We all know that reforestation would help mitigate the effects of climate change, but now scientists have calculated that it could make up 37 percent of the needed reductions of carbon emissions if land is reallocated to growing forests. (The necessary emissions reduction is based on the internationally-accepted amount that would limit global warming to within two degrees Celsius.)

Here’s the math:

Currently, land ecosystems (and human activities affecting them) are responsible for emitting the equivalent of about 1.5 billion tons of CO2 each year. (For comparison, total human-caused emissions are around 48 billion tons each year.) This is the balance of about 11 billion tons of emissions (caused by things like deforestation and agricultural practices) and the 9.5 billion tons of our CO­2 emissions that land ecosystems helpfully soak up. It’s possible to change both of those numbers so that land ecosystems remove more CO2 from the atmosphere than they add.

To handle the economics, the researchers from The Nature Conservancy produce two estimates—one for a world where a weak price of $10 per ton has been placed on CO2 emissions, and one with a stronger price of $100. That sets the definition of “cost-effective” for conservation efforts.

Ignoring costs for a moment, they found a whopping theoretical maximum of almost 24 billion tons of CO2 per year through 2030 that could either be prevented from reaching the atmosphere or actively removed from it. At a carbon emissions price of $100 per ton, a little more than 11 billion tons of that maximum is cheap enough to save you money by avoiding some of the tax on net emissions. That’s fully 37 percent of the reductions needed to limit warming to no more than 2°C—an international goal.

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