accessed 3rd of January 2019 retrieved from https://www.bbc.co.uk/news/science-environment-32497537 6 -     Sophie Fauset et al. Hyperdominance in Amazonian forest carbon cycling. Nature Communications volume 6, Article number: 6857 (2015). Accessed 3rd of January 2019 retrieved from https://www.nature.com/articles/ncomms7857 7- Brienen, R.J.W et al. (2015) Long-term decline of the Amazon carbon sink, Nature, h ttps://www.nature.com/articles/nature14283 8 – National Geographic – Deforestation - Learn about the man-made and natural causes of deforestation–and how it's impacting our planet. Accessed 20th of January 2019 retrieved from https://www.nationalgeographic.com/environment/global-warming/deforestation/

9 -  Michael T. Coe, Toby R. Marthews, Marcos Heil Costa, David R. Galbraith, Nora L. Greenglass, Hewlley M. A. Imbuzeiro, Naomi M. Levine, Yadvinder Malhi, Paul R. Moorcroft, Michel Nobre Muza, Thomas L. Powell, Scott R. Saleska, Luis A. Solorzano, and Jingfeng Wang. (2015) Deforestation and climate feedbacks threaten the ecological integrity of south–southeastern Amazonia. 368, Philosophical Transactions of the Royal Society B: Biological Sciences. Accessed 20th of January 2019 retrieved from http://rstb.royalsocietypublishing.org/content/368/1619/20120155

10 - Lathuillière MJ, Mark S, Johnson MS & Donner SD. (2012). Water use by terrestrial ecosystems: temporal variability in rainforest and agricultural contributions to evapotranspiration in Mato Grosso, Brazil. Environmental research Letters Volume 7 Number 2. http://iopscience.iop.org/article/10.1088/1748-9326/7/2/024024/meta

11- Nathalie Butt, Paula Afonso de Oliveira & Marcos Heil Costa (2011). Evidence that deforestation affects the onset of the rainy season in Rondonia, Brazil JGR Atmospheres, Volume 116, Issue D11. https://doi.org/10.1029/2010JD015174

12 – WWF, Amazon Deforestation. Accessed 20th of January 2019 retrieved from http://wwf.panda.org/our_work/forests/deforestation_fronts/deforestation_in_the_amazon/

13 - Berenguer, E., Ferreira, J., Gardner, T. A., Aragão, L. E. O. C., De Camargo, P. B., Cerri, C. E., Durigan, M., Oliveira, R. C. D., Vieira, I. C. G. and Barlow, J. (2014), A large-scale field assessment of carbon stocks in human-modified tropical forests. Global Change Biology, 20: 3713–3726. https://onlinelibrary.wiley.com/doi/full/10.1111/gcb.12627

14 - N.HBatjes, J.ADijkshoorn, (1999). Carbon and nitrogen stocks in the soils of the Amazon Region. Geoderma, Volume 89, Issues 3–4, Pages 273-286. Accessed 20th of January 2019 retrieved from https://www.sciencedirect.com/science/article/pii/S001670619800086X

15 – WWF, Impacts of climate change in the Amazon. Accessed 20th of January 2019 retrieved from http://wwf.panda.org/knowledge_hub/where_we_work/amazon/amazon_threats/climate_change_amazon/amazon_climate_change_impacts/

Written by Rob Gamesby

©2015 Cool Geography

• Copyright Policy
• Privacy & Cookies
• Testimonials
• Feedback & support

Amazon Deforestation and Climate Change

Join Gisele Bundchen when she meets with one of Brazil’s top climate scientists to discuss the complexity of the Amazon rainforest and its connection to Earth’s atmosphere.

Anthropology, Geography

High on a tower overlooking the lush Amazon canopy, Gisele Bundchen and Brazilian climate scientist Antonio Nobre talk about the importance of the rainforest and the impact of cutting down its trees.

As Nobre explains, the rainforest is not only home to an incredible diversity of species, it also has a critical cooling effect on the planet because its trees channel heat high into the atmosphere. In addition, forests absorb and store carbon dioxide (CO 2 ) from the atmosphere—CO 2 that is released back into the atmosphere when trees are cut and burned.

Nobre warns that if deforestation continues at current levels, we are headed for disaster. The Amazon region could become drier and drier, unable to support healthy habitats or croplands.

Find more of this story in the “Fueling the Fire” episode of the National Geographic Channel’s Years of Living Dangerously series.

Transcript (English)

- Growing up in Southern Brazil, my five sisters and I ate meat pretty much every day. It's just part of the culture here. Per capita, Brazilians are one of the top consumers of beef on the planet. Now, with the world's growing appetite for beef, Brazil has also become a major exporter and is aiming to increase its market share, partly by selling to the US, the world's biggest consumer of beef, and to China, where demand for beef has grown 25% in just 10 years. I understand the need to develop and grow, but does that have to come at the expense of the rainforest and the climate? The Amazon Rainforest is about the same size as the continental United States. One-fifth of the world's fresh water runs through it, and it is home to more species of animals and plants than anywhere on Earth. The Amazon represents more than half of the remaining rainforests on the planet. This forest is so vast, but it is not indestructible. To find out what's at stake, I'm going to talk to one of Brazil's top climate scientist, Dr. Antonio Nobre. So Antonio, tell us a little bit about this amazing green carpet of heaven over here.

- Well, most people don't have the opportunity to come from the top of the forest. If you see all this many shades of green as you see here, it's because biodiversity is the essence of this type of forest. Every species of trees has thousands of species of bugs, and also if you get a leaf of one of the species, and you look to the microbes that is sitting on the top of leaf, you find millions of species, millions, and this is all below our radar screen, so to speak, because we don't realize, it's invisible. And the trees are shooting water from the ground, groundwater up high in the sky, and this goes up into the atmosphere and releases the heat out there, and this radiates to space. And this is very important as a mechanism to cool the planet. They're like air conditioners. Open air conditioning, that's what the forest is.

- So in other words, if we lose all these trees, we are losing the air conditioning that cools off the whole planet.

- Not only that.

- Not only that?

- No. The trees are soaking up carbon, you know the pollution that we produce, like carbon dioxide? Yeah, yeah, yeah.

- Burning gasoline in our cars, you release carbon dioxide in the air, or burning coal, and the trees use carbon dioxide as a raw material.

- So the trees are storing all this carbon, so if you come and cut it down and burn it out, does that mean that all that carbon goes up in the air?

- Absolutely. Yeah.

- What would happen if this forest was gone?

- When the forest is destroyed, climate changes, and then forest that's left is damaged as well. And then the forest grows drier and drier and eventually catch fire. So in the extreme, the whole area becomes a desert. And that's what is in store if we deforest. So we have to quit deforestation yesterday, not 2020 or '30. And there is no plan C. You know, you have plan A. Plan A is business as usual. Keep plundering with all the resources and using as if it were infinite. Plan B is what many people are attempting, changing the matrix of energy and using clean sources, stop eating too much meat, and replanting forests If that doesn't work, then we go to plan C. What's plan C? I have no idea.

- Going to another planet.

- But we can't do that.

- We don't have another planet, so either we work with plan B or we're-

- Basically, yeah. We're done, and so plan B has to work. It has to work.

- People have to take accountability, 'cause it can't just be like, I'm leaving over here and whatever happens over there, who cares?

- It's not my problem.

- It's not my problem, because it is everyone's problem.

- Yes. People should wake up. It's like when you're in the midst of an unfolding disaster, what do you do? You panic? No. You move it. Move, move, move, move. That's what we need to do.

Transcripción (Español)

- El año en que vivimos en peligro.

- Cuando era niña en el sur de Brasil, mis cinco hermanas y yo comíamos carne casi todos los días. Es parte de la cultura aquí. Per cápita, los brasileños son uno de los mayores consumidores de carne de res en el planeta. Ahora, con el creciente apetito mundial por la carne de res, Brasil también se ha convertido en un importante exportador y está buscando aumentar su participación en el mercado, en parte vendiendo a los Estados Unidos, el mayor consumidor de carne de res del mundo, y a China, donde la demanda de carne de res ha crecido un 25 % en tan solo 10 años. Entiendo la necesidad de desarrollarse y crecer, pero ¿tiene que ser a expensas de la selva tropical y el clima? La selva amazónica tiene casi el mismo tamaño que los Estados Unidos continentales. Una quinta parte del agua dulce del mundo fluye a través de ella. Y es hogar de más especies de animales y plantas que cualquier otro lugar en la Tierra. El Amazonas representa más de la mitad de las selvas tropicales restantes en el planeta. Estado Mato Grosso, Brasil Esta selva es tan vasta, pero no es indestructible. Para descubrir lo que está en juego, voy a hablar con uno de los principales científicos climáticos de Brasil, el Dr. Antonio Nobre. Antonio, cuéntanos un poco acerca de esta increíble alfombra verde de cielo que tenemos aquí.

- Bueno, la mayoría de las personas no tienen la oportunidad de venir hasta la cima de la selva. Si ves todos los diferentes tonos de verde como estos aquí, es porque la biodiversidad es la esencia de este tipo de selva. Cada especie de árboles tiene miles de especies de insectos, y también si tomas una hoja de una de las especies, y miras a los microbios en la parte superior de la hoja, encuentras millones de especies, millones, y todo esto queda por debajo de nuestro radar, porque no nos damos cuenta, es invisible. Y los árboles están extrayendo agua del subsuelo, hasta lo alto en el cielo, y esto sube a la atmósfera y libera el calor allí, y esto se irradia al espacio. Este es un mecanismo muy importante para enfriar el planeta. Son como aires acondicionados. Aire acondicionado al aire libre, eso es el bosque.

- En otras palabras, si perdemos todos estos árboles, estamos perdiendo el aire acondicionado que enfría todo el planeta.

- No solo eso.

- ¿No solo eso?

- No. Los árboles están absorbiendo carbono, ¿la contaminación que producimos, como el dióxido de carbono?

- Al quemar gasolina en los autos, se libera dióxido de carbono al aire, o quemando carbón, y los árboles usan el dióxido de carbono como materia prima.

- Entonces los árboles están almacenando todo este carbono, así que si lo cortas y lo quemas, ¿eso significa que todo ese carbono sube al aire?

- Absolutamente. Sí.

- ¿Qué pasaría si este bosque desapareciera?

- Cuando el bosque es destruido, el clima cambia, y luego el bosque que queda también se daña. Luego el bosque se vuelve cada vez más seco y eventualmente se incendia. En caso extremo, toda el área se convierte en un desierto. Eso es lo que nos espera si deforestamos. Así que tenemos que dejar de deforestar desde ayer, no en 2020 o 2030. No hay un plan C. Tienes un plan A. El plan A es seguir como siempre. Continuar saqueando todos los recursos y usarlos como si fueran infinitos. El plan B es lo que muchos están intentando, cambiar la matriz de energía y usar fuentes limpias, dejar de comer demasiada carne y reforestar bosques. Si eso no funciona, entonces pasamos al plan C. ¿Cuál es el plan C?

- No tengo idea.

- Ir a otro planeta.

- Pero no podemos hacer eso.

- No tenemos otro planeta, así que o trabajamos con el plan B o estamos-

- Acabados.

- Básicamente, sí. Estamos acabados, así que el plan B tiene que funcionar. Tiene que funcionar.

- Las personas deben asumir responsabilidad, porque no puedes nada más pensar, yo vivo aquí y lo que suceda por allá, ¿a quién le importa?

- A mí qué.

- No es mi problema, porque es un problema de todos.

- Sí. La gente debería despertar. Es como cuando estás en medio de un desastre en desarrollo, ¿qué haces? ¿Entrar en pánico? No. Lo mueves. Que se mueva. Eso es lo que necesitamos hacer.

The Amazon rain forest absorbs one-fourth of the CO2 absorbed by all the land on Earth. The amount absorbed today, however, is 30% less than it was in the 1990s because of deforestation. A major motive for deforestation is cattle ranching. China, the United States, and other countries have created a consumer demand for beef, so clearing land for cattle ranching can be profitable—even if it’s illegal. The demand for pastureland, as well as cropland for food such as soybeans, makes it difficult to protect forest resources.

Many countries are making progress in the effort to stop deforestation. Countries in South America and Southeast Asia, as well as China, have taken steps that have helped reduce greenhouse gas emissions from the destruction of forests by one-fourth over the past 15 years.

Brazil continues to make impressive strides in reducing its impact on climate change. In the past two decades, its CO2 emissions have dropped more than any other country. Destruction of the rain forest in Brazil has decreased from about 19,943 square kilometers (7,700 square miles) per year in the late 1990s to about 5,180 square kilometers (2,000 square miles) per year now. Moving forward, the major challenge will be fighting illegal deforestation.

Articles & Profiles

Instructional links, media credits.

The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit. The Rights Holder for media is the person or group credited.

Last Updated

May 9, 2024

User Permissions

For information on user permissions, please read our Terms of Service. If you have questions about how to cite anything on our website in your project or classroom presentation, please contact your teacher. They will best know the preferred format. When you reach out to them, you will need the page title, URL, and the date you accessed the resource.

If a media asset is downloadable, a download button appears in the corner of the media viewer. If no button appears, you cannot download or save the media.

Text on this page is printable and can be used according to our Terms of Service .

Interactives

Any interactives on this page can only be played while you are visiting our website. You cannot download interactives.

Related Resources

The Amazon’s crucial water cycle faces collapse, scientists say

Wildfires, deforestation and global warming could permanently destroy the water cycle that sustains parts of the Amazon rainforest if action is not taken in the coming decades, according to a study published Wednesday in the journal Nature.

The study suggests that 10% to 47% of the landscape is at risk of transitioning away from rainforest by 2050 if warming and rates of deforestation aren’t dramatically curbed.

“So many stressors are intensifying — climatic ones and land use stressors — when you combine these, they all end up causing water stress in the forest,” said Bernardo Flores, a lead author of the paper who is an ecologist and post-doctoral researcher at the University of Santa Catarina, in Florianópolis, Brazil. “It can reach a point where the forest is no longer capable of persisting.” 

