Rainforest Fails to Absorb Excess Carbon During El Nino

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WORLDWIDE FOREST/BIODIVERSITY CAMPAIGN NEWS

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12/22/98

OVERVIEW & COMMENTARY by EE

A recently published study by Woods Hole Research Laboratory in the

journal Nature suggests that the Brazilian Amazon actually releases

millions of tons of carbon during El Nino years, the reverse of what

is usually the case--and some 2/7 of what it usually fixes in a year.

This may have tremendous implications for global climate change.

g.b.

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Title: Rain Forest Fails to Absorb Excess Carbon during El Nino

Source: Associated Press

Date: December 17, 1998

Byline: JOSEPH B. VERRENGIA AP Science Writer

Instead of inhaling extra carbon dioxide, Brazil's rain forest does

the opposite in an El Nino year, exhaling millions of tons of the

heat-trapping gas and potentially adding to global warming, scientists

say.

The rain forest, under normal conditions, acts as the "lungs" of the

planet. Its dense canopy of trees stretches for thousands of miles,

releasing oxygen and absorbing as much as 700 million tons of carbon

dioxide a year.

But when global climate conditions are scrambled by El Nino and the

rain forest becomes parched, scientists from the Woods Hole Research

Laboratory in Massachusetts determined the Amazon Basin produces as

much as 200 million tons of excess carbon dioxide a year.

The calculations by Hanqin Tian and others are in today's journal

Nature. The study examined three El Nino episodes from 1980 to 1994.

It did not include measurements of the record-setting El Nino in 1997-

98, but the trend is clear, researchers said.

"In El Nino years, which bring hot and dry weather to much of the

Amazon, the ecosystems act as a source of carbon," Tian said.

Scientists say understanding the planet's fluctuating carbon cycle is

a key step in accurately predicting -- and managing -- global warming

in the 21st century.

Some studies show global temperatures have been creeping up by as much

as one degree as industry, traffic, deforestation and other human

activities generate more carbon dioxide and other greenhouse gases --

so called because they trap heat from the sun.

Many natural features on the planet act as "carbon sinks" to absorb

excess carbon and help to stabilize the planet's climate. The oceans

and the rain forests absorb the largest shares, along with tundra and

rangeland.

But not always.

During an El Nino, a vast pool of warm water expands in the equatorial

Pacific. It upsets weather patterns around the world. In the Amazon,

it triggers severe droughts.

Under such severe stress, the forest can't adequately photosynthesize

and store carbon dioxide, Tian said.

His results correspond with the results of carbon cycle simulation

developed at the Max Planck Institute in Germany, which developed a

computer model showing the Amazon acting as a carbon source during

three El Nino episodes between 1982-94.

Researchers at Max Planck said the Woods Hole study is based on

limited field measurements in a small sampling area, and failed to

answer the fundamental question of what is canceling the rain forest's

role as a carbon sink.

"Such understanding is crucial for long-term predictions," said Colin

Prentice, who with Planck colleague Jon Lloyd reviewed the new study

for Nature.

Several groups of scientists are trying to understand the world's

carbon cycle.

Last week, researchers launched a three-year study to find the

"missing sink" to account for lower-than-expected carbon dioxide

levels in the Northern Hemisphere. A likely suspect: trees that have

regrown in previously logged forests and farmland.

"Something in the Northern Hemisphere is sucking up the carbon," said

climatologist Kevin Gurney of Colorado State University. "The missing

sink isn't new, but where it is located and how it works are still

unresolved."

Because of the hemisphere's large cities and industrialization, carbon

dioxide levels are expected to be higher. But measured carbon

emissions have been 2 billion tons lower than expected in recent

years.

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