December 14, 2012
Absent of deforestation, Amazon rainforest might survive global warming.
Estimated genetic ages of trees in the study. Photo by Rhett A. Butler
Christopher Dick of the University of Michigan and the Smithsonian Tropical Research Institute (STRI), Simon Lewis of the University of Leeds, Mark Maslin of University College London, and Eldredge Bermingham of STRI analyzed the age of 12 widely distributed Amazon tree species. They found that nine of the species emerged prior to the Pliocene Epoch some 2.6 million years ago, seven dated to the Miocene Epoch (5.6 million years ago), and three were more than eight million years old.
The findings indicate that many Amazon tree species have survived warm periods in the past and are therefore likely to survive climate change projected for the year 2100. Air temperatures in the Amazon during the early Pliocene were similar to Intergovernmental Panel on Climate Change projections for the region in 2100 under a moderate carbon emissions scenario, while temperatures in the late Miocene (5.3-11.5 million years ago) are roughly what the IPCC forecasts under a highest carbon emissions scenario.
The study seems to be at odds with other research suggesting that many Amazon trees would face extinction from higher temperatures alone. For example a 2008 study published in the Proceedings of the National Academy of Sciences (PNAS) projected up to 50 percent of "rare" species across the Amazon could disappear.
Canopy tree in Peru. Photo by Rhett A. Butler
"The past cannot be compared directly with the future. While tree species seem likely to tolerate higher air temperatures than today, the Amazon forest is being converted for agriculture and mining, and what remains is being degraded by logging, and increasingly fragmented by fields and roads," said Lewis in a statement. " Species will not move as freely in today's Amazon as they did in previous warm periods, when there was no human influence. Similarly, today's climate change is extremely fast, making comparisons with slower changes in the past difficult."
The authors therefore suggest conservation policies focused on preventing deforestation. They also recommend cuts to global greenhouse gas emissions.
"With a clearer understanding of the relative risks to the Amazon forest, we conclude that direct human impacts – such as forest clearances for agriculture or mining – should remain a focus of conservation policy," said Lewis. "We also need more aggressive action to reduce greenhouse gas emissions in order to minimize the risk of drought and fire impacts to secure the future of most Amazon tree species."
The Amazon is Earth's largest rainforest. Nearly two-thirds of the Amazon lies within the borders of Brazil, which has made great progress in reducing deforestation since 2004. However deforestation in Amazon countries outside Brazil is holding relatively steady.
CITATION: Dick, C. W., Lewis, S. L., Maslin, M. and Bermingham, E. (2012), Neogene origins and implied warmth tolerance of Amazon tree species. Ecology and Evolution. doi: 10.1002/ece3.441
blog comments powered by Disqus
Scientists slam Telegraph blogger's claims that climate change will be good for the Amazon
(07/12/2012) Recent blog posts on The Telegraph and the Register claiming that tropical rainforests like the Amazon are set to benefit from climate change are 'uninformed' and 'ridiculous' according to some of the world's most eminent tropical forest scientists. The posts, published Sunday and Monday by Tim Worstall, a Senior Fellow at London's Adam Smith Institute, asserted that a new Nature study indicates that 'climate change will mean new and larger tropical forests.' But some of the world's leading tropical forest experts took aim at Worstall's logic, noting the limitations of the study as well as the other factors that are endangering rainforests.
Climate change and deforestation pose risk to Amazon rainforest
(05/20/2011) Deforestation and climate change will likely decimate much of the Amazon rainforest, says a new study by Brazil’s National Institute for Space Research (INPE) and the UK's Met Office Hadley Centre. Climate change and widespread deforestation is expected to cause warmer and drier conditions overall, reducing the resistance of the rainforest ecosystem to natural and human-caused stressors while increasing the frequency of extreme rainfall events and droughts by the end of this century. While climate models show that higher temperatures resulting from global climate change will threaten the resilience of the Amazon, current deforestation is an immediate concern to the rainforest ecosystem and is likely driving regional changes in climate.
