 |
|
Amazon forest shows unexpected resiliency during drought
September 24, 2007Drought-stricken regions of the Amazon forest grew particularly vigorously during the 2005 drought, according to new research.
The counterintuitive finding contradicts a prominent global climate model that predicts the Amazon forest would begin to "brown down" after just a month of drought and eventually collapse as the drought progressed.
"Instead of 'hunkering down' during a drought as you might expect, the forest responded positively to drought, at least in the short term," said study author Scott R. Saleska of The University of Arizona. "It's a very interesting and surprising response."
UA co-author Kamel Didan added, "The forest showed signs of being more productive. That's the big news."
The 2005 drought reached its peak at the start of the Amazon's annual dry season, from July through September. Although the double whammy of the parched conditions might be expected to slow growth of the forest's leafy canopy, for many of the areas hit by drought, the canopy of the undisturbed forest became significantly greener -- indicating increased photosynthetic activity.
Saleska, a UA assistant professor of ecology and evolutionary biology, and his colleagues at the UA and at the University of São Paulo in Brazil used data from two NASA satellites to figure out that undisturbed Amazon forest flourished as rainfall levels plummeted.
"No one had looked at the observations that are available from satellites," said Didan, an associate research scientist in the UA's department of soil, water and environmental science. "We took the opportunity of the most recent drought, the 2005 drought, to do so."
"A big chunk of the Amazon forest, the southwest region where the drought was severest, reacted positively," said Didan, a NASA-EOS MODIS associate science team member.
The study, "Amazon Forests Green-up during 2005 drought," is online in the current issue of Science Express, the early-online version of the journal Science. The paper will be published in the October 26, 2007, issue of Science.
Saleska and Didan's co-authors are Alfredo Huete, UA professor of soil, water and environmental science and NASA-EOS MODIS science team member, and Humberto Ribeiro da Rocha of the department of atmospheric science at the University of São Paulo in Brazil. The research was funded by NASA.
The UA scientists and their Brazilian colleague already knew the Amazon forest took advantage of the annual dry season's relatively cloudless skies to soak up the sun and grow. The UA scientists and some other researchers had conducted previous research using satellite data in combination with field measurements and showed that intact Amazon forest increases photosynthesis, actually "greening up," during the dry season.
However, no one had examined how the forest responded to a drought. The severe 2005 drought and the detailed, long-term observations from two NASA satellites -- one that maps the greenness of vegetation, one that measures rainfall in the tropics -- gave the researchers what they needed to see how the Amazon forest responds to a major drought.
The researchers used the month-to-month maps of changes in vegetation status across the Amazon available from the Moderate Resolution Imaging Spectroradiometer, or MODIS, carried by the Terra satellite, launched in 1999. The team gathered observations of rainfall in the Amazon from the Tropical Rainfall Measuring Mission spacecraft, launched in 1997.
The seven-to-nine years of observations from the satellites allowed the scientists to map "normal" rainfall and greenness conditions in non-drought years. When the team compared those conditions to the same months of the 2005 drought, the researchers found that areas of Amazon's intact forests that had received below-normal rainfall in 2005 also had above-average greenness.
Global climate models predict the Amazon forest will cut back photosynthesis quickly when a drought starts. That slowdown in plant growth would create a positive feedback loop -- as the forest shuts down more and more, it removes less and less carbon dioxide from the atmosphere. The CO2 ordinarily sequestered by growing trees would remain in the atmosphere, increasing global warming and further accelerating the forest's decline and additional CO2-fueled warming.
By contrast, the UA-led team's findings suggest the opposite happens, at least in the short-term. The drought-induced flush of forest growth would dampen global warming, not accelerate it. During the 2005 drought, Amazon forest trees flourished in the sunnier-than-average weather, most likely by tapping water deep in the forest soil. To grow, trees must take up carbon dioxide, thus drawing down the levels of atmospheric CO2. That negative feedback loop would slow warming from greenhouse gases.
Evolutionarily, the forest's resilience in the face of a single drought year makes sense, Saleska said. During El Nino, which occurs about every four to eight years, the Amazon forest receives significantly less rain than average.
The limit of the forest's resiliency is unknown, Saleska said, adding, "But if you take away enough water for long enough, the trees will die."
University of Arizona
UA co-author Kamel Didan added, "The forest showed signs of being more productive. That's the big news."
The 2005 drought reached its peak at the start of the Amazon's annual dry season, from July through September. Although the double whammy of the parched conditions might be expected to slow growth of the forest's leafy canopy, for many of the areas hit by drought, the canopy of the undisturbed forest became significantly greener -- indicating increased photosynthetic activity.
Saleska, a UA assistant professor of ecology and evolutionary biology, and his colleagues at the UA and at the University of São Paulo in Brazil used data from two NASA satellites to figure out that undisturbed Amazon forest flourished as rainfall levels plummeted.
