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Snowy forests ‘increase warming’
Planting trees in snowy areas may worsen global warming as their
canopies absorb sunlight which would otherwise be reflected by the
snow, a study says.The report in US journal
Proceedings of the National Academy of Sciences says the pine forests
of Europe, Siberia and Canada may contribute to warming.Only tropical forests effectively cool the earth by absorbing carbon dioxide and creating clouds, the report says.
But the report’s authors stress they are not advocating chopping down trees.
They say forests are a valuable resource and remain vital for bio-diversity, providing a home for animals and plants.
‘Lively discussion’
Scientists have long argued that planting and preserving forests helps
reduce global warming because trees absorb carbon dioxide from the
atmosphere and convert it to oxygen.Trees also absorb water from the ground, helping to form clouds that shield the earth from sunlight.
But the report’s findings, discussed last year at an American
Geophysical Union meeting and now published in the Proceedings of the
National Academy of Sciences, suggest planting forests indiscriminately
may be counter-productive.
“Our new study shows that only tropical rainforests are strongly
beneficial in helping slow down global warming,” Govindasamy Bala of
the Lawrence Livermore National Laboratory says.In cooler areas of the earth, tree cover helps store
sunlight reflected by snow on the ground and this “cancels or exceeds”
the net cooling effect, Mr Bala told the AFP news agency.Another author of the report, Ken Caldeira of the
Carnegie Institution, said the report suggested it is “more important
to preserve and restore tropical forests than had been previously
realised”.But, he told the Associated Press news agency, he was
“a little concerned about this being misapplied as an excuse to chop
down the forests in the name of saving the environment”.Computer models produced by the report’s authors suggested deforestation in higher latitudes could reduce global warming.
Steven W Running, a professor of ecology at the University of Montana,
praised the report’s authors for “sparking a lively scientific
discussion”.But Mr Running, who was not involved in the report,
said it was too early to base policy on the report’s conclusion that
certain types of reforestation might be counter-productive.
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