| There are roughly 16 million square miles of
forest on Earth (or 42 million square kilometers), a swath that
covers almost a third of the land surface. Those wooded environments
play a key role in both mitigating and
enhancing the strength of global warming.
NCAR researcher Gordon
Bonan reviewed the current state of understanding of how
forests affect global climate for a
special issue of Science on Forest Ecology that
hit newstands on June 12, 2008.
"As politicians and the general public become more aware
of climate change, there will be greater interest in legislative
policies to mitigate global warming," says Bonan. "Forests
have been proposed as a possible solution, so it is imperative
that we understand fully how forests influence climate."
The teeming life of forests, and the physical structures containing
them, are in continuous flux with incoming solar energy, the
atmosphere, the water cycle and the carbon cycle—in addition
to the influences of human activities. The complex relationships
both add to and subtract from the equations that dictate the warming
of the planet.
"In the Amazon, tropical rainforests remove carbon dioxide
from the atmosphere," says Bonan. "This helps mitigate
global warming by lowering greenhouse
gas concentrations in the atmosphere. These forests also
pump moisture into the atmosphere through evapotranspiration.
This cools climate and also helps to mitigate global warming."
While even the earliest European settlers in North America recognized
that the downing of forests affected local climates, the global
impact of such activities has been uncovered over more recent
decades as new methods, analytical tools, satellites, and computer
models have revealed the global harm that forest devastation
can cause.
Calculating the specific harm from a specific local impact is
a highly complicated problem involving the mechanisms behind
these effects, and the effects themselves.
"We need better understanding of the many influences of
forests on climate, both positive and negative feedbacks, and
how these will change as climate changes," says Bonan. "Then
we can begin to identify and understand the potential of forests
to mitigate global warming."
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 Webcast: Forests and Climate Change. NSF's
Josh Chamot talks with
NCAR scientist Gordon Bonan about
how forests affect climate. Bonan
discusses how forests can both cool and, in some cases,
warm our planet and describes efforts to better understand
the complicated feedbacks between forests and climate.
Click here or
on the image to open an NSF page where the webcast can
be launched. (Video courtesy National Science Foundation/National
Center for Atmospheric Research.)
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Forests
play an integral role in Earth's climate. Each
forest type—tropical, temperate and boreal—has
varying impacts on the climate, serving to both cool
and warm the Earth. Forests help reduce global warming
by absorbing an important greenhouse gas, carbon dioxide,
through photosynthesis and by cooling the atmosphere
through evaporation and transpiration. However, some
forests, such as boreal forests in the northern latitudes,
can be darker than their surrounding terrain and absorb
the Sun's energy more readily, which can lead to increasing
warming. The play between these competing influences
is an area that scientists are intensely studying. [ENLARGE] (Illustration
by Nicolle Rager Fuller, National Science Foundation.) |
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| Nearly a third of
Earth's landmass is forested. Different species
of vegetation have adapted to conditions near the equator
(tropical),
mid-way between the equator and the poles (temperate),
and closest to the poles (boreal,
also called taiga). Each forest type has differing
influences on local, regional and global climate. [ENLARGE] (Illustration
by Nicolle Rager Fuller, National Science Foundation.) |
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• by
Joshua A. Chamot
National Science Foundation
Spring-Summer 2008 |
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