United States
Environmental Protection
Agency
Office of Policy,
Planning, and
Evaluation
EPA230-F-92-009
May 1992
oEFA
Climate Change
Discussion Series
Forests occupy one-third of the land
area of the United States. Trees pro-
vide wood products, improve air and
water quality, provide wildlife habi-
tat, and, through photosynthesis, re-
move carbon dioxide (C02) from the
atmosphere. Human alterations of for-
est ecosystems now account for C02
emissions equal to about 10 to 30 per-
cent of total global emissions from hu-
man activities (anthropogenic emis-
sions). Carbon stored in vegetation and
soils is released by clearing, fire, or de-
cay. The deforestation of Europe and
North America in the past contributed
to current global C02 levels. Now defor-
Forestry
estation of 17 million hectares of tropi-
cal forests each year—an area larger
than Austria or Tennessee—is eroding
the planefs photosynthetic base and
adding roughly 1 to 2 billion tons of
carbon (in the form of C02) to the
atmosphere annually. Limiting for-
est loss and planting new trees are
immediately available, proven tech-
nologies, as well as potentially cost-
effective means of reducing the build-
up of C02 in the atmosphere. Also,
tree growth reduces erosion, improves
water quality (decreases pesticide and
herbicide use on cropland) provides
alternative uses for marginal croplands,
increases timber supply, and creates
potential wildlife habitat. A1990 study
by the Intergovernmental Panel on
Climate Change, involving several hun-
dred scientists, concluded that a dou-
bling of C02 in the atmosphere would
most likely lead to a warming of 3" to
8°F (1.5° to 4.5°C) by the end of the
century. This warming and resulting
shifts in precipitation could have a
substantial impact on the quality of
forest ecosystems. In addition to tem-
perature and precipitation changes,
forests are sensitive to other factors
(e.g., pests, fire, C02 levels), influ-
enced by potential of climate change.
Reducing "Greenhouse Gas" Emissions
Increasing tree planting in
community areas
Every tree planted in an ur-
ban area not only takes up
C02, but it also shades build-
ings and pavement in hot
weather and shields build-
ings from winds in cold
weather. Thus, the trees re-
duce energy needed for air
conditioning and heating
and thereby reduce associ-
ated C02 emissions. Three
well-placed trees around a
house can cut home air-con-
ditioning energy needs by
10 to 50 percent.
Increasing tree planting on
privately owned lands and
improving management of
private non-industrial forest lands
Private forest lands—excluding land
in industrial ownership)—accounts for
57 percent of all U.S. forest lands.
Many crop and pasture lands, highly
erodible and marginally productive,
are suitable for tree planting. The
America the Beautiful Program, if fully
implemented, would plant one billion
trees per year on private lands for 20
years to achieve a few percent offset
The Benefits of Trees
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in U.S. fossil fuel emissions. This plant-
ing program will also be a component
of the U.S. Action Plan to mitigate
greenhouse gas emissions.
International Reforestation
Millions of hectares of degraded land
are potentially available for reforesta-
tion, especially in the tropics. Al-
though over one hundred million hect-
ares would have to-be planted to off-
set 10 percent of the world's
current annual fossil fuel
emission, preliminary esti-
mates suggest that the cost of
absorbed carbon could be
competitive with other op-
tions. If planting schemes
can be designed to meet the
need for forest products and
offset deforestation pressure
on primary forests, they will
have an added carbon ben-
efit. Furthermore, a refores-
tation strategy could offer a
stream of valuable ecological
and economic benefits in ad-
dition to reducing C02 con-
centrations, such as produc-
tion of forest products, main-
tenance of biodiversity, wa-
tershed protection, non-
point pollution reduction, and recre-
ation.
Increasing paper recycling
By lowering demand for new pa-
per, recycling could decrease en-
ergy related greenhouse gas emis-
sions from paper production and re-
duce greenhouse gas emissions by
slowing forest harvesting.
