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 So 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
|Contact: Mari N. Jensen|
University of Arizona