Satellite Images Reveal Amazon Forest Shrinking Faster

[Guest guest]

Source >

http://news./s/csm/20051021/wl_csm/odeforest_1

 

Satellite images reveal Amazon forest shrinking faster

 

By Peter N. Spotts, Staff writer of The Christian

Science Monitor Fri Oct 21, 4:00 AM ET

 

Brazil's

Amazon rain forest - one of the most biologically

productive regions on the planet - is disappearing

twice as fast as scientists previously estimated.

 

 

That is the stark conclusion ecologist Gregory Asner

and his colleagues reached after developing a new way

to analyze satellite images to track logging there.

 

The team traces the additional loss to illegal

selective logging, which removes trees piecemeal from

a forest, rather than carving large swaths. This has

made it easier to hide. This project is the first time

satellites have been used to track selective logging.

 

For the region, this activity increases the forest's

vulnerability to wildfires and undermines its

biological productivity. Illegal selective logging in

the region releases nearly 100 million tons of

additional carbon dioxide into the atmosphere each

year.

 

Ecologists and Brazilian officials long have known

that illegal selective logging occurs, says Dr. Asner,

a researcher at the Carnegie Institution's Department

of Global Ecology, based at Stanford University in

Palo Alto, Calif. But gauging its extent by looking at

changes in forest cover has been difficult. Sawmill

surveys can yield results that either are incomplete

or unreliable. Previous methods for analyzing Landsat

satellite images couldn't render such tiny details.

 

Asner and his colleagues suspected their more tightly

focused view would bring bad news. But the extent of

the damage still surprised them. As the team huddled

around a supercomputer terminal watching the first

numbers emerge, " They were more than double what I

expected, " Asner recalls. " It's exciting science, but

sobering. "

 

For Daniel Nepstad, an ecologist at the Woods Hole

Research Center an environmental policy and research

organization in Woods Hole, Mass., the study " puts to

rest a long-standing debate about how extensive

selective logging is in the Amazon. "

 

The results come from new supercomputer software the

team developed. Over several years, the research group

- which included scientists from Brazil - gradually

squeezed more detail out of satellite images.

Initially the team could detect changes to a patch of

forest roughly 14 miles on a side. That shrank to a

patch 98 feet on a side - small enough to spot the

holes selective logging leave in the forest canopy.

Asner's group fed Landsat images from 1999 to 2002

into the computer, which hunted for the telltale

holes.

 

The results boosted the estimates of deforestation

during the period from 60 to 123 percent, depending on

which of the five logging-intensive Brazilian states

they examined. The group verified the results with

field surveys. Their results appear in Friday's

edition of the journal Science.

 

Over the long term, Asner adds, he plans to use the

technique to look at other tropical rain forests, such

as those in Peru and Bolivia.

 

Deforestation can radically alter the environmental

" services " the forests provide - from scrubbing the

atmosphere of CO2 and harboring useful plants and

animals to reducing erosion.

 

For example, in a related Science research paper,

Columbia University ecologist Daniel Bunker and

colleagues found that above-ground carbon storage

varied widely, depending on which tree species vanish

from within a patch of tropical rain forest and what

triggered their loss.

 

In a 123-acre tropical-forest research site in Panama,

they experimented with different mixes of species. The

results show that carbon storage is strongly

influenced by the types of trees present and the ways

in which they are lost. Selective logging of prized

hardwoods removes a small number of species from a

forest. But it substantially reduces the forest's

above-ground carbon storage because the lost wood is

dense.

 

The bottom line, Dr. Bunker says, is that preserving

species diversity may be the best way to ensure humans

continue to reap the services healthy ecosystems

provide.

 

 

 

 

 

 

 

Start your day with - Make it your home page!

http://www./r/hs