reforestation

A reforestation project in Brazil

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Restoring farmland to its natural state could be crucial to countering carbon emissions and tackling biodiversity loss. New modelling suggests that it isn’t only the total area of land restored that matters – its location does too.

Bernardo Strassburg at the Pontifical Catholic University in Brazil and his colleagues have concluded that returning 30 per cent of the farmland in several key areas around the world to its natural state would remove 465 gigatonnes of carbon dioxide from the atmosphere – almost half of the total rise in this greenhouse gas since the Industrial Revolution. The team doesn’t address exactly how long it would take for the restored land to capture so much CO2.

The restoration effort would be so successful because natural forests and grasslands can store far more carbon than farmland. Restoration would have other benefits too: it could prevent 71 per cent of the animal extinctions expected to occur in the decades ahead.

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The high-priority areas the team identified include coastal areas of Brazil and West Africa, and much of South-East Asia.

The researchers analysed data related to 2870 million hectares globally that have been converted to farmland. About 54 per cent of the land was originally forest and 25 per cent was grassland. The rest was originally shrubland, arid land or wetland.

They evaluated the land types based on three criteria: animal habitat, carbon storage potential and the cost-effectiveness of conversion to its original state. The highest priority areas were those that were optimal for all three, but the team also took into account a distribution that would restore a variety of ecosystems, including wetlands and shrublands.

To study biodiversity effects, their model included maps of the geographic distribution of more than 22,000 animal species.

“There is a well-known ecological relation between how much a species has lost of its original range and the probability of extinction,” says Strassburg. “As habitat is restored, the probability of extinction is reduced.”

Even a smaller amount of restoration would still have a significant effect, the modelling suggests. A 15 per cent restoration could avoid around 60 per cent of extinctions while ultimately capturing 299 gigatonnes of CO2.

The approach would require international cooperation, with restoration unconstrained by national borders. The modelling showed that if restoration were instead to take place at the national level, with each individual country restoring 15 per cent of its converted land, but without working with neighbours to restore lands according to a region-wide complementary strategy, the biodiversity benefits might drop by 28 per cent and the climate benefits by 29 per cent.

The modelling may inform restoration commitments in the International Union for Conservation of Nature’s Post-2020 Global Biodiversity Framework.

Journal reference: Nature, DOI: 10.1038/s41586-020-2784-9

source: newscientist.com

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