Giving Compass' Take:

• Gabriel Popkin reports that tree-planting efforts could curb climate change - but more work is needed to do this impactfully. 

• How can funders work to effectively increase tree coverage around the world? 

• Learn about tree-planting drones working to restore forests

Two papers published recently in major journals claim to do the same thing: show where forests should be restored. But they used starkly different approaches that lead to sharply varying conclusions.

One study, published in Science, found that the globe contains a United States-sized area of unforested land capable of growing trees, and those trees could, in theory, soak up two thirds of humanity's carbon emissions to date. The other, published in Science Advances, analyzed the tropics only and arrived at a slightly smaller area estimate, but also suggested "restoration hotspots" where bringing back forests is most affordable and likely to succeed.

The need to restore forest, both to protect biodiversity and to stabilize the climate, is urgent, experts say. Some 80 percent of the world's land species need forests to live. Trees also fight climate change by taking up carbon dioxide—the main gas responsible for warming—from the air and turning it into wood and roots.

But especially in the tropics, forests are falling far faster than they are growing; a Belgium-sized swath of tropical forests disappeared in 2018 alone. Deforestation accounts for around 10 percent of humans' carbon emissions, and the Intergovernmental Panel on Climate Change last fall said forest restoration is critical to limiting global warming to less than 1.5 degrees Celsius, the level many scientists consider potentially catastrophic.

Recognizing this, countries around the world have committed to bringing back vast tracts of previously cleared forests. Many have signed on to agreements such as the Bonn Challenge, launched in 2011 to restore 150 million hectares of forest by 2020; leaders recently upped their goal to 350 million hectares—an area larger than India—to be restored by 2030.

Yet most countries don't know where new forests will provide the most bang for the buck in terms of carbon or biodiversity, or even how much land they have available for restoration. "We talk a lot about restoration," says Fred Stolle, a remote-sensing expert at U.S.-based World Resources Institute, "but how are we going to do that?"

To provide that information, a team led by ecologist Thomas Crowther of ETH Zurich in Switzerland analyzed the amount of tree cover in satellite images of protected forest areas around the world. "The approach we use—you can't argue, it's so simple," Crowther says.

Read the full article about tree-planting efforts by Gabriel Popkin at Pacific Standard.