Land Use and Climate Shifts
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.
*******************************
RELAYED TEXT STARTS HERE:
Title: Study: Land Use as Important as Emissions in Climate Shifts
Source: Associated Press
Status: Copyright 1998, contact source for permission to reprint
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.