We Need Forests to Fight Climate Change, but Planting Trees to Reduce Emissions Is Harder than It Looks

Kyla Mandel / Huffington Post

 (February 5, 2021) — A peat bog forms over thousands of years as plants decay into a dense, dark, soggy soil that traps their carbon content within. Peatlands are the world’s most efficient carbon sink, storing twice as much planet-warming carbon dioxide as forests.

So when, at the end of last year, the UK government approved a tree-planting project on 100 acres of peat bog in northern England, conservationists raised the alarm.

Contractors dug long trenches to drain the water and planted rows of conifer trees that “act like straws,” sucking up water and drying out the soil, explained Joshua Styles, botanist and founder of the North-West Rare Plant Initiative. As the soil dried out, thousands of years worth of carbon started to be released. The Forestry Commision halted the project and apologized, saying it had failed to properly assess the location.

The mistake is just one example of how tree-planting efforts to tackle climate change can wildly miss the mark. “If you don’t want to do any harm to the environment,” Styles told HuffPost, “it needs to be properly thought out.”

As governments and corporations set ambitious climate goals, planting trees has emerged as a favorite way to offset greenhouse gas emissions. The carbon absorbed by new trees is intended to make up for what is being released. But this seemingly simple climate solution isn’t as easy as plopping seedlings in the soil. 

Getting tree planting right, experts explain, means accounting for which trees to plant where, how long those trees will live and how local communities will benefit. Many tree-planting schemes are plagued by poor planning and a lack of foresight that could mean they won’t actually make up for the emissions they’re meant to offset and may even do more harm than good.

Forests are crucial for combating climate change. They absorb one-third of the emissions caused by the burning of fossil fuels. On the flip side, cutting down and degrading forests contributes around 12% of global emissions, according to estimates from the International Union for Conservation of Nature. 

There are different ways governments and businesses can use forests to offset the carbon they release into the atmosphere. One is to prevent deforestation or support efforts to restore existing forests to optimal health. The United Nations’ REDD+ program allows countries and companies — such as Microsoft, Toyota, Shell and BNP Paribas — to pay to protect forests in other parts of the world to help them meet their emission reduction goals.

Then there is tree planting, an increasingly popular option.

More than 60 countries have joined the Bonn Challenge set up by the German government and the IUCN that aims to restore 865 million acres by 2030. The Trillion Trees campaign — which made headlines last year when President Donald Trump committed the US to the initiative despite also planning to open Alaska’s old-growth forests to logging — counts Mastercard, HP, Microsoft, Amazon and Pepsi among its corporate pledge-makers. 

“A lot of these programs are focused on digging a hole and putting a tree in the ground. That’s very different than growing a tree to get the benefits you want.” — Karen Holl, professor of environmental studies at the University of California, Santa Cruz

Many of the airline industry’s recent climate commitments rely, in large part, on tree planting. In 2019, British budget airline EasyJet, for example, announced that it would invest over $33 million in tree planting and other efforts to offset its jet fuel emissions, while Delta’s pledge to become carbon neutral will largely focus on planting trees and restoring wetlands. 

But environmentalists say the tree-planting approach often feels more like PR than serious climate action. 

“The expansion of forestry framed as a climate change mitigation solution is being used for corporate greenwashing, as an excuse for continued use of fossil fuels,” said Alison Smith, co-author of a new Oxford University review of tree planting and other nature-based solutions to climate change.

Even in the best-case scenario, planting trees doesn’t necessarily cancel out the climate damage caused by the release of greenhouse gases — and it’s really hard to get right. 

Putting The ‘Plan’ In Tree Planting

Tree planting initiatives have “to be done very carefully to avoid perverse effects,” said Eric Lambin, environmental sciences professor at Stanford University. 

That starts with where you plan to plant.

Ideally, trees should be planted in areas that used to be forests but were degraded or destroyed. Planting trees in other areas — such as grasslands or peat bogs — or replacing natural forests with rows of identical species, will result in a loss of biodiversity, which makes ecosystems less resilient to threats such as fire and pests, and potentially a loss of stored soil carbon. Placing tree plantations on cropland risks pushing farmers to clear new land — possibly forests — for cultivation. 

Different geographies present particular challenges. For instance, if you’re planting in the snowy northern boreal region, trees’ darker surfaces may absorb and help trap more heat than the white snow cover, explained Susan Cook-Paton, a senior restoration scientist at The Nature Conservancy, which has been running its “Plant a Billion” trees initiative since 2008.

And “you have to pick the right trees to survive in the environment,” she added. Native tree species will have a better chance at handling a given area’s conditions — from drought and monsoons to warding off regional pests — and supporting biodiversity. Non-native trees, on the other hand, may increase the risk of fire, change the soil, or even decompose and release carbon more quickly. 

Aerial view of a field planted with eucalyptus seedlings in Brazil

You have to “plan for permanence,” said Karen Holl, professor of environmental studies at the University of California, Santa Cruz.

“Tree planting” isn’t a term she likes much. We should think of it as “tree growing,” she said. “A lot of these programs are focused on digging a hole and putting a tree in the ground. That’s very different than growing a tree to get the benefits you want.” 

In addition to storing carbon — which takes decades to accumulate  — these benefits may include flood protection, cooling and shade, or fruit. 

Growing trees is an inherently slow process. It takes anywhere from just under a decade to 30 years or more for a tree to mature. As time ticks on, the trees get to work: They store carbon, purify the air, protect the soil, and enable new habitats to form. That means long-term thinking needs to be embedded in whatever target is adopted.

But businesses and countries banking on trees to reduce their carbon footprints are failing to plan far enough into the future, according to Holl. Beyond setting a goal for how many seedlings are planted, she would like initiatives to incorporate goals for how many of those trees survive after 10, 20, or 50 years.

