The Surprising Downsides to Planting Trillions of Trees

In one recent study in the journal Nature, for example, researchers examined long-term restoration efforts in northern India, a country that has invested huge amounts of money into planting over the last 50 years. The authors found “no evidence” that planting offered substantial climate benefits or supported the livelihoods of local communities

An analysis of satellite imagery and interviews with hundreds of households, however, revealed that decades of planting by the government — amounting to hundreds of millions of seedlings — “had almost no impact on forest canopy cover,” Fleischman wrote on Twitter. The researchers also measured a shift in the type of trees within the ecosystem, away from species that locals prefer for firewood and animal fodder. In other words, residents of Himachal Pradesh actually had fewer useful forest resources.

What went wrong? Some of the trees may have died quickly because they were planted in poor-quality habitat, Fleischman suspects. Farm animals could have also destroyed the saplings if they were planted in former grazing lands, he said

In Mexico, a $3.4 billion tree-planting campaign launched by the government in 2018 actually caused deforestation, as Bloomberg News’ Max de Haldevang reported earlier this year. The program known as Sembrando Vida, or Sowing Life, pays farmers to plant trees on their land, but in some cases, they would clear a chunk of forest before putting seedlings in the ground. One analysis by the World Resources Institute, an environmental group, suggests that it caused almost 73,000 hectares of forest loss in 2019

Researchers have also blamed large tree-planting efforts in China and Brazil for degrading grassland ecosystems. As I’ve previously reported, grasslands store vast amounts of carbon — most of which is below ground — and provide homes for countless species. Yet these ecosystems are sometimes considered degraded and are targeted for forest restoration campaigns

A bigger problem still is that many large planting campaigns don’t account for the underlying social or economic conditions that fuel deforestation in the first place. People may cut down trees to collect firewood or carve out land for their animals. In those cases, putting seedlings in the ground won’t do much to end deforestation.

To be clear, there are plenty of successful restoration programs — and they’re getting better, said Chazdon, who’s also an adviser for the WEF trillion trees campaign. “There is ample evidence that when restoration is done properly, it works,” she said.

Over the last 35 years, a nonprofit called Instituto de Pesquisas Ecológicas has worked with local communities to plant some 2.7 million native trees, as Mongabay’s Liz Kimbrough reports. The trees provide useful products that locals want, such as fruit to eat and wood for building, and a new revenue stream from selling seedlings. At the same time, the new trees create a network of forest corridors that has helped populations of the tamarin recover. In this case, it really does seem to be a win-win-win