Mitigating Global Warming
Trees May Not Play as Big a Role as Scientists Hoped
by Monte Basgall
The latest findings from FACE, the Free
Air Carbon Dioxide Enrichment experiments where four patches
of Duke Forest woodland are receiving doses of air from
the mid-21st century, suggest that trees can't play as big
a role in mitigating global warming as some had hoped.
"That has dramatic implications for climate treaty negotiations
where the United States' position has been that forest growth
will soak up a lot of carbon dioxide and that the growth might
actually increase as carbon dioxide rises so that the effect
will be even bigger," said William
H. Schlesinger, James B. Duke Professor of biogeochemistry,
FACE project co-principal investigator, and the Nicholas School's
new dean.
"Our results would say you can't come anywhere close to
counting on that to solve the global warming problem," he
added in an interview.
Circles of towers at FACE are bathing 100-foot diameter swaths
of predominantly loblolly pine forests with 1 1/2 times Earth's
current atmospheric concentrations of CO2. Those levels are
expected to be the norm everywhere by about 2050 because of
human activities such as fossil fuel burning and land clearing.
That carbon dioxide glut is primarily of concern because
CO2 traps the sun's heat in the atmosphere. Rising
levels of the gas are already beginning to warm the Earth,
scientists believe, and continuing pollution only will lead
to more global warming.
Researchers also want to know how surplus carbon dioxide
will change forest plants and trees that take in the gas from
the air and incorporate it into fiber. And that's what FACE
investigations, coordinated and administered by scientists
at the Nicholas School's Division of Environmental Sciences
and Policy, are beginning to measure.
"The FACE experiment in the Duke Forest is unique in that
it provides a large-scale, long-term experiment of how forests
will respond to the atmosphere of the future," Schlesinger
said. "We may expect changes in tree growth, water use, and
susceptibility to attack by insects and pathogens.
"Changes in forest biomass, or in the amount of carbon stored
in soil organic matter, will affect the rise of carbon dioxide
in the atmosphere, which affects the Earth's climate," he
continued. "With FACE, we can study these variables and offer
experiment-based estimates of carbon storage that are of immediate
use to policy makers around the world."
Publishing their findings in the most prestigious research
journals, scientists from around the United States who work
at FACE already have found that tree response to CO2
can be dramatic, though subject to change over time.
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