Getting to the root of saving Earth
Worldwide boom in planting trees can hurt as well as help
A tree planted for every T-shirt purchased or swipe of a credit card. Trees planted by countries to meet global pledges and by companies to bolster their sustainability records.
As the climate crisis deepens, businesses and consumers are joining nonprofit groups and governments in a global tree planting boom. Last year saw billions of trees planted around the world. These efforts can be a triple win, providing livelihoods, absorbing and locking away planet-warming carbon dioxide, and improving ecosystems.
But when done poorly, the projects can worsen the problems they were meant to solve. Planting the wrong trees in the wrong place can reduce biodiversity, speeding extinctions and making ecosystems far less resilient.
Addressing biodiversity loss, already a global crisis akin to climate change, is becoming more urgent. An estimated 1 million species are at risk of disappearing, many within decades. And ecosystem collapse also imperils the food and water supplies that humans rely on.
Amid that, companies and countries are increasingly investing in tree planting that carpets large areas with commercial, nonnative species in the name of fighting climate change. These trees sock away carbon but provide little support to the webs of life that once thrived in those areas.
“You’re creating basically a sterile landscape,” said Paul Smith, who runs Botanic Gardens Conservation International, an umbrella group that works to prevent plant extinctions.
There’s a rule of thumb in the tree-planting world: One should plant “the right tree in the right place.” Some add, “for the right reason.”
But, according to interviews with scientists, policy experts, forestry companies and tree planting organizations, people often disagree on what’s “right.” For some, it’s big tree farms for carbon storage and timber. For others, it’s providing fruit trees to small-scale farmers. For others still, it’s allowing native species to regenerate.
“It’s kind of the Wild West,” said Forrest Fleischman, a professor of environmental policy at the University of Minnesota.
There is not enough land on Earth to tackle climate change with trees alone, but if paired with drastic cuts in fossil fuels, trees can be an important natural solution. They absorb carbon dioxide through their leaves and stash it away in their branches and trunks (though trees also release carbon when they burn or rot). That ability to collect that gas is why forests are often called carbon sinks.
In Central Africa, TotalEnergies, the French oil and gas giant, has announced plans to plant trees on nearly 100,000 acres in the Republic of Congo. The project on the Bateke Plateau would sequester more than 10 million tons of carbon dioxide over 20 years, according to the company.
“Total is committing to the development of natural carbon sinks in Africa,” said Nicolas Terraz, who was then Total’s senior vice president for Africa, exploration and production, in a company news release on the project in 2021. On the Bateke Plateau, an acacia species from Australia, intended for selective logging, will cover a large area.
The project, part of a Congolese government program to expand forest cover and increase carbon storage, would create jobs, the company said, and ultimately broaden the ecosystem’s biodiversity as local species are allowed to grow in over decades.
But scientists warn that the plan may be an example of one of the worst kinds of forestation efforts: planting trees where they would not naturally occur. These projects can devastate biodiversity, threaten water supplies and even increase temperatures because, in some cases, trees absorb heat that grasslands — or, in other parts of the world, snow — would have reflected.
“We don’t want to cause harm in the name of doing good,” said Bethanie Walder, executive director of the Society for Ecological Restoration, a global nonprofit.
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.’ ”
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 1 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.”
When businesses promise to plant a tree for every purchase of a given product, they typically do so via nonprofit groups. The support may reforest after wildfires or provide fruit and nut trees to farmers. But even these projects can compromise biodiversity.
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.
“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.
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.