The Amazon contains about 10% of the world’s land-based biodiversity and stores incredible amounts of carbon in its dense trees. The rainforest is a carbon sink, meaning it stores more carbon than it produces. Pushing the rainforest past its limit could accelerate climate change and have terrible consequences for local communities, including Indigenous groups who depend on it. 

Flores said that the changes outlined in the study are already happening but that he was optimistic they could be slowed or even halted. 

“I’m hoping in this paper, our findings will show the urgency if we don’t act within the next 30 years,” Flores said. 

The study focuses on overlapping stressors to the Amazon, namely from warming temperatures, extreme droughts, deforestation and fires. It describes how those factors could combine to break down the Amazon’s water and carbon cycles. 

“The Amazon is massive and maintains its own water cycle,” said Ernesto Alvarado, a research associate professor at the University of Washington’s School of Environmental and Forest Sciences, who was not involved in the study. “If the balance breaks, it’s a major problem.” 

If deforestation, wildfires, droughts and climate change reduce the amount of forested land that absorbs water, less moisture would be available to the atmosphere from plants, reducing the amount of rain to sustain the landscape. 

About 15% of the Amazon has already been lost, Flores said. 

“If we lose 10% more of the forest, we will pass the critical threshold we identified in accumulated forest loss and deforestation,” Flores said. “We will have 25% of the Amazon that won’t be forest anymore — and this could trigger a large-scale tipping point.”  

Alvarado, who in the past has studied how resilient the Amazon forest is after disturbance, said he’s visited areas that were once rainforests but now look like the U.S. Midwest. 

“This paper resonates,” he said. 

Previous research suggested the Amazon could tip into an unstable state when global temperatures rise 2-6 degrees Celsius above pre-industrial averages. 

“The studies are broadly consistent,” Tim Lenton, a professor at the University of Exeter in the United Kingdom and founder of the Global Systems Institute, said in an email. “What is great about the new study is it unpacks in more spatial detail than previous work which locations are at most risk and from which drivers, by 2050.” 

The new study suggests that limiting warming to 1.5 degrees Celsius — the goal of the 2015 Paris climate agreement — would provide enough safety margin to prevent ecosystems from transitioning away from forest. 

Losing a large portion of the Amazon could turn a key carbon sink into a source of emissions, as wildfires burn and plants and animals decompose, no longer able to survive. 

“Many aspects of these transitions are irreversible — many species will go extinct and never come back,” Flores said.

Evan Bush is a science reporter for NBC News. He can be reached at [email protected].

There's a Hidden Water Cycle in The Amazon We Barely Know Anything About

Earth's largest remaining tract of tropical rainforest is kept alive by a complex water cycle that we're only just beginning to understand. Yet our activities are changing it before we can see the full picture, a new report finds.

The rivers and tributaries of the Amazon rainforest hold around a fifth of Earth's fresh water, nourishing a stunning variety of mammals, birds, plants and amphibians. It also helps support the 47 million people in the surrounding basin region which includes mountain forests, wetlands, and river systems across nine South American countries .

The complex hydroclimatic system that sustains this region interconnects over the Andes mountains, Amazon lowlands and Atlantic Ocean (the AAA pathway), cycling water molecules from Earth's surface into the air and back again. Researchers have previously compared this system to a pump that recycles moisture , supporting regional rainfall.

"Up to now, most research and conservation efforts have focused on the terrestrial rainforest biome, yet rainforest persistence hinges on the AAA pathway," Florida International University hydrologist Claire Beveridge and colleagues point out in their review .

This multidirectional water cycle not only supplies the rain but shifts soils too – from the Andes mountains, through the rivers, into the forests, and eventually into the ocean. These waves of nutrients washing through with the water help support the densely packed and highly diverse terrestrial and aquatic habitats.

The AAA pathway provides about 40 percent of the Atlantic's sediment input, contributing to many ocean nutrient cycles .

"The Amazon River plume extends several thousands of kilometers into the Atlantic Ocean, and its composition makes it vital to ocean nutrient balance and carbon dioxide sequestration," the researchers write .

While the Amazon has always gone through cycles of floods and droughts thanks to the natural El Niño and La Niña climate patterns, these cycles no longer fully account for all the changes being observed.

Temperatures are rising, particularly in the south of the region, causing the AAA system to fluctuate more extremely. This has brought record floods to the north and lengthened dry spells and fire seasons, raising the risk of glaciers melting in the Andes.

Deforestation and other land cover changes are also influencing the AAA system and exacerbating climate change in a dangerous feedback loop.

"The combined changes along the AAA pathway and their cumulative impacts are occurring at faster speeds than social–ecological systems can adapt, threatening their resilience ," warn Beveridge and team.

The researchers urge for further investigation into the AAA pathway, an immediate stop to deforestation, and restoration programs to repair vulnerable areas. Keeping the Amazon Basin wet is also crucial for global efforts to mitigate climate change .

"In this century, there's been a huge increase in the number and extent of protected areas like national parks, reserves and Indigenous territories that are recognized officially in the Amazon, but the focus has really been on forests and terrestrial ecosystems," says FIU freshwater scientist Anderson.

"It's now time to extend support for conservation to freshwater systems like rivers."

This research was published in PNAS .

Frontiers for Young Minds

• Download PDF

Drought, Floods, Climate Change, and Forest Loss in the Amazon Region: A Present and Future Danger?

The Amazon is the world’s largest rainforest and it plays an important role in global and regional climate, including the exchange of water between the rainforest and the atmosphere. Extremes of climate, such as droughts or floods, can be dangerous for both humans and natural systems. Droughts and floods may alter the moisture exchange between forests and the atmosphere and can affect the survival of the Amazon forest. Actions to avoid or to reduce global warming and forest loss are discussed in this article.

Why Should We Care About the Amazon Rainforest?

When people think about the Amazon rainforest, they often consider it to be the lungs of the planet, removing carbon dioxide (CO 2 ) from the air and releasing oxygen for animals, including humans, to breathe. People also think about snakes, monkeys, spiders, orchids, and the incredible diversity of life hosted by the rainforest. All of this is important, but there’s more than that.

The rainforest interacts with the atmosphere in several ways, which affect the local and world-wide climate. Figure 1 shows that the rainforest interacts with the atmosphere to provide moisture within the Amazon basin. The winds near the ocean surface bring moisture from the tropical Atlantic Ocean into the Amazon. Some of this moisture falls as rain, some can quickly be returned to the atmosphere by the tropical forest through the processes of evaporation and release from leaves and soil. Some of this water vapor will come back as rain right over the rainforest and some will travel on to neighboring regions. Between 30 and 70% of the rainfall within the Amazon basin consists of water that evaporated from the rainforest [ 1 , 2 ].

• Figure 1 - Regional water cycle in the Amazon region [ 1 ].
• Humidity is transported to the Amazon region by the trade winds from the tropical Atlantic. After the rain, the rainforest produces intense evaporation and transpiration and recycling of moisture. After that much of the evaporation and transpiration returns to the Amazon region in the form of rainfall.

The rainforest can influence temperatures and rainfall, helping to modify its own climate, which also serves to modify the climate of the entire continent. If the rainforests disappear, this could increase the risk of a major climate crisis for the whole planet. Since trees remove CO 2 from the atmosphere, scientists are worried that continued loss of the Amazon rainforest could take away one valuable absorber of CO 2 . In addition, loss of the rainforest could affect natural rainfall cycles in the Amazon region in ways that may endanger the functioning of the forest. These changes in rainfall might lead to a drier and warmer climate in that region, and an increased risk of fire and erosion.

How Do Climate Extremes and Climate Change Affect the Amazon Region?

Severe climate extremes (much too wet or much too dry) have affected the Amazon region in recent years. The droughts in 2005, 2010, and 2016, and the floods in 2009, 2012, and 2014 provide examples of how changes in climate can affect the ecosystem and the people living in the region. Luiz Aragao [ 3 ] showed that, during the drought in 2016, the number of fires increased by 36% compared with the preceding 12 years in the region. The dry season in the southern Amazon region, where the deforestation rates are the highest, has been lasting about 3–4 weeks longer, with the rains arriving later than normal [ 4 ]. This long dry season increases the risk of fires. In the warmer future climate, droughts may be more frequent and/or intense, and longer dry seasons may increase the risk of fires, which can impact the people living in that area and the biodiversity in the entire Amazon region.

To study how the climate might be in the future, research groups around the world have used mathematics. How? They represent all natural processes using equations describing the heat and moisture balance in the region and the exchange of heat and moisture between the ground, the vegetation, and the air, plus exchanges with neighboring regions. The equations must be solved using supercomputers. This mathematical representation of nature is referred to as a climate model. Climate models show that global warming or deforestation can lead to drier and warmer conditions in the central and eastern Amazon region. In a paper that I published in 2018 [ 4 ], I showed that more extreme swings between drought and floods may reach a point of no return, after which climate change will be irreversible. This may threaten the very existence of the Amazon tropical rainforest.

What Are Aerial Rivers and What Role Do They Play in Rainfall?

The pioneering work of the Brazilian scientist Prof. Enéas Salati in 1979 [ 2 ] explained the water balance for the Amazon region. A significant amount of water evaporated from the forest comes back as rainfall, and this process is known as moisture recycling . Another scientist [ 5 ] showed how moisture recycling has allowed the forest to survive up to the present day. Figure 2 shows an artistic view of moisture transport in the Amazon region. Moisture evaporated from the Atlantic Ocean is carried by the surface winds into the region. The winds get even more humidity from the moisture recycling provided by the forest. The moist air first moves westward, but as it approaches the eastern flank of the Andes mountains, it is deflected toward south-eastern South America. This transport is like a river in the air that brings moisture and rain to south and to central regions of Brazil and part of Argentina.

• Figure 2 - How moisture is carried in and out of Amazonia.
• Water evaporates from the tropical Atlantic Ocean and is transported into the Amazon region by the trade winds. These winds produce rainfall over the region but also gains water from forest recycling. This moist air current moves toward the east side of the Andes and then change direction forced by the Andes and channeling moisture transport to southern Brazil and Northern Argentina, behaving as a “river of moisture” or “aerial river” (source: Rios Voadores project: www.riosvoadores.com.br ).

Josefina Arraut refined the concept of aerial rivers in 2012 [ 6 ]. These are like rivers on land, except that this moisture flow is in the form of water vapor and clouds and takes place in the atmosphere. The volume of moisture transported in the atmosphere by the aerial river east of the Andes is about 230,000 m 3 /s, which is approximately the same as the flow of water from the Amazon River into the Atlantic Ocean!

What Could Happen to the Climate If the Forests Disappear?

Deforestation is seen as an environmental menace. It reduces moisture recycling from the vegetation to the atmosphere, and it also reduces the volume of water transported in the aerial river. If the Amazon were totally or partially deforested, the climate problems that this would cause would be felt as far away as the United States or even China [ 7 ]. In South America, cutting down even portions of the Amazon forest can affect the quality of the rainy season in southern Brazil and northern Argentina. As the forests begin to disappear, less water in the atmosphere would mean less rain, making it difficult for farmers to grow crops. This could reduce the amount of food available for humans and other animals, and many agricultural businesses could also lose money. In addition to causing problems, such as prolonged droughts or storms, a deforested planet could see a further increase in global warming. In the early part of this century, several scientists [ 8 , 9 ] already saw that climate change could reach dangerous levels if global air temperatures were to warm by an average of 4°C. The world’s climate would pass a tipping point and the Amazon forest could collapse, possibly turning most of the southern and eastern Amazon into a savannah [ 10 ].

What Can We Do to Avoid Dangerous Climate Change?

As I have explained in this article, climate change poses a great danger to our environment. Therefore, regulations in every country are needed to reduce greenhouse gas emissions and to prevent forest loss, to give humans a chance for a more sustainable future. In December 2015, many countries participated in the Conference of Parties that met in Paris, where major concerns about climate change and its worldwide impacts were discussed. As a result of this meeting, the Paris Agreement established measures to reduce global warming and proposed that countries must make efforts to reduce global CO 2 emissions and to stop or reduce global deforestation. If the Paris Agreement is followed, global warming in the upcoming decades should be below 2°C, which would reduce the risk of dangerous consequences on the climate.

Conclusions

Changes in climate experienced by the Amazon region will have effects on the rainforest, as well as on the population and biodiversity of the organisms living there. Research should focus on understanding the impacts of climate change in the Amazon region, particularly the effects of drought and fire on humans and animals. Furthermore, drought, floods, and their impacts on people and ecosystems should be better explored. If the climate continues to get warmer, the risk of intense floods, fires, and droughts is expected to increase, and measures must be taken to minimize the impacts of these events. Continued fires and deforestation in the Amazon could cripple the fight against climate change. We must protect and restore the great Amazon rainforest to help guarantee that climate change will not affect our survival.

Author Contributions

The sole author contributed to all aspect of the preparation and writing of the paper.

Drought : ↑ An absence of rain for long periods.

Flood : ↑ The overflowing of the normal boundaries of a stream or other body of water.

Deforestation : ↑ Forest loss, conversion of forest to non-forest.

Global Warming : ↑ A gradual increase in the overall temperature of the earth’s atmosphere, generally attributed to the greenhouse effect caused by increased levels of greenhouse gases, mainly carbon dioxide.

Climate Change : ↑ Long-lasting changes to the climate of a region.

Moisture Recycling : ↑ A process in which water evaporates from a forest and falls again as rain over the same area.

Aerial Rivers : ↑ In the context of this paper, aerial rovers or flying rivers are air currents that bring water vapor from the tropical Atlantic and Amazonia down as far south as southern Brazil and Northern Argentina.

Tipping Point : ↑ The amount of change needed to prevent a system from returning to its initial state.

Conflict of Interest

The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Original Source Article

↑ Marengo, J. A., Souza, C. Jr., Thonicke, K., Burton, C., Halladay, K., Betts, R., et al. 2018. Changes in climate and land use over the Amazon region: current and future variability and trends. Front. Earth Sci . 6:228. doi: 10.3389/feart.2018.00228

[1] ↑ Marengo, J. A., Nobre, C. A., Chou, S. C., Tomasella, J., Sampaio, G., Alves, L., et al. 2011. Dangerous Climate Change in Brazil, A Brazil-UK Analysis of Climate Change and Deforestation Impacts in the Amazon . Sao Jose dos Campos: INPE, 54.