NOTE: Climate change refers to potential modification of the earth's climate resulting from increasing atmospheric concentrations of greenhouse gases such as carbon
dioxide (C02), methane (CH<), nitrous oxide (N20), and chlorofluorocarbons (CFCs). Through a naturally occurring process known as the "greenhouse effect," these
gases act lo warm the earth by trapping heat in the atmosphere. This process plays an important role in maintaining the earth's current temperature and climate. By
increasing concentrations of greenhouse gases, human activities are trapping more heat in the atmosphere and potentially changing the earth's climate.
Printed on Recycled Paper

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Potential Impacts
Changes in the range, productivity, and species
composition of forests
Future climates may no longer support the current
mix of species found in different regions of the
United States.
Forests may experience northward shifts in ranges
of species, as well as dieback of species along the south-
ern reaches as a result of higher temperatures, drier
soils, and other climatic changes or shifts in the cli-
matic belts of temperature and precipitation.
Changes may begin soon
A faster rate of mortality among mature trees, a de-
cline in seedlings, and a decline in growth of new spe-
cies may be visible in a few decades.
Climate change alters factors affecting forest health
Drier soils could lead to more frequent fires.
Wanner climates may cause the range of forest pests
and diseases to expand.
Climate change could also exacerbate stress on for-
ests caused by air pollution and continued depletion
of stratospheric ozone.
Higher C02 concentrations can increase growth and
reduce water demand. The combined effect of this with
higher temperatures is uncertain.
The response of forests to climate
change will not only affect timber
supplies, but will also affect biodiver-
sity, runoff, recreational opportuni-
ties, and the climate through feed-
back scenarios. Anticipatory actions
are necessary to prepare for the po-
tential impacts of climate change.
Today's forest management deci-
sions will determine the location and
composition of forests during the
next century when changes in climate
are likely. Potential adaptive re-
sponses include:
Maintaining forest diversity and extent
Potential mechanisms for maintain-
ing large and diverse forests include
strengthening and enlarging pro-
	Adaptation	
tected natural areas and creating con-
servation corridors (migratory path-
ways) between protected areas to ac-
commodate range shifts. Maintain-
ing diversity and extensiveness should
improve the resilience of forests by in-
creasing their ability to adapt to a wide
range of climate changes.
Modifying harvesting practices and for-
est and pest control programs
Harvesting practices that preserve
existing forest diversity, increase
species and age class diversity and
allow for rapid removal of dead or
dying trees, especially along south-
ern and lower-elevation boundaries,
could increase diversity and resil-
ience of forests.
Changes in current programs for fire
and pest monitoring and control may
be warranted in response to new and
more severe threats.
Developing and planting heat-, dmugfa-,
pest-resistant, fast-growing species and
varieties
Planting heat-, drought-, and pest-
resistant varieties in areas vulnerable
to dieback could also increase resil-
ience to climate change. In recent
years, some companies began plant-
ing such species on some of their
lands. Faster-growing trees would
enhance the ability of foresters to
shorten rotation times in response
to rapid changes in the climate.
Based upon the two EPA Reports to Congress, The Potential Effects of Global Climate Change On The United States, Washington, DC,
1989; and Policy Options for Stabilizing Global Climate., Washington, DC, 1989; and EPA's Adapting to Climate Change: What Govern-
ments Can Do, Washington, DC, 1991; and World Resources 1990-91 by World Resources Institute, Washington, DC, 1991
EPA's Climate Change Outreach Program is designed to raise awareness about climate change and provide assistance to state and local
governments, industry, and non-governmental organizations in the evaluation of cost-effective response strategies. For further information
about this program, please contact Joel Smith at 202/260-8825.
U.S. EPA Climate Change Discussion Series 1992
Global Climate Change	Sea Level Rise
Adaptation to	Transportation
Climate Change	Energy
Forestry	Water Resources
Agriculture	Biodiversity
Order from: CLIMATE CHANGE INFORMATION
US. EPA
Office of Policy Analysis
Climate Change Division (PM221)
401 M Street, SW.
Washington, DC 20460
USA
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