The ravages of deforestation, wildfires, windstorms and insects on global
forests during this century are revealed in unprecedented detail in a new study
based on data from the NASA-U.S. Geological Survey Landsat 7 satellite.
The maps resulting from the study are the first to document forest loss and
gain using a consistent method around the globe, at high resolution. They allow
scientists to compare forest changes in different countries and monitor annual
deforestation. With each pixel in a Landsat image showing an area about the size
of a baseball diamond, researchers see enough detail to tell local, regional and
global stories.
“Now, we have 12 years of annual forest loss over the globe,” said Matthew
Hansen, whose team at the University of Maryland in College Park, Md., led the
new study.
Twelve years of global deforestation, wildfires,
windstorms, insect infestations and more are captured in a new set of forest
disturbance maps created from billions of pixels acquired by the Landsat 7
satellite.
Image Credit: NASA Goddard, based on data from Hansen et al.,
2013.
Image Token:
Feature Link:
Hansen and colleagues analyzed 143 billion pixels in 654,000 Landsat images
to compile maps of forest loss and gain between 2000 and 2012. During that
period, 888,000 square miles (2.3 million square kilometers) of forest were
lost, and 309,000 square miles (800,000 square kilometers) regrew. The
researchers, including scientists from the University of Maryland, Google, the
State University of New York, Woods Hole Research Center, the U.S. Geological
Survey (USGS) and South Dakota State University, published their work in the
Nov. 15 issue of the journal Science.
Key to the project was collaboration with team members from Google Earth
Engine, who reproduced in the Google Cloud the models developed at the
University of Maryland for processing and characterizing the Landsat data.
Using Landsat imagery and cloud computing,
researchers mapped forest cover worldwide as well as forest loss and gain. Over
12 years, 888,000 square miles (2.3 million square kilometers) of forest were
lost, and 309,000 square miles (800,000 square kilometers)
regrew.
Image Credit: NASA Goddard, based on data from Hansen et al.,
2013.
Image Token:
During the study period, Brazil cut its deforestation rate from approximately
15,400 square miles (40,000 square kilometers) per year to approximately 7,700
square miles (20,000 square kilometers) per year.
"That's the result of a concerted policy effort to reduce deforestation, and
it sets a standard for the rest of the world," Hansen said.
The team found that the deforestation rate in other countries increased.
Indonesia's deforestation rate doubled in the study period, from approximately
3,900 square miles (10,000 square kilometers) per year in 2000-2003 to more than
7,700 square miles (20,000 square kilometers) in 2011-2012.
The border between Malaysia and Indonesia on the
island of Borneo stands out in the Landsat-based map of forest disturbance. Red
pixels represent forest loss between 2000 and 2012.
Image Credit: NASA Goddard, based on data from Hansen et al.,
2013.
Image Token:
Prior to this study, country-to-country comparisons of forestry data were not
possible at this level of accuracy. Different countries define forests
differently, making previous global comparisons difficult with existing
inventories.
"When you put together datasets that employ different methods and
definitions, it's hard to synthesize," Hansen said. "But with Landsat, as a
polar-orbiting instrument that takes the same quality pictures everywhere, we
can apply the same algorithm to forests in the Amazon, in the Congo, in
Indonesia, and so on. It's a huge improvement in our global monitoring
capabilities."
"Since the first Landsat satellite launched 41 years ago, scientists have
been improving their land cover analysis as computers have become more
powerful," said Jeff Masek, Landsat project scientist at NASA's Goddard Space
Flight Center in Greenbelt, Md. "Projects like Hansen's took a big leap forward
once USGS made the data freely available on the Internet in 2008."
"This is the first time somebody has been able to do a wall-to-wall, global
Landsat analysis of all the world's forests -- where they're being cleared,
where they're regrowing, and where they're subject to natural disturbances,"
Masek said, noting that the maps could be routinely updated to aid in carbon
accounting and other studies of land cover change.
The maps also illustrate the impact of politics on land cover. On the island
of Borneo, the maps clearly show the border between Malaysia and Indonesia.
Malaysia's heavy logging along forest roads is visible right up to the
Indonesian border, where forests were still largely intact as of 2012. In Côte
d'Ivoire, a civil war in 2002 corresponded with intense deforestation of several
previously protected nature reserves.
Civil unrest in Côte d'Ivoire was associated with
widespread deforestation in national parks, including Marahoué National Park.
Other protected areas, such as Tai National Park, remained
intact.
Image Credit: NASA Goddard, based on data from Hansen et al.,
2013.
Image Token:
A different pattern of change appears in the southeastern U.S., where
landowners harvest trees for timber and quickly plant their replacements.
"Of this eco-region in the southeast, 30 percent of the forest land was
regrown or lost during this period," Hansen said. "It's incredibly intensive.
Trees are really treated like a crop in this region."
The forest cover maps also capture natural
disturbances such as this 2011 tornado path in Alabama. In this map, the colors
represent forest loss by year, with yellows representing loss closer to 2000 and
reds representing later forest loss, up to 2012.
