Afforestation will hardly dent global warming

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

This is partly because forests take decades to mature and CO2 is a long-lasting molecule, able to lurk for centuries in the atmosphere. But another reason is that forests, even as they absorb greenhouse gas, are darker than croplands and thus absorb more solar heat – and in high latitudes, this may even result in net warming. Vivek Arora of the University of Victoria in British Columbia and Alvaro Montegro of St. Francis Xavier University in Nova Scotia modeled five scenarios in which afforestation was carried out over 50 years, from 2011 to 2060.

They used a Canadian programme called CanESM1 that simulated the impacts on land, sea and air if Earth’s surface temperature rose by some 3 degree Celsius by 2100 compared to 1850. Even if all the cropland in the world were afforested, this would reduce the warming by only 0.45 degree Celsius by a timescale of 2081-2100, according to the study, which appears in the journal Nature Geo science.

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