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TOPIC: Katrina Damage to Gulf Coast Forests
http://groups.google.com/group/entstrees/browse_thread/thread/86f314f11c67e0e0?hl=en
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Date: Tues, Jan 1 2008 5:57 pm
From: "Edward Frank"
ENTS,
http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=17880
Besides its destruction to homes and human lives, Hurricane Katrina
dealt a severe blow to the U.S. Gulf Coast's forests. Using NASA
satellite data, a team of researchers at Tulane University and the
University of New Hampshire concluded that the hurricane destroyed
or severely damaged some 320 million large trees. Besides felling
trees, the storm changed the role that many Gulf Coast forests play
in the global carbon budget.
Acquired in late 2005, this aerial photograph shows an area of
forest in the Pearl River Basin, which extends from central
Mississippi to the Louisiana border. Although forest damage is
obvious, it is hardly uniform. Next to wide swaths of felled trees,
intact forest remains. Cypress and tupelo trees proved more
resistant to Katrina's winds than hardwood forest trees in this
area, including oak, maple, and sweetgum. So while hardwood trees
lie in tatters in this image, the more resilient trees remain
upright.
Just as trees differ in their ability to resist winds, forests
differ in their ability to store carbon. Young and growing forests,
including those that had flourished along the Gulf Coast, are
particularly effective in sucking carbon dioxide from the air
through photosynthesis. These forests subsequently store carbon in
plants and soils, acting as carbon sinks. After a hurricane snaps
millions of branches and trunks-as Hurricane Katrina did in
Mississippi, Alabama, and Louisiana-photosynthesis slows, drawing
less carbon dioxide from the atmosphere. In addition, microorganisms
that decompose the resulting dead vegetation release a hefty dose of
carbon dioxide into the atmosphere. In short, Katrina converted many
Gulf Coast forests from carbon sinks to carbon sources.
The research team concluded that the carbon released by Gulf Coast
forests after Hurricane Katrina approximated 60 to 100 percent of
the carbon stored by all the forests in the United States in an
average year. If warming temperatures caused by greenhouse gas
emissions increase the likelihood of tree-destroying storms, a
self-reinforcing cycle could develop in which hurricane-damaged
forests release more carbon into Earth's atmosphere, enhancing
global warming.
To conduct this study, the research team used a combination of
remote sensing, computer models, and field investigations. Starting
with Landsat imagery of the Pearl River Basin, along the
Louisiana-Mississippi border, the team calculated the amounts of
green vegetation, surface litter, wood, dead vegetation, soil, and
shade. Comparing Landsat images taken at the same time of year
before and after the storm, the team developed maps of tree
mortality and damage. Next, the team compared changes detected by
Landsat to those detected by Moderate Resolution Imaging
Spectroradiometer (MODIS) data to scale up the damage around to
Pearl River Basin to the Gulf Coast region affected by Katrina.
References
a.. Chambers, J.Q., Fisher, J.I., Zheng, H., Chapman, E.L. Baker,
D.B., and Hurtt, G.C. (2007). Hurricane Katrina's carbon footprint
on U.S. Gulf Coast forests. Science, 318(5853): 1107.
doi:10.1126/science.1148913
b.. Cook-Anderson, G. (2007, November 15) Forests damaged by
Hurricane Katrina become major carbon source. NASA. Accessed
December 28, 2007.
c.. Pearl River Basin. U.S. Geological Survey. Accessed December 28,
2007.
Photograph courtesy Louisiana State University Hurricane Katrina and
Rita Cooperative Clearinghouse.
Edward Frank
"If we knew what it was we were doing, it would not be called
research, would it?" --Albert Einstein
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