Why reforestation is more complicated than you think

Responsible reforestation is not as simple as planting any tree, anywhere. For forests to thrive, it has to be the right species, in the right place, for the right reason.

By Christina Nunez — June 22, 2022

In November 2018, a forest fire ignited in the extreme drought conditions of Butte County in Northern California, tearing down the steep terrain and through small towns in a literal firestorm. By the time the Camp Fire was contained, it turned out to be the deadliest and most destructive blaze in California’s history, killing 85 people and burning 153,336 acres.

Now scientists like Joseph Stewart, an ecologist and postdoctoral researcher at the University of California, Davis, are researching how to repair and replant the region. Some forest fires make way for new tree growth and a stronger, more resilient ecosystem. But after an intense blaze such as the CampFire, the trees may be gone for good if the super-dry conditions lead to higher seedling mortality.

“Even if there are seeds left, there’s less chance that the forest is going to be able to come back on its own,” says Stewart. His research focuses on two questions: what to plant and where — particularly after mega-fires like the Camp Fire. The devastation yields an opportunity where he and other scientists can devise strategies to bring forests back and, at the same time make them more resistant to climate change. “We’ve got a pretty challenging situation in terms of the amount of forest that is in degraded conditions right now,” Stewart says. “But the flip side of that is, there’s a lot of opportunity to learn from our efforts to repair and make our forests more resilient as we’re engaging in those efforts.”


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The complexity of reforestation, or the act of restoring a razed or degraded forest back to a living landscape, goes beyond the basic work of just planting trees. Planting to replace what was lost can seem like the most obvious answer. After all, a single mature tree can store carbon, produce oxygen, filter water, provide shelter and food for people and wildlife, and stop soil erosion … the list of benefits goes on. But it’s not as simple as planting any tree, anywhere. This is the heart of responsible reforestation: right species, right place, right reason. The goal is to ensure a lasting, thriving ecosystem where native species support the wildlife — everything from fungi and insects to birds and mammals — that has evolved alongside them. Halting and reversing the destruction of forests means protecting and managing them for the long term.

A helicopter hovers over conifers while fighting the Camp Fire in California in 2018

Getty Images

Fighting the Camp Fire in Butte County, California. The area's reforestation plan includes planting seeds have been harvested from areas that make them better suited for hotter and drier conditions.

Forests in crisis

Over the past three decades, 420 million hectares of the world’s forests have vanished, according to estimates from the United Nations’ Food and Agriculture Organization (FAO). That area represents a little more than half the contiguous United States. These are losses the world can’t afford. Trees are a critical buffer against climate change. Forests absorb an estimated 7.6 billion metric tonnes of carbon dioxide a year from the planet’s atmosphere, or one and a half times the US annual total, according to a recent study by the World Resources Institute.

Trees are being destroyed by building development, wildfires, landslides, and other environmental factors, but agriculture drives almost 90% of deforestation, according to a recent FAO study: Conversion to cropland accounts for more than half, livestock grazing almost 40%. 

Recognizing the crisis, leaders of 140 countries representing 91% of the world’s forests agreed to “halt and reverse forest loss and land degradation by 2030” at the COP26 climate talks in Glasgow last year. 

“Nature-based solutions for forests and land — things like forest protection, improved forest management, and forest restoration — can help reverse all those trends that we’re seeing around the world,” says Linda Walker, senior director of corporate engagement, forests, for World Wildlife Fund (WWF). 

A broad group that includes scientists, governments, nonprofits, and businesses is exploring what reforestation actually means when done right.

Learning the right way to reforest 

Reforestation has gotten some big boosts in recent years, such as the World Economic Forum’s initiative, a plan to conserve, restore, and grow 1 trillion trees globally by 2030, and the Jane Goodall Institute, an organization founded by renowned scientist and conservationist Dr. Jane Goodall to protect and restore forests. WWF’s Walker says that even though much of the world’s forestland remains at risk, the opportunity to reverse course is promising. 

Several companies, including HP, are part of the project, which emphasizes the word “grow” over “plant,” its website notes, because “simply putting a seedling in the ground is not sufficient—that tree needs to be supported to maturity to reach its full potential. It also needs to be the right species, planted in the right conditions.” 

Reforestation means restoring a forest to where it once was, not creating a new forest where there never was one, which might mean destroying a different, but critical, ecosystem. The consequences for ignoring this fundamental premise can be costly in terms of both carbon and cash, and ongoing scientific research offers clues about what works and what doesn’t. 

In South Africa, non-native Australian acacias planted in the 19th and 20th centuries ended up taking over natural grasslands and lowering the water table, and now the annual chore of clearing them costs millions of dollars. Scientists from the Botanic Gardens Conservation International and the Royal Botanic Gardens, Kew, cite the acacia example in a post introducing “10 Golden Rules for Restoring Forests,” which lays out simple best practices, such as selecting the right area and planting species that can maximize biodiversity. 

Paying attention to these lessons will determine the success or failure of the many public and private reforestation efforts now underway around the world. 

“We can only effectively plant trees in locations where at some point in time they were cut down or destroyed,” notes Ansgar Kahmen, a botanist and professor of environmental science at the University of Basel who studies how reforestation changes in the face of a changing climate. “I think we’re fooling ourselves if we think we can keep burning fossil fuels and planting a tree will compensate for it.”

workers planting saplings in the Florida Panhandle

The Arbor Day Foundation

Workers plant longleaf pine saplings in the Florida Panhandle’s Econfina Creek Water Management Area.

