Trees for crops 'will not halt warming'

PARIS: Schemes to convert croplands, or marginal lands, to forests will make almost no inroads on global warming this century, a new scientific study says.
Afforestation is being encouraged under the UN's Kyoto Protocol on the theory forests are ''sinks'' that soak up carbon dioxide from the air through photosynthesis.
But environmental researchers said even massive conversion of land to forestry would have only a slender benefit to the greenhouse gas problem.

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This is partly because forests take decades to mature, but another reason is that forests, even as they absorb greenhouse gas, are darker than croplands and thus absorb more solar heat.
Vivek Arora, of the University of Victoria in British Columbia, and Alvaro Montenegro, of St Francis Xavier University in Nova Scotia, modelled five scenarios in which afforestation was conducted over 50 years to 2060.
They used a Canadian program called CanESM1, which simulated the impacts on land, sea and air if Earth's surface temperature rose 3 degrees by 2100, compared with 1850.
Even if all the cropland in the world were afforested, this would reduce the warming by only 0.45 of a degree by 2100, according to the study in the journal Nature Geoscience.
Fifty per cent afforestation of available land would arrest warming by just 0.25 degrees.
Both scenarios are, of course, wildly unrealistic because of the need to grow food.
The study said afforestation does have other benefits, for the economy and the ecosystem.
''There's nothing wrong with afforestation,'' Dr Montenegro said.
''It is positive, but our findings say that it's not a response to temperature control if we are going to be emitting [greenhouse gases] this way.''