[2] ↑ Salati, E., Dall’Olio, A., Matsui, E., and Gat, J. R. 1979. Recycling of water in the Amazon basin: an isotopic study. Water Resour Res . 15:1250–8. doi: 10.1029/WR015i005p01250

[3] ↑ Aragão, L. E. O. C., Anderson, L. O., Fonseca, M. G., Rosan, T. M., Vedovato, L. B., Wagner, F. H., et al. 2018. 21st Century drought-related fires counteract the decline of Amazon deforestation carbon emissions. Nat. Commun. 9:536. doi: 10.1038/s41467-017-02771-y

[4] ↑ Marengo, J. A., Souza, C. Jr., Thonicke, K., Burton, C., Halladay, K., Betts, R., et al. 2018. Changes in climate and land use over the Amazon region: current and future variability and trends. Front. Earth Sci . 6:228. doi: 10.3389/feart.2018.00228

[5] ↑ Nobre, A. D. 2014. The Future Climate of Amazonia: Scientific Assessment Report . São José dos Campos: CCST-INPE.

[6] ↑ Arraut, J. M., Nobre, C., Henrique de Melo Jorge, B., Obregon, G., and Marengo, J. A. 2012. Aerial rivers and lakes: looking at large-scale moisture transport and its relation to Amazonia and to subtropical rainfall in South America. J. Clim. 25:543–56. doi: 10.1175/2011JCLI4189.1

[7] ↑ Lawrence, D., and Vandecar, K. 2015. Effects of tropical deforestation on climate and agriculture. Nat. Clim. Change 5:27–36. doi: 10.1038/nclimate2430

[8] ↑ Cox, P. M., Betts, R. A., Jones, C. D., Spall, S. A., and Totterdell, I. J. 2000. Acceleration of global warming due to carbon-cycle feedbacks in a coupled climate model. Nature 408:184–7. doi: 10.1038/35041539

[9] ↑ Oyama, M. D., and Nobre, C. A. 2003. A new climate-vegetation equilibrium state for Tropical South America. Geophys. Res. Lett . 30:2199. doi: 10.1029/2003GL018600

[10] ↑ Lovejoy, T. E., and Nobre, C. A. 2018. Amazon tipping point. Sci. Adv. 4:2340. doi: 10.1126/sciadv.aat2340

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

• View all journals
• Explore content
• About the journal
• Publish with us
• Sign up for alerts
• Published: 19 June 2024

Amazon forest biogeography predicts resilience and vulnerability to drought

• Shuli Chen   ORCID: orcid.org/0000-0001-9852-8716 1 ,
• Scott C. Stark   ORCID: orcid.org/0000-0002-1579-1648 2 ,
• Antonio Donato Nobre 3 ,
• Luz Adriana Cuartas 4 ,
• Diogo de Jesus Amore 4 ,
• Natalia Restrepo-Coupe   ORCID: orcid.org/0000-0003-3921-1772 1 , 5 ,
• Marielle N. Smith   ORCID: orcid.org/0000-0003-2323-331X 2 , 6 ,
• Rutuja Chitra-Tarak 7 ,
• Hongseok Ko 1 ,
• Bruce W. Nelson   ORCID: orcid.org/0000-0002-0488-6895 8 &
• Scott R. Saleska 1 , 9  

Nature ( 2024 ) Cite this article

3300 Accesses

114 Altmetric

Metrics details

• Climate-change ecology
• Ecosystem ecology

Amazonia contains the most extensive tropical forests on Earth, but Amazon carbon sinks of atmospheric CO 2 are declining, as deforestation and climate-change-associated droughts 1 , 2 , 3 , 4 threaten to push these forests past a tipping point towards collapse 5 , 6 , 7 , 8 . Forests exhibit complex drought responses, indicating both resilience (photosynthetic greening) and vulnerability (browning and tree mortality), that are difficult to explain by climate variation alone 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 . Here we combine remotely sensed photosynthetic indices with ground-measured tree demography to identify mechanisms underlying drought resilience/vulnerability in different intact forest ecotopes 18 , 19 (defined by water-table depth, soil fertility and texture, and vegetation characteristics). In higher-fertility southern Amazonia, drought response was structured by water-table depth, with resilient greening in shallow-water-table forests (where greater water availability heightened response to excess sunlight), contrasting with vulnerability (browning and excess tree mortality) over deeper water tables. Notably, the resilience of shallow-water-table forest weakened as drought lengthened. By contrast, lower-fertility northern Amazonia, with slower-growing but hardier trees (or, alternatively, tall forests, with deep-rooted water access), supported more-drought-resilient forests independent of water-table depth. This functional biogeography of drought response provides a framework for conservation decisions and improved predictions of heterogeneous forest responses to future climate changes, warning that Amazonia’s most productive forests are also at greatest risk, and that longer/more frequent droughts are undermining multiple ecohydrological strategies and capacities for Amazon forest resilience.

This is a preview of subscription content, access via your institution

Access options

Access Nature and 54 other Nature Portfolio journals

Get Nature+, our best-value online-access subscription

24,99 € / 30 days

cancel any time

Subscribe to this journal

Receive 51 print issues and online access

185,98 € per year

only 3,65 € per issue

Buy this article

• Purchase on Springer Link
• Instant access to full article PDF

Prices may be subject to local taxes which are calculated during checkout

Similar content being viewed by others

Divergent forest sensitivity to repeated extreme droughts

Basin-wide variation in tree hydraulic safety margins predicts the carbon balance of Amazon forests

Sensitivity of South American tropical forests to an extreme climate anomaly

Data availability.

All remote sensing data and products (vegetation/photosynthetic indices ( https://lpdaac.usgs.gov/products/mcd19a3v006/ , http://data.globalecology.unh.edu/data/GOSIF_v2 ), climate variables ( https://disc2.gesdisc.eosdis.nasa.gov/data/TRMM_L3/TRMM_3B43.7/ , https://goldsmr4.gesdisc.eosdis.nasa.gov/data/MERRA2_MONTHLY/M2TMNXRAD.5.12.4/ , https://airs.jpl.nasa.gov/data/get-data/standard-data/ ), land cover ( https://lpdaac.usgs.gov/products/mcd12q1v006/ , https://forobs.jrc.ec.europa.eu/TMF ), tree characteristics (canopy height, https://webmap.ornl.gov/ogc/dataset.jsp?dg_id=10023_1 ) and soil texture ( https://maps.isric.org/ )) are publicly available online. The ground-based demographic validation data are publicly available in refs. 2 , 26 . The ground-based hydraulic trait validation data are publicly available in ref. 50 . The HAND data are from ref. 25 , which derived them from the digital elevation model from the Shuttle Radar Topography Mission. The soil fertility data are available in ref. 43 .

Code availability

Code for reproducing the modelling analysis and figures is posted at Code Ocean ( https://codeocean.com/capsule/2432086/tree ).

Pan, Y. et al. A large and persistent carbon sink in the world’s forests. Science 333 , 988–993 (2011).

Brienen, R. J. W. et al. Long-term decline of the Amazon carbon sink. Nature 519 , 344–348 (2015).

Article   ADS   CAS   PubMed   Google Scholar  

Wigneron, J.-P. et al. Tropical forests did not recover from the strong 2015–2016 El Niño event. Sci. Adv. 6 , eaay4603 (2020).

Article   ADS   CAS   PubMed   PubMed Central   Google Scholar  

Gatti, L. V. et al. Amazonia as a carbon source linked to deforestation and climate change. Nature 595 , 388–393 (2021).

Boulton, C. A., Lenton, T. M. & Boers, N. Pronounced loss of Amazon rainforest resilience since the early 2000s. Nat. Clim. Chang. 12 , 271–278 (2022).

Article   ADS   Google Scholar  

Flores, B. M. et al. Critical transitions in the Amazon forest system. Nature 626 , 555–564 (2024).

Article   CAS   PubMed   PubMed Central   Google Scholar  

Oyama, M. D. & Nobre, C. A. A new climate‐vegetation equilibrium state for Tropical South America. Geophys. Res. Lett. 30 , 2199 (2003).

Science Panel for the Amazon. Amazon Assessment Report 2021 (UN SDSN, 2021).

Saleska, S. R., Didan, K., Huete, A. R. & da Rocha, H. R. Amazon forests green-up during 2005 drought. Science 318 , 612 (2007).

Brando, P. M. et al. Seasonal and interannual variability of climate and vegetation indices across the Amazon. Proc. Natl Acad. Sci. USA 107 , 14685–14690 (2010).

Xu, L. et al. Widespread decline in greenness of Amazonian vegetation due to the 2010 drought. Geophys. Res. Lett. https://doi.org/10.1029/2011gl046824 (2011).

Yang, J. et al. Amazon drought and forest response: largely reduced forest photosynthesis but slightly increased canopy greenness during the extreme drought of 2015/2016. Glob. Change Biol. 24 , 1919–1934 (2018).

Anderson, L. O. et al. Vulnerability of Amazonian forests to repeated droughts. Philos. Trans. R. Soc. Lond. B 373 , 20170411 (2018).

Anderegg, W. R. L., Trugman, A. T., Badgley, G., Konings, A. G. & Shaw, J. Divergent forest sensitivity to repeated extreme droughts. Nat. Clim. Change 10 , 1091–1095 (2020).

Feldpausch, T. R. et al. Amazon forest response to repeated droughts. Glob. Biogeochem. Cycles 30 , 964–982 (2016).

Phillips, O. L. et al. Drought sensitivity of the Amazon rainforest. Science 323 , 1344–1347 (2009).

Esquivel-Muelbert, A. et al. Tree mode of death and mortality risk factors across Amazon forests. Nat. Commun. 11 , 5515 (2020).

Tansley, A. G. The use and abuse of vegetational concepts and terms. Ecology 16 , 284–307 (1935).

Article   Google Scholar  

Whittaker, R. H., Levin, S. A. & Root, R. B. Niche, habitat, and ecotope. Am. Nat. 107 , 321–338 (1973).

Jiménez-Muñoz, J. C. et al. Record-breaking warming and extreme drought in the Amazon rainforest during the course of El Niño 2015–2016. Sci. Rep. 6 , 33130 (2016).

Article   ADS   PubMed   PubMed Central   Google Scholar  

Marengo, J. A. & Espinoza, J. C. Extreme seasonal droughts and floods in Amazonia: causes, trends and impacts. Int. J. Climatol. 36 , 1033–1050 (2016).

Longo, M. et al. Ecosystem heterogeneity and diversity mitigate Amazon forest resilience to frequent extreme droughts. N. Phytol. 219 , 914–931 (2018).

Violle, C., Reich, P. B., Pacala, S. W., Enquist, B. J. & Kattge, J. The emergence and promise of functional biogeography. Proc. Natl Acad. Sci. USA 111 , 13690–13696 (2014).

Costa, F. R. C., Schietti, J., Stark, S. C. & Smith, M. N. The other side of tropical forest drought: do shallow water table regions of Amazonia act as large-scale hydrological refugia from drought?. N. Phytol. 237 , 714–733 (2022).

Nobre, A. D. et al. Height above the nearest drainage—a hydrologically relevant new terrain model. J. Hydrol . 404 , 13–29 (2011).

Sousa, T. R. et al. Palms and trees resist extreme drought in Amazon forests with shallow water tables. J. Ecol. 108 , 2070–2082 (2020).

Esteban, E. J. L., Castilho, C. V., Melgaço, K. L. & Costa, F. R. C. The other side of droughts: wet extremes and topography as buffers of drought negative effects in an Amazonian forest. N. Phytol. 229 , 1995–2006 (2020).

Oliveira, R. S. et al. Linking plant hydraulics and the fast-slow continuum to understand resilience to drought in tropical ecosystems. N. Phytol. 230 , 904–923 (2021).

Garcia, M. N., Domingues, T. F., Oliveira, R. S. & Costa, F. R. C. The biogeography of embolism resistance across resource gradients in the Amazon. Glob. Ecol. Biogeogr. 32 , 2199–2211 (2023).

Chitra-Tarak, R. et al. Hydraulically-vulnerable trees survive on deep-water access during droughts in a tropical forest. N. Phytol. 231 , 1798–1813 (2021).

Brum, M. et al. Hydrological niche segregation defines forest structure and drought tolerance strategies in a seasonal Amazon forest. J. Ecol. 107 , 318–333 (2019).

Tumber-Dávila, S. J., Schenk, H. J., Du, E. & Jackson, R. B. Plant sizes and shapes above and belowground and their interactions with climate. N. Phytol. 235 , 1032–1056 (2022).

Giardina, F. et al. Tall Amazonian forests are less sensitive to precipitation variability. Nat. Geosci. 11 , 405–409 (2018).

ter Steege, H. et al. Continental-scale patterns of canopy tree composition and function across Amazonia. Nature 443 , 444–447 (2006).

Article   ADS   PubMed   Google Scholar  

McDowell, N. et al. Mechanisms of plant survival and mortality during drought: why do some plants survive while others succumb to drought? N. Phytol. 178 , 719–739 (2008).

Anderegg, W. R. L. et al. Meta-analysis reveals that hydraulic traits explain cross-species patterns of drought-induced tree mortality across the globe. Proc. Natl Acad. Sci. USA 113 , 5024–5029 (2016).

Lyapustin, A. I. et al. Multi-angle implementation of atmospheric correction for MODIS (MAIAC): 3. Atmospheric correction. Remote Sens. Environ. 127 , 385–393 (2012).

Li, X. & Xiao, J. A Global, 0.05-degree product of solar-induced chlorophyll fluorescence derived from OCO-2, MODIS, and reanalysis data. Remote Sens. 11 , 517 (2019).

Aragão, L. E. O. C. et al. Spatial patterns and fire response of recent Amazonian droughts. Geophys. Res. Lett. https://doi.org/10.1029/2006gl028946 (2007).

Hastie, T. J. & Tibshirani, R. J. Generalized Additive Models (CRC, 1990).

Pearl, J. Causal inference in statistics: an overview. Statist. Surv. 3 , 96–146 (2009).

