Ronald Reagan was right! redux............

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<http://www.guardian.co.uk/science/story/0,3605,1684379,00.html>

Global warming: blame the forests

· Research identifies plants as source of methane
· Climate scientists shocked by new findings

Alok Jha, science correspondent
Thursday January 12, 2006
The Guardian

They have long been thought of as the antidote to harmful greenhouse
gases, sufferers of, rather than contributors to, the effects of
global warming. But in a startling discovery, scientists have realised
that plants are part of the problem.

According to a study published today, living plants may emit almost a
third of the methane entering the Earth's atmosphere.

The result has come as a shock to climate scientists. "This is a
genuinely remarkable result," said Richard Betts of the climate change
monitoring organisation the Hadley Centre. "It adds an important new
piece of understanding of how plants interact with the climate."

Methane is second only to carbon dioxide in contributing to the
greenhouse effect. "For a given mass of methane, it is a stronger
greenhouse gas, but the reason it is of less concern is that there's
less of it in the atmosphere," said Dr Betts.

But the concentration of methane in the atmosphere has almost tripled
in the last 150 years, mainly through human-influenced so-called
biogenic sources such as the rise in rice cultivation or numbers of
flatulent ruminating animals. According to previous estimates, these
sources make up two-thirds of the 600m tonnes worldwide annual methane
production.

Frank Keppler, of the Max Planck Institute for Nuclear Physics, who
led the team behind the new research, estimated that living plants
release between 60m and 240m tonnes of methane per year, based on
experiments he carried out, with the largest part coming from tropical
areas.

David Lowe, of the National Institute of Water and Atmospheric
Research in New Zealand, said the new work, published in Nature, is
important for two reasons. "First, because the methane emissions they
document occur under normal physiological conditions, in the presence
of oxygen, rather than through bacterial action in anoxic
environments," he wrote in an accompanying article. "Second, because
the estimated emissions are large, constituting 10-30% of the annual
total of methane entering Earth's atmosphere."

Yadvinder Malhi, a specialist in the relationship between vegetation
and climate at Oxford University, said the plant source of methane had
probably been missed in the past because scientists have a poor
understanding of the way methane circulates in the atmosphere. "There
are a variety of sources and sinks of methane and there are huge error
bars on those terms," he said. "What's been uncertain is where the
methane is coming from and where it's going. Unlike carbon dioxide,
methane is much more dynamic; it lasts about 10 years in the
atmosphere."

Biogenic methane has traditionally been assumed to come from organic
materials as they decompose in oxygen-free environments. But Dr
Keppler found plants emit the gas even in normal, oxygen-rich
surroundings: between 10 and 1,000 times more methane than dead plant
material. When the plants were exposed to the sun, the rate of methane
production increased. "Until now all the textbooks have said that
biogenic methane can only be produced in the absence of oxygen," Dr
Keppler said. "For that simple reason, nobody looked closely at this."

The discovery sheds further light on the complex relationship between
greenhouse gases and the environment. "If you're after predictions of
global average temperature, it won't make a huge amount of
difference," said Dr Betts. "But it shows how complicated it is to
exactly quantify reforesting or deforesting in comparison with current
fossil fuel emissions."

It will also intensify debates on whether targets in climate change
treaties such as the Kyoto Protocol should be based entirely on carbon
emissions, which are easily measured, or also take sinks into account,
which remove carbon from the atmosphere but are more difficult to
measure.

For climate scientists, the new work clears up a few unexplained
features in the environment.

"The rate of methane increase in the atmosphere has slowed down in the
last 10 years and there was no really convincing explanation of why
that's been going on," said Dr Mahli. "This paper argues that tropical
deforestation may be a factor there."

In addition, the new research could help to explain the source of
plumes of methane observed by satellites over tropical forests. "The
sheer biomass of the forest may be a factor there," said Dr Mahli.

The fact that plants produce methane does not mean that planting
forests is a bad idea, however. "Putting a tree where there was no
tree before locks up a lot of carbon and this [new research] perhaps
reduces the overall benefit of that by a fraction," said Dr Mahli.

Some mysteries remain: how and why plants produce methane is unclear.
Dr Keppler's team said the search for an answer is likely open up a
new area of research into plant biochemistry.

Other surprise results

Tree planting

Researchers in North Carolina found that planting trees to soak up
carbon dioxide can suck water and nutrients from the ground, dry up
streams and change the soil's mineral balance

Aerosols

A recent study in Nature found cutting air pollution could trigger a
surge in global warming. Aerosols cool the Earth by reflecting
radiation back into space. Scrapping them would have adverse
consequences

Global dimming

In 2003 scientists noticed levels of sunlight reaching the Earth's
surface had dropped by 20% in recent years because of air pollution
and bigger, longer-lasting clouds