JPL
Careers
Education
Science & Technology
JPL Logo
JPL Logo
Earth
.

NASA Finds Amazon Drought Leaves Long Legacy of Damage

Aug 09, 2018
This image, taken during a September 2010 drought, shows a line of dead and damaged trees after a surface fire in the Amazon rainforest in western Brazil. When dryer-than-normal conditions exist, fires from the open edges encroach on the forests and burn dry and stressed trees. Under normal conditions, when the rainforests are wetter, this is far less common.
Credit: NASA/JPL-Caltech
This image, based on measurements taken by the Tropical Rainfall Measuring Mission (TRMM), shows the areas of the Amazon basin that were affected by the severe 2005 drought. Areas in yellow, orange, and red experienced light, moderate, and severe drought, respectively. Green areas did not experience drought.
Credit: NASA/JPL-Caltech /Google
This image, taken during a September 2010 drought, shows a dead tree in the Amazon rainforest in western Brazil.
Credit: NASA/JPL-Caltech

A single season of drought in the Amazon rainforest can reduce the forest's carbon dioxide absorption for years after the rains return, according to a new study published in the journal Nature.

A single season of drought in the Amazon rainforest can reduce the forest's carbon dioxide absorption for years after the rains return, according to a new study published in the journal Nature. This is the first study to quantify the long-term legacy of an Amazon drought.

A research team from NASA's Jet Propulsion Laboratory in Pasadena, California, and other institutions used satellite lidar data to map tree damage and mortality caused by a severe drought in 2005. In years of normal weather, the undisturbed forest can be a natural carbon "sink," absorbing more carbon dioxide from the atmosphere than it puts back into it. But starting with the drought year of 2005 and running through 2008 -- the last year of available lidar data -- the Amazon basin lost an average of 0.27 petagrams of carbon (270 million metric tons) per year, with no sign of regaining its function as a carbon sink.

At about 2.3 million square miles (600 million hectares), the Amazon is the largest tropical forest on Earth. Scientists estimate that it absorbs as much as one-tenth of human fossil fuel emissions during photosynthesis. "The old paradigm was that whatever carbon dioxide we put up in [human-caused] emissions, the Amazon would help absorb a major part of it," said Sassan Saatchi of NASA's JPL, who led the study.

But serious episodes of drought in 2005, 2010 and 2015 are causing researchers to rethink that idea. "The ecosystem has become so vulnerable to these warming and episodic drought events that it can switch from sink to source depending on the severity and the extent," Saatchi said. "This is our new paradigm."

Drought from the Ground

For scientists on the ground in the Amazon, "The first thing we see during a drought is that the trees may lose their leaves," Saatchi said. "These are rainforests; the trees almost always have leaves. So the loss of leaves is a strong indication the forest is stressed." Even if trees eventually survive defoliation, this damages their capacity to absorb carbon while under stress.

Observers on the ground also notice that droughts tend to disproportionately kill tall trees first. Without adequate rainfall, these giants can't pump water more than 100 feet up from their roots to their leaves. They die from dehydration and eventually fall to the ground, leaving gaps in the forest canopy far overhead.

But any observer on the ground can monitor only a tiny part of the forest. There are only about hundred plots used for research and a few tower sites for long-term monitoring of the Amazon forests. "The detailed measurements in these sites are extremely important for understanding forest function, but we can never use them to say what this giant ecosystem is doing in a timely fashion," Saatchi said. To do that, he and his colleagues turned to satellite data.

Drought from Space

The research team used high-resolution lidar maps derived from the Geoscience Laser Altimeter System aboard the Ice, Cloud, and land Elevation Satellite (ICESat). These data reveal changes in canopy structure, including leaf damage and gaps. The researchers developed a new method of analysis to convert these structural changes into changes in aboveground biomass and carbon. They eliminated pixels showing burned or deforested areas to calculate the carbon impact of drought on intact forests alone.

