Planting northern forests would increase global
19:00 11 July 01
Fred Pearce, Amsterdam
Talks to salvage the Kyoto Protocol could be undermined
before they even start by research suggesting that planting
forests to curb global warming could backfire.
The world's nations are due to meet in Bonn from 16 July to
thrash out ways to combat climate change. The protocol
gives governments the option to plant trees to soak up carbon
dioxide, rather than cutting emissions of the greenhouse gas.
But this provision is deeply flawed, warns Richard Betts of
Britain's Meteorological Office. He says it does not take into
account other ways that new forests can affect climate.
"Carbon accounting alone will overestimate the contribution
of afforestation to reducing climate warming," he told New
On Tuesday, Betts presented the first detailed calculations
showing that planting trees across the snow-covered swathes
of Siberia and North America will heat the planet rather than
cool it. And even away from the tundra, the cooling potential
of forests is much less than previously supposed, he told a
climate conference in Amsterdam.
Green on white
His findings may further undermine support for the Kyoto
Protocol. Several industrialised countries are wavering
following the withdrawal of the US from the proposed treaty
earlier in 2001.
Green forest canopies reflect much less solar radiation than
most other land surfaces. They also absorb more, heating the
Earth's surface. This effect is greatest where forests replace
snowy tundra, which normally reflects large amounts of solar
Betts calculates that at northern latitudes, warming as a result
of planting forests will overwhelm any cooling effect due to
the trees soaking up CO2.
Both Canada and Russia want to plant forests in their empty
tundras to help meet their Kyoto commitments, because a
hectare of immature forest can absorb more than 100 tonnes
of carbon each year, despite growing slowly.
But Betts calculates that the net warming effect of
heat-absorbent forests in both regions is equivalent to an
annual emission of 75 tonnes of carbon per hectare.
His new calculations also halve estimates for the carbon sink
potential of western European forests.
"Even in places where the cooling effect is still dominant,"
says Betts, "the cooling influence is generally much smaller
than expected when considering carbon sequestration alone."
So should some countries be destroying forests instead? "I
am not suggesting that we deforest," says Betts. "But
afforestation is not always an effective alternative to cutting
fossil fuel emissions."