APAJÓS
NATIONAL FOREST, Brazil — Viewed from the top of a tower 150 feet over
an exuberant canopy of green, the vast Amazon jungle appears to be a
neatly functioning organism. Trees in immeasurable numbers stretch
away to the horizon here, their leaves open to the sun, eager to feed
on the light that streams down from the sky and perforates the
stifling tropical heat.
Down on the ground, however, the longstanding debate about the
Amazon's role in global climate change is intensifying. The Amazon is
the largest tropical forest in the world — bigger than all of Europe,
with Brazil's section alone more than half the size of the continental
United States. And it has always been assumed to be essential to
inhibiting global warming by drawing in carbon dioxide during
photosynthesis.
Carbon dioxide is one of the main gases that contribute to global
warming and the much-dreaded greenhouse effect. But it has never been
established whether the rain forest here is in fact functioning as a
giant sink that "sequesters," or traps and absorbs, carbon.
Some scientists have suggested that indiscriminate deforestation
has turned the Amazon into a net source of such gases, spewing huge
amounts of carbon dioxide into the air.
Scientists have been investigating that question for a decade now,
and the answer is sure to have important political and scientific
ramifications both for Brazil and the rest of the world.
If in fact the Amazon is a net source of carbon gas emissions, or
if the amounts of gas emitted and sequestered are in a rough permanent
equilibrium, some of the fundamental assumptions of the 1998 Kyoto
Protocol on climate change may have to be reconsidered. No one knows
precisely the amount of greenhouse gases that Brazil is already
pumping into the atmosphere. A national inventory of carbon emissions,
due to have been announced four years ago, has still not been made
public. And although the new left-wing government that took power in
Brasília early this year was elected with the support of
environmentalists, it has given no indication when it intends to
publish those figures.
Scientists at the National Institute for Amazon Research in Manaus
estimate that carbon emissions in Brazil may have risen by as much as
50 percent since 1990. By their calculations, what is euphemistically
called "land use changes" now produce annual emissions of 400 million
tons of greenhouse gases, dwarfing the 90 million tons generated
annually by fossil fuel use in Brazil and making this country one of
the 10 leading emitters of greenhouse gases in the world.
All across the Brazilian Amazon, the jungle is being razed for
cattle pasture, crops, logging, highways and human settlements at an
increasingly faster rate, contributing to fears that the climate
balance here may soon be permanently tipped. Last year alone, the land
that was deforested rose by 40 percent over 2001, to nearly 10,000
square miles, an area larger than New Jersey.
Brazilian scientists, in conjunction with American and European
colleagues, are engaged in what is known as the "Large-Scale
Bio-Atmosphere Experiment in the Amazon," or L.B.A. The goal is to
resolve uncertainties about carbon emissions. Begun in the mid-1990's,
the program gathers data at 15 sites, including two in this national
forest about 50 miles south of the confluence of the Tapajós River and
the Amazon.
At each location, a tower 195 feet high measures the jungle's
emissions of carbon dioxide and other gases and also collects readings
of wind velocity and direction. To get a picture as broad and accurate
as possible, some measuring posts have been placed on flat land, some
in sloping areas, others in virgin forest and others still in
"disturbed forest," where logging has occurred and secondary growth is
present.
"Right now we cannot provide a definitive answer to the question of
whether the Amazon is source or sink," Dr. Flavio Luizão, president of
the International Scientific Committee of the L.B.A., said in an
interview in Manaus. "But in another three or four years, I think we
will be able to reach a consensus."
Initial readings published in 1995 were so extraordinarily high,
showing up to nine tons of carbon sequestered yearly on each 2.5 acre
plot, that scientists began to question both their results and their
methodology. For one thing, they could not find the forest itself
growing at the rapid rate implied by those figures.
Since then, years of additional measurements point to a more modest
but still crucial role for the Amazon in absorbing emissions of carbon
dioxide. Even if the forest were storing one ton per 2.5 acres, the
estimate now most commonly cited by researchers, it would be trapping
nearly 100 million tons of carbon dioxide each year.
"Each locale has its own specificities," said Dr. Antônio Manzi of
the Amazon research institute, who oversees the data-gathering
program. "But generally there is a bit of sequestering of carbon" by
the forest in its natural state.
If that is true, the jungle's ability to store carbon gas
diminishes as deforestation advances and may eventually reach a
saturation point as the amount of land razed grows. But researchers
stress that the Amazon is important in climate change because the
jungle plays an additional role in the global warming debate that is
independent of the question of whether it traps and absorbs carbon
gases.
"Deforestation itself is a major contributor to global warming,"
said Dr. Stephan Schwartzman, senior scientist at the Washington-based
group Environmental Defense. "Just deforestation in the Amazon and
fires, especially in El Niño years, are themselves perfectly capable
of annulling any gains from the Kyoto Protocol as it now stands."
Natural factors may hurt the forest as well, contributing to the
problem. The threat posed by the extremely dry conditions that prevail
in the Amazon during increasingly frequent El Niño years is being
documented in an experiment conducted by the Amazon Institute for
Environmental Research, or IPAM. Extended dry periods can hurt the
forest and diminish its capacity to grow and store carbon.
"Even with current rainfall systems, many forests are coming close
to the limit where they shed their protective layer and become
vulnerable to burning or slowed-down growth and die," said Dr. Dan
Nepstad, an American scientist who works both with IPAM and the Woods
Hole Research Center in Massachusetts. "By replacing the forest with
pasture, you will clearly exacerbate drought and contribute to lower
levels of fixed carbon."
Brazil has not put forth a consistent position on how to handle
global warming, although both officials and the popular press
criticize the United States as the principal culprit. Brazil is not a
signer of the section of the Kyoto Protocol that promises reduced
carbon emissions and has also opposed some important aspects of the
"clean development mechanism" in the convention.
"As a developing country and in observance of the principle of
common but differentiated responsibilities, Brazil is not obliged to
reach targets in the reduction of greenhouse effect gases," the
Brazilian Foreign Ministry said in a statement released in response to
a request for comment on its position.
But perhaps the aspect of government policy that scientists here
and abroad find most puzzling is Brazil's two-pronged position on the
issue of so-called carbon credits.
Brazil supports the notion of awarding such payments for replanting
in areas where forests have already been razed, but opposes the
granting of such credits for "avoided deforestation" and in fact has
itself passed up opportunities to take advantage of those credits
itself.
The Environmental Ministry is on record favoring such credits, but
the Foreign Ministry is officially opposed for reasons that are not
fully clear, and it is the Foreign Ministry that ultimately controls
Brazilian policy on the issue.
The issue of carbon emissions is a politically charged issue here.
Brazil bristles at any suggestion by foreigners that its stewardship
over the bulk of the world's largest remaining tropical forest is in
any way deficient, and many Brazilians also believe that global
efforts to monitor and limit deforestation are merely a smoke screen
to bring about the "internationalization" of the Amazon, along the
lines of Antarctica.
Some government officials have gone so far as to argue that Brazil
produces no emissions whatsoever from deforestation, maintaining that
crops planted after deforestation absorb all of the carbon produced.
But studies by the National Institute for Amazon Research indicate
that only 7 percent of carbon emissions are reabsorbed by planted
crops.
"The rest of the tropics is going to run out of forest before the
Amazon does," Dr. Philip M. Fearnside, director of the ecology program
at the Amazon research institute, predicted. "The last acres, the last
big areas of tropical carbon stocks left standing in the world, are
here. That is why what happens here in Brazil, what the government
eventually decides to do, is more important than ever."