Land Use Changes Cause Significant Carbon Loss

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WORLDWIDE FOREST/BIODIVERSITY CAMPAIGN NEWS

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8/14/99

OVERVIEW & COMMENTARY by EE

Climate change and land-use caused ecosystem changes are intimately

related. Scientists estimate that logging, burning and agriculture

are the second major source of human induced carbon, having

contributed 75% as much carbon to the atmosphere as fossil fuel use.

While it is not as simple as planting trees to stop climate change,

increased understanding of the carbon cycle should provide strong

scientific basis for stopping deforestation, preserving remaining old-

growth ancient forests, restoration ecology and plantations--all as a

portion of a more comprehensive plan to reign in the internal

combustion engine and pursue sustainable energy sources.

g.b.

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Title: Land Use Changes Cause Significant Carbon Loss

Source: UniSci - Daily University Science News

Contact: Chris Field, Ellen Carpenter

http://unisci.com/

Date: August 11, 1999

Scientists will report today that the amount of vegetation that has

been lost to logging, burning and agriculture throughout human history

is the equivalent of about 180 billion tons of carbon -- carbon

transferred to the atmosphere as the greenhouse gas carbon dioxide.

This report is to be issued at today's meeting of the Ecological

Society of America in Spokane, Washington.

Since the dawn of the industrial age, fossil fuel use by humans has

been the main source of carbon dioxide added to the atmosphere.

However, according to Christopher Field, a Carnegie Institution of

Washington biologist and coauthor of the study, the net amount of

carbon emitted from land-use changes over time is about seventy-five

percent of the total amount of carbon emitted from fossil fuel

burning.

Previous calculations of carbon losses from changes in Earth's

vegetation compared the way things were in 1850 to the way things are

today. In the first study taking into account human land use prior to

the mid-1800s, Field and Ruth DeFries, a University of Maryland

geographer and lead author of the paper, found that an additional 60

billion tons of carbon was lost before the industrial age.

"There has been a huge loss of carbon from the world's ecosystem over

the time that humans have been involved in agriculture, and this loss

has intensified terrifically in the last few centuries," said Field.

DeFries and Field's study used an "untouched-by-human-hands" model of

the Earth's vegetation cover extrapolated from current land-use data

and compared the model to data collected by National Oceanographic and

Atmospheric Association (NOAA) satellites.

"We take into account existing vegetation and compare it to our best

guess of what the Earth would be like if humans did not disturb the

landscape," said DeFries.

The study looked at carbon loss by considering areas where forests

were turned into cropland or pasture, where woodlands have been

degraded, and where savannas have turned into desert as a result of

human activity.

Today, the bulk of carbon lost from the Earth's vegetation is in the

tropics, where forests are burned for agricultural purposes, but this

was not always the case.

Prior to 1850, massive portions of European, Asian, and North American

forests were cleared. At that time, humans were not concerned about

adding carbon to the atmosphere or its effect on global temperatures.

Although today the deforestation problem is mainly confined to the

tropics, "historically, it was a much more global problem," said

Field. "It's simply that we had deforested much of the mid-latitudes

before the start of the century."

The largest amount of carbon loss came from Asia with about 70 billion

tons. North America, Europe and Africa lost between 20 and 30 billion

tons each since humans began altering the landscape, according to the

study.

Today, a variety of practices, including farmland abandonment and

subsequent forest regrowth in the mid-latitudes; changing agricultural

practices; and prevention of forest fires are helping to generate

plant growth and take up carbon dioxide during photosynthesis.

But, Field warned, new studies show that the carbon dioxide taken up

by regrowing forests can't possibly compensate for the amount that

humans are currently adding to the atmosphere. "It's not going to grow

us out of the carbon problem," he said.

The study is supported by NASA's Earth Observing System (EOS) as part

of an interdisciplinary science team to study the interactions between

Earth's atmosphere and biosphere.

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