From: Glen Barry
Subject: BIOD: Spare Trees or Spoil the Jungle
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Spare the Tree or You May Spoil More Than the Jungle
Forest Networking a Project of Ecological Enterprises

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.


Title:   If You Don't Spare The Tree, You May Spoil More Than the
Source:  Christian Science Monitor
Status:  Copyright 1998 by source, contact for reprint permissions
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.

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

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

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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