New study finds that it would be better to leave fossil fuels in the ground rather than attempting to offset ever-increasing emissions

Tree planting is a false solution to the climate crisis. And there just isn't enough land to offset emissions from burning fossil fuels.

Tree planting is often put forward as a way of addressing the climate crisis. “The most efficient way to sequester carbon is the tree,” Marc Benioff, CEO of Salesforce, told CNBC after the launch of the Trillion Trees Initiative at the World Economic Forum in 2020. Four years later, only 0.3% of the target had been actually planted.

But the failure to meet tree planting targets is the least of the problems with relying on trees to “sequester carbon”.

A new study, published in Communications Earth & Environment asks two questions:

• Is carbon offsetting economically viable?

• How much space is needed for afforestation to compensate for carbon emissions?

The study, titled “Carbon offsetting of fossil fuel emissions through afforestation is limited by financial viability and spatial requirements,” is written by Alain Naef from the Department of Economics at the ESSEC Business School in France, Nina Friggens from the Department of Geography at the University of Exeter in the UK, and Patrick Njeukam from the ESSEC Business School.

“Prohibitively expensive”

The study focusses on the 200 largest fossil-fuel companies in terms of the reserves they hold. In total they hold 182 billion tons of carbon. If extracted and burned this would release 673 billion tons of CO₂e.

The total market capitalisation of these 200 companies is just over US$7 trillion. The cost of planting trees to offset the emissions from burning their fossil fuels reserves would be almost US$11 trillion. Buying carbon credits on the EU Emissions Trading System would cost almost US$60 trillion. And using direct air capture technology would cost almost US$674 trillion.

The study concludes that “offsetting through carbon markets or direct air capture is prohibitively expensive”.

“Looking at the cost of offsetting, the takeaway is that it is likely be more effective to stop these emissions in the first place rather than offsetting them,” the authors write.

The study focuses on afforestation, currently the cheapest offsetting technology. The authors show that tree planting would require more land than was previously thought:

Afforestation is often proposed as a carbon sequestration solution, but offsetting emissions from fossil fuel reserves would require covering an area the size of North and Central America solely with trees, displacing communities, farmland and existing habitats.

Nina Friggens, one of the study’s authors, told the LA Times that,

“We have to be careful as a society to think that we can continue to burn fossil fuels and emit CO₂ in a sort of business-as-usual scenario and just offset it later. The picture on that is increasingly looking very unviable.”

And Friggens told AP that, “The general public maybe understand offsetting to be a sort of magic eraser, and that’s just not where we’re at.”

Jonathan Foley, the executive director of Project Drawdown, told AP that carbon emissions are like an overflowing bathtub.

“Trees are the sponges and the mops we use to clean up the mess. But if the taps are still running and the water’s pouring out over the edges of your bathtub, destroying your bathroom and your home, maybe you’ve got to learn to turn off the taps too.”

Fossil fuel regulation “slow to materialise”

Burning fossil fuels represents almost 90% of global CO₂ emissions.

The study points out, “fossil-fuel companies currently face little incentive to reduce the extraction and use of fossil fuels, and regulatory measures to limit these activities have been slow to materialise”.

The phrase “slow to materialise” is an academic euphemism. More than 30 years of UN climate meetings have produced only vague promises of climate action and false solutions.

Fossil fuels were first mentioned in a UNFCCC agreement in 2023 at COP28 in Dubai. And the agreement text merely “calls on Parties to contribute” to “Transitioning away from fossil fuels in energy systems”.

It could hardly have been weaker.

The study concludes that it would be best “not to burn fossil fuel in the first place and simply leave them in the ground” rather than burning them and attempting to “offset” the increased greenhouse gases in the atmosphere.

The authors note that this finding is “in line with a large literature”.

Tree planting is a false solution

The authors point out the problems with attempting to store carbon in trees:

Even when afforestation projects successfully sequester carbon, that tree biomass carbon store is temporary and limited to the life of the tree, unless the resulting timber is preserved. Furthermore, carbon stored in tree biomass is also vulnerable to being lost due to extreme weather events such as droughts, fires, or hurricanes, or due to disease and to insect outbreaks. Afforestation may even exacerbate negative climate impacts such as increased fire risk or severity and lowering surface albedo in boreal and arctic regions, leading to increased warming.

The study runs a thought experiment: how much land would be needed to “offset” the emissions from burning the top 200 companies’ oil, coal, and gas reserves. Trees would replace everything: cities, roads, agricultural land, existing forest, and everything on the land.

“This is of course, not realistic,” the authors point out, but it “gives us the maximum offsetting potential of our planet.”

They conclude that the whole of North and Central America and part of South America would be needed to offset 673 billion tons of CO₂e.

Friggens told the LA Times that,

“That would displace all infrastructure, agriculture and preexisting habitats. It’s not something that we are at all suggesting that we do — it’s just to illustrate the size of the problem.”

Lucy Hutyra is a distinguished professor of Earth and Environment at Boston University. She told the LA Times that the study highlights “the immense social and economic costs associated with burning fossil fuels”.

The study “clearly supports the argument that these reserves are best left unexploited”, Hutyra said.

At a press briefing last week, the lead author of the study, Alain Naef, said, “Our key message from this paper is that this oil and gas should remain in the ground.”