Greenhouse Gases Rise From Katrina Damaged Forests

Greenhouse Gases Rise From Katrina Damaged Forests

November 2007 
 Losses inflicted by 
Hurricane Katrina on Gulf Coast forest trees are great enough to cancel 
out a year's worth of new tree growth in other parts of the country, 
according to a new study led by biologist Jeffrey Chambers of Tulane 
University. 
"The carbon that will be released as these trees decompose is enough to 
cancel out an entire year's worth of net gain by all U.S. forests. And 
this is only from a single storm," says Chambers, lead author of an 
article detailing the team's findings, "Hurricane Katrina's Carbon 
Footprint on Gulf Coast Forests," published in the November 16 issue of 
the journal Science. 
The study was carried out by researchers at Tulane and the University of 
New Hampshire using NASA satellite sensing technology and data, ecological 
field investigations and statistical analysis. 
The investigators estimate that 320 million large trees were killed or 
severely damaged by the intense hurricane that made landfall on August 29, 
2005.

Katrina affected five million acres of forest across Mississippi, 
Louisiana and Alabama, with damage ranging from downed trees, snapped 
trunks and broken limbs to stripped leaves. 
Young forests are valued as carbon sinks, which remove carbon dioxide from 
the atmosphere and store it in growing vegetation and soils. In the 
aftermath of a storm as intense as Katrina, vegetation killed by the storm 
decomposes over time, reversing the carbon storage process, making the 
forest a carbon source. 
"The loss of so many trees will cause these forests to be a net source of 
carbon dioxide to the atmosphere for years to come," said Chambers. "If, 
as many believe, a warming climate causes a rise in the intensity of 
extreme events like Hurricane Katrina, we're likely to see an increase in 
tree mortality, resulting in an elevated release of carbon by impacted 
forest ecosystems." 
As the Earth's climate warms, evidence is accumulating that hurricanes, 
tornados and frontal systems will gain in energy, producing more violent 
storms and stronger winds. 
Increased wind disturbance will cause more tree mortality and damage, and 
this dead wood will release additional carbon to the atmosphere, 
potentially amplifying global warming. 
"The carbon cycle is intimately linked to just about everything we do, 
from energy use to food and timber production and consumption," said 
Chambers. 
"As more and more carbon is released to the atmosphere by human 
activities, the climate warms, triggering an intensification of the global 
water cycle that produces more powerful storms, leading to destruction of 
more trees, which then act to amplify climate warming," he explained. 
Study co-author George Hurtt of the University of New Hampshire Institute 
for the Study of Earth, Oceans, and Space says, "This could potentially 
escalate the problem of global warming." 
Hurtt, an ecologist who specializes in mathematical modeling, says the 
next step is to put the data into sophisticated computer models to better 
gauge the magnitude of the potential positive feedback mechanism. 
"We now need to figure out how strong of a feedback this might be, how 
much more severe these storms might become for every unit of global 
warming, and how the forests will be affected by the storms." Hurtt says. 
"Until that work is done, it's not clear if current projections are overly 
alarmist or too conservative." 
NASA provided satellite data for the study and many of the methods used 
were first developed as part of a NASA Large Scale Biosphere-Atmosphere 
Experiment in Amazonia, led by Chambers. 
"It is surprising to learn that one extreme event can release nearly as 
much carbon to the atmosphere as all U.S. forests can store in an average 
year," said Diane Wickland, manager of the Terrestrial Ecology Program at 
NASA Headquarters in Washington. 
"Satellite data enabled Chambers' research team to pin down the extent of 
tree damage so that we now know how these kinds of severe storms affect 
the carbon cycle and our atmosphere," she said. 
The study was funded by the U.S. Department of Energy's National Institute 
of Climatic Change Research. 

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