Tree Planting Is Booming. Here’s How That Could Help, or Harm, the Planet. – The New York Times

“They’re planting the same species all over the world,” said Meredith Martin, an assistant professor of forestry at North Carolina State University who found that nonprofit tree planting efforts in the tropics tend to prioritize the livelihood needs of people over biodiversity or carbon storage. Over time, she said, these efforts risk reducing biodiversity in forests.

Nonprofit tree planting groups often say they plant nonnative species because local communities ask for them. But deeper engagement can yield a different story, said Susan Chomba, who oversees forest restoration and conservation in Africa for the World Resources Institute, a global research nonprofit group. When given the chance to consider what they want to accomplish on their land, farmers will recall, for instance, that when they had more trees, they also had streams, she said. They want the water back.

“Then you say, ‘In your traditional, local knowledge, what kind of tree species are suitable for returning water into the ecosystem?’” Dr. Chomba continued. “They will give you a whole range of indigenous tree species.”

A major hurdle is lack of supply at local seed banks, which tend to be dominated by popular commercial species. Some groups overcome this problem by paying people to collect seeds from nearby forests.

Another solution, experts say, is to let forests come back on their own. If the area is only lightly degraded or sits near existing forest, a method called natural regeneration can be cheaper and more effective. Simply fencing off certain areas from grazing will often allow trees to return, with both carbon sequestration and biodiversity built in.

“Nature knows much more than we do,” Dr. Chazdon said.