"No one had looked at the observations that are available from satellites," said Didan, an associate research scientist in the UA's department of soil, water and environmental science. "We took the opportunity of the most recent drought, the 2005 drought, to do so."
"A big chunk of the Amazon forest, the southwest region where the drought was severest, reacted positively," said Didan, a NASA-EOS MODIS associate science team member.
The study, "Amazon Forests Green-up during 2005 drought," is online in the current issue of Science Express, the early-online version of the journal Science. The paper will be published in the October 26, 2007, issue of Science.
Saleska and Didan's co-authors are Alfredo Huete, UA professor of soil, water and environmental science and NASA-EOS MODIS science team member, and Humberto Ribeiro da Rocha of the department of atmospheric science at the University of São Paulo in Brazil. The research was funded by NASA.
The UA scientists and their Brazilian colleague already knew the Amazon forest took advantage of the annual dry season's relatively cloudless skies to soak up the sun and grow. The UA scientists and some other researchers had conducted previous research using satellite data in combination with field measurements and showed that intact Amazon forest increases photosynthesis, actually "greening up," during the dry season.
However, no one had examined how the forest responded to a drought. The severe 2005 drought and the detailed, long-term observations from two NASA satellites -- one that maps the greenness of vegetation, one that measures rainfall in the tropics -- gave the researchers what they needed to see how the Amazon forest responds to a major drought.
The researchers used the month-to-month maps of changes in vegetation status across the Amazon available from the Moderate Resolution Imaging Spectroradiometer, or MODIS, carried by the Terra satellite, launched in 1999. The team gathered observations of rainfall in the Amazon from the Tropical Rainfall Measuring Mission spacecraft, launched in 1997.
The seven-to-nine years of observations from the satellites allowed the scientists to map "normal" rainfall and greenness conditions in non-drought years. When the team compared those conditions to the same months of the 2005 drought, the researchers found that areas of Amazon's intact forests that had received below-normal rainfall in 2005 also had above-average greenness.
Global climate models predict the Amazon forest will cut back photosynthesis quickly when a drought starts. That slowdown in plant growth would create a positive feedback loop -- as the forest shuts down more and more, it removes less and less carbon dioxide from the atmosphere. The CO2 ordinarily sequestered by growing trees would remain in the atmosphere, increasing global warming and further accelerating the forest's decline and additional CO2-fueled warming.
By contrast, the UA-led team's findings suggest the opposite happens, at least in the short-term. The drought-induced flush of forest growth would dampen global warming, not accelerate it. During the 2005 drought, Amazon forest trees flourished in the sunnier-than-average weather, most likely by tapping water deep in the forest soil. To grow, trees must take up carbon dioxide, thus drawing down the levels of atmospheric CO2. That negative feedback loop would slow warming from greenhouse gases.
Evolutionarily, the forest's resilience in the face of a single drought year makes sense, Saleska said. During El Nino, which occurs about every four to eight years, the Amazon forest receives significantly less rain than average.
The limit of the forest's resiliency is unknown, Saleska said, adding, "But if you take away enough water for long enough, the trees will die."
University of Arizona
Amazon Forest News and Current Amazon Forest Events RSSExtinction most likely for rare trees in the Amazon rainforest
Common tree species in the Amazon will survive even grim scenarios of deforestation and road-building, but rare trees could suffer extinction rates of up to 50 percent, predict Smithsonian scientists and colleagues in the Aug. 12 issue of the journal Proceedings of the National Academy of Science.
Can feces save the species?
It's a tough job, but somebody, or at least some dogs, have to do it. In the Cerrado region of Brazil, four dogs trained to detect animal feces by scent are helping researchers monitor rare and threatened wildlife such as jaguar, tapir, giant anteater and maned wolf in and around Emas National Park, a protected area with the largest concentration of threatened species in Brazil.
Fire, ice, and invasion
The November 2007 Special Issue of Frontiers in Ecology and the Environment focuses on paleoecology, which uses fossilized remains and soil and sediment cores to reconstruct past ecosystems.
Amazon rainforest at risk from initiative to connect South American economies
An unprecedented development plan to link South America's economies through new transportation, energy and telecommunications projects could destroy much of the Amazon rainforest in coming decades, according to a new study by Conservation International (CI) scientist Tim Killeen.
Large size crucial for Amazon forest reserves
An international research team has discovered that the size of Amazon forest reserves is yet more important than previously thought.
Growth in Amazon cropland may impact climate and deforestation patterns
Scientists using NASA satellite data have found that clearing for mechanized cropland has recently become a significant force in Brazilian Amazon deforestation. This change in land use may alter the region's climate and the land's ability to absorb carbon dioxide.
Researchers discover trees in Amazon much older than assumed, raising questions on global climate impact of region
Trees in the Amazon tropical forests are old. Really old, in fact, which comes as a surprise to a team of American and Brazilian researchers studying tree growth in the world's largest tropical region.
