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FOREST CONSERVATION NEWS TODAY

Carbon Sinks Useful but Not Permanent

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11/10/01

OVERVIEW & COMMENTARY by Forests.org

A new study in the journal "Nature" concludes that land and ocean

processes have protected the atmosphere by absorbing some of the

excess carbon dioxide released from the burning of fossil fuels and

deforestation, but this effect is not likely to be permanent. Land

use changes in the Northern Hemisphere have been partly responsible

for carbon uptake during the 1990s. In the U.S., trees and other

growth expanded on abandoned agricultural land and a reduction in

fires allowed forests to spread. Increased plant growth spurred by

increasing carbon dioxide and nitrogen deposits - a process more

noticeable in Europe and Asia - also helped remove carbon dioxide.

But there is a limit to how much forests can fill in and spread.

Eventually new trees and grasses reach maturity and soak up less

carbon dioxide. In addition, global climate change may have impacts

upon the well-being of ecosystems and cause them to decline in extent

and vigor. Warm and dry weather was found to reduce the ability of

terrestrial ecosystems to act as global sinks. The study concludes

that while sinks have a role to play in absorbing excess carbon

dioxide, it is possible that the net global terrestrial carbon sink

may disappear altogether in the future.

The amount of carbon able to be stored by carbon sinks is far less

than the quantities emitted by burning fossil fuels. The failure of

the World's leaders to heed the best scientific knowledge in regard

to the efficacy of carbon sinks, and their emphasis upon carbon sinks

in recent Kyoto negotiations, is hindering the development of policy

adequate to address the looming climate crisis. Effective climate

change policy must focus tightly upon reducing emissions, replacing

fossil fuels with renewable energy sources, energy conservation and

efficiency, and ending deforestation while increasing the extent of

regenerating natural forests.

Expanding the extent of large, mature natural forests is the

terrestrial carbon sink strategy most likely to achieve relatively

permanent carbon storage. The emphasis should be upon preventing

further carbon release through deforestation and other land-use

changes, and maximizing the likelihood of new long-term carbon

sequestration. This is best achieved through preservation of large

and strictly protected old growth forest ecosystems, and regeneration

and restoration of widespread late-successional natural standing

forests that are benignly managed. An emphasis upon industrial

forest plantations where natural forests have been cleared must be

resoundingly rejected. Forest conservation is a requirement for

global ecological sustainability.

g.b.

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Title: Study Casts Doubt on Uses of Carbon Sinks

Source: Copyright 2001 Environment News Service

Date: November 8, 2001

Byline: Cat Lazaroff

WASHINGTON, DC, November 8, 2001 (ENS) - The earth's land based

ecosystems absorbed all of the carbon released by deforestation plus

another 1.4 billion tons emitted by fossil fuel burning during the

1990s, a new study suggests. But the study also warns that so called

carbon sinks cannot be counted on to mop up carbon dioxide emissions

indefinitely.

Carbon dioxide (CO2) is the primary greenhouse gas entering the

atmosphere from human activities. Ongoing negotiations regarding

international efforts to reduce the impacts of greenhouse gases have

included discussions about carbon sinks - natural and manmade areas

where plant growth absorbs carbon emitted from human sources.

A study published this week in the journal "Nature" indicates that

carbon sinks were able to mop up most of the naturally and

artificially emitted carbon dioxide over the past decade. However,

with carbon emissions on the rise, and vegetated areas continuing to

shrink, that situation is likely to change, the researchers said.

"We could easily see this robust transfer of carbon out of the

atmosphere and into land based ecosystems that occurred in the

1990s slow down in the future," said the paper's lead author, David

Schimel, of the National Center for Atmospheric Research (NCAR).

Fossil fuel burning, cement manufacture, and deforestation gave off

about seven billion tons of carbon per year during the 1980s and

eight billion tons each year during the 1990s, about half of it

ending up in the earth's atmosphere, the study shows.

In the 1980s the amount of carbon released to the atmosphere from

deforestation about equaled that taken up by land ecosystems into

various sinks. During the 1990s the balance tipped, and 1.4 billion

tons more carbon ended up in land based ecosystems than in the

atmosphere, despite continuing deforestation.

"Land and ocean processes have, in essence, provided a major, but far

from permanent, subsidy to humans, protecting the atmosphere from

many of the consequences of deforestation and burning fossil fuels,"

said co-author professor Chris Field from the Carnegie Institution of

Washington.

Land use changes in the Northern Hemisphere have been partly

responsible for carbon uptake during the 1990s, the researchers

found. In the United States, trees and other growth expanded on

abandoned agricultural land, while a reduction in fires allowed

forests to spread. Increased plant growth spurred by increasing

carbon dioxide and nitrogen deposits - a process more noticeable

in Europe and Asia - also helped clear the air of CO2 buildup.

"Forests can only replace farms for so long," explained Schimel.

"Eventually new trees and grasses reach maturity and soak up less

carbon dioxide. Similarly, there's a limit to how much forests can

fill in and spread, even with successful fire suppression."

Over time, the effects of climate change on ecosystems will probably

reduce sinks globally, write the authors. Meanwhile, carbon dioxide

emissions are expected to continue to rise because of human

activities.

The results have potential implications for the Kyoto Protocol

negotiations now underway in Morocco. Under the Kyoto Protocol, an

addition to the United Nations framework climate change treaty, 38

industrialized nations have agreed to cut their emissions of six

greenhouse gases linked to global warming.

Recent difficulties in talks over the Protocol have included a lack

of scientific knowledge about the strength and distribution of carbon

sinks and how they vary from year to year.

The new "Nature" study, produced by a team of 30 leading carbon

scientists from around the world, draws on a large body of research

to build up a new and comprehensive picture of carbon sinks on land.

"It is a major step forward in understanding where terrestrial carbon

sinks actually are, why they are there, and how long they will

operate into the future," said Dr Will Steffen, one of the authors

and executive director of the International Geosphere-Biosphere

Programme (IGBP), which coordinated the production of the paper.

The paper represents a major advance in terms of reconciling two

different approaches to measuring the strength of carbon sinks and

sources. Historically, researchers have used two types of

measurements: 1) direct measurement of CO2 in the atmosphere, and

2) on the ground measurements on the basis of forest growth and soil

uptake etc. Until now, these two techniques have provided

inconsistent results.

In this study the authors show that, on the broad scale, they are

consistent. The authors point out that there are many regional

differences in the strength of terrestrial carbon sinks. Much of

Siberia, for example, has been warming at a rate of about 0.5o C per

decade since the 1960s and an increase in wild fires and insect

damage appears to have converted this region from a sink into a

temporary carbon source with considerable year to year variability.

"Although carbon sinks have a role to play in absorbing excess carbon

dioxide, it is possible that the net global terrestrial carbon sink

may disappear altogether in the future," said lead author Professor

David Schimel from the Max Planck Institute for Biogeochemistry in

Jena, Germany.

There is also considerable annual variability in sink strength

associated with climatic variations such as the El Nino Southern

Oscillation in tropical and nontropical regions. Globally, there

appears to be a net release of carbon to the atmosphere during

warm, dry years and a net uptake during cooler years.

"This observation gives a hint of how terrestrial sinks may

respond to longer term climate changes such as increased

temperatures," said Dr Steffen.

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