Rainforest expert agrees with IPCC: warns of 'tipping point' for Amazon

Jeremy Hance
mongabay.com
February 03, 2010



Amid questions over the Amazon forests' capacity to survive climate change, a renowned tropical biologist says that in fact the fears are real, reports Tierramerica.

Speaking at the Biodiversity Science Policy Conference in Paris, Thomas Lovejoy, biodiversity chair at the Washington DC-based Heinz Center for Science, Economics and the Environment, and chief biodiversity adviser to the president of the World Bank, described the Amazon rainforest as "very close to a tipping point".

The triple combination of rampant deforestation, fires, and rising temperatures could devastate the rainforest ecosystem within 65 years, explained Lovejoy, shrinking the Amazon rainforest to one-third of its original size. Such a contraction would result in countless extinctions, losses in vital freshwater sources, a decline in regional rainfall, and the weakening of one of the world's most important carbon sinks.


Patchwork of legal forest reserves, pasture, and soy farms in the Brazilian Amazon. Photo by Rhett A Butler.
Lovejoy's assessment is in line with the Intergovernmental Panel on Climate Change's (IPCC), which warned that climate change could produce a drier Amazon, resulting in a 40 percent loss of the ecosystem. The IPCC has recently come under criticism for this assessment, yet despite sloppy citations (the IPCC cited a WWF report rather than scientific studies) the organization's statement is in line with a number of tropical ecology studies.

Lovejoy told Tierramerica that the "tipping point for the Amazon is 20 percent deforestation" based on a report by the World Bank entitled, Assessment of the Risk of Amazon Dieback. At this point deforestation combined with spreading fires and overall warming of 2 degrees Celsius would cause parts of the Amazon's hydrogeologic system to break down.

Since the Amazon rainforest creates at least half the rainfall needed to sustain itself, the loss of forest cover and general drying would create a feedback cycle whereby large areas of the forest would revert to savannah. This process would release tens of billions of additional carbon into the atmosphere.

The threshold of 20 percent is close: already 17 to 18 percent of the Amazon has been lost. However, other studies have found that 'die-off' point for the Amazon rainforest would occur only after 40-60 percent of the forest was lost. The differences in such findings displays the complicated nature of climate science, however the studies all agree that the Amazon faces unparalleled pressures that if unchecked will result in massive forest loss.


Deforestation in the Brazilian Amazon. Photo by Rhett A Butler.
The strength of the World Bank report is that it does not focus solely on deforestation or climate change, but on the synergistic effects of deforestation, warmer temperatures, and fires.

Another tropical forest expert, Simon Lewis of Leeds University, told the BBC that while the IPCC citation of WWF was bizarre, the IPCC findings were hardly incorrect.

"It is very well known that in Amazonia, tropical forests exist when there is more than about 1.5 meters of rain a year, below that the system tends to 'flip' to savannah," he explained. "Indeed, some leading models of future climate change impacts show a die-off of more than 40 percent Amazon forests, due to projected decreases in rainfall."







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CITATION:
Jeremy Hance
mongabay.com (February 03, 2010).

Rainforest expert agrees with IPCC: warns of 'tipping point' for Amazon .

http://news.mongabay.com/2010/0203-hance_amazontip.html