Complications of climate change

The challenge of what to plant, and where, becomes trickier with climate change. Ongoing research is aimed at discovering which trees will thrive in a warming world. 

At a research site in northern Switzerland equipped with a crane that hoists researchers into the canopy, Kahmen and colleagues are simulating drought on a subset of trees by putting a roof over them, diminishing the amount of rain they get. The goal is to see not only how species respond, but which might be most adaptable. 

“There’s a big debate in Europe at the moment: What are the appropriate trees that we should reforest with? And there is no consensus,” Kahmen says. “It actually opens a big ecological discussion. What is a native tree in the future?” 

These kinds of questions are relevant far beyond Europe, as forests are being planted in different regions, with varying objectives, worldwide. Between 2000 and 2018, 46 million hectares of forest were planted, almost a quarter of which replaced naturally regenerating forests, according to a 2020 remote sensing survey from the FAO. 

But merely restoring tree cover does not guarantee long-term success, particularly as saplings face conditions that might be different from those of their ancestors. “Ecosystems do have some resilience, but we don’t really know what this resilience is for different species that we work with, and how fast they can actually acclimate,” Kahmen says. 

Scientists like Kahmen and Stewart are developing the research and technology needed to inform planted trees’ survival in the decades to come. Stewart has built computer-based tools that can help ecosystem managers identify, for example, which wildfire-scarred areas are not likely to regenerate on their own and may need intervention, and which species are likely to thrive as environmental and climate conditions evolve. 

“With the climate changing as fast as it has, tree populations often aren’t adapted to the local conditions anymore,” Stewart says. For example, climate models predict that conifer forests like the one destroyed by the Camp Fire, made up of ponderosa pine and Douglas fir, will be replaced by mixed forests of oaks and pines, chaparral, or grassland.

The goal is to ensure a lasting, thriving ecosystem where native species support the wildlife — everything from fungi and insects to birds and mammals — that has evolved alongside them.

In such cases, seeds might come from slightly different locations than where they are being replanted. The Bureau of Land Management’s reforestation plan for the Camp Fire includes a technique called assisted migration, where planted seeds have been harvested from areas that make them better suited for hotter and drier conditions than the trees that once stood.

Finding, and funding, the right balance 

Even the best science on planting the right trees and enhancing forest resilience will be wasted if planting efforts do not consider the local communities and people. Plenty of well-meaning efforts have proceeded without a knowledge of local ecosystems or what communities want. A 2019 University of Vermont study found, for example, that a quarter of Detroit residents opted out of a city-sponsored tree-planting program because they didn’t trust the city to maintain the trees. 

And in the United Kingdom, government efforts to plant trees raised alarms in communities where vulnerable peatlands were affected. Other misguided projects have placed trees on native grasslands, harming an ecosystem that already stores carbon and water. 

“It’s like two sides of a coin,” says Ben Wilinsky, director, partnerships and innovation, for the Arbor Day Foundation (ADF), which just turned 50 years old and has projects and partners in more than 45 countries. “One is, where is the ecological need greatest from a climate, community, and biodiversity standpoint? The other is, who’s ready to [plant]?” 

The science, outreach, and preparation needed to reforest responsibly, not to mention the projects themselves, require significant funding. Since establishing its Sustainable Forests Cooperative in 2019, HP has forged forest-stewardship partnerships with environmental organizations including ADF, WWF, and the Jane Goodall Institute. HP is WWF’s largest partner to date, pledging $80 million in 2021 to address the impact of printing with HP printers. The partnerships support HP’s goal of zero deforestation for HP paper and paper-based packaging. WWF also helped HP develop a groundbreaking methodology to account for not only HP-brand paper but any paper used for printing. HP aims to counteract deforestation for any paper in its products and print services by 2030. 

The scope of HP’s reforestation efforts is broad geographically but also targeted regionally, from work in Brazil’s Atlantic Forest with WWF to planting more than 1 million trees in the United States with ADF, including in wildfire-devastated regions in California.

On-the-ground partners

partners Reforestation projects can avoid pitfalls through careful ecological study and community engagement. In Brazil, WWF works through a local organization, Copaíba, to build relationships with landowners and others on the ground. A fifth-generation coffee farmer who rehabilitated degraded areas to connect patches of existing forest on her land told WWF, “Living in a balance between coffee production and the environment provides a benefit not only for our family but for all the other people who will enjoy these resources.” The farmer also wants her three-year-old daughter to inherit land that will be prosperous over the long term.

“There’s a recognition that every single landowner might have a different interest in doing this restoration,” Walker says, mentioning objectives including soil erosion prevention, pest management, and ecotourism. “Some landowners are not interested, and we respect that.” 

In many regions, forests fall because locals have an economic incentive to sell or use the timber or clear the land for agriculture. ADF’s Wilinsky echoes Walker in pointing out that reforestation efforts depend on local support and a plan for future management to change that paradigm. 

“It’s definitely more than just planting a tree,” he says. “These are livelihood programs. ‘If it pays, it stays’ is a term that we hear a lot. How are these communities set up for long-term success?” Ensuring the survival of fresh saplings for decades to come goes hand in hand with protecting the forests we already have. That’s because, for all our urgency to plant trees, forested land is a finite resource. We can’t magically make more of it. “In my 30 years of conservation work, this is one of the most exciting, but sobering, times,” says Walker. “The urgency has never been greater, but also the interest has never been greater.”