Tree Planting Is Booming. Here’s How That Could Help, or Harm, the Planet.

Eucalyptus, for instance, grows fast and straight, making it a lucrative lumber product. Native to Australia and a few islands to the north, its leaves feed koalas, which evolved to tolerate a potent poison they contain. But in Africa and South America — where the trees are widely grown for timber, fuel and, increasingly, carbon storage — they provide far less value to wildlife. They are also blamed for depleting water and worsening wildfires.

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.

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.

“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 one trillion trees with help from private investment. “Historically, there have been bad actors, but we need to bring them into the fold and doing the right thing.”

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.

In Wales, one of the most deforested countries in Europe, the government is offering incentives for tree planting. But growers need only include 25 percent 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.

Investors prefer them because they bring better prices, said Enrique Toledo, general manager of Reforesta Perú. “They are well-known species internationally and there is an unsatisfied demand for wood.”