Land Use and Climate Shifts

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WORLDWIDE FOREST/BIODIVERSITY CAMPAIGN NEWS

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Forest Networking a Project of Ecological Enterprises

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12/11/98

OVERVIEW & COMMENTARY by EE

Land use is an important component of climate change, the following

article reports. Major landscape alterations, including intensive

farming and logging, are implicated for causing major changes in

precipitation and other climatic effects. Increasingly, I have become

aware of the system connections between deforestation and the

greenhouse effect, and the fact that solutions for either will require

addressing both concurrently.

g.b.

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Title: Study: Land Use as Important as Emissions in Climate Shifts

Source: Associated Press

Date: December 9, 1998

SAN FRANCISCO (AP) -- Intensive farming, logging and other landscape

changes play a major role in the world's climate, say scientists who

also report that the 20th century is the warmest in 1,200 years.

Wholesale changes in the land coincide with rising temperatures and

rainfall shifts in a role equal to that of the usual suspect of global

warming -- industrial pollution from factories, power plants and

traffic.

The conclusions, discussed Tuesday at the meeting of the American

Geophysical Union, were based on computer model simulations and field

observations across the globe, from South America to Africa to

Florida.

The findings suggest that international guidelines under negotiation

to control climate change by limiting industrial emissions may also

need to target farmers, loggers and developers.

"Land use is a significant contributor to climate change," said

climatologist Jonathan Foley of the University of Wisconsin. "It's as

important as what you do to the climate when you double carbon dioxide

in the atmosphere."

In a separate study, researchers at the National Oceanographic and

Atmospheric Administration said the 20th century is the warmest in the

past 1,200 years. They based the conclusion on ancient climate

information trapped in cores from glaciers and ocean sediments sampled

around the world.

The warming trend coincides with land-use changes on several

continents as human populations grew and farming expanded, researchers

said.

"Twentieth century warming is real," said NOAA's Jonathan Overpeck.

Foley's examination of the Amazon River basin in Brazil found that

cutting down the rain forest not only reduces its ability to store

carbon dioxide, but the bare land left after deforestation cannot

return as much water to the atmosphere.

Annual rainfall is reduced by as much as 20 percent in some places,

according to a computer simulation by Foley and scientists in Brazil.

"The ability of the land to cool itself is diminished," he said.

In southern Florida, swamp draining for construction and farming this

century raised local temperatures by an average of at least a half-

degree, said Roger Pielke, a Colorado State University atmospheric

scientist who co-authored the study. That's sufficient to be

considered more than the climate's natural variability.

Summer precipitation is reduced by 10 percent after the landscape

changes, he said.

"Perhaps the wildfires this summer in Florida were exacerbated by the

degree of landscape change," Pielke said.

Similar changes were observed in southeast Asia, north Africa and

other locations. Stripped land that once was covered by vegetation

cannot store heat, and releases it into the atmosphere, upsetting the

climate balance, said Elfatih Eltahir, an environmental engineer at

the Massachusetts Institute of Technology.

Climate change isn't always limited to drier conditions, however. The

switch in the past century from prairie to irrigated farmland in Texas

and Oklahoma has resulted in an increase in thunderstorms there,

Pielke said.

The authors also said more study is need to see how changes have

contributed to climate shifts over long periods of time.

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