Tree-planting projects abound. Which should you support?

Trees and forests around the world are under strain from climate change. They also are threatened by logging and development. To address these problems—and to increase the capture of carbon dioxide from the atmosphere—campaigns are popping up around the globe to help save the world by planting trees.

See National Geographic’s May issue devoted to forests.

Amazon founder Jeff Bezos has pledged $2 billion to restore forests. Last year a Latin American e-commerce company raised $400 million in bonds for forest restoration. Air travelers increasingly are looking for ways to offset the CO2 emitted by their flights by paying for forest restoration or protection.

Growing forests is no substitute for rapidly curbing fossil fuel emissions. But more forest can help around the margins. Still, many tree planting programs are new, with no track record to judge how they may perform. Among such programs, a lack of transparency and accountability is common. Some amount to little more than greenwashing; others mean well but face a raft of problems—and some actually do damage.

Where will your support for tree planting efforts be likely to do the most good? Two forest restoration experts, Karen Holl, an ecologist at the University of California, Santa Cruz, and Pedro Brancalion, a forestry professor at Brazil’s University of São Paulo, recently published a series of questions to help consumers navigate this complex world. Holl and Brancalion don’t critique campaigns by name—though for their next project they hope to do a deep assessment of which organizations are most effective. For now, they hope their questions will help individuals and investors find answers, while encouraging tree-growing organizations to make information more easily accessible.

Here are five of their questions, to ask yourself before you give (read the full list here):

What do you hope to achieve, and how does this tree-growing organization meet those goals?

There are many reasons to grow trees and support tree growing. But those reasons can contradict one another. For example, a 2021 study of 174 tree-planting groups in 74 countries showed that the majority planted just a few types of trees designed to help landowners produce food, timber, or firewood. Those tree species may help rural communities in the near term, but planting in this way is far less likely to increase biodiversity or maximize the potential to store carbon and reduce climate change.

Other studies have shown similar things. The Bonn Challenge, sponsored by the German government and the International Union for Conservation of Nature, wants to reforest 865 million acres around the world by 2030. But a huge chunk of the commitments toward that goal, according to one study, included plans for growing single-species tree plantations to provide products­—even though plantations do little to restore wildlife and absorb only a fraction of the CO2 of a wild forest.

In fact, the cheapest and most successful way to protect or enhance CO2 storage and biodiversity may not involve planting trees at all. It’s often about protecting existing forests or allowing native forests a chance to come back on their own. “Natural regeneration works really well in many cases”—especially in the fast-growing tropics, Brancalion says. And yet it’s a far less common approach, in part because planting a tree sounds easier than restoring a real forest.

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How has this organization resolved the initial drivers of forest loss or degradation?

Planting trees effectively is more complex than many people realize. It only works when used to reforest an area that previously held trees. Even then, reforesting will only work long-term if the pressure that led to trees being removed is understood—and is no longer a factor.

Deforestation has many causes; among them are demand for wood products, ground-clearing  for agriculture or development, and losses from storms, wildfires, or drought. Areas subject to repeated wildfires worsened by climate change may not be suitable for replanting, or may require different trees that can do well despite the changes. Holl and Brancalion have seen forests restored and fenced only to have the fences removed and trees damaged or taken out because local farmers needed the land for pasture.

Are local stakeholders involved in the project, and what benefits will they receive?

Many tree-planting organizations are based in the United States or Europe, but are trying to grow trees in developing nations where more people rely on the land for income and livelihoods. One factor that consistently determines project success or failure is whether local people are involved and see a benefit to the planting—not just at the outset, but over the lifespan of the operation. If income is lost, it must be replaced. Otherwise, new trees may be cleared or landowners may clear existing forests elsewhere.

Consider Brazil, where reforestation programs are common. In one of the nation’s poorest regions, which is home to jaguars and giant anteaters, scientists and activists have found success linking isolated fragments of Atlantic Forest that are normally separated by farms and cattle ranches. By planting 2.4 million trees, they created a wildlife corridor, a pathway now traveled by endangered species. Adjacent to that corridor, fruit trees, coffee plantations, and casava are grown and local people are running tree nurseries, which has increased incomes and food security while also allowing these area residents to feel some ownership of the health of nearby forests.

Brancalion has also been experimenting with planting fast-growing non-native, commercial tree species alongside native trees. The non-native trees can be cut and sold for wood or paper, helping to provide income while locals wait for adjacent native forests to regrow.

How will potential negative consequences of the project be minimized?

A lot can go wrong with tree planting. Mass tree-growing operations in Turkey, Sri Lanka, and the Philippines have resulted in millions of dead seedlings because the wrong species were planted, or trees were planted in poor soils, or there was too little water, or no one cared for the trees after they were planted. A campaign on China’s Loess Plateau actually reduced farmland by a quarter and reduced the amount of water available for people; that ultimately led to a decrease in nearby native forest cover.

In deciding where to place your support, ask organizations to explain how they will prevent seedlings dying, avoid the destruction of existing ecosystems, make sure water yields aren’t reduced, and ensure that negative social consequences are avoided.

“Start with their web pages,” Holl says. “Most of these groups provide glossy stories, but they don’t provide facts. And what you really need is data.” If organizations don’t post it, request it.

How long will the project be tracked, and how will maintenance be adjusted in response to what monitoring shows?

It may be possible, as some campaigns promise, to plant a tree for one dollar—but it’s rarely possible to keep one alive for that price. If trees are to sequester carbon and protect biodiversity, they must thrive for decades. That requires planning, from the time a program is launched, for maintaining the trees’ health for years—a planning extent that’s extremely rare.

In a 2019 study across major areas of Brazil, Brancalion and Holl found that 80 percent of tree planting operations tend to track tree survival for 30 months or less. After Ethiopia, in 2019, claimed to have planted 350 million trees in one day, Holl and her students could find very little information that showed how many of those trees had survived. Holl also reviewed tree-planting proposals for the World Economic Forum for its trillion-tree initiative but found very few plans even monitored results for two years. Impacts on water quality or local livelihoods are scarcely monitored at all.

Rather than asking a campaign how many trees it wants to plant, Holl and Brancalion recommend asking how many trees each organization plans to have still living in five, 10 or—better yet—20 years.