Article   MathSciNet   Google Scholar  

Aragão, L. E. O. C. et al. 21st Century drought-related fires counteract the decline of Amazon deforestation carbon emissions. Nat. Commun. 9 , 536 (2018).

Zuquim, G. et al. Making the most of scarce data: mapping soil gradients in data‐poor areas using species occurrence records. Methods Ecol. Evol. 10 , 788–801 (2019).

Hengl, T. et al. SoilGrids250m: global gridded soil information based on machine learning. PLoS ONE 12 , e0169748 (2017).

Article   PubMed   PubMed Central   Google Scholar  

Simard, M., Pinto, N., Fisher, J. B. & Baccini, A. Mapping forest canopy height globally with spaceborne lidar. J. Geophys. Res. https://doi.org/10.1029/2011jg001708 (2011).

Christina, M. et al. Almost symmetrical vertical growth rates above and below ground in one of the world’s most productive forests. Ecosphere 2 , 1–10 (2011).

da Costa, A. C. L. et al. Effect of 7 yr of experimental drought on vegetation dynamics and biomass storage of an eastern Amazonian rainforest. N. Phytol. 187 , 579–591 (2010).

Nepstad, D. C., Tohver, I. M., Ray, D., Moutinho, P. & Cardinot, G. Mortality of large trees and lianas following experimental drought in an Amazon forest. Ecology 88 , 2259–2269 (2007).

Article   PubMed   Google Scholar  

Phillips, O. L. et al. Drought–mortality relationships for tropical forests. N. Phytol. 187 , 631–646 (2010).

Tavares, J. V. et al. Basin-wide variation in tree hydraulic safety margins predicts the carbon balance of Amazon forests. Nature 617 , 111–117 (2023).

Duffy, P. B., Brando, P., Asner, G. P. & Field, C. B. Projections of future meteorological drought and wet periods in the Amazon. Proc. Natl Acad. Sci. USA 112 , 13172–13177 (2015).

Wunderling, N. et al. Recurrent droughts increase risk of cascading tipping events by outpacing adaptive capacities in the Amazon rainforest. Proc. Natl Acad. Sci. USA 119 , e2120777119 (2022).

Makarieva, A. M. et al. The role of ecosystem transpiration in creating alternate moisture regimes by influencing atmospheric moisture convergence. Glob. Chang. Biol. 29 , 2536–2556 (2023).

Article   CAS   PubMed   Google Scholar  

Costa, M. H. et al. in Amazon Assessment Report 2021 (eds Nobre, C. et al.) Ch. 7 (UN SDSN, 2021).

Betts, M. G. et al. When are hypotheses useful in ecology and evolution? Ecol. Evol. 11 , 5762–5776 (2021).

Glass, D. J. & Hall, N. A brief history of the hypothesis. Cell 134 , 378–381 (2008).

Huete, A. et al. Overview of the radiometric and biophysical performance of the MODIS vegetation indices. Remote Sens. Environ. 83 , 195–213 (2002).

Santos, V. A. H. F. D. et al. Causes of reduced leaf-level photosynthesis during strong El Niño drought in a Central Amazon forest. Glob. Change Biol. 24 , 4266–4279 (2018).

Wu, J. et al. Partitioning controls on Amazon forest photosynthesis between environmental and biotic factors at hourly to interannual timescales. Glob. Change Biol. 23 , 1240–1257 (2017).

Wu, J. et al. Leaf development and demography explain photosynthetic seasonality in Amazon evergreen forests. Science 351 , 972–976 (2016).

Mohammed, G. H. et al. Remote sensing of solar-induced chlorophyll fluorescence (SIF) in vegetation: 50 years of progress. Remote Sens. Environ. 231 , 111177 (2019).

Sun, Y. et al. OCO-2 advances photosynthesis observation from space via solar-induced chlorophyll fluorescence. Science 358 , eaam5747 (2017).

Shekhar, A., Buchmann, N. & Gharun, M. How well do recently reconstructed solar-induced fluorescence datasets model gross primary productivity? Remote Sens. Environ. 283 , 113282 (2022).

Huffman, G. J., Adler, R. F., Bolvin, D. T. & Nelkin, E. J. in Satellite Rainfall Applications for Surface Hydrology (eds Gebremichael, M. & Hossain, F.) 3–22 (Springer, 2010).

Gelaro, R. et al. The Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2). J. Clim. 30 , 5419–5454 (2017).

Aumann, H. H. Atmospheric infrared sounder on the Earth observing system. Opt. Eng. 33 , 776 (1994).

Kahn, B. H. et al. The Atmospheric Infrared Sounder version 6 cloud products. Atmos. Chem. Phys. 14 , 399–426 (2014).

Susskind, J., Blaisdell, J. M. & Iredell, L. Improved methodology for surface and atmospheric soundings, error estimates, and quality control procedures: the atmospheric infrared sounder science team version-6 retrieval algorithm. J. Appl. Remote Sens. 8 , 084994 (2014).

Sun, J. et al. Global evaluation of terrestrial near-surface air temperature and specific humidity retrievals from the Atmospheric Infrared Sounder (AIRS). Remote Sens. Environ. 252 , 112146 (2021).

Bastian, O. et al. In Development and Perspectives of Landscape Ecology (eds Bastian, O. & Steinhardt, U.) 49–112 (Springer, 2002).

Rennó, C. D. et al. HAND, a new terrain descriptor using SRTM-DEM: mapping terra-firme rainforest environments in Amazonia. Remote Sens. Environ. 112 , 3469–3481 (2008).

Brunner, I., Herzog, C., Dawes, M. A., Arend, M. & Sperisen, C. How tree roots respond to drought. Front. Plant Sci. 6 , 547 (2015).

Oliveira, R. S. et al. Embolism resistance drives the distribution of Amazonian rainforest tree species along hydro‐topographic gradients. N. Phytol. 221 , 1457–1465 (2019).

Levis, C. et al. Persistent effects of pre-Columbian plant domestication on Amazonian forest composition. Science 355 , 925–931 (2017).

Fan, Y., Li, H. & Miguez-Macho, G. Global patterns of groundwater table depth. Science 339 , 940–943 (2013).

Cunha, H. F. V. et al. Direct evidence for phosphorus limitation on Amazon forest productivity. Nature 608 , 558–562 (2022).

Chadwick, O. A., Derry, L. A., Vitousek, P. M., Huebert, B. J. & Hedin, L. O. Changing sources of nutrients during four million years of ecosystem development. Nature 397 , 491–497 (1999).

Article   ADS   CAS   Google Scholar  

Darela-Filho, J. P. et al. Reference maps of soil phosphorus for the pan-Amazon region. Earth Syst. Sci. Data 16 , 715–729 (2024).

Liu, H.-Y., Sun, W.-N., Su, W.-A. & Tang, Z.-C. Co-regulation of water channels and potassium channels in rice. Physiol. Plant. 128 , 58–69 (2006).

Fan, Y., Miguez-Macho, G., Jobbágy, E. G., Jackson, R. B. & Otero-Casal, C. Hydrologic regulation of plant rooting depth. Proc. Natl Acad. Sci. USA 114 , 10572–10577 (2017).

Hasanuzzaman, M., Araújo, S. & Gill, S. S. The Plant Family Fabaceae: Biology and Physiological Responses to Environmental Stresses (Springer, 2021).

Friedl, M. A. et al. MODIS Collection 5 global land cover: algorithm refinements and characterization of new datasets. Remote Sens. Environ. 114 , 168–182 (2010).

Hess, L. L. et al. Wetlands of the lowland Amazon basin: extent, vegetative cover, and dual-season inundated area as mapped with JERS-1 synthetic aperture radar. Wetlands 35 , 745–756 (2015).

Gómez, J., Schobbenhaus, C. & Montes, N. E. Geological Map of South America 2019. Scale 1: 5 000 000. Commission for the Geological Map of the World (CGMW), Colombian Geological Survey and Geological Survey of Brazil (2019); https://doi.org/10.32685/10.143.2019.929 .

Vancutsem, C. et al. Long-term (1990–2019) monitoring of forest cover changes in the humid tropics. Sci. Adv. 7 , eabe1603 (2021).

ForestPlots.net, et al. Taking the pulse of Earth’s tropical forests using networks of highly distributed plots. Biol. Conserv. 260 , 108849 (2021).

Shi, H. et al. Assessing the ability of MODIS EVI to estimate terrestrial ecosystem gross primary production of multiple land cover types. Ecol. Indic. 72 , 153–164 (2017).

Sims, D. A. et al. On the use of MODIS EVI to assess gross primary productivity of North American ecosystems. J. Geophys. Res. 111 , G04015 (2006).

Rahman, A. F., Sims, D. A., Cordova, V. D. & El-Masri, B. Z. Potential of MODIS EVI and surface temperature for directly estimating per-pixel ecosystem C fluxes. Geophys. Res. Lett. 32 , L19404 (2005).

Sims, D. A. et al. A new model of gross primary productivity for North American ecosystems based solely on the enhanced vegetation index and land surface temperature from MODIS. Remote Sens. Environ. 112 , 1633–1646 (2008).

Huete, A. R. et al. Amazon rainforests green-up with sunlight in dry season. Geophys. Res. Lett. 33 , L06405 (2006).

Huete, A. R. et al. Multiple site tower flux and remote sensing comparisons of tropical forest dynamics in Monsoon Asia. Agric. For. Meteorol. 148 , 748–760 (2008).

Huete, A. R. Vegetation indices, remote sensing and forest monitoring. Geogr. compass 6 , 513–532 (2012).

Samanta, A. et al. Amazon forests did not green-up during the 2005 drought. Geophys. Res. Lett. 37 , L05401 (2010).

Morton, D. C. et al. Amazon forests maintain consistent canopy structure and greenness during the dry season. Nature 506 , 221–224 (2014).

Saleska, S. R. et al. Dry-season greening of Amazon forests. Nature 531 , E4–E5 (2016).

Maeda, E. E., Heiskanen, J., Aragão, L. E. O. C. & Rinne, J. Can MODIS EVI monitor ecosystem productivity in the Amazon rainforest? Geophys. Res. Lett. 41 , 7176–7183 (2014).

Magney, T. S., Barnes, M. L. & Yang, X. On the covariation of chlorophyll fluorescence and photosynthesis across scales. Geophys. Res. Lett. 47 , e2020GL091098 (2020).

Chambers, J. Q. et al. Respiration from a tropical forest ecosystem: partitioning of sources and low carbon use efficiency. Ecol. Appl. 14 , 72–88 (2004).

Smith, M. N. et al. Seasonal and drought-related changes in leaf area profiles depend on height and light environment in an Amazon forest. N. Phytol. 222 , 1284–1297 (2019).

Janssen, T. et al. Drought effects on leaf fall, leaf flushing and stem growth in the Amazon forest: reconciling remote sensing data and field observations. Biogeosciences 18 , 4445–4472 (2021).

Quesada, C. A. et al. Basin-wide variations in Amazon forest structure and function are mediated by both soils and climate. Biogeosciences 9 , 2203–2246 (2012).

Lloyd, J. et al. Edaphic, structural and physiological contrasts across Amazon Basin forest–savanna ecotones suggest a role for potassium as a key modulator of tropical woody vegetation structure and function. Biogeosciences 12 , 6529–6571 (2015).

Wold, S., Esbensen, K. & Geladi, P. Principal component analysis. Chemometr. Intellig. Lab. Syst. 2 , 37–52 (1987).

Article   CAS   Google Scholar  

Doan, H. T. X. & Foody, G. M. Reducing the impacts of intra-class spectral variability on soft classification and its implications for super-resolution mapping. In Proc. IEEE International Geoscience and Remote Sensing Symposium 2585–2588 (IEEE, 2007).

Malhi, A. & Gao, R. X. PCA-based feature selection scheme for machine defect classification. IEEE Trans. Instrum. Meas. 53 , 1517–1525 (2004).

Canty, M. J. Image Analysis, Classification and Change Detection in Remote Sensing: With Algorithms for ENVI/IDL and Python, Third Edition (CRC, 2014).

Grafton, R. Q. et al. Realizing resilience for decision-making. Nat. Sustain. 2 , 907–913 (2019).

Nikinmaa, L. et al. Reviewing the use of resilience concepts in forest sciences. Curr. For. Rep. 6 , 61–80 (2020).

Gunderson, L. H. Ecological resilience—in theory and application. Annu. Rev. Ecol. Syst. 31 , 425–439 (2000).

Samanta, A. et al. Amazon forests did not green-up during the 2005 drought. Geophys. Res. Lett. https://doi.org/10.1029/2009gl042154 (2010).

Haining, R. P. & Haining, R. Spatial Data Analysis: Theory and Practice (Cambridge Univ. Press, 2003).

Burnham, K. P., Anderson, D. R. & Huyvaert, K. P. AIC model selection and multimodel inference in behavioral ecology: some background, observations, and comparisons. Behav. Ecol. Sociobiol. 65 , 23–35 (2011).

Clark, J. S. Models for Ecological Data (Princeton Univ. Press, 2020).

Pearl, J. Causality (Cambridge Univ. Press, 2009).

Ankan, A., Wortel, I. M. N. & Textor, J. Testing graphical causal models using the R package ‘dagitty’. Curr. Protoc. 1 , e45 (2021).

Arif, S. & MacNeil, M. A. Applying the structural causal model framework for observational causal inference in ecology. Ecol. Monogr. 93 , e1554 (2023).

Arif, S. & MacNeil, M. A. Predictive models aren’t for causal inference. Ecol. Lett. 25 , 1741–1745 (2022).

Wood, S. N. Generalized Additive Models: An Introduction with R, Second Edition (CRC, 2017).

Quaresma, M., Carpenter, J. & Rachet, B. Flexible Bayesian excess hazard models using low-rank thin plate splines. Stat. Methods Med. Res. 29 , 1700–1714 (2020).

Article   MathSciNet   PubMed   Google Scholar  

Schempp, W. & Zeller, K. eds. Constructive Theory of Functions of Several Variables: Proceedings of a Conference Held at Oberwolfach, April 25 - May 1, 1976 (Springer, 1977).

