Why planting trees is no silver bullet against climate change

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“Nature-based solutions” are gaining traction as a means of fighting climate change while protecting biodiversity. Tree planting, a key part of several countries’ COP26 pledges, is one such proposal – but experts say that reforestation, while essential, is far from a silver bullet against climate crises. 

Two of the world’s biggest fossil-fuel producers, Russia and Saudi Arabia, have promised in recent weeks to go carbon neutral by 2060. Both Moscow and Riyadh plan to offset much of their carbon emissions from fossil fuels by planting millions of trees.        

And they are not alone. COP26 host Boris Johnson wants to make tree planting a priority at the UN climate conference along with additional action on “coal, cars and cash”.

“To be net-zero for carbon you must be net-positive for trees, and by 2030 we want to be planting far more trees across the world than we are losing,” the British prime minister said in August.

Tree-planting belongs to a wider set of environmental measures known as “nature-based solutions”, which the UN and many scientists say are critical to averting catastrophic climate change – and which COP26 organisers hope to propel into the mainstream.

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The International Union for Conservation of Nature (IUCN), which coined the term, defines nature-based solutions as “actions to protect, sustainably manage, and restore natural and modified ecosystems”. Protecting and expanding forests is central to this approach.

“Forests, and in particular tropical forests, absorb about a third of the greenhouse gases emitted every year,” explained Anne Larigauderie, executive secretary of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES), which works with the UN on protecting biodiversity, in an interview with FRANCE 24. “They could do much more if we stopped deforestation and invested more in forest management and the protection of these ecosystems.”

Mangrove restoration is often cited as a key example, as these unique ecosystems act as natural barriers against coastal erosion and flooding. 

Simply planting trees, though, does not cut it. 

“Nature-based solutions must have a double benefit,” said Freddy Rey, a specialist in ecological engineering at France’s National Institute of Agronomic Research (INRAE). “At least one must concern nature, and the other, society – for example, the fight against climate change, health, food security or protection from natural hazards.”

In France, INRAE’s researchers have added vegetation along the banks of some waterways to fight erosion and therefore flooding. Rey said this offers a more lasting alternative to traditional dams.

“Over time the vegetation will spread, whereas artificial barriers will wear down,” he told FRANCE 24. According to the IUCN, nature-based solutions are often less costly in the long term than the construction and maintenance of technological infrastructure.

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‘Buzz’ around nature-based solutions

Of course, planting trees and expanding green spaces are not new ideas. But Rey said that, at least in France, the "nature-based solutions" label has succeeded in “creating a buzz” around ecological practices, especially among elected officials. Lawmakers are working with INRAE to develop solutions to local environmental issues. NGOs are also playing a role, like the group France Nature Environment, which last year published a guide for cities seeking to implement these kinds of solutions.

While practices like reforestation may be “low tech” they still require highly specialised research and innovation.

“Far from simply ornamental greening projects – whose maintenance often involves intensive use of water, energy and fertilisers – nature-based solutions rest on scientific knowledge and technical know-how drawn largely from ecological engineering,” said one recent study.

Larigauderie of IPBES laments that, at major international climate talks, “people often talk about technical and technological solutions … and don’t pay enough attention to nature as a source of solutions”.

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For all the promise they hold, nature-based solutions should not be seen as a miracle cure for the climate. The natural world constantly shifts and evolves, and researchers must adapt accordingly. Planting along shores and waterways, for example, has its limits.

“While we’ve mastered the design methods for civil engineering based on mechanical and physical properties, the same isn’t true for plant engineering, which brings into play living materials whose properties are much harder to control,” said INRAE researcher André Evette in a statement.

Mountainous regions, lakes and actively used waterways present particular challenges. 

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Disguising ‘climate-trashing’

“We shouldn’t think we’re going to change the world with plant stems. We’re not going to stop tidal waves with branches,” said Rey. “You need a balance between these nature-based solutions and the know-how of civil engineering.” 

Some NGOs, such as Friends of the Earth, meanwhile fear that nature-based solutions can “disguise climate-trashing business as usual”. 

“Under the guise of Nature Based Solutions, big business and governments continue to expand … industrial agriculture and fossil fuel extraction, while claiming to address their climate impacts through investment in activities such as mass tree planting,” Friends of the Earth wrote in a recent statement.

Larigauderie likewise noted that the concept can be slippery, and warns against putting too much stake in it.

“Nature will not be able to absorb a frantic increase in our consumption,” she cautioned. “The number one message is that we must reduce our energy consumption, and rethink our lifestyles and agriculture. Nature can do a lot for us, but we must also correct ourselves.”  

The COP26 summit will take stock of the actions taken by governments to meet the targets set by the 2015 Paris Agreement and the stiff challenges that remain if they are to keep global warming below 1.5° or even 2° Celsius. Building on the recent COP15 talks on biodiversity, COP26 has nature-based solutions on the agenda, with one of its 10 working days devoted to the theme of nature.

Many hope it will be just the beginning for what the UN calls “an essential part of the overall global effort to achieve the goals of the Paris Agreement”.

This article was adapted from the original in French.

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