Climate change in the Amazon

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Unnatural habitat? Recent climate change models suggest that a warmer and drier environment for the Amazon region could convert from 30% up to 60% of the rainforest into this kind of landscape.
© WWF-Canon / Juan PRATGINESTOS

A changing Amazon?

As habitat destruction trends interact with climate change, the concern is that the Amazon will be caught up in a set of “feedback loops” that could dramatically speed up the pace of forest lost and degradation and bring the Amazon Biome to a point of no return. This threshold, also referred to as a tipping point, may occur when Amazonian forests die and are progressively replaced by fireprone brush and savanna (ecological tipping point), and rainfall is inhibited on a regional scale (climatic tipping point).

The climate and deforestation-driven substitution of forests to savanna-like and semiarid vegetation has been dubbed the Amazon forests’ “die back” (Cox et al. 2000, Cox et al. 2004; Nobre et al. 1991; Oyama and Nobre 2003). While there is still debate among scientists about this concept, some climate-simulation vegetation models predict that such a die-back could occur by the end of this century.

For some scientists (Nepstad, 2008), however, this timeframe may be optimistic as these models do not include land-use change or the synergistic effects of deforestation and regional climate change. If these factors were taken into account, we could face a dire scenario in which current trends in livestock, agriculture, logging expansion, fire and drought could destroy or severely damage 55% of the Amazon rainforest by the year 2030 (Nepstad 2008).
 / ©: Nepstad 2008
Soil moisture levels across the Amazon during four periods of severe drought. (Nepstad, 2008).
© Nepstad 2008

Soil moisture in the Amazon

Soil moisture levels across the Amazon during four periods of severe drought. (Nepstad, 2008).

Rainforests taken over by savannas?

With modelling studies projecting a warmer and drier environment for the Amazon, climate change paints a bleak future for the region – a future where both people and biodiversity stand to lose.
Well tuned, the Amazon’s hydrological engine plays a major role in maintaining the global and regional climate.

Water released by plants into the atmosphere through evapotranspiration (evaporation and plant transpiration) and to the ocean by the rivers, influences world climate and the circulation of ocean currents. This works as a feedback mechanism, as the process also sustains the regional climate on which it depends.

What is happening in the Amazon?

But scientists are noticing something disturbing in the Amazon rainforest - the hydrological engine is beginning to fail. Two major factors are at play.

One factor is the El Niño Southern Oscillation (ENSO), a climatic phenomenon which influences much of the climatic variability in Latin America. Although ENSO events are a natural occurrence, human-induced climate change is expected to increase their frequency in the future.

ENSO is associated with dry conditions in northeast Brazil, the northern Amazon, the Peruvian-Bolivian Altiplano, and Pacific coast of Central America. Meanwhile, southern Brazil and northwestern Peru have exhibited unusually wet conditions during ENSO events.

Another factor is deforestation, which in addition to removing forest cover causes a dramatic change in rainfall patterns and distribution. These findings imply that current deforestation in the Amazon has already altered the regional climate. They also support previous reports of increased shallow cloudiness over deforested areas.

Worrying climatic prospects for the Amazon

Climate change and deforestation could convert the majority of the Amazon rainforest into savanna, with massive impacts on the world’s biodiversity and climate.

  • Guardian: Amazon could shrink by 85% due to climate change, scientists say
  • NPR: A Drying Amazon Could Speed Climate Change

The long-term weather forecast for the Amazon

Models suggest that by the year 2050, temperatures in the Amazon will increase by 2–3°C. At the same time, a decrease in rainfall during dry months will lead to widespread drying.

There are serious consequences to these changes. Projected increases of temperatures and decreased rainfall during already dry months could result in longer and perhaps more severe droughts, along with substantial changes in seasonality.

What should we expect?

Coupled with land-use changes, we can expect the degradation of freshwater systems, loss of ecologically and agriculturally valuable soils, increased erosion, decreased agricultural yields, increased insect infestation, and spread of infectious diseases.

The changing nature of the Amazon

Over time, global climate change and more deforestation will likely lead to increased temperatures and changing rain patterns in the Amazon, which will undoubtedly affect the region’s forests, water availability, biodiversity, agriculture, and human health.

Between 30% and 60% of the Amazon rainforest could become a dry savanna

Research carried out under the auspices of INPE – Brazil's National Space Research Institute – shows that a warmer and drier environment for the region could convert from 30% up to 60% of the Amazon rainforest into a type of dry savanna.

A closer look at the impacts of climate change on…

We are running a serious risk of losing a large piece of the Amazonian tropical forest. If warming exceeds a few degrees Celsius, the process of ‘savannisation’ may well become irreversible.

Carlos NobreSenior Scientist
INPE - Brazil National Space Research Institute

The carbon dioxide factor

There are concerns that the Amazon region could become a net source rather than a sink (storage) of carbon dioxide (CO2), a gas emitted mainly from burning fossil fuels, coal, oil and natural gas - and the major driver for global climate change.

Currently, the Amazon rainforests are still a sink for CO2, despite some 20% of CO2 emissions globally arising from deforestation. However, it is projected that increased temperatures, decreased precipitation and the 'savannization' of the Amazon will cause the region to become a source of CO2, instead of a sink.

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