With the potential to remove billions of tons of climate-warming carbon dioxide from the atmosphere, tree planting on deforested and degraded landscapes has become probably the most popular and well-funded method of restoring the planet’s forests and halting climate change.
From the slew of country-led reforestation initiatives such as the Bonn Challenge and AFR100 to the World Economic Forum’s 1 Trillion Trees Initiative to youth-led NGO Plant-for-the-Planet’s Trillion Trees campaign, tree planting efforts are coming in all shapes and sizes. It has become the main method many countries have adopted to meet the emissions reduction targets they agreed to when they ratified the Paris Agreement on climate change in 2015.
Of course, planting trees has many other benefits. More tree cover can help stop coastal and land erosion, prevent disastrous flooding and provide habitats for wildlife, including many species that are threatened with extinction. But while it offers substantial promise for helping overcome the climate crisis, it is also a strategy in which much can go wrong if its complexity isn’t taken into consideration.
In countries as far apart as China and Mexico, for example, well-intentioned tree planting programs led participants to cut down existing native forests as the schemes made replacing them with seedlings more profitable than keeping them intact. In both Haiti and South Africa, exotic species that were supposed to be useful – fixing nitrogen in soil, for example, or halting erosion – ended up having to be eradicated because they proved to be invasive and lowered the water table. According to a study last year in Nature Sustainability, decades of expensive large-scale tree planting programs in northern India “have not proven effective.” The programs not only failed to increase the proportion of forest cover canopy, but they also shifted forest composition away from the broadleaf varieties valued by local people.
Many other countries have had similar experiences with tree planting that were meant to solve one challenge but ended up creating others.
“Planting trees is a great box-ticker,” says Terry Sunderland, director of International Cooperation and Engagement at the University of British Columbia’s Faculty of Forestry, “but it doesn’t tell you what trees did they plant, where did they plant them and on whose land. Was there a culture that was excluded because of that tree planting? What’s the mortality rate [of the trees]? The problem is that we have gotten into this mindset that planting trees is nothing but good.”
Another caveat for tree planting’s benefits has to do with biodiversity – or the lack thereof, when it has not been considered. This is particularly the case for monoculture tree plantations, which many developing countries plant to win carbon credits and boost their GDP. Large corporations looking for offsets often do the same, such as recently when French oil company Total Energies planted millions of acacia trees on the Batéké Plateaux, a massive stretch of arid savanna in the Democratic Republic of Congo. These plantations may add more trees to the planet (assuming forests weren’t cleared for their planting) – and ideally boost livelihoods too – but they don’t include the multitude of other life forms that inhabit forests.
For Tom Crowther, founder of the RESTOR digital mapping platform and co-chair of the UN Decade on Ecosystem Restoration, the first thing to evaluate is whether planting trees is even the best approach to restoring deforested areas, or if simply protecting the area so that the forests can naturally regenerate is a more effective and ecologically responsible path to take.
“It’s true that in some cases, the soil is particularly degraded, or there’s a local community that wants to gain the economic benefits of specific types of trees,” he says. “So when it calls for active intervention that includes tree planting, obviously getting the right mixture and diversity of species – preferably native species – is of course the highest priority. Obviously there are sometimes synergies and trade-offs with the economic value of those forests, and they should be very carefully considered, very specific to each location.”
In the end, challenges boil down to what many experts say is needed most: better information, showing how each tree planting effort will affect scientific, political, social and economic concerns.
Last year, conservation and environmental science news platform Mongabay introduced a reforestation directory built on research from more than 350 tree planting and reforestation projects in 80 countries. Using criteria from the Forest Landscape Restoration (FLR) approach, it shows how much information is publicly disclosed.
“I kept getting asked what are good projects to support,” explains Rhett Butler, founder of Mongabay. “I thought that’s an easy question to answer, but when I dug into it, I realized it’s not at all. So I wanted to create more transparency in the space.”
According to Mongabay’s introduction of its Reforestation App, it addresses an overall “lack of transparency and reporting surrounding the specifics of tree planting projects via their publicly accessible websites. For instance, nearly half did not specify the number of trees to be planted or the size of the project, and two-thirds of the projects did not disclose the species planted. More than two-thirds of projects did not disclose how they follow up on projects or the survival rates of planted trees.”
However, Butler adds, the database is at an early stage and more information has been coming in. “Because it also increased disclosure by people who manage or run tree planting projects, we found that when private developers were aware we were doing this they started to put more information about their projects online,” he says.
Many foresters hold that planting some monoculture plantations isn’t always a bad idea – it can provide local people with firewood, for example, so that they don’t need to chop down trees in existing forests. Interspersing new trees within naturally regenerating forests, meanwhile, helps invite more species of seed-spreading birds and animals that help propagate more biodiverse growth. But better monitoring, flexibility and adaptation, as well as more transparency in the sector is going to be needed if the promise of tree planting is to become a reality.
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