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Professor John Shepherd, co-author of study
"Land carbon sinks can only make a very modest contribution"
 real 28k

Sunday, 8 July, 2001, 23:34 GMT 00:34 UK
Carbon sinks 'little help to climate'
Pine forest WWW
Forests can absorb limited amounts of carbon dioxide
By BBC News Online's environment correspondent Alex Kirby

Scientists say relying on trees and vegetation to absorb carbon dioxide (CO2) will do little to tackle global warming.

They say the amount of carbon these "sinks" can store is far less than the quantities emitted by burning fossil fuels.

Some countries want to use sinks extensively to meet their commitments under the Kyoto Protocol on climate change. But the scientists say there is really no alternative to actual emission cuts.

In a report published by the UK's science academy, the Royal Society, they say sinks cannot be a long-term substitute for emissions cuts.

They say governments meeting on 19 July in the German city of Bonn to negotiate the protocol's detailed working should not rely too heavily on forests and farmlands to soak up CO2.

Rather the report suggests countries should focus on restructuring the generation and use of energy, and on technological innovations such as improved fuel efficiency and technology transfer to the developing world.

Ultimate solution

The chairman of the working group that prepared the report is Professor David Read.

He said: "These measures may be socially and politically more painful to implement than land carbon sinks.

"But they must provide the ultimate solution to the problem of reducing the amounts of greenhouse gases in the atmosphere."

Forest fire AP
Trees release CO2 when they die
The report focuses on terrestrial sinks - although it is possible to store CO2 in the oceans, land sinks are the only ones dealt with under Kyoto.

Professor Read said: "We do not fully understand the processes that control how much CO2 is absorbed by vegetation and soils acting as sinks.

"And we need more reliable methods of quantifying and verifying their contribution towards targets set by the protocol.

"They may help to reduce greenhouse gas levels in the atmosphere during the short term.

"But the amounts of CO2 that can be stored are small compared with emissions from the burning of fossil fuels."

Land-based vegetation and soils currently absorb about 40% of global CO2 emissions from human activities.

The report recommends that the capacity of these sinks should be increased. It warns that changes in farming and forestry, like the widespread use of nitrogen-based fertilisers, can be problematic.

While they are intended to increase the amount of CO2 absorbed by sinks, it says, they may actually increase climate change by releasing other greenhouse gases, like methane and nitrous oxide.

'Bit of a sideshow'

The report says the maximum contribution from such changes, and from slowing deforestation, is modest.

It estimates it at a quarter of the emissions cuts needed by 2050 to avoid large increases in global average temperatures.

Professor John Shepherd, a member of the working party, told BBC News Online: "Sinks are really a bit of a sideshow to the main event.

Cornfield BBC
Farming may release CO2, not store it
"It would be better to spend less time worrying about them and look instead at the real long-term problems.

"The size of the potential sinks is quite modest, and they'd all be used up in a few decades.

"And they're not very stable. If you chop down the trees you release the carbon, and if you convert the land to wetland you release methane.

Carbon emitters

"Global warming itself may turn them from sinks to sources of carbon.

"Rising temperatures will make the bacteria more active, and they'll break down the carbon faster."

Talks last November on finalising the protocol broke down, partly over disagreements on sinks.

Japan is leading calls in Bonn for sinks to be widely exploited. It wants to meet almost 60% of its cuts in this way.

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17 May 01 | Sci/Tech
Science academies back Kyoto
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