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(October 22) Just how many trees should we plant to stay under 1.5 degrees? Two ecologists have an idea.

In the latest IPCC Report, the panel recommends adding 1 billion hectares of forest to limit global warming by 1.5°C by 2050. Ecologists Jean Francois Bastin and Tom Crowther and their co-authors wanted to figure out whether today’s earth could support that many extra trees – and where they might go. The ecologists are researchers at the Crowther Lab based at the Swiss Federal Institute of Technology in Zurich, and have determined that around 0.9 billion hectares of land worldwide are suitable for reforestation, with Canada ranked #3 on the reforestation list. These 0.9 billion hectares would be equivalent in size to the US and would translate to 1-1.5 trillion trees capable of capturing two-thirds of human made carbon emissions.

A Benchmark for Global Action: “The restoration of trees remains among the most effective strategies for climate change mitigation,” states Dr. Jean Francois Bastin, lead author for the study.

The researchers mapped the global potential tree coverage to show that 4.4 billion hectares of canopy cover could exist under the current climate. Excluding existing trees and agricultural and urban areas, we found that there is room for an extra 0.9 billion hectares of canopy cover, which could store 205 gigatonnes of carbon in areas that would naturally support woodlands and forests.

Their findings highlight global tree restoration as our most effective climate change solution to date. However, climate change will alter this potential tree coverage. We estimate that if we cannot deviate from the current trajectory, the global potential canopy cover may shrink by ~223 million hectares by 2050, with the vast majority of losses occurring in the tropics.

“Our study provides a benchmark for a global action plan, showing where new forests can be restored around the globe.. Action is urgent, and governments must now factor this into their national strategies to tackle climate change,” concludes Dr. Bastin.

Canada is #3 for Reforestation Potential: The study also shows which parts of the world are most suited to forest restoration. The greatest potential can be found in just six countries: Russia (151 million hectares); the US (103 million hectares); Canada (78.4 million hectares); Australia (58 million hectares); Brazil (49.7 million hectares); and China (40.2 million hectares).

Many current climate models are wrong in expecting climate change to increase global tree cover, the study warns. It finds that there is likely to be an increase in the area of northern boreal forests in regions such as Siberia, but tree cover there averages only 30 to 40 percent. These gains would be outweighed by the losses suffered in dense tropical forests, which typically have 90 to 100 percent tree cover.

To learn more about author Thomas Crowther, click here.

To learn more about the global tree cover, click here.

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