- The World Wide Fund for Nature (WWF)
says the world's changing climate poses a grave risk to one third of its
forests.
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- WWF says this has serious implications
for many plant and animal species, three-quarters of which depend on the
forests for their survival.
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- Most scientists believe climate change
is being caused by human activity, especially the burning of fossil fuels
like coal, oil and gas.
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- Carbon dioxide given off as the fuels
burn is trapping more and more of the sun's heat close to the earth, instead
of letting it radiate safely back into space.
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- Multiple effects
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- The inexorable rise in temperature is
affecting forests in several ways, says WWF.
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- Latitudes nearer the poles are becoming
warmer -- in fifty years or less, southern Britain may have a climate like
central France today. Yet some tree species may not be able to keep up
with the advancing heat front.
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- The climate is likely to become stormier.
That may mean an increased risk of fire for tropical forests already dried
out by drought.
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- Sea levels will continue to rise. Mangrove
swamps, home to a wealth of species, may be at risk.
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- And in some places, trees will respond
to climate change by encroaching on new areas, taking over African savannahs
and Alpine meadows.
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- But forests will not only suffer from
climate change. Increasingly, they will contribute to it.
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- As a tree grows, it absorbs carbon dioxide
from the atmosphere to help it to maturity.
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- Once it is full-grown, the tree "locks
up" the carbon dioxide it contains, and prevents it from re-entering
the atmosphere.
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- But when the tree decays, or is burnt,
all the carbon dioxide it contains is released, adding to the greenhouse
effect.
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- Scientists estimate that up to one fifth
of all greenhouse gases come from the burning, not of fossil fuels, but
of "biomass" -- trees and other plants.
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- Some of the burning is accidental. But
an increasing number of fires are started deliberately, to clear land for
farming or other human purposes.
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- A problem or an opportunity ?
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- The world's forests are key players in
the Buenos Aires climate conference, running from 2 to 13 November.
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- Because the forests can lock up such
immense quantities of carbon dioxide, some countries are arguing that it
makes more sense to plant trees than to reduce their own greenhouse emissions.
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- The argument comes mainly from countries
in the superleague of polluters, like the USA.
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- There is some evidence to support them.
A team of American researchers says the nation's trees could be sucking
up just about all the 1.6 billion tonnes of carbon dioxide that the US
emits every year.
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- But other climatologists say the researchers,
the Carbon Modeling Consortium, had to rely on sparse data, and on models
whose assumptions have not been thoroughly tested.
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- The members of the Consortium are all
respected scientists. But, in the words of the weekly New Scientist magazine,
"much more research is needed before these findings are nearly strong
enough to inform policy".
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- And there is a warning from WWF to the
delegates in Buenos Aires.
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- "Forests are threatened by climate
change, so countries should not rely on them to soak up carbon dioxide",
it says. "There is no substitute for cutting emissions at source".
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