Trees Are Not Enough to Save the Climate | Net Zero

“I haven’t met any anti-tree people yet,” said Marc Benioff, chief executive of Salesforce. He could, however, meet some tree realists.

Benioff spoke at an event announcing the World Economic Forum’s big climate initiative to plant a trillion trees by 2030. The goal is to sequester enough carbon to slow down and perhaps reverse climate change. It’s a reaction to the WEF’s conclusion that the top five long-term risks to the planet are all tied to the inexorable rise of greenhouse gases. Even US President Donald Trump, who has remained opposed to most climate policies, jumped on WEF's tree wagon.

Beware magical solutions. As with anything we learned in high school, the true story is more complex. Planting trees at the scale many are planning to do is a challenge and could cause unintended consequences, warns Nathalie Seddon, professor of biodiversity at the University of Oxford and director of Nature-based Solutions Initiative.

First, most tree-planting programs pick only one or two species to plant. These monoculture forests might be good at locking up carbon quickly, but less diverse tree systems attract less diverse sets of animals and thus become less resilient to the coming changes. In a warming world, where the number of extreme weather events become more frequent, the forests risk destruction because of droughts, floods, fires or pestilence. That would, of course, release the sequestered carbon.

Second, where the trees are planted matters. The trillion-tree plan is likely to need a billion hectares of land—about the same size as China, the world’s third-largest country by area. But even if we find that much land, there are other problems.

A 2007 study found that deforestation in the North American boreal regions can actually cool the planet: Dark forests trap more of the sun’s heat than lighter, open land, which reflects rather than absorbs. Or, vice versa, sometimes planting trees in the wrong place can have a warming effect on the planet. The science of the so-called “albedo effect” and forests in high northern latitudes is far from certain.

Third, there is a risk of “green colonialism.” People derive value from their ecosystems. Without the buy-in of local people, many tree planting programs fail. In Bangladesh, Seddon says, a reforested mangrove plantation was turned back to a shrimp farm within years, because local people weren’t engaged.

Trees for the Future, a charity founded 30 years ago, found that fewer 5% of the trees it planted survived to maturity without local supervision. In recent years, instead of focusing on tree-planting, it focuses on an approach that makes local farmers richer through planting trees. The result is the creation of “forest gardens” that quadruple the farmers’ income, improve the family’s nutritional diets, and lower the cost of planting to as little as $0.10 per tree.

Seddon has worked in nature conservation for more than 30 years, and she welcomes the huge interest in planting. Her biggest worry is that tree planting is being used for greenwashing. Under the Bonn Challenge, many countries, companies and organizations signed up to restoring 350 million hectares of forests. Dig deeper and it becomes clear that 66% of that is for monoculture forests or agroforestry rather than actual restoration.

Tree-planting programs might be used as a “get-out-of-jail card” by the fossil fuel industry, governments, or even individuals. “We have to keep fossil fuels in the ground and we need to look after nature,” Seddon said. “One is not an alternative for the other.”

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