New source of global warming gas found: plants
Wed Jan 11, 1:06 PM ET
German scientists have discovered a new source of methane, a
greenhouse gas that is second only to carbon dioxide in its impact
on climate change.
The culprits are plants.
They produce about 10 to 30 percent of the annual methane found in
the atmosphere, according to researchers at the Max-Planck
Institute for Nuclear Physics in Heidelberg, Germany.
The scientists measured the amount of methane released by plants in
controlled experiments. They found it increases with rising
temperatures and exposure to sunlight.
"Significant methane emissions from both intact plants and detached
leaves were observed ... in the laboratory and in the field," Dr
Frank Keppler and his team said in a report in the journal
Nature.
Methane, which is produced by city rubbish dumps, coal mining,
flatulent animals, rice cultivation and peat bogs, is one of the
most potent greenhouse gases in terms of its ability to trap
heat.
Concentrations of the gas in the atmosphere have almost tripled in
the last 150 years. About 600 million tonnes worldwide are produced
annually.
The scientists said their finding is important for understanding
the link between global warming and a rise in greenhouse
gases.
It could also have implications for the Kyoto Protocol, which calls
for developed countries to cut their emissions of greenhouse gases
by 5.2 percent below 1990 levels by 2008-12.
Keppler and his colleagues discovered that living plants emit 10 to
100 times more methane than dead plants.
Scientists had previously thought that plants could only emit
methane in the absence of oxygen.
David Lowe, of the National Institute of Water and Atmospheric
Research in New Zealand, said the findings are startling and
controversial.
"Keppler and colleagues' finding helps to account for observations
from space of incredibly large plumes of methane above tropical
forests," he said in a commentary on the research.
But the study also poses questions, such as how such a potentially
large source of methane could have been overlooked and how plants
produced it.
"There will be a lively scramble among researchers for the answers
to these and other questions," Lowe added.