Image Credit: NASA Goddard, based on data from Hansen et al.,
2013.
Image Token:
In Alabama, Landsat also detected miles-long streaks of destroyed forest.
When the researchers examined the year-by-year record, they found the damage
occurred in 2011 after a violent tornado season.
Since 1972, the Landsat program has played a critical role in monitoring,
understanding and managing the resources needed to sustain human life such as
food, water and forests. Landsat 8 was launched Feb. 11 and is managed jointly
by NASA and USGS to continue the 40-plus years of Earth observations.
To view the forest cover maps in Google Earth Engine, visit:
For more information about the Landsat satellites, visit:
Kate Ramsayer
NASA's Goddard Space Flight Center, Greenbelt, Md.
NASA's Goddard Space Flight Center, Greenbelt, Md.
NASA-USGS Landsat Data Yield Best View to Date of Global Forest Losses, Gains
The ravages of deforestation, wildfires, windstorms, and insects on global
forests during this century are revealed in unprecedented detail in a new study
based on data from the NASA-U.S. Geological Survey Landsat 7 satellite.
The maps resulting from the study are the first to document forest loss and
gain using a consistent method around the globe, at high resolution. They allow
scientists to compare forest changes in different countries and monitor annual
deforestation. With each pixel in a Landsat image showing an area about the size
of a baseball diamond, researchers see enough detail to tell local, regional and
global stories.
Prior to this study, country-to-country comparisons of forestry data were not
possible at this level of accuracy. Different countries define forests
differently, making previous global comparisons difficult with existing
inventories.
"When you put together datasets that employ different methods and
definitions, it's hard to synthesize," said Matthew Hansen, whose team at the
University of Maryland in College Park, Md., led the new study. "But with
Landsat, as a polar-orbiting instrument that takes the same quality pictures
everywhere, we can apply the same algorithm to forests in the Amazon, in the
Congo, in Indonesia, and so on. It's a huge improvement in our global monitoring
capabilities."
Hansen and colleagues analyzed 143 billion pixels in 654,000 Landsat images
to compile maps of forest loss and gain between 2000 and 2012. During that
period, 888,000 square miles (2.3 million square kilometers) of forest were
lost, and 309,000 square miles (800,000 square kilometers) regrew. The
researchers, including scientists from the University of Maryland, Google, the
State University of New York, Woods Hole Research Center, the U.S. Geological
Survey (USGS) and South Dakota State University, published their work in the
Nov. 15 issue of the journal Science.
Key to the project was collaboration with team members from Google Earth
Engine, who reproduced in the Google Cloud the models developed at the
University of Maryland for processing and characterizing the Landsat data.
During the study period, Brazil cut its deforestation rate from approximately
15,400 square miles (40,000 square kilometers) per year to approximately 7,700
square miles (20,000 square kilometers) per year.
"That's the result of a concerted policy effort to reduce deforestation, and
it sets a standard for the rest of the world," Hansen said.
The team found t the deforestation rate in other countries increased.
Indonesia's deforestation rate doubled in the study period, from approximately
3,900 square miles (10,000 square kilometers) per year in 2000-2003 to more than
7,700 square miles (20,000 square kilometers) in 2011-2012.
"Since the first Landsat satellite launched 41 years ago, scientists have
been improving their land cover analysis as computers have become more
powerful," said Jeff Masek, Landsat project scientist at NASA's Goddard Space
Flight Center in Greenbelt, Md. "Projects like Hansen's took a big leap forward
once USGS made the data freely available on the Internet in 2008."
"This is the first time somebody has been able to do a wall-to-wall, global
Landsat analysis of all the world's forests -- where they're being cleared,
where they're regrowing, and where they're subject to natural disturbances,"
Masek said, noting that the maps could be routinely updated to aid in carbon
accounting and other studies of land cover change.
The maps also illustrate the impact of politics on land cover. On the island
of Borneo, the maps clearly show the border between Malaysia and Indonesia.
Malaysia's heavy logging along forest roads is visible right up to the
Indonesian border, where forests were still largely intact as of 2012. In Côte
d'Ivoire, a civil war in 2002 corresponded with intense deforestation of several
previously protected nature reserves.
A different pattern of change appears in the southeastern U.S., where
landowners harvest trees for timber and quickly plant their replacements.
"Of this eco-region in the southeast, 30 percent of the forest land was
regrown or lost during this period," Hansen said. "It's incredibly intensive.
Trees are really treated like a crop in this region."
In Alabama, Landsat also detected miles-long streaks of destroyed forest.
When the researchers examined the year-by-year record, they found the damage
occurred in 2011 after a violent tornado season.
Since 1972, the Landsat program has played a critical role in monitoring,
understanding and managing the resources needed to sustain human life such as
food, water and forests. Landsat 8 was launched Feb. 11 and is managed jointly
by NASA and USGS to continue the 40-plus years of Earth observations.
To view the forest cover maps in Google Earth Engine, visit:
For more information about the Landsat satellites, visit:
NASA
Guillermo Gonzalo Sánchez Achutegui
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