They found that following drought, fallen trees, defoliation and canopy damage produced a significant loss in canopy height, with the most severely impacted region declining an average of about 35 inches (0.88 meters) in the year after the drought. Less severely affected regions of the forest declined less, but all continued to decline steadily throughout the remaining years of the data record.

Saatchi noted that half of the forest's rainfall is made by the forest itself -- water that transpires and evaporates from the vegetation and ground, rises into the atmosphere, and condenses and rains out during the dry season and the transition to the wet season. A drought that kills forest trees thus not only increases carbon emissions, it reduces rainfall and extends dry-season length. Those changes increase the likelihood of future drought.

If droughts continue to occur with the frequency and severity of the last three events in 2005, 2010 and 2015, Saatchi said, the Amazon could eventually change from a rainforest to a dry tropical forest. That would reduce the forest's carbon absorption capacity and its biological diversity.

The paper in Nature is titled "Post-drought Decline of the Amazon Carbon Sink." Co-authors are affiliated with UCLA, Boston University, Oregon State University in Corvallis, and the U.S. Forest Service's International Institute of Tropical Forestry in Rio Piedras, Puerto Rico.

News Media Contact

Written by Carol Rasmussen

Esprit Smith

818-354-4269

Esprit.Smith@jpl.nasa.gov

2018-188

Related News

Weather .

A Pioneering NASA Mini Weather Satellite Ends Its Mission

Climate Change .

NASA Satellites Help Quantify Forests’ Impacts on the Global Carbon Budget

Mars .

NASA’s Perseverance Pays Off Back Home

Climate Change .

Warming Seas Are Accelerating Greenland’s Glacier Retreat

Earth .

NASA, US and European Partner Satellite Returns First Sea Level Measurements

Technology .

NASA Confirms New SIMPLEx Mission Small Satellite to Blaze Trails Studying Lunar Surface

Earth .

New Data Confirm 2020 SO to Be the Upper Centaur Rocket Booster From the 1960's

Earth .

Follow Sentinel-6 Michael Freilich in Real Time As It Orbits Earth

Climate Change .

US-European Mission Launches to Monitor the World's Oceans

Climate Change .

Sentinel-6 Michael Freilich Satellite Prepared for Launch

Explore More

Image .

Pacaya and Fuego Volcanoes, Guatemala

Image .

Mt. Etna--February 26, 2021

Image .

Mt. Etna February 2021

Image .

Tumbiana Stromatolite

Image .

Banjul, The Gambia

Image .

Lake Salda Rocks

Image .

Lake Salda Beach

Image .

Serabit el-Khadim, Egypt

Image .

Glacier Undercutting in Action

Image .

Hulhumale, Maldives

About JPL
Who We Are
Executive Council
Directors of JPL
JPL History
Documentary Series
Virtual Tour
Annual Reports
Missions
All
Current
Past
Future
News
All
Earth
Mars
Solar System
Universe
Technology
Galleries
Images
Videos
Audio
Podcasts
Infographics
Visions of the Future
Slice of History
Engage
JPL and the Community
Lecture Series
Public Tours
Events
Team Competitions
JPL Speakers Bureau
Topics
Solar System
Mars
Earth
Climate Change
Stars and Galaxies
Exoplanets
Technology
JPL Life
For Media
Contacts and Information
Press Kits
More
Asteroid Watch
Robotics at JPL
Subscribe to Newsletter
Universe Newsletter
Social Media
Get the Latest from JPL
Follow Us

JPL is a federally funded research and development center managed for NASA by Caltech.

More from JPL
Careers Education Science & Technology Acquisitions JPL Store
Careers
Education
Science & Technology
Acquisitions
JPL Store
Related NASA Sites
Basics of Spaceflight
Climate Kids
Earth / Global Climate Change
Exoplanet Exploration
Mars Exploration
Solar System Exploration
Space Place
NASA's Eyes Visualization Project
Voyager Interstellar Mission
NASA
Caltech
Privacy
Image Policy
FAQ
Feedback
Site Manager: Veronica McGregor
Site Editors: Tony Greicius, Randal Jackson, Naomi Hartono