Northern Hemisphere is growing greener
Published 9:00 pm Wednesday, September 5, 2001
Associated Press
WASHINGTON — The Northern Hemisphere has been getting greener, according to researchers studying satellite data.
They say plant life north of 40 degrees north latitude — roughly that of New York, Madrid, Spain and Beijing — has been growing more vigorously since 1981. The researchers say the growth could be the result of warmer temperatures.
"When we looked at temperature and satellite vegetation data, we saw that year to year changes in growth and duration of the growing season of northern vegetation are tightly linked to year-to-year changes in temperature," Liming Zhou of Boston University said in a statement.
The area of vegetation has not extended, but the existing vegetation has increased in density, he said.
The report by Zhou, as well as others at Boston University and NASA’s Goddard Space Flight Center in Greenbelt, Md., will appear in the September 16 issue of the Journal of Geophysical Research —- Atmospheres, published by the American Geophysical Union.
They found the increased greening of Europe and Asia was especially persistent over a broad swath of land from central Europe through Siberia to far-east Russia, where most of the vegetation is forests and woodlands.
In North America, there was a fragmented pattern of change notable only in the forests of the east and grasslands of the upper Midwest.
They also found dramatic changes in the timing of both the appearance and fall of leaves over the two decades of satellite data.
The growing season is now an average of almost 18 days longer in Eurasia, they said, with spring arriving a week early and autumn delayed by 10 days.
In North America, the growing season appears to be as much as 12 days longer.
Carbon dioxide, a major component of the gases thought to be causing the so-called greenhouse warming of the earth, is absorbed by vegetation. If the northern forests are greening, they may already be taking in carbon, the researchers speculated.
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