Those who study forest restoration emphasize that trees are not a cure-all.

12. Those who study forest restoration emphasize that trees are not a cure-all. “I fear that many corporations and governments are seeing this as an easy way out,” said Robin Chazdon, a professor of tropical forest restoration at the University of the Sunshine Coast in Australia. “They don’t necessarily have to work as hard to reduce their emissions because they can just say, ‘Oh, we’re offsetting that by planting trees’.”

13. Experts acknowledge that forest restoration and carbon sequestration are complex, and that commercial species have a role to play. People need timber, a renewable product with a lower carbon footprint than concrete or steel. They need paper and fuel for cooking.

14. Planting fast-growing species for harvest can sometimes help preserve surrounding native forests. And, by strategically adding native species, tree farms can help biodiversity by creating wildlife corridors to link disconnected habitat areas.

15. “This restoration movement can’t happen without the private sector,” said Michael Becker, head of communications at 1t.org, a group created by the World Economic Forum to push for the conservation and growth of 1 trillion trees with help from private investment. “Historically, there have been bad actors, but we need to bring them into the fold and do the right thing.” 16. A challenge is that helping biodiversity doesn’t offer the financial return of carbon storage or timber markets.Many governments have set standards for reforestation efforts, but they often provide broad leeway.

17. In Wales, one of the most deforested countries in Europe, the government is offering incentives for tree planting. But growers need only include 25% native species to qualify for government subsidies. In Kenya and Brazil, rows of eucalyptus grow on land that was once ecologically rich forest and savanna. In Peru, a company called Reforesta Perú is planting trees on degraded Amazonian land, but it’s increasingly using cloned eucalyptus and teak, intended for export.

18. When businesses promise to plant a tree for every purchase of a given product, they typically do so via nonprofit groups that work with communities around the world. The support may reforest after wildfires or provide fruit and nut trees to farmers. But even these projects can compromise biodiversity.

THE DANGER OF MONOCULTURE 19. The planet is home to nearly 60,000 tree species. A third are threatened with extinction, mainly from agriculture, grazing and exploitation. But globally, only a tiny fraction of species are widely planted, according to tree planting groups and scientists.

20. “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. 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.

21. 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,” Chazdon said.