Short-term thinking can be costly. After the Indian Ocean tsunami hit Sri Lanka in 2004, government bodies and NGOs spent roughly $13 million restoring mangrove trees; mangrove roots help stop erosion and protect shoreline from storms. But many of the trees were planted poorly — often in unsuitable locations or at the wrong depth — and seedlings weren’t tended to. Only one-quarter of the sites planted had more than 10% of their trees still living five years later.

“If you plant a bunch of trees thinking you’ve offset your emissions, and they’re all dead within 20 years, then you’ve done nothing.” — William Anderegg, assistant professor of biology at the University of Utah

Often, governments offer subsidies and tax breaks for people who plant trees on their land, but incentives can backfire, Lambin warned. 

“Many landowners will be tempted to collect the subsidy for planting trees even if their land does not meet the conditions for environmentally sound plantations,” he explained. A study he co-authored on Chile’s official tree planting scheme, in effect between 1974 to 2012 — which several other South American nations modeled their plans after — found that government subsidies were used to replace existing forests with monoculture tree plantations.

Even when trees are planted in the right places, you need to design payment programs in a way that ensures farmers continue to protect forests over the long term, added the study’s lead author, Robert Heilmayr, assistant professor of environmental studies at the University of California, Santa Barbara. 

Given the first few years of planting require the most attention to ensure trees’ survival, it’s common for subsidies to be paid out over a five-year period. To ensure longer-term growth, said Lambin, governments can require the subsidy to be repaid if the plantation is converted to a different use (such as back to farmland). Landowners can also sometimes receive tax breaks for as long as the trees stay standing.

Yet there are a lot of ways a tree can die — the buzz of a saw, the borehole of a beetle, or the inferno of wildfire — and the majority of seedlings typically don’t survive. 

“There is a limit to the carbon that can be stored by newly planted trees — and this carbon is at risk if trees are harvested or if they die from fire, drought or disease as the climate continues to warm,” said Smith. 

“If you plant a bunch of trees thinking you’ve offset your emissions, and they’re all dead within 20 years, then you’ve done nothing,” said William Anderegg, assistant professor of biology at the University of Utah. 

Tree growth and tree cover (how much of an area of land is populated by trees) must be monitored to make sure the trees stay standing long enough to achieve a project’s goals. The complex and arduous process typically involves collaboration between nonprofit project organizers, conservation groups and government agencies.

Traditionally, monitoring was done by people on the ground. Part of this involved someone going into the forest and wrapping a tape measure around the trees to measure growth — an important metric for calculating carbon sequestration. While this method still plays an important role in providing on-the-ground detail, increasingly, tree-planting groups are using satellites and other remote technology like drones to measure biomass as well as look for changes in tree cover.

“After about five years, if the forest is continuing to grow the way we expect, we can feel pretty good about its long term potential,” said Eric Sprague, vice president of reforestation at American Forests, the country’s oldest preservation organization, which partners with companies such as Ikea and Bank of America and helps monitor progress for One Tree Pledge, an organization that plants trees as carbon offsets for individuals and construction companies.

“Being able to judge success takes time,” said Holl.

Trees accumulate carbon over decades of growth and release that stored carbon if they die or are felled. 

More Than Just Trees

To have the best chance of getting it right, the experts agreed, tree-planting projects should prioritize factors beyond just carbon offsets, like water and air quality. “When you can manage a forest to provide multiple benefits, that’s often a much more promising approach,” said Heilmayr.

Above all, long-term success requires involving the local community. 

“Poorly designed projects sometimes ignore the rights of local people to govern their natural resources, undermining the legitimacy and long-term success of the project,” said Nathalie Seddon, co-author of the Oxford paper. 

“There’s a pretty broad history … of these large international groups coming in and basically treading all over Indigenous rights,” Anderegg noted. In the end, these projects tend to fail the people who rely on historic lands or forests for their livelihoods and may bring about unintended ecological consequences.

In India, the government’s effort to plant teak trees to combat the country’s emissions has sparked an ongoing conflict with Indigenous communities who say their rights are being violated and that the original ecology of the land they live on is being destroyed; no other trees can grow once the teak is planted, and animals are likely to be driven away as the vegetation changes. 

Projects that lean towards agroforestry, when the trees are integrated with farming, can be more successful because the community is able to earn income in the process, Holl added.

But she said there were few examples that check all the boxes — from choosing the best seedlings to benefiting the local community and sustaining the forest over time. She did cite one case study in Ethiopia where locals were involved from the outset of the project, people consistently watered and fertilized the trees over time, and they used methods to encourage the trees to regenerate naturally, recolonizing the earth with their own seeds. The people who planted the trees had ownership over them, roughly doubling the trees’ survival rate between 1990 and 2019. Combined, all of these efforts helped boost forest cover from 3% to 17%.

“There’s a lot of focus on [tree planting] being a simple, easy, feel-good solution,” said Anderegg. But there is a “growing realization that this is hard and needs to be done right.”

“In the absolute best-scenario,” he added, “it only gets us 10 to 15% of the way towards solving climate change.” 

Even if every single project were a complete success, some experts dispute whether there would even be enough available land on Earth to grow the billions of trees so many governments and companies have hung their hopes on.

Many are wary, even skeptical, about any overreliance on forests to combat rising carbon emissions. 

“If you’re company X and you’re going to either offset your carbon or reduce emissions, reducing your emissions is very, very certain and very likely permanent,” Anderegg said. While it takes decades before the full climate benefit of trees kick in, “shutting down a coal power plant is instantaneous.”

“There’s a lot of focus on people wanting to plant our way out of climate change,” Holl said. “But if we do not aggressively reduce our emissions, then tree growing is not going to get us out of this.” 

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