Laurance, W. F. et al. Relationship between soils and Amazon forest biomass: a landscape-scale study. For. Ecol. Manage. 118 , 127–138 (1999).

Levine, N. M. et al. Ecosystem heterogeneity determines the ecological resilience of the Amazon to climate change. Proc. Natl Acad. Sci. USA 113 , 793–797 (2016).

Addicott, E. T., Fenichel, E. P., Bradford, M. A., Pinsky, M. L. & Wood, S. A. Toward an improved understanding of causation in the ecological sciences. Front. Ecol. Environ. 20 , 474–480 (2022).

Textor, J., van der Zander, B., Gilthorpe, M. S., Liskiewicz, M. & Ellison, G. T. Robust causal inference using directed acyclic graphs: the R package ‘dagitty’. Int. J. Epidemiol. 45 , 1887–1894 (2016).

PubMed   Google Scholar  

de Castilho, C. V. et al. Variation in aboveground tree live biomass in a central Amazonian Forest: effects of soil and topography. For. Ecol. Manage. 234 , 85–96 (2006).

Velleman, P. F. & Welsch, R. E. Efficient computing of regression diagnostics. Am. Stat. 35 , 234–242 (1981).

Webb, C. O., Cannon, C. H. & Davies, S. J. in Tropical Forest Community Ecology (eds Carson, W. P. & Schnitzer, S. A.) 79–97 (Wiley–Blackwell, 2008).

Humboldt’s legacy. Nat. Ecol. Evol. 3 , 1265–1266 (2019).

Reichstein, M., Bahn, M., Mahecha, M. D., Kattge, J. & Baldocchi, D. D. Linking plant and ecosystem functional biogeography. Proc. Natl Acad. Sci. USA 111 , 13697–13702 (2014).

Nelson, B. W., Gonçalves, N. B., Chen, S. & Saleska, S. Persistent effect of 2015 El Niño drought on NIR reflectance of central Amazon upland forests? In Anais do XX Simpósio Brasileiro de Sensoriamento Remoto 1636–1638 (INPE, 2023).

Oliveira, R. S., Dawson, T. E., Burgess, S. S. O. & Nepstad, D. C. Hydraulic redistribution in three Amazonian trees. Oecologia 145 , 354–363 (2005).

Nunes, M. H. et al. Forest fragmentation impacts the seasonality of Amazonian evergreen canopies. Nat. Commun. 13 , 917 (2022).

Van der Meer, T., Te Grotenhuis, M. & Pelzer, B. Influential cases in multilevel modeling: a methodological comment. Am. Sociol. Rev. 75 , 173–178 (2010).

Boers, N., Marwan, N., Barbosa, H. M. J. & Kurths, J. A deforestation-induced tipping point for the South American monsoon system. Sci. Rep. 7 , 41489 (2017).

Download references

Acknowledgements

We thank J. Schietti for early discussions of the idea that remote sensing might be used to investigate the effect of water-table depth on forest drought response; T. R. Sousa for sharing and discussing plot-based forest demographic data (from along the BR-319 road) 26 ; G. Zuquim for sharing an early version of mapped basin-wide soil fertility data 43 ; H. ter Steege for sharing mapped basin-wide tree characteristics data 34 ; T. R. Sousa and J. Schietti for comments on an earlier version of the manuscript; L. Alves for advice on forest demography plots; R. Palacios for recommending the use of GAM models; M. N. Garcia for discussions about soil fertility; N. Boers for advice on the South American monsoon system; T. C. Taylor and V. Ivanov for discussions; J. Cronin and S. McMahon for detailed advice and comments; and S.C.’s doctoral dissertation committee members W. K. Smith, J. Hu and B. Enquist for constructive criticism and advice on the direction of this work. This work was supported by US National Aeronautics and Space Administration, fellowship 80NSSC19K1376 (S.C.); US National Science Foundation, DEB grant 1950080 (S.C.S. and M.N.S.); US National Science Foundation, DEB grant 2015832 (S.R.S.); US National Science Foundation, DEB grant 1754803 (S.R.S., N.R.-C.), US National Science Foundation, DEB grant 1754357 (S.C.S.); Brazil National Council for Scientific and Technological Development (CNPq) scholarships 371626/2022-6, 372734/2021-9,381711/2020-0 (D.d.J.A.); and US Department of Energy’s Next Generation Ecosystem Experiments-Tropics (R.C.-T.).

Author information

Authors and affiliations.

Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ, USA

Shuli Chen, Natalia Restrepo-Coupe, Hongseok Ko & Scott R. Saleska

Department of Forestry, Michigan State University, East Lansing, MI, USA

Scott C. Stark & Marielle N. Smith

National Institute for Space Research (INPE), São José dos Campos, Brazil

Antonio Donato Nobre

National Center for Monitoring and Early Warning of Natural Disasters (CEMADEN), São José dos Campos, Brazil

Luz Adriana Cuartas & Diogo de Jesus Amore

Cupoazu LLC, Etobicoke, Ontario, Canada

Natalia Restrepo-Coupe

School of Environmental and Natural Sciences, College of Science and Engineering, Bangor University, Bangor, UK

Marielle N. Smith

Los Alamos National Laboratory, Earth and Environmental Sciences, Los Alamos, NM, USA

Rutuja Chitra-Tarak

Brazil’s National Institute for Amazon Research (INPA), Manaus, Brazil

Bruce W. Nelson

Department of Environmental Sciences, University of Arizona, Tucson, AZ, USA

Scott R. Saleska

You can also search for this author in PubMed   Google Scholar

Contributions

S.C. and S.R.S. designed the analysis, based on early conception by A.D.N. and S.R.S., and on funded proposals to investigate ‘the other side of tropical forest drought’ led by S.C.S., M.N.S. and S.R.S. (from NSF) and by S.C. and S.R.S. (from NASA). A.D.N., L.A.C. and D.d.J.A. updated their HAND data product and interpreted it for this analysis. B.W.N. and N.R.-C. contributed remote-sensing expertise and analysis. R.C.-T. contributed statistical modelling expertise and analysis. H.K. contributed code, especially for the variogram analysis. S.C. organized the datasets (with assistance from N.R.-C.), conducted the analysis and wrote the initial draft. S.C., S.R.S. and S.C.S. revised the draft. All of the authors contributed to writing the final version.

Corresponding authors

Correspondence to Shuli Chen or Scott R. Saleska .

Ethics declarations

Competing interests.

The authors declare no competing interests.

Peer review

Peer review information.

Nature thanks Christopher Baraloto, David Bauman, Jovan Tadic and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Peer reviewer reports are available.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Extended data figures and tables

Extended data fig. 1 drought maps 2005, 2010 and 2015/16 droughts and gosif-based forest responses droughts..

(a)-(c): Maximum cumulative water deficit (MCWD) standardized anomalies. (relative to the long term mean MCWD across years, blue=positive, orange=negative) during drought for ( a ) 2005, ( b ) 2010, and ( c ) 2015 droughts. MCWD is calculated (see Methods, ‘Climate variables’) as the maximum water deficit reached for each hydrologic year (from May of the nominal year to the following April). The “drought region” is defined as pixels whose MCWD anomaly is more than one SD below the mean (light orange to red). (d)-(f): GOSIF-based forest response to droughts . GOSIF anomalies during drought, relative to the long term mean GOSIF (green=positive, orange=negative) in drought regions for the ( d ) 2005, ( e ) 2010 and ( f ) 2015 droughts, respectively. ( g ) EVI (left axis) and GOSIF (right axis) anomalies in the 2005 drought elliptical region (as depicted in Figs. 1a , 2a , and here in Extended Data Fig. 1d ) show consistent patterns versus HAND (bin averages ±95% CI, with N = 6,547 5-km pixels for both EVI and GOSIF); ( h ) GOSIF anomalies (bin averages points ±95% CI and solid regression line) vs. water-table depths (indexed by HAND) support hypothesis 1 (with negative slopes, consistent with EVI in Fig. 3a ) for the 2005 (green, slope = −0.016 ± 0.006 SE m −1 ), 2010 (purple, slope = −0.012 ± 0.003 SE m −1 ), and 2015 (blue, slope = −0.010 ± 0.003 SE m −1 ) droughts, paired with HAND distributions in each drought region (bottom graphs, right axis, with N = 34,980, 30,004, 43,475 5-km pixels for 2005, 2010, and 2015 droughts, respectively).

Extended Data Fig. 2 Ecotope factors of the Amazon basin.

( a ) Height Above Nearest Drainage (HAND), a proxy for water-table depth 25 ; ( b ) Soil fertility, as exchangeable base cation concentrations 43 ; ( c ) Average forest heights as acquired by lidar 45 ; ( d ) Soil sand content 44 ; ( e ) Proportion of trees belonging to the Fabaceae family 34 ; ( f ) MCWD variability (see the ‘Climate anomalies for drought definition and mapping’ section of  methods ), in terms of the standard deviation of the long-term MCWD timeseries. High variance in climate and low soil fertility in Guiana shield might contribute to the greatest proportion of trees belonging to the family Fabaceae with the very high wood density; ( g ) Averaged minimum monthly precipitation (low=green, high=orange). The north-west everwet Amazon is distinguished by lacking a dry season (precipitation exceeds evapotranspiration). ( h ) Community-weighted wood density 34 . Panels a-d are used as ecotope predictors in the GAM analysis of Supplementary Table 1 . (Data sources: see the ‘Climate variables’ and ‘Climate anomalies for drought definition and mapping’ sections of methods ).

Extended Data Fig. 3 Spatial distributions of climate dynamics in the 2005, 2010 and 2015 droughts.

a – i , Spatial distributions of climate dynamics in the 2005 (left column), 2010 (middle column) and 2015 (right column) droughts for: (a)-(i): Drought dynamics showing drought onset date (row 1, a-c), drought end date (row 2, d-f), and drought duration (row 3, g-i, end date minus start date). Pixel-by-pixel drought responses (EVI in Figs. 1 – 4 ; or GOSIF in Extended Data Figs. 1 & 5 ) are taken as the standardized anomalies that occur during the pixel-specific drought period defined here. (j)-(r): climatic anomalies of: photosynthetic active radiation (PAR) (row 4, j-l), vapor pressure deficit (VPD) (row 5, m-o), and precipitation (row 6, p-r). precipitation (Data source: see the ‘Climate variables’ section of  methods ).

Extended Data Fig. 4 Regions in the Amazon basin.

that emerge from a principal components analysis (PCA) followed by classification: ( a ) PCA of the Amazon basin 0.4° x 0.4° pixel data (coloured according to a supervised classification into three classes identified by variance minimization), projected onto their first two principal components, which are composed mainly of three dimensions, one defined by wood density and proportions of the family Fabaceae (first principal component, horizontal axis), one defined by minimum monthly precipitation and MCWD variability (second principal component, vertical axis), and a third defined mainly by soil fertility; the classes are significantly separated in PCA space (psuedo-F ratio =950, df=2, 3805, p ~ 0, permanova test); ( b ) The Amazon pixels coloured according to their class (corresponding to the colours in a), showing that the classification of (a) maps pixels into distinct, mostly contiguous spatial regions.) ( c ) Standardized values, for each region, of each group of characteristics (ordered by water availability, soil fertility, and tree traits/characteristics), illustrate distinct regional niches: the everwet Amazon is highest in minimum precipitation and lowest (highest negative) in MCWD variability; the Southern Amazon is moderately high in mean fertility, and the Guiana Shield has the tallest mean forest height and greatest wood density. ( d ) scree plot of the eigenvalues (principal components) of the PCA shown in (a), plotted in rank order.

Extended Data Fig. 5 Amazon forest drought responses in different regions using the EVI and GOSIF remote sensing indices.

Amazon forest EVI (top row) and GOSIF (bottom row) responses to multiple droughts in the Guiana shield (left column) and the ever-wet northwest (right column). These generally do not support the “other side of drought” hypothesis 1, because they show generally consistently positive slopes with water-table depth (HAND), in contrast to negative slope responses in the Southern Amazon (Fig. 3a ). Plots show observations (bin average points ±95% CI, and solid regression lines) and unified multi-drought GAM predictions (±95% CI shaded region, for models in Supplementary Table 1b, c ), with climate fixed to region-wide median drought conditions for each drought.) Observations for EVI (a-b): N = 83 and 666 0.4° pixels for 2005 and 2015 droughts respectively, in the Guiana shield (a), and N = 147, 368, and 648 for 2005, 2010 and 2015 droughts respectively in the ever-wet Amazon (b). Observations for GOSIF (c-d): N = 1876, and 25,460 5-km pixels for 2005 and 2015 droughts, respectively, in Guiana shield (c), and N = 1,914, 8,261, and 19,918 for 2005, 2010 and 2015 droughts, respectively, in the ever-wet Amazon (d). Purple points (2010) are not shown in panels a,c, because the 2010 drought did not significantly affect the Guiana shield.

