By January 20, 2012 3 Comments Read More →

Amazon rainforest turning from a carbon sink to a source of carbon

rainforest trees and shrubs engulfed in flames

The increased fire risk in the Amazon could turn the region from a carbon sink to a net source of atmospheric carbon. (Image courtesy of NASA Earth Observatory.)

Often cited as the lungs of the planet, it’s well-known that the Amazon rainforest is under attrition. Agriculture, mining, urban development, hydroelectric dams and global warming each pose separate threats. It seems that the lungs are suffering from the equivalent of lung cancer or emphysema.

But just how bad is it, and how bad is it going to get? Some studies have suggested that the Amazon is quite resilient, able to withstand periodic drought and able to rebound after extensive deforestation. But this is not cause for rosy optimism, according to an article just published in the prestigious journal Nature. (Davidson E. A. et al. 2012. The Amazon basin in transition, Nature 481, 321–328. doi:10.1038/nature10717) A multi-institution team of US and Brazil authors conclude that the Amazon basin is in transition. From the pristine wilderness of nature shows and adventurous expeditions, it is moving toward what the authors call a “disturbance-dominated regime.”

Covering an area almost the size of the contiguous United States, the size of the Amazon has served as a buffer to changes wrought by various types of land use and drought instigated by climate change. The key finding of this paper is that anthropogenic change is on the verge of surpassing natural change. The authors conclude that the Amazon is shifting from a net sink of carbon to a net contributor. Given the necessity of a brake on carbon emissions to prevent runaway global warming, such a conclusion is worrisome indeed.

In support of their conclusions, the authors project a dramatic increase in fire risk by 2050, particularly in the region’s southeast, due to a combination of deforestation and climate change. Human activities such as agricultural expansion and logging interact with effects of global climate change to increase forest drying, hence fire risk. The long-term consequences are dire: increased flood damage, decreased productivity in agricultural and other sectors, higher incidence of respiratory disease and disruption of air traffic. The decrease in water run-off reduces water for human use, river navigation and hydropower generation.

The big question facing land managers and policy makers, particularly as emerging economies look to expand: is it worth it? Clearly there are trade-offs. But with such gloomy prospects, it efforts to conserve what remains and mitigate climate change effects might provide a greater economic pay-off than uncontrolled development. Hopefully we won’t have to wait to 2050 for the decision-makers to come to the same conclusion.

3 Comments on "Amazon rainforest turning from a carbon sink to a source of carbon"

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  1. Amazonia: The Lungs of the Planet | The Witness Tree | February 21, 2012
  1. This is more than disturbing. There is another contribution to global warming from the equatorial rainforests that you did not mention. Global warming has resulted in great night time temperatures than day time temperatures. At night plants respire like animals. All chemical reactions are dependent on temperature. Therefore, plants are respiring more at night (due to increased temperatures) and there has been documented release of more carbon dioxide from equatorial rainforests during the last several years + tree ring data to support the atmospheric data.

    Human beings on Earth need to start helping to save their local ecosystems during the UN decade of biodiversity..

  2. Philippe says:

    Many forest ecosystems in the tropics, high latitudes and high altitudes become increasingly sensitive to drought and therefore fires, diseases and pests.

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