Woods Hole Research Center plans controlled burn in Amazon rainforest
Fire is an important agent of transformation in the Amazon landscape. Every year, low intensity fires burn thousands of square miles of Amazon forest.
Watching over the Amazon forest by remote sensing
Areas deforested in Brazil increased from 152 000 km_ in 1976 to 517 000 km_ in 1996. That figure is the equivalent of the surface area of France (1). Deforestation is a complex process and involves a host of changing and widely differing situations. The factors behind it are many and varied. They include rising demand for agricultural land, international trade needs for timber and political decisions regarding strategic planning and development. Researchers of the IRD Space Unit conducted an investigation from January 2000 to December 2002, on deforestation in the Amazon Basin. Their overall procedure is based on the use of remote-sensing data obtained from satellites and aircraft. The app
More Amazon Forest News Articles
 | Beloved by Toni Morrison Staring unflinchingly into the abyss of slavery, this spellbinding novel transforms history into a story as powerful as Exodus and as intimate as a lullaby. Sethe, its protagonist, was born a slave and escaped to Ohio, but eighteen years later she is still not free. She has too many memories of Sweet Home, the beautiful farm where so many hideous things happened. And Sethe’s new home is... |
 | Sula by Toni Morrison Two girls who grow up to become women. Two friends who become something worse than enemies. In this brilliantly imagined novel, Toni Morrison tells the story of Nel Wright and Sula Peace, who meet as children in the small town of Medallion, Ohio. Their devotion is fierce enough to withstand bullies and the burden of a dreadful secret. It endures even after Nel has grown up to be a pillar of the... |
 | The Lorax (Classic Seuss) by Dr. Seuss, Theodor Seuss Geisel When Dr. Seuss gets serious, you know it must be important. Published in 1971, and perhaps inspired by the "save our planet" mindset of the 1960s, The Lorax is an ecological warning that still rings true today amidst the dangers of clear-cutting, pollution, and disregard for the earth's environment. In The Lorax, we find what we've come to expect from the illustrious doctor: brilliantly whimsical... |
 | The Forest People by Colin Turnbull The Forest People -- Colin M. Turnbull's best-selling, classic work -- describes the author's experiences while living with the BaMbuti Pygmies, not as a clinical observer, but as their friend learning their customs and sharing their daily life.Turnbull conveys the lives and feelings of the BaMbuti whose existence centers on their intense love for their forest world, which, in return for their... |
 | The River of Doubt: Theodore Roosevelt's Darkest Journey by Candice Millard At once an incredible adventure narrative and a penetrating biographical portrait, The River of Doubt is the true story of Theodore Roosevelt’s harrowing exploration of one of the most dangerous rivers on earth.The River of Doubt—it is a black, uncharted tributary of the Amazon that snakes through one of the most treacherous jungles in the world. Indians armed with poison-tipped... |
 | Light in August (The Corrected Text) by William Faulkner Joe Christmas does not know whether he is black or white. Faulkner makes of Joe's tragedy a powerful indictment of racism; at the same time Joe's life is a study of the divided self and becomes a symbol of 20th century... |
 | National Audubon Society Field Guide to North American Trees--E: Eastern Region (Eastern) by NATIONAL AUDUBON SOCIETY For the untrained observer, it can be quite a challenge to sort out the many trees that make up a stand of older forest in, say, New England or the Ozarks. This well-illustrated guidebook, covering 364 species, comes to the rescue with photographs organized in several ways: by, for example, the shape of the leaf or needle, by the fruit, by the flower or cone, and by autumn coloration. Following... |
 | Unbowed: A Memoir (Vintage) by Wangari Maathai In Unbowed, Nobel Prize winner Wangari Maathai recounts her extraordinary journey from her childhood in rural Kenya to the world stage. When Maathai founded the Green Belt Movement in 1977, she began a vital poor people’s environmental movement, focused on the empowerment of women, that soon spread across Africa. Persevering through run-ins with the Kenyan government and personal losses,... |
 | The Wild Trees: A Story of Passion and Daring by Richard Preston Hidden away in foggy, uncharted rain forest valleys in Northern California are the largest and tallest organisms the world has ever sustained–the coast redwood trees, Sequoia sempervirens. Ninety-six percent of the ancient redwood forests have been destroyed by logging, but the untouched fragments that remain are among the great wonders of nature. The biggest redwoods have trunks up to... |
 | A Field Guide to Eastern Trees (Peterson Field Guides) by George A. Petrides This field guide features detailed descriptions of 455 species of trees native to eastern North America, including the Midwest and the South. The 48 color plates, 11 black-and-white plates, and 26 text drawings show distinctive details needed for identification. Color photographs and 266 color range maps accompany the species... |
| © 2008 BrightSurf.com |