Extended Data Fig. 6 Implementing Structured Causal Modeling (SCM) of Amazon forest drought response using Directed acyclic graphs (DAGs).

a – d , Development of a Directed acyclic graph (DAG) representing the structure of factors influencing tropical forest responses to drought. ( a ) Initially hypothesized DAG characterizing the causal relationships among climatic, environmental, and forest variables (measured variables depicted as blue nodes, unmeasured rooting depth is depicted in grey) leading to forest drought response (other colour node), with arrows representing the hypothesized causal links. ( b ) DAG-data consistency tests for initial DAG , with the largest 20 approximated non-linear correlation coefficients (estimated via root mean square error of approximation, RMSEA) between unlinked variables in (a). (Note: unlinked variables in a DAG are hypothesized to have zero correlation or zero conditional correlation; thus, the second row of panel b tests “DR_ | | _DSL | DL” -- whether DR is independent of DSL conditioned on DL, by estimating the non-linear correlation between DR and the residuals of DSL regressed on DL.) Correlations greater than an acceptability threshold (dashed vertical lines at ±0.30) fail the test of conditional independence, addressed by adding to the DAG either a direct causal link (indicated by a green symbol), or links to a common cause (pink symbol) (such added arrows are included in panel c). ( c ) Final DAG after correcting for conditional independency inconsistencies of the initial DAG in A, in light of ecological considerations. Also illustrates use of the backdoor criterion to determine the causal effect of ‘drought length (DL)’ (the exposed predictor node and associated forward causal paths, in green) on forest drought response (corresponding to the model in Extended Data Fig. 10c ), while blocking the confounding variable dry season length, DSL (hypothesized to itself affect DL) and its associated causal backdoor paths (which are considered non-causal paths with respect to the exposed variable DL) (in pink). ( d ) DAG-Data consistency tests for final DAG (panel c), showing the largest 20 RMSEA values. (e)-(j): GAM regression model predictions (±95% CI shaded region) of causal effects of different variables derived from DAG, employing backdoor criterion, for the Southern Amazon, average across all three droughts: ( e ) of HAND (no backdoor to be blocked) (f) of PAR (adjusting for back door paths through drought length, dry season length) ( g ) of Drought length (adjusting for back door path through dry season length) on EVI responses (adjusted EVI prediction) ; the whole Amazon basin during the 2015 drought: ( h ) of forest height, categorized by shallow (blue, HAND = 0-10 m) and deep (red, HAND = 20–40 m) water tables (adjusting for back door paths through soil fertility, soil texture and dry season length), ( i ) of soil fertility (adjusting for back door path through dry season length) ( j ) of soil texture (no backdoor path to be blocked).

Extended Data Fig. 7 The sensitivities of forest drought response to soil texture and drought timing.

( a ) The sensitivity of forest response to soil texture (sand content) and water- table depth (HAND) in basin-wide GAM analysis. GAM-predicted adjusted EVI anomaly (left axis) versus soil sand content (%), with water table-depth in colour (shallow=blue to deep=red), paired with distributions of mean forest height in each soil texture bin (bottom graph, right axis, with N = 3,318, and 1,142 0.4° pixels for shallow and deep water tables, respectively). ‘Adjusted’ GAM predictions are made by setting non-displayed predictors (climate variables, tree-height, soil fertility) to their median values during the drought. (b)-(d): The sensitivity of forest responses to dry versus wet season drought periods, across the three-droughts: ( b ) distribution of the proportion of drought that was in the dry season (0 = all in the wet season to 1= all in the dry season) for drought-affected pixels in each of the three droughts; ( c ) GAM-predicted EVI anomaly versus PAR, for different proportions of dry season drought (blue=all wet to red=all dry, corresponding to coloured tick marks in the vertical axis of b). ( d ) Adjusted EVI anomaly from GAM prediction versus drought length, for different proportions of dry-season drought (blue to red, as in panel c).

Extended Data Fig. 8 Scale-dependence of Southern Amazon forest responses to drought, showing that detected response patterns are largely invariant across different scales of analysis.

( a ) At 0.4 degree (40-km) scale (across the Southern Amazon. all three droughts): Climate-adjusted EVI responses (standardized anomalies from MODIS) vs. water-table depths (indexed by HAND) for observations (solid points ±95% CI and solid regression line) and for unified multi-drought GAM predictions (model of Supplementary Table 1a , shaded bands and dashed regression line slopes) for the 2005 (green, slope = −0.019 ± 0.001 SE m −1 ), 2010 (purple, slope = −0.020 ± 0.002 SE m −1 ), and 2015 (blue, slope = −0.028 ± 0.002 SE m −1 ) droughts (with N = 1,384, 1,673, and 1,837 0.4° pixels for 2005, 2010, and 2015 droughts, respectively); ( b ) At 1-km scale (across the Southern Amazon, all three droughts), as in (a): climate-adjusted EVI responses vs. HAND for observations (solid points and regression line) and corresponding GAM (with the same Supplementary Table 1a model now fit at 1 km scale, revealing autocorrelation in observations causing too-narrow confidence bands, and slight model underpredictions of the extremes of the 2005 greenup and the 2010 browdown, but maintaining the similar negative dependence on HAND across all droughts); ( c ) At 30 to 180 m scales (for a forest region around Manaus, 2015-2016 drought only): Delta EVI, the fraction change in EVI due to the drought = (after-drought EVI (July 2016) - pre-drought EVI (August 2015))/pre-drought EVI (Landsat OLI8, at 30 m resolution) vs. water-table depths (indexed by HAND) for Landsat observations (solid points ±95% CI and solid regression line) at native (30 m) and aggregated to 90 and 180-m scales (with N = 105,359, 11,901, and 2,999 pixels for 30-m, 90-m, and 180-m scales, respectively). Also shown in the bottom of each panel is the distribution of water-table depth (HAND proxy) at each scale. Aggregations to larger (coarser) scales induce an apparent regression towards the mean in the water-table depth distributions (as more extreme water-table depths at finer scales become diluted by averaging to large scales), while similar dilution of extremes in EVI response (not shown) preserves the overall relation between EVI responses and watertable depth (especially evident in the Landsat analysis where the slopes through data aggregated at different scales do not detectably differ).

Extended Data Fig. 9 Remote sensing validation with forest inventory plot demography.

( a ) Remotely sensed map of MAIAC EVI (1-km resolution), overlaid with aboveground NPP (ANPP) rates from 321 ground-monitored forest plots (red circles, % standing biomass y −1 ) as aggregated to 1 degree grid plots (RAINFOR plots in Brienen et al. 2 ), with both EVI and ANPP taken during the 2000–2011 interval. ANPP rate is calculated as Aboveground Biomass (AGB) gain (Mg/(ha·yr)) (total annual AGB productivity of surviving trees plus recruitment, plus inferred growth of trees that died between censusing intervals) divided by initial AGB (Mg/ha) (standing above ground biomass at the start of the census interval). ( b ) ANPP rates as predicted by EVI (points from (a) plus solid regression line with statistics; Dashed line and associated statistics in grey represent linear regression without the high leverage point, shown in red, defined by Cook’s distances > 4/n, where n=number of points 134 ). EVI is the mean extracted from intervals matching the average census interval of the corresponding plots in Brienen et al. 2 (c)–(e) MAIAC EVI anomalies (1-km pixels) versus ground-monitored tree demography in shallow water table forests during the 2015-2016 drought 26 for : (c) mortality, (d) recruitment, and (e) mortality:recruitment ratios in 1-ha plots. (f)–(h): GOSIF anomalies (5-km pixels) versus ground-monitored (f) mortality, (g) recruitment, and (h) mortality:recruitment ratios; Solid lines and statistics (R 2 and p-values) represent standard linear regression fits to all data. Red points, if they exist, are high leverage, i.e. with Cook’s distances > 4/n, where n=number of points 134 , and dotted lines and associated statistics in grey represent standard linear regressions without such points, showing that remote detection of ground-derived demographic trends is robust. R 2 values reported here are consistent with the expectation that they should be less than for remote detection of tropical forest GPP (R 2  = 0.5-0.7), because GPP contributes only partially to the NPP driver of demography (as discussed in the 'Validation by forest plot metrics of demography and of physiological drought tolerance' section of Methods). Considering multple comparisons (six regressions), the probability, under the null hypothesis, of seeing five or more significant regresssions out of six is p = 0.000002 (Binomial test).

Extended Data Fig. 10 Modeled forest response to the 2015 drought and implications of the derived map of Amazon forest biogeography.

a – c , Forest response to the 2015 drought in drought-affected pixels. ( a ) Observed EVI anomalies (resampled at 0.4 degrees to match model resolution which accounts for spatial autocorrelation (see Supplementary Fig. 1 ). ( b ) GAM-predicted EVI anomalies (model of Supplementary Table 1d ). ( c ) Residual EVI anomalies (panel a observations minus panel b predictions). The GAM well-predicts the pattern of response (Panel b), but under-estimates the extremes of the responses (as evident from residuals in panel c continuing to show greening/browning patterns beyond the predictions). ( d ) Map of Amazon forest biogeography of resilience/vulnerability, overlaid with mean winds (arrows, at height 650 hPa) and location of the arc of deforestation . The most productive as well as the most vulnerable forests (in red) are also those most experiencing deforestation (in the “arc of deforestation”) which is causing local climatic warming/drying 4 , further stressing these vulnerable forests. These “arc of deforestation”/vulnerable forests are often upwind forests 135 (especially when the Intertropical convergence zone, ITCZ, swings to the south) that are critical for hydrological recycling in the Amazon.

Supplementary information

Supplementary information, reporting summary, peer review file, rights and permissions.

Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.

Reprints and permissions

About this article

Cite this article.

Chen, S., Stark, S.C., Nobre, A.D. et al. Amazon forest biogeography predicts resilience and vulnerability to drought. Nature (2024). https://doi.org/10.1038/s41586-024-07568-w

Download citation

Received : 28 November 2022

Accepted : 15 May 2024

Published : 19 June 2024

DOI : https://doi.org/10.1038/s41586-024-07568-w

Share this article

Anyone you share the following link with will be able to read this content:

Sorry, a shareable link is not currently available for this article.

Provided by the Springer Nature SharedIt content-sharing initiative

By submitting a comment you agree to abide by our Terms and Community Guidelines . If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Quick links

• Explore articles by subject
• Guide to authors
• Editorial policies

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

• Climate modelling
• Extreme weather
• Health and Security
• Temperature
• China energy
• Oil and gas
• Other technologies
• China Policy
• International policy
• Other national policy
• Rest of world policy
• UN climate talks
• Country profiles
• Guest posts
• Infographics
• Media analysis
• State of the climate
• Translations
• Daily Brief
• China Briefing
• Comments Policy
• Cookies Policy
• Global emissions
• Rest of world emissions
• UK emissions
• EU emissions
• Global South Climate Database
• Newsletters
• COP21 Paris
• COP22 Marrakech
• COP24 Katowice
• COP25 Madrid
• COP26 Glasgow
• COP27 Sharm el-Sheikh
• COP28 Dubai
• Privacy Policy
• Attribution
• Geoengineering
• Food and farming
• Nature policy
• Plants and forests
• Marine life
• Ocean acidification
• Ocean warming
• Sea level rise
• Human security
• Public health
• Public opinion
• Risk and adaptation
• Science communication
• Carbon budgets
• Climate sensitivity
• GHGs and aerosols
• Global temperature
• Negative emissions
• Rest of world temperature
• Tipping points
• UK temperature
• Thank you for subscribing

Social Channels

Search archive.

Receive a Daily or Weekly summary of the most important articles direct to your inbox, just enter your email below. By entering your email address you agree for your data to be handled in accordance with our Privacy Policy .

• Amazon rainforest is taking up a third less carbon than a decade ago

Robert McSweeney

The amount of carbon that the Amazon rainforest is absorbing from the atmosphere and storing each year has fallen by around a third in the last decade, says a new 30-year study by almost 100 researchers.

This decline in the Amazon carbon sink amounts to one billion tonnes of carbon dioxide – equivalent to over twice the UK’s annual emissions, the researchers say.

If this pattern exists in other forests around the world, deeper cuts in human-caused carbon dioxide emissions are needed to meet climate targets, the researchers say.

Three billion trees

The Amazon rainforest is the largest rainforest in the world. Spanning nine countries in South America, it’s 25 times the size of the UK.

Using a process known as photosynthesis, the Amazon’s three billion trees convert carbon dioxide, water and sunlight into the fuel they need to grow, locking up carbon in their trunks and branches.

As they grow, Amazon trees account for  a quarter  of the carbon dioxide absorbed by the land each year.  Studies suggest  that as human-caused carbon dioxide emissions increase, forests will absorb and store more carbon, assuming they have enough water and nutrients to grow.

But a new study, published today in  Nature , suggests the Amazon has passed saturation point for how much extra carbon it can take up.

Diminishing carbon sink

A team of almost 500 people monitored trees in more than 300 sites across eight countries. Between 1983 and 2011, the researchers measured the trees in each plot, recording the number, size and density to calculate how much carbon each one stored.

The trees took up more carbon and grew more quickly during the 1990s, before levelling off since the year 2000. You can see this in the middle chart below.

Top graph shows trend in biomass (i.e. the amount of carbon stored), middle graph shows trend in productivity (i.e. tree growth), and the bottom graph shows trend in biomass mortality (i.e. tree deaths). Data before 1990 (dotted black line) was from a small number of sites, so there is more variation in these years. Source: Brienen et al. ( 2015 )

But during this growth spurt, Amazon trees have been dying off more quickly, as the bottom graph shows.

The combination of flat growth rate and increasing tree deaths means the amount of carbon the Amazon stores has declined by around 30% since the 1990s, the researchers say. You can see this in the top graph.

Live fast, die young

So what is causing more trees to die? Co-author Prof Oliver Phillips from the University of Leeds, tells Carbon Brief it could be down to the growth spurt fuelled by rising carbon dioxide levels:

“The faster trees grow, the sooner they reach maturity, and the sooner they may eventually age. “

As tall trees are more vulnerable to high winds and drought, faster growth may also be putting trees at risk from weather extremes, Phillips says. During the Amazon droughts in 2005 and 2010, for example, the researchers found short-term peaks in deaths of large trees. Though the overall trend of more trees dying began before either drought, the researchers say.

In an accompanying News & Views article , Prof Lars Hedin , professor of ecology and evolutionary biology at Princeton University, also points to drought as a possible underlying reason for declining carbon storage:

“A more likely explanation is that the influence of one or more constraining factors, such as water availability, temperature stress or nutrient limitation, has increased as forest biomass has expanded.”

But the exact causes don’t change the overarching finding that the forest is storing less carbon, says lead author Dr Roel Brienen , also from the University of Leeds:

“Regardless of the causes behind the increase in tree mortality, this study shows that predictions of a continuing increase of carbon storage in tropical forests may be too optimistic.”

Carbon sinking

We won’t see an immediate effect of declining Amazon carbon storage on atmospheric carbon dioxide levels, the researchers say. The carbon from dead trees is released slowly as they decompose. But apart from the fraction of carbon that ends up in the soil on the forest floor, the rest will eventually reach the atmosphere.

