Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New Study Indicates Risk of Amazon Rainforest Dieback Due to Global Warming is Higher than Previously Projected

22.10.2013
A new study co-authored by Boston University Professor of Earth & Environment Ranga Myneni suggests the southern portion of the Amazon rainforest is at a much higher risk of dieback due to climate change than projections made 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 last three decades, the researchers 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. According to the study, 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 Rong Fu, co-author and professor at The University of Texas at Austin’s Jackson School of Geosciences 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 ten 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 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 up 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.

“The more severe 2010 drought impacted twice the forested area than the 2005 drought and could have likely resulted in substantial carbon loss from the forests,” says Myneni, who has previously studied these droughts with NASA satellite sensor data.

Myneni and his 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.

Some scientists have speculated that the combination of longer dry seasons, higher surface temperatures and more fragmented forests due to 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, the researchers think it is much less vulnerable to climate change.

The co-authors of this study include Rong Fu, Lei Yin, Robert Dickinson, Lei Huang and Sudip Chakraborty at The University of Texas at Austin’s Jackson School of Geosciences; Wenhong Li at Duke University; Paola A. Arias at Universidad de Antioquia in Colombia; Katia Fernandes at Columbia University’s Lamont-Doherty Earth Observatory; Brant Liebmann at the National Oceanic & Atmospheric Administration (NOAA); Rosie Fisher at the National Center for Atmospheric Research; and Ranga Myneni at Boston University.

This work is supported by the National Science Foundation (AGS 0937400) and NOAA Climate Program Office Modeling, Analysis, Prediction and Projection Program (NA10OAAR4310157) and the NASA Earth Science Division.

Note to Reporters: A preprint of the article is available to journalists on the following secure reporters-only web site: http://www.eurekalert.org/pio/pnas.php

About Boston University—Founded in 1839, Boston University is an internationally recognized private research university with more than 30,000 students participating in undergraduate, graduate, and professional programs. As Boston University’s largest academic division, the College and Graduate School of Arts & Sciences is the heart of the BU experience with a global reach that enhances the University’s reputation for teaching and research. In 2012, BU joined the Association of American Universities (AAU), a consortium of 62 leading research universities in the United States and Canada.

Author contact for the study:

Professor Ranga Myneni
Department of Earth & Environment
Boston University
675 Commonwealth Ave
Boston, MA 02215
(617) 358-5742
rmyneni@bu.edu

Professor Ranga Myneni | Newswise
Further information:
http://www.bu.edu

More articles from Ecology, The Environment and Conservation:

nachricht Bioinvasion on the rise
15.02.2017 | Universität Konstanz

nachricht Litter Levels in the Depths of the Arctic are On the Rise
10.02.2017 | Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Switched-on DNA

20.02.2017 | Materials Sciences

Second cause of hidden hearing loss identified

20.02.2017 | Health and Medicine

Prospect for more effective treatment of nerve pain

20.02.2017 | Health and Medicine

VideoLinks
B2B-VideoLinks
More VideoLinks >>>