Can Planting 1 Trillion Trees Prevent Climate Change?

Researchers associated with Crowther Lab in Switzerland have found that global tree restoration to the 900 million acres (0.9 billion hectares) canopy cover setting, an area approximately the size of the United States, is our most effective climate change solution to date. 

In recent years, climate change has loomed like a dark ghost around the world, contributing to everything from gentrification in Miami to refugees fleeing drought and crop shortages in Guatemala. However, the urgency of the issue reached new heights when the United Nations Intergovernmental Panel on Climate Change (IPCC) stated in 2018 that rapid, "wide-ranging and unprecedented changes in all aspects of society" would be needed to reduce carbon dioxide. Prevent levels and catastrophic global warming by 2030.

Scientists have indeed proposed drastic measures—just not in the way you might think. In the same IPCC report, the UN suggests that adding 2.5 billion acres (1 billion hectares) of forest to the world could limit global warming to 2.7 degrees Fahrenheit (1.5 degrees Celsius) by 2050. planting new trees. A lot .

And now, the UN may have data to support its proposal.

Trees Recover Carbon

In a study published July 5, 2019 in the journal Science, a group of researchers associated with the Crowther Lab in Switzerland found that global tree restoration reached the 223 million acres (900 million hectares) canopy cover setting. The size of the US - "our most effective climate change solution to date". These trees will store 205 billion tons (186 metric tons) of carbon, or roughly two-thirds of the carbon emitted "as a result of human activities since the Industrial Revolution," according to a press release. Despite some reports saying that this much forest restoration is roughly equivalent to 1 trillion trees, this statistic is actually linked to an estimate from an older 2015 study.

Crowther Lab's study lead author Jean-François Bastin breaks down his 2019 analysis by email. “The idea was to predict what tree cover can be expected when you remove the 'human factor', i.e. what types of forests will occur naturally and where in the absence of any other development,” he says. Bastin and his team used a form of artificial intelligence known as "machine learning" to create "a model that would relate tree cover to climate/soil/topography, based on 78,000 observations of tree cover in protected areas."

Bastin explains that the researchers then further mirrored the data to estimate "the planet's total potential tree cover." Next, the team excluded land in use for urban settlements, cropland and existing forests, giving the total amount of land available for restoration. The study includes a map showing that many trees of the world can support different parts of the coverage; The top three areas are Russia, Canada and the USA.

A Worldwide Effort in Reforestation

The timing of the work could not have been more perfect in many ways, as it aligns with current global efforts in ecological restoration. An example is the Trillion Tree Vision, which aims to restore 1 trillion trees by 2050. Another is the Bonn Challenge (150 million hectares), a partnership between the German government and the UN's International Union for Conservation of Nature, which aims to restore 371 million acres (150 million hectares) of degraded and deforested land to restoration and 864 million acres (350 million hectares) by 2030.

You may be thinking that this sounds pretty easy. Let's all roll up our sleeves and save the planet by planting one tree at a time - right? But some experts say the situation is actually a little more complicated than this rosy picture. Especially if most countries don't help to help.

"Implementing forest restoration at the scale discussed in this paper is not as easy as it sounds," says Jim Hallett, chairman of the board of the Ecological Restoration Association. “By 2018, there were over 420 million acres (170 million hectares) of commitments by 58 countries, exceeding the Bonn Challenge target. Current estimates suggest that around 29 percent of the committed land is currently under restoration, but most of these works have been completed. By several countries done."

By 2021, the Bonn Challenge has exceeded its goal of restoring 371 million acres of land and has pledged to restore 518 million acres (210 million hectares) of deforested land from more than 60 countries.

Hallett addresses the major challenges facing restoration on such a global scale, "including funding, governance, land tenure, and the capacity to do property [and] work." Hallett concludes: "In some contexts, there is ample evidence that the project will fail if the benefits of restoration are not shared equally. So incentive programs need to be carefully developed."

While Hallett acknowledges that forest restoration is important to address climate change, restoration alone will not be enough. After all, it takes time to implement such large restoration projects and for these trees to store carbon. Hallett emphasizes that "the prospect of future restoration should not be used as an excuse to degrade pristine lands."

A forest area the size of the National Mall disappears every 15 minutes around the world.

Will Planting Trees Really Work?

Other scholars question not only the practicality of the study's claims, but also the study's methodology. "Many of the claimed restoration sites are clearly unsuitable for more trees than they currently support. If you look closely at the map, a large proportion of these areas are in areas where the soils are permanently frozen," says Eike Luedeling, a climate change agent. Researcher and professor of horticultural sciences at the University of Bonn.

Luedeling continues, "The methodology implicitly (possibly not on purpose) implies that carbon stock is proportional to canopy cover, meaning that ecosystems without trees contain no carbon. This is clearly false and strongly inflates the [restoration] global estimate."

Jan Börner, Luedeling's colleague and professor of sustainable land use economics at the University of Bonn, is similarly skeptical. Börner says some of the areas proposed for restoration as part of the current study are already being used for other purposes. Börner considers the study "interesting academic work ... but as a [climate change] mitigation strategy proposal (and advertised as such!), it sends a misleading signal to the international climate policy debate".

But don't worry yet. Both Bastin and Hallett stress that the UN has declared the period from 2021 to 2030 as the "Decade of Ecosystem Restoration", which could spur nations to act quickly - and some countries are already directly tackling the initiative. And according to Hallett, forest restoration does much more than impact climate change, including conserving – even increasing – biodiversity and protecting the ecosystem that we humans rely on for our food and water.

But even the study's authors admit that it will take a lot of goodwill to make this grand vision a reality.

"We need universal action: international organisations, NGOs, governments, all citizens - anyone can participate," Bastian says. "Local communities and small organizations can be particularly effective. While they don't have the same reach as national agencies, they have the advantage of knowing what works best in their own backyard."

This story is part of Covering Climate Now, a global collaboration of more than 250 news organizations to strengthen coverage of the climate story.

Now This Ambitious

Ethiopia made headlines for planting 350 million trees in just one day at the end of July 2019 as part of efforts to combat deforestation and climate change