The key question now is whether carbon uptake is falling in other forests too, says Prof Peter Smith from the University of Aberdeen, coordinating lead author of the Agriculture, Forestry and Other Land Use chapter of the latest Intergovernmental Panel on Climate Change report:

“It is not known if this trend is replicated more widely across tropical forests, but it does show that we need more measurements to quantify this elsewhere.”

If declining carbon storage does turn out to be more widespread, that would spell bad news for the climate, Smith says:

“Until now, the biosphere has been re-absorbing a proportion of the carbon dioxide we have released through fossil fuel burning and land use change. If that re-absorption declines as suggested here, more carbon dioxide will remain in the atmosphere, thereby accelerating climate change.”

Forests have been doing as a huge favour for decades, says Phillips. But the new study shows forests’ capacity to buffer climate change is shrinking, which means the need to reduce emissions is rising at the same time.

Brienen, R.J.W et al. (2015) Long-term decline of the Amazon carbon sink, Nature, doi:10.1038/nature14283

Main image: Early morning mist over the Amazon rainforest.

Hedin, L.O. (2015) Signs of saturation in the tropical carbon sink, Nature,  doi:10.1038/519295a

Expert analysis direct to your inbox.

Get a round-up of all the important articles and papers selected by Carbon Brief by email. Find out more about our newsletters here .

Case Study: The Amazon Rainforest

The amazon in context.

Tropical rainforests are often considered to be the “cradles of biodiversity.” Though they cover only about 6% of the Earth’s land surface, they are home to over 50% of global biodiversity. Rainforests also take in massive amounts of carbon dioxide and release oxygen through photosynthesis, which has also given them the nickname “lungs of the planet.” They also store very large amounts of carbon, and so cutting and burning their biomass contributes to global climate change. Many modern medicines are derived from rainforest plants, and several very important food crops originated in the rainforest, including bananas, mangos, chocolate, coffee, and sugar cane.

In order to qualify as a tropical rainforest, an area must receive over 250 centimeters of rainfall each year and have an average temperature above 24 degrees centigrade, as well as never experience frosts. The Amazon rainforest in South America is the largest in the world. The second largest is the Congo in central Africa, and other important rainforests can be found in Central America, the Caribbean, and Southeast Asia. Brazil contains about 40% of the world’s remaining tropical rainforest. Its rainforest covers an area of land about 2/3 the size of the continental United States.

There are countless reasons, both anthropocentric and ecocentric, to value rainforests. But they are one of the most threatened types of ecosystems in the world today. It’s somewhat difficult to estimate how quickly rainforests are being cut down, but estimates range from between 50,000 and 170,000 square kilometers per year. Even the most conservative estimates project that if we keep cutting down rainforests as we are today, within about 100 years there will be none left.

How does a rainforest work?

Rainforests are incredibly complex ecosystems, but understanding a few basics about their ecology will help us understand why clear-cutting and fragmentation are such destructive activities for rainforest biodiversity.

High biodiversity in tropical rainforests means that the interrelationships between organisms are very complex. A single tree may house more than 40 different ant species, each of which has a different ecological function and may alter the habitat in distinct and important ways. Ecologists debate about whether systems that have high biodiversity are stable and resilient, like a spider web composed of many strong individual strands, or fragile, like a house of cards. Both metaphors are likely appropriate in some cases. One thing we can be certain of is that it is very difficult in a rainforest system, as in most other ecosystems, to affect just one type of organism. Also, clear cutting one small area may damage hundreds or thousands of established species interactions that reach beyond the cleared area.

Pollination is a challenge for rainforest trees because there are so many different species, unlike forests in the temperate regions that are often dominated by less than a dozen tree species. One solution is for individual trees to grow close together, making pollination simpler, but this can make that species vulnerable to extinction if the one area where it lives is clear cut. Another strategy is to develop a mutualistic relationship with a long-distance pollinator, like a specific bee or hummingbird species. These pollinators develop mental maps of where each tree of a particular species is located and then travel between them on a sort of “trap-line” that allows trees to pollinate each other. One problem is that if a forest is fragmented then these trap-line connections can be disrupted, and so trees can fail to be pollinated and reproduce even if they haven’t been cut.

The quality of rainforest soils is perhaps the most surprising aspect of their ecology. We might expect a lush rainforest to grow from incredibly rich, fertile soils, but actually, the opposite is true. While some rainforest soils that are derived from volcanic ash or from river deposits can be quite fertile, generally rainforest soils are very poor in nutrients and organic matter. Rainforests hold most of their nutrients in their live vegetation, not in the soil. Their soils do not maintain nutrients very well either, which means that existing nutrients quickly “leech” out, being carried away by water as it percolates through the soil. Also, soils in rainforests tend to be acidic, which means that it’s difficult for plants to access even the few existing nutrients. The section on slash and burn agriculture in the previous module describes some of the challenges that farmers face when they attempt to grow crops on tropical rainforest soils, but perhaps the most important lesson is that once a rainforest is cut down and cleared away, very little fertility is left to help a forest regrow.

What is driving deforestation in the Amazon?

Many factors contribute to tropical deforestation, but consider this typical set of circumstances and processes that result in rapid and unsustainable rates of deforestation. This story fits well with the historical experience of Brazil and other countries with territory in the Amazon Basin.

Population growth and poverty encourage poor farmers to clear new areas of rainforest, and their efforts are further exacerbated by government policies that permit landless peasants to establish legal title to land that they have cleared.

At the same time, international lending institutions like the World Bank provide money to the national government for large-scale projects like mining, construction of dams, new roads, and other infrastructure that directly reduces the forest or makes it easier for farmers to access new areas to clear.

The activities most often encouraging new road development are timber harvesting and mining. Loggers cut out the best timber for domestic use or export, and in the process knock over many other less valuable trees. Those trees are eventually cleared and used for wood pulp, or burned, and the area is converted into cattle pastures. After a few years, the vegetation is sufficiently degraded to make it not profitable to raise cattle, and the land is sold to poor farmers seeking out a subsistence living.

Regardless of how poor farmers get their land, they often are only able to gain a few years of decent crop yields before the poor quality of the soil overwhelms their efforts, and then they are forced to move on to another plot of land. Small-scale farmers also hunt for meat in the remaining fragmented forest areas, which reduces the biodiversity in those areas as well.

Another important factor not mentioned in the scenario above is the clearing of rainforest for industrial agriculture plantations of bananas, pineapples, and sugar cane. These crops are primarily grown for export, and so an additional driver to consider is consumer demand for these crops in countries like the United States.

These cycles of land use, which are driven by poverty and population growth as well as government policies, have led to the rapid loss of tropical rainforests. What is lost in many cases is not simply biodiversity, but also valuable renewable resources that could sustain many generations of humans to come. Efforts to protect rainforests and other areas of high biodiversity is the topic of the next section.

Amazon River 'Breathes' Carbon Dioxide from Rain Forest

Bacteria living in the Amazon River can digest woody materials shed by the surrounding rain forest by turning these pieces of tree bark and stems into carbon dioxide as they are washed down the river, according to a new study. The findings bolster the Amazon basin's reputation as being the lungs of the planet, taking in carbon dioxide and releasing oxygen, but show that the carbon dioxide doesn’t necessarily stay trapped in the trees.

Researchers at the University of Washington found that bacteria in the Amazon River can break down almost all of the tree and plant materials in the water, and this process is a major generator of the carbon dioxide breathed by the river.

"Rivers were once thought of as passive pipes," study co-author Jeffrey Richey, a professor of oceanography at the University of Washington in Seattle, said in a statement. "This shows they're more like metabolic hot spots." [ The World's Longest Rivers ]

To thrive, plants convert sunlight, carbon dioxide and water into food, in a process known as photosynthesis . As they grow, bits of wood and leaves are shed that eventually decompose on the ground, or get washed into the river during periods of rainfall.

Food for the river

Previously, it was believed that much of this plant matter floated down the Amazon River to the ocean, where it ultimately became buried in the seafloor. A decade ago, scientists at the University of Washington discovered that rivers exhale vast amounts of carbon dioxide into the atmosphere, but it was still not known if — or how — river bacteria could break down such tough materials, the researchers said.

"People thought this was one of the components that just got dumped into the ocean," Nick Ward, a doctoral student in oceanography at the University of Washington, and lead author of the new study, said in a statement. "We've found that terrestrial carbon is respired and basically turned into carbon dioxide as it travels down the river."

Sign up for the Live Science daily newsletter now

Get the world’s most fascinating discoveries delivered straight to your inbox.

A compound called lignin forms the main part of a tree's woody tissue, and is the second most common component of terrestrial plants, the researchers said. But rather than flowing into oceans and settling on the seafloor for centuries or millennia, bacteria in the Amazon River can break lignin down within two weeks, the new study found.

In fact, only 5 percent of the Amazon rain forest's plant-based carbon ends up reaching the ocean, the researchers said.

The carbon cycle

While these findings have important implications for global carbon models, they also shed light on the ecology of the Amazon , as well as other river ecosystems.

"The fact that lignin is proving to be this metabolically active is a big surprise," Richey said. "It's a mechanism for the rivers' role in the global carbon cycle — it's the food for the river breath."

From their analysis, the researchers determined that about 40 percent of the Amazon's lignin breaks down in soils, 55 percent is digested by bacteria in the river system, and 5 percent is washed into the ocean, where it breaks down or sinks to the ocean floor.

"People had just assumed, 'Well, it's not energetically feasible for an organism to break lignin apart, so why would they?'" Ward said. "We're thinking that as rain falls over the land it's taking with it these lignin compounds, but it's also taking with it the bacterial community that's really good at eating the lignin."

The study's findings were published online May 19 in the journal Nature Geoscience.

Follow Denise Chow on Twitter @denisechow . Follow LiveScience @livescience , Facebook  & Google+ . Original article on  LiveScience.com .

Denise Chow was the assistant managing editor at Live Science before moving to NBC News as a science reporter, where she focuses on general science and climate change. Before joining the Live Science team in 2013, she spent two years as a staff writer for Space.com, writing about rocket launches and covering NASA's final three space shuttle missions. A Canadian transplant, Denise has a bachelor's degree from the University of Toronto, and a master's degree in journalism from New York University.

Hot Tub of Despair: The deadly ocean pool that traps and pickles creatures that fall in

Earth from space: Shapeshifting rusty river winds through Madagascar's 'red lands'

Florida family files claim with NASA after ISS space junk crashes into home

Most Popular

• 2 Astronauts stranded in space due to multiple issues with Boeing's Starliner — and the window for a return flight is closing
• 3 China rover returns historic samples from far side of the moon — and they may contain secrets to Earth's deep past
• 4 Astronomers discover the 1st-ever merging galaxy cores at cosmic dawn
• 5 Earth's rotating inner core is starting to slow down — and it could alter the length of our days
• 2 2,000-year-old Roman military sandal with nails for traction found in Germany
• 3 'The early universe is nothing like we expected': James Webb telescope reveals 'new understanding' of how galaxies formed at cosmic dawn
• 4 Self-healing 'living skin' can make robots more humanlike — and it looks just as creepy as you'd expect
• 5 'Holy grail' of solar technology set to consign 'unsustainable silicon' to history

SUBMIT A STORY IDEA

When in drought: Researchers map which parts of the Amazon are most vulnerable to climate change

A hillside near the Wayqecha field station in Peru. The Amazon rainforest spans an area twice the size of India, and is one of the world's largest carbon sinks.

Jake Bryant

In the late 2000s, Scott Saleska  noticed something strange going on in the Amazon rainforest. 

In 2005, a massive drought struck the region. Two years later, Saleska – a University of Arizona professor in the  Department of Ecology and Evolutionary Biology – published surprising research that used satellite images to find that the drought resulted in more green growth in large swaths of the Amazon. On the other hand, field researchers saw plants brown and some die in response to the drought. 

Research published today in the journal Nature reveals what caused the scientific mismatch. Shuli Chen , a doctoral degree candidate in ecology and evolutionary biology who works with Saleska, is the lead author. 

Chen and Saleska teamed up with Antonio Nobre, an Earth scientist at Brazil's National Institute for Space Research, who was using satellites to detect how landscape topography and groundwater tables interact with forests. 

The trio and their co-authors from Brazil, the U.S. and the United Kingdom used 20 years of data – from 2000 to 2020, which includes drought data from 2005, 2010 and a more widespread drought in 2015 and 2016 – to tease out how drought impacts the most biodiverse forest on Earth, which spans an area twice the size of India, and is one of the world's largest carbon sinks.  

They found that different regions of the Amazon rainforest respond to drought differently because of differences in local forest environments and differences in the properties of trees themselves. This work goes beyond wide-scale climate factors and homes in on how local environments drive drought response, Chen said. The team created maps to illustrate their findings. 

In the southern reaches of the Amazon rainforest, mostly over rock formations that geologists call the Brazilian Shield – with relatively fertile soil and forests with shorter trees – drought response was controlled by access to groundwater. Trees with access to shallow water tables "greened up" during drought, the researchers found, while trees over deeper water tables experienced more foliage browning and tree death. In contrast, the northern Amazon, dominated by what geologists call the Guiana Shield – home to tall trees with deep roots and less fertile soil – was more drought resilient regardless of water table depth.

This new understanding of regional differences provides a framework for conservation decisions and improved predictions of forest responses to future climate changes, according to the researchers. It also warns that the Amazon's most productive forests are also at the greatest risk.

"It's like we brought a blurry image into focus," Chen said. "When we talk about the Amazon being at risk, we talk about it as if it were all one thing. This research shows that the Amazon is a rich mosaic in which some parts are more vulnerable to change than others, and it explains why. This is key to understanding the system and ultimately protecting it." 

Building the mosaic

The research team used remote sensing satellite data – which relayed forest canopy health by measuring greenness and photosynthetic activity – to track how variations in non-climatic factors including water table depth, soil fertility and overall forest height affect forest resilience in the face of drought.

This is an example of rainforest trees close to a water table taken at the catchment stream of a research site in the Cuieiras Reserve, just outside of Manaus, Brazil.

For trees with access to shallow water tables in the fertile soils of the southern Amazon, droughts result in more growth and healthier canopies for a few reasons. 

