Spare the Tree or You May Spoil More Than the Jungle

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WORLDWIDE FOREST/BIODIVERSITY CAMPAIGN NEWS

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Forest Networking a Project of Ecological Enterprises

http://forests.org/

1/13/98

OVERVIEW, SOURCE & COMMENTARY by EE

The Christian Science Monitor reports on recent forest conservation

research. Studies indicate that changing the vegetation on a landscape can

dry out formerly lush areas. A fascinating theory holds that the arid

regions of Australia may have become so through human clearing of

vegetation. The findings could be a warning that wholesale forest

destruction changes the way land absorbs and reflects sunshine and radiates

heat, resulting in changes to precipitation patterns. While anecdotal

evidence around large forest areas I have seen in Papua New Guinea support

this hypothesis, this scientific report lends extra credence to the links

between forest cover and climatic stability.

Additionally, research in the Amazon rainforest indicates that trees in

tropical rainforests there have ages ranging from 200 years to 1,400 years.

Such ancient trees in significant numbers "suggests that sustainable forest

management will require either enormous areas of managed forest or long

harvesting cycles." It is amazing how little we know about forests,

tropical rainforest in particular, despite their integral role in

maintaining the Earth upon which we depend. Our evolutionary brilliance is

tarnished as we continue to dismantle the World's ecological structures.

g.b.

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Title: If You Don't Spare The Tree, You May Spoil More Than the

Jungle

Source: Christian Science Monitor

Date: Tuesday January 13, 1998

Byline: Robert C. Cowen, Staff writer

BOSTON -- Earth scientist Gifford Miller has a warning for destroyers

of tropical jungles and other natural-plant communities: Spare that

tree and safeguard your climate.

His research in Australia suggests that, if it weren't for human

depredation, the dry outback might be a wetter, more hospitable place today.

Widespread burning starting about 45,000 years ago may have replaced

vegetation that favors rainfall with vegetation that discourages it.

A careful scientist and chairman of the University of Colorado's geological-

sciences department at Boulder, Dr. Miller was restrained in his

presentation of this ongoing research at a meeting of the American

Geophysical Union in San Francisco last month. He noted that

he and his colleagues do not yet have definitive proof of the human-climate-

change connection.

In a recent telephone interview, however, he explained that their research

has already made two important points. First, human occupation coincided

with significant change of vegetation. Second, lake sediments show it also

coincided with a significant increase in

annual monsoon rainfall over a wide region, including Africa and India. Yet

Australia's monsoon rains faltered.

INSET:

NO LONGER A JUNGLE OUT THERE: Children play on lumber from the Amazon

rain forest in Paraopeas, Brazil. New research indicates that

changing the vegetation landscape can dry out formerly lush areas.

Miller added that "the only thing [operational] on a large-enough scale" to

account for this anomaly is vegetation change. Computer-based simulations

that Miller and his colleagues have run indicate that a vegetated interior

Australia would enjoy twice as much rain as it now receives in monsoon

season.

The climate change that strengthened monsoons elsewhere probably was linked

to known periodic changes in solar energy that are due to periodic changes

in Earth's orbit around the sun. The computer studies indicate that the

effect of vegetative change "is even stronger than" these well-known orbital

effects.

A smoking gun

Miller concludes that "we've got a smoking gun" pointing to vegetation

change as the factor that made interior Australia dry. It remains to be

proved conclusively that the "smoke" came from humanly set fires.

Meanwhile, Miller says the findings so far "should be a warning" against

wholesale forest destruction. Changes in vegetation cover can change the way

land absorbs and reflects sunshine and radiates heat. They can change

precipitation patterns.

Plants recycle moisture locally by absorbing rain water through their roots

and transpiring it back into the air through their leaves. Half of the

Amazon jungle precipitation is recycled in this way during the rainy season.

Such vegetation effects are part of a complex climate system involving

land, sea, and air. Replacing forest with grass land or lush grassland

with dryland scrub can have unintended long-term climate effects. "Without

knowing what those consequences are, we should proceed with caution [in

making changes]," Miller warns.

Trying to understand those consequences is a daunting task. Just pinning

down the nature of Australia's prehuman vegetation is tough. The alkaline

soil doesn't preserve fossil vegetation or pollen. However, fossil eggshells

from Australia's flightless birds hold clues to what the birds were eating

tens of thousands of years ago. Miller's study already shows that a more

arid and mixed vegetation was replacing lush grasses by 35,000 years ago.

Many unknowns

Meanwhile, scientists continue to find how little they know about tropical

rain forests. For example, understanding the age distribution of trees is

basic to understanding the ecology of a forest.

You can't count tree rings because the lack of seasonality means annual tree

rings don't form. Jeffrey Chambers at the University of California, Santa

Barbara, and colleagues report a study using radio-carbon dating in the

current issue of Nature. They sampled 20 trees from 13 species near Manaus

in Brazil.

They find, to their surprise, that ages range from 200 years to 1,400 years.

They observe that the presence of ancient trees in significant numbers

suggests that sustainable forest management will require either enormous

areas of managed forest or long harvesting cycles.

As another example, an international team made a pilot study of what happens

to the diversity of plants and animals when tropical jungle is disturbed.

They worked in the Mbalmayo Forest Reserve in Cameroon. Ecologists often try

to estimate biodiversity by studying a few "indicator" species. In the Jan.

1 issue of Nature, the team says this quick-and-dirty scheme can give

"highly misleading" results. The team adds that to complete a comprehensive

study for a single representative hectare (2.5 acres) "in a reasonable time"

would "absorb 10 to 20 percent of the estimated entire global work force of

7,000 [qualified experts]."

Scientists have scarcely begun to understand the long-term impact of changes

in vegetation. They know that gaining such understanding will take a far

greater effort than now is being devoted to the job. As Miller said, unless

and until that effort is made, we "should proceed with caution" in altering

the vegetation landscape.

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