Two massive droughts evidence that climate change is 'playing Russian roulette' with Amazon
(02/03/2011) In 2005 the Amazon rainforest underwent a massive drought that was labeled a one-in-100 year event. The subsequent die-off of trees from the drought released 5 billion tons of CO2. Just five years later another major drought struck. The 2010 drought, which desiccated entire rivers, may have been even worse according to a new study in Science, adding on-the-ground evidence to fears that climate change may inevitably transform the world's greatest rainforest.
(06/21/2010) The Sunday Times over the weekend retracted a column that accused the Intergovernmental Panel on Climate Change (IPCC) of making a 'bogus rainforest claim' when it cited a report warning that up to 40 percent of the Amazon could be "drastically" affected by climate change. The 'Amazongate' column, authored by Jonathan Leake, Science & Environment Editor of the Sunday Times, was immediately seized upon by climate skeptics as further evidence to discredit the IPCC just two weeks after it was found to be using shoddy glacier data in its 2007 climate assessment. But now the Sunday Times has removed Leake's column from its web site and issued on apology, admitting that the Amazon claim was indeed supported by scientific research. The Sunday Times also acknowledged misconduct in the way one of the story's sources—Simon Lewis of the University of Leeds in Britain—was quoted.
Scientists: new study does not disprove climate change threat to Amazon
(03/19/2010) Recently, Boston University issued a press release on a scientific study regarding the Amazon's resilience to drought. The press release claimed that the study had debunked the Intergovernmental Panel on Climate Change's (IPCC) theory that climate change could turn approximately 40 percent of the Amazon into savanna due to declining rainfall. The story was picked up both by mass media, environmental news sites (including mongabay.com), and climate deniers' blogs. However, nineteen of the world's top Amazonian experts have issued a written response stating that the press release from Boston University was "misleading and inaccurate".
Drought threatens the Amazon rainforest as a carbon sink
(03/05/2009) Drought in the Amazon is imperiling the rainforest ecosystem and global climate, reports new research published in Science. Analyzing the impact of the severe Amazon drought of 2005, a team of 68 researchers across 13 countries found evidence that rainfall-starved tropical forests lose massive amounts of carbon due to reduced plant growth and dying trees. The 2005 drought — triggered by warming in the tropical North Atlantic rather than el Niño — resulted in a net flux of 5 billion tons of carbon dioxide (CO2) into the atmosphere — more than the combined annual emissions of Japan and Europe — relative to normal years when the Amazon is a net sink for 2 billion tons of CO2.
Half the Amazon rainforest will be lost within 20 years
(02/27/2008) More than half the Amazon rainforest will be damaged or destroyed within 20 years if deforestation, forest fires, and climate trends continue apace, warns a study published in Philosophical Transactions of the Royal Society B. Reviewing recent trends in economic, ecological and climatic processes in Amazonia, Daniel Nepstad and colleagues forecast that 55 percent of Amazon forests will be "cleared, logged, damaged by drought, or burned" in the next 20 years. The damage will release 15-26 billion tons of carbon into the atmosphere, adding to a feedback cycle that will worsen both warming and forest degradation in the region. While the projections are bleak, the authors are hopeful that emerging trends could reduce the likelihood of a near-term die-back. These include the growing concern in commodity markets on the environmental performance of ranchers and farmers; greater investment in fire control mechanisms among owners of fire-sensitive investments; emergence of a carbon market for forest-based offsets; and the establishment of protected areas in regions where development is fast-expanding.
Amazon rainfall linked to Atlantic Ocean temperature
(02/25/2008) Climate models increasingly forecast a dire future for the Amazon rainforest. These projections are partly based on recent research that has linked drought in the Amazon to sea surface temperatures in the tropical Atlantic. As the tropical Atlantic warms, the southern Amazon -- the agricultural heartland of Brazil -- may see higher temperatures and less rainfall.