First, during typical conditions, their roots are submerged in water, which limits access to oxygen. During drought, water recedes a bit, but doesn't go away, exposing more root and allowing an increase in oxygen uptake. At the same time, trees get a photosynthetic boost from the additional sunlight. 

Trees in the same region that grow over deeper water tables, on the other hand, have come to rely on rainwater. They are more vulnerable to drought. 

The slow-growing trees in the northern Amazon – with their tall canopies, deep roots and relatively infertile soil – have adapted to harsh conditions, Chen said, making them hardy in the face of drought. 

The Guiana Shield in the northern Amazon contains less fertile soil and deeper water tables than the Brazilian Shield in the south. These conditions led to slow-growing tall trees with deeper rooting systems able to access the water, making them hardier in the face of drought, Chen said.

"Our results are not just important for the Amazon, it's important for the whole world, because the rainforest has a significant stock of our carbon. If that carbon is lost – because trees burn or are deforested, that adds to carbon dioxide in the atmosphere, which in makes global warming even worse," Saleska said.

Beyond the Amazon

The Amazon rainforest also plays a vitally important role in the Earth's hydrologic cycle.

While the Amazon River is the biggest on Earth – discharging more water to the ocean than the next seven largest rivers combined – an "atmospheric river" of water vapor flows in the opposite direction through the air above Amazon rainforests, carrying up to twice as much water than its terrestrial twin.

Water evaporates from the Atlantic Ocean surface and wind carries it over the eastern Amazon rainforest. When that water falls as rain, it's absorbed by the trees, which then move it up their stems, trunks and vines before emitting it back into the air as water vapor, like slow-motion geysers.

This is happening on a grand scale, with a hundred billion Amazonian trees feeding the atmospheric river that carries water from east to west across the rainforest. Trees in the western Amazon receive about 50% of their water from trees upwind, Saleska said.

"If you imagine either cutting down or losing those trees, because they're vulnerable, and you're getting more droughts, that doesn't just affect those trees, that affects the trees downstream of the atmospheric river too," said study co-author Nobre. "You basically threaten the integrity of the whole system."

This water recycling capability also supplies water to agriculture in other parts of South America, beyond the Amazon, he said. 

Saleska, who also serves on the science steering committee of the Science Panel for the Amazon, an international initiative by scientists dedicated to the Amazon, said that the new research will be invaluable for that work. 

"If we care about preserving biodiversity, conserving valuable ecosystems, conserving valuable forests, knowing this kind of information is really critically helpful," Saleska said.

Resources for the Media

Mikayla Mace Kelley Science Writer [email protected] 520-621-1878

Scott Saleska Department of Ecology and Evolutionary Biology [email protected] 520-626-1500

Shuli Chen Department of Ecology and Evolutionary Biology [email protected]

What's the buzz? 10 things you (probably) didn't know about cicadas

Veterans with service dogs may have fewer PTSD symptoms, higher quality of life

Poetry Center helps bring a splash of color to one of Tucson's busiest streets

Bennu holds the solar system's 'original ingredients,' might have been part of a wet world

University of arizona in the news.

The Conversation Today Federal funding for major science agencies is at a 25-year low

CNN Thursday Surprising asteroid sample reveals Bennu may have originated from an ocean world

Stateline Wednesday Cooler states now forced to grapple with extreme heat fueled by climate change

Arizona Daily Star Wednesday Local opinion: Integrating online education at the University of Arizona is a strategic move for enhanced access and financial stability

The Conversation Wednesday Service dogs can reduce the severity of PTSD for veterans

• Español (Spanish)
• Français (French)
• Bahasa Indonesia (Indonesian)
• Brasil (Portuguese)
• हिंदी (Hindi)

Camera-trap study brings the lesula, Congo’s cryptic monkey, into focus

• Only found in the rainforests of the Democratic Republic of the Congo, the lesula monkey (Cercopithecus lomamiensis) was first described by scientists in 2012.
• A 2023 Animals study finds that the lesula is mostly terrestrial, unlike the other species of guenon monkeys in the region.
• The study also finds that the lesula is active during the day, has a seasonal reproductive cycle, and lives in family groups of up to 32 individuals, with males dispersing out to form bachelor groups.
• Researchers say the Tshuapa, Lomami and Lualaba Rivers Landscape, where the study was conducted, holds incredible primate diversity.

In 2012, the description of a new monkey species from the Congo Basin with an unforgettable, humanlike countenance made global news. Now, a camera trap study reveals how the lesula (Cercopithecus lomamiensis) has carved out a unique niche on the forest floor.

The lesula is a slender, medium-sized monkey with a long tail, found only in a remote part of the Congo Basin called the Tshuapa, Lomami and Lualaba Rivers Landscape, or TL2, in the Democratic Republic of Congo (DRC). Though long known to local people, the species had remained unknown to science until research teams with the Lukuru Foundation’s TL2 Project, photographed an individual during surveys of the area.

Taxonomic and genetic analysis showed that the lesula was a type of guenon monkey (genus Cercopithecus), the most species-rich group of African primates. Little was known definitively about the lesula’s ecology or behavior when it was first described, but there were already tantalizing hints that the lesula might be quite different from the other mostly arboreal species of guenon monkeys in the landscape.

Now, using camera traps, researchers have found that the lesula spends far more time on the ground than other related monkeys in the area. It’s also active during the day and lives in larger groups than previously thought, according to the 2023 study in the journal Animals . The research also highlights the importance of the TL2 landscape for primates.

“We have six different guenons … living in this landscape and they’re sorting it out … so it’s that diverse and productive that it can support all these different species in the same place at the same time — and the lesula is one of them,” says study author Kate Detwiler, a professor of anthropology at Florida Atlantic University.

The Congo Basin holds the second-largest rainforest on Earth, which covers 178 million hectares (440 million acres) across six countries, and is one of the largest carbon sinks on the planet. These forests contain an astounding array of biodiversity, including iconic mammals like the okapi (Okapia johnstoni), bonobos (Pan paniscus) and forest elephants (Loxodonta cyclotis). The rainforest is also home to more than 1,000 species of birds and 600 types of tree. It also supports countless communities and Indigenous peoples.

Across the region, shifting cultivation and charcoal production are the primary drivers of deforestation, while the commercial bushmeat trade is hitting wildlife hard. The DRC, which contains more than half of all the Congo Basin’s primary rainforest, has the highest rates of deforestation of all the Congo Basin nations.

Yet the DRC’s remote TL2 landscape, surrounded by powerful meandering rivers, remains astoundingly intact, and at 4 million hectares (10 million acres) — the size of Switzerland — is a haven for biodiversity, including the lesula. Since 2016, the core of the area has been protected within the nearly 900,000-hectare (2.2-million-acre) Lomami National Park. The main threat here is poaching.

To figure out how the lesula uses the forest, researchers needed to observe them. But they quickly realized that the classic methods of studying primates — finding them, getting them used to human presence (a process known as habituating) and following the groups — weren’t going to work.

For starters, lesulas are incredibly hard to find, even for seasoned primatologists like Detwiler. She visited the study area for three weeks in 2012, and didn’t manage to see a lesula until the last day, when two unexpectedly crossed the trail in front of her. “And it was for less than 10 seconds!” she recalls. “It was like, wow, they’re really cryptic.”

The researchers were also wary of habituating the lesula because the monkeys are threatened by hunting. Habituation would make lesulas lose their natural fear of humans and put them at greater risk of being killed.

Instead, the researchers decided to use camera traps. Still, that was logistically challenging and expensive, says Junior Amboko, a graduate student at Florida Atlantic University and one of the study authors. The TL2 landscape is very remote; supplies like fuel, batteries and food have to be brought in from bigger towns over a hundred miles away, and travel is slow and difficult.

Nevertheless, the researchers set up three camera trap grids between 2013 and 2016, two within the protected area and one in the buffer zone. As the lesula was thought to be mostly terrestrial, they set the cameras along forest trails at ground level — and because they were interested in behavior, they programmed them to video mode.

In all, the cameras recorded 15,000 videos, including nearly 600 clips of the lesula. Analyzing those clips was a monumental task that required a steady stream of research students, Detwiler says. But finally, a picture of the lesula’s distinct behavioral ecology emerged.

Like the other guenon monkeys in the area, the lesula is almost exclusively active during the day, with just a few videos recorded at dawn or dusk, and its reproductive patterns are tied to the rains, like other guenons.

But in other ways, the lesula has found a unique niche. It spends far more time on the forest floor than the other monkeys; there were nearly 600 video clips of lesulas moving around on the ground, compared to only 10 clips of other guenon species.

The videos also revealed that lesulas live in larger groups than previously thought, of up to 32 individuals. Family groups are usually composed of one adult male, numerous females and their young, while males are also found alone or in bachelor groups. However, the authors note that the average group size recorded by the cameras was smaller. This could be because the cameras only recorded animals in front of the lens, and more research is needed. (Unfortunately, the lesulas didn’t pose for a family portrait.)

These findings have practical conservation applications. A previous study using the same camera-trapping data set and combined with data on the frequency of lesula morning calls, concluded that the monkey isn’t currently heavily impacted by hunting. However, the lesulas traveled in smaller groups in the buffer zone where hunters were active, compared to in the national park. Living in smaller, quieter groups might be one way that they evade hunters, Detwiler says. Baseline data on group size could thus help researchers detect when populations are under stress.

John Hart, with the TL2 Project, says the landscape here still holds many mysteries — and new methods like camera traps are helping us peer beneath the trees to reveal the forest’s secrets. Some of the videos showed lesulas in the same frame as blue duikers (Philantomba monticola) and other species. Hart says he hopes further analysis will show if these associations are intentional or if the species are simply “meeting at the same restaurant.”

The study also raises new questions about how lesulas use the forest canopy. Though the species is primarily terrestrial, observations show it also climbs trees — and Detwiler says she wants to know why. She’s already planning a new study, where the team will place camera traps at different heights in the canopy.

The answers could tie into our own evolutionary history. Detwiler says understanding the lesula may shed light on “what Australopithecus was doing when it evolved to come down [from the trees].” Like the lesula, Australopithecus , an early human ancestor that lived some 2 million years ago, walked on the ground but still climbed trees. “So, if those types of species are living in front of us, we can ask, ‘OK, what are you doing up there?’”

Togo monkey seizure turns spotlight on illicit wildlife trafficking from DR Congo

Banner Image: Lesula_mom_baby_main: A lesula female and infant in the TL2 Landscape in the central Congo Basin. Lesula live in family groups of up to 32 individuals, usually composed of one adult male, several females, and young. Image by Florida Atlantic University

Fournier, C. S., Graefen, M., McPhee, S., Amboko, J., Noonburg, E. G., Ingram, V., … Detwiler, K. M. (2023). Impact of hunting on the lesula monkey (Cercopithecus lomamiensis) in the Lomami River Basin, Democratic Republic of the Congo. International Journal of Primatology, 44(2), 282-306. doi:10.1007/s10764-022-00337-4

Fournier, C. S., McPhee, S., Amboko, J. D., & Detwiler, K. M. (2023). Camera traps uncover the behavioral ecology of an endemic, cryptic monkey species in the Congo Basin. Animals, 13(11), 1819. doi:10.3390/ani13111819

Hart, J. A., Detwiler, K. M., Gilbert, C. C., Burrell, A. S., Fuller, J. L., Emetshu, M., … Tosi, A. J. (2012). Lesula: A new species of Cercopithecus monkey endemic to the Democratic Republic of Congo and implications for conservation of Congo’s Central Basin. PLOS ONE, 7(9), e44271. doi:10.1371/journal.pone.0044271

Special series

Forest trackers.

• Narco activity takes heavy toll on Colombia’s protected forests, satellite data show
• Photos confirm narcotraffickers operating in Peru’s Kakataibo Indigenous Reserve
• Bolivia’s El Curichi Las Garzas protected area taken over by land-grabbers
• Authorities struggle to protect Bolivian national park from drug-fueled deforestation

• New approach to restore coral reefs on mass scale kicks off in Hawai‘i
• Indonesia’s Avatar sea nomads enact Indigenous rules to protect octopus
• Ghost nets haunt marine life in Malaysian marine park, study finds
• Icelandic government grants new license to whaling company to hunt 128 fin whales

Amazon Conservation

• Environmental agents intensify strike amid record fires in Brazil
• Fire bans not effective as the Amazon and Pantanal burn, study says
• Reintroduction project brings golden parakeets back to the skies of Brazil’s Belém
• Indigenous Wai Wai seek markets for Brazil nuts without middlemen

Land rights and extractives

• Critics see payback in Indonesia’s plan to grant mining permits to religious groups
• Impunity and pollution abound in DRC mining along the road to the energy transition
• Women weave a culture of resistance and agroecology in Ecuador’s Intag Valley
• Hyundai ends aluminum deal with Adaro Minerals following K-pop protest

Endangered Environmentalists

• Mongabay video screening at Chile’s Supreme Court expected to help landmark verdict in Brazil
• Indonesian activist freed in hate speech case after flagging illegal shrimp farms
• Final cheetah conservationists freed in Iran, but the big cat’s outlook remains grim
• Indonesian activists face jail over FB posts flagging damage to marine park

Indonesia's Forest Guardians

• On a Borneo mountainside, Indigenous Dayak women hold fire and defend forest
• Fenced in by Sulawesi national park, Indigenous women make forestry breakout
• In Borneo, the ‘Power of Mama’ fight Indonesia’s wildfires with all-woman crew
• Pioneer agroforester Ermi, 73, rolls back the years in Indonesia’s Gorontalo

Conservation Effectiveness

• How effective is the EU’s marquee policy to reduce the illegal timber trade?
• The conservation sector must communicate better (commentary)
• Thailand tries nature-based water management to adapt to climate change
• Forest restoration to boost biomass doesn’t have to sacrifice tree diversity

Southeast Asian infrastructure

• Study: Indonesia’s new capital city threatens stable proboscis monkey population
• Indonesia’s new capital ‘won’t sacrifice the environment’: Q&A with Nusantara’s Myrna Asnawati Safitri
• Small farmers in limbo as Cambodia wavers on Tonle Sap conservation rules
• To build its ‘green’ capital city, Indonesia runs a road through a biodiverse forest

you're currently offline