Navigation Links
Risk of Amazon rainforest dieback is higher than IPCC projects
Date:10/21/2013

A new study suggests the southern portion of the Amazon rainforest is at a much higher risk of dieback due to stronger seasonal drying than projections made by the climate models used in the latest report by the Intergovernmental Panel on Climate Change (IPCC). If severe enough, the loss of rainforest could cause the release of large volumes of the greenhouse gas carbon dioxide into the atmosphere. It could also disrupt plant and animal communities in one of the regions of highest biodiversity in the world.

Using ground-based rainfall measurements from the past three decades, a research team led by Rong Fu, professor at The University of Texas at Austin's Jackson School of Geosciences, found that since 1979, the dry season in southern Amazonia has lasted about a week longer per decade. At the same time, the annual fire season has become longer. The researchers say the most likely explanation for the lengthening dry season is global warming.

"The dry season over the southern Amazon is already marginal for maintaining rainforest," says Fu. "At some point, if it becomes too long, the rainforest will reach a tipping point."

The new results are in stark contrast to forecasts made by climate models used by the IPCC. Even under future scenarios in which atmospheric greenhouse gases rise dramatically, the models project the dry season in the southern Amazon to be only a few to 10 days longer by the end of the century, and therefore the risk of climate change-induced rainforest dieback should be relatively low.

The report appears this week in the journal Proceedings of the National Academy of Sciences.

"The length of the dry season in the southern Amazon is the most important climate condition controlling the rainforest," says Fu. "If the dry season is too long, the rainforest will not survive."

To see why the length of the dry season is such a limiting factor, imagine there is heavier than usual rainfall during the wet season. The soil can only hold so much water and the rest runs off. The water stored in the soil at the end of the wet season is all that the rainforest trees have to last them through the dry season. The longer the dry season lasts, regardless of how wet the wet season was, the more stressed the trees become and the more susceptible they are to fire.

The researchers say the most likely explanation for the lengthening dry season in the southern Amazon in recent decades is human-caused greenhouse warming, which inhibits rainfall in two ways. First, it makes it harder for warm, dry air near the surface to rise and freely mix with cool, moist air above. And second, it blocks cold front incursions from outside the tropics that could trigger rainfall. The climate models used by the IPCC do a poor job representing these processes, which might explain why they project only a slightly longer Amazonian dry season, says Fu.

The Amazon rainforest normally removes the greenhouse gas carbon dioxide from the atmosphere, but during a severe drought in 2005, it released 1 petagram of carbon (about one-tenth of annual human emissions) to the atmosphere. Fu and her colleagues estimate that if dry seasons continue to lengthen at just half the rate of recent decades, the Amazon drought of 2005 could become the norm rather than the exception by the end of this century.

"Because of the potential impact on the global carbon cycle, we need to better understand the changes of the dry season over southern Amazonia," says Fu.

Some scientists have speculated that the combination of longer dry seasons, higher surface temperatures and more fragmented forests resulting from ongoing human-caused deforestation could eventually convert much of southern Amazonia from rainforest to savanna.

Earlier studies have shown that human-caused deforestation in the Amazon can alter rainfall patterns. But the researchers didn't see a strong signal of deforestation in the pattern of increasing dry season length. The dry season length increase was most pronounced in the southwestern Amazon while the most intense deforestation occurred in the southeastern Amazon.

Because the northwestern Amazon has much higher rainfall and a shorter dry season than the southern Amazon, Fu and others think it is much less vulnerable to climate change.


'/>"/>

Contact: Marc Airhart
mairhart@jsg.utexas.edu
512-471-2241
University of Texas at Austin
Source:Eurekalert  

Related biology news :

1. Field Museum scientists estimate 16,000 tree species in the Amazon
2. LSU research responsible for naming 15 new species of Amazonian birds
3. Garcinia Cambogia Weight Loss Supplement from Revocure is now Back in Stock on Amazon
4. Amazon River exhales virtually all carbon taken up by rain forest
5. No-win situation for agricultural expansion in the Amazon
6. Ecology, economy and management of an agro-industrial Amazon frontier
7. Researchers question evaluation methods for protected areas in the Amazon
8. From the Amazon rainforest to human body cells: Quantifying stability
9. Amazon deforestation brings loss of microbial communities
10. Deforestation in the Amazon equals net losses of diversity for microbial communities
11. Climate warming unlikely to cause near-term extinction of Amazon trees, but threats remain
Post Your Comments:
*Name:
*Comment:
*Email:
Related Image:
Risk of Amazon rainforest dieback is higher than IPCC projects
(Date:1/6/2017)... -- Delta ID Inc., a leader in consumer-grade iris scanning ... CES® 2017. Delta ID has collaborated with Gentex Corporation ... of iris scanning as a secure, reliable and convenient ... car, and as a way to elevate the security ... ID and Gentex will demonstrate (booth #7326 LVCC) a ...
(Date:1/3/2017)... LAS VEGAS , Jan. 3, 2017 ... announced the introduction of Onitor Track, an innovative biometric ... and men, showcasing this month at the 2017 Consumer ... . In the U.S., the World ... affect more than two-thirds of adults who are overweight ...
(Date:12/20/2016)... , Dec. 20, 2016 The ... sharing, rental and leasing is stoking significant interest ... radio frequency technology, Bluetooth low energy (BLE), biometrics ... as the next wave of wireless technologies in ... access system to advanced access systems opens the ...
Breaking Biology News(10 mins):
(Date:1/12/2017)... ... January 12, 2017 , ... Each year, Crain’s Detroit Business News ranks the ... evaluates the patent estate of a company, its impact and significance, and the likelihood ... the way in technologies that transform energy sources such as low dose X-ray and ...
(Date:1/12/2017)... ... January 12, 2017 , ... After ... Lisa Rosendahl’s doctors gave her only a few months to live. Now a ... that has stabilized Rosendahl’s disease and increased both the quantity and quality of ...
(Date:1/12/2017)... and Pune, India , January 12, 2017 ... Toxicity Testing Market by Type and End Users - Global Opportunity Analysis and Industry ... million by 2022 from $2,921 million in 2015, growing at a CAGR of 15.07% ... ... Allied Market Research Logo ...
(Date:1/11/2017)... Colo. (PRWEB) , ... January 11, 2017 , ... ... the journal Clinical Cancer Research show early promise of the investigational anti-cancer agent ... despite a median 5 previous treatment regimens. Twenty-seven percent of these heavily pretreated ...
Breaking Biology Technology: