Creating forests can't realistically cancel out fossil fuel emissions

In theory, planting trees can wipe away the carbon cost of burning fossil fuels. But a new peer-reviewed analysis shows just how massive that effort would need to be.

To balance the reserves of the 200 largest oil, gas, and coal companies, the world would have to create an engineered forest covering about 9.4 million square miles – an area larger than all of North America.

“Afforestation on that scale would push people off their land and erase existing habitats,” said Alain Naef, an environmental economist at ESSEC Business School and lead author of the study.

Afforestation alone cannot fix emissions

Afforestation, the deliberate creation of new forests, is often promoted as the cheapest natural sink for industrial emissions.

One gigaton equals one billion metric tons, and the companies’ reserves would release 673 gigatons of carbon dioxide if burned.

The team asked whether trees alone could sponge up that mass before 2050. They calculated how much carbon a newly planted hectare can absorb, then scaled that to the entire fossil portfolio sitting underground.

The answer was 24.75 million square kilometers, roughly 15 percent of Earth’s land surface.

The scale of the problem

Turning that much ground into forest would match the 9.35 million‑square‑mile footprint of North America. Converting it would mean uprooting farms, towns, and existing ecosystems on every continent except Antarctica.

Even if space were found, the trees would need decades to reach maturity, during which the carbon budget for staying below 1.5 °C keeps shrinking.

The Intergovernmental Panel on Climate Change puts the remaining global carbon budget at roughly 400 gigatons far less than what Big Oil alone could emit.

Afforestation offsets cost more than oil profits

To see whether firms could simply pay for offsets, the researchers applied the 2022 average European Union carbon‑market price of just over €80 (about $90) per ton, a figure confirmed by market analysts.

At that level, 95 percent of the companies would show a negative “net environmental valuation.”

“It would be more profitable to leave the fuel in the ground than to extract and offset it later,” the researchers concluded.

They looked at cheaper forestry credits, around $16 per ton, and cutting‑edge direct air‑capture technology, near $1,000 per ton. The first leaves two‑thirds of firms underwater, and the second sinks them all. 

Why forests aren’t free

Today, Earth’s woods and soils already soak up about 30 percent of the carbon we emit each year. Expanding that sink sounds simple, but biology argues back.

Fast‑growing plantations guzzle water and nutrients, push out biodiversity, and, in dry or fire‑prone regions, can even raise local temperatures.

Most of the land earmarked in the calculation is now cropland or rangeland. Replacing it would tighten food supplies and likely spike prices.

Meanwhile, one lightning strike, drought, or beetle swarm can send centuries of stored carbon back into the sky in a single season.

Naef’s group tested a social cost of carbon of $190 per ton, close to the U.S. Environmental Protection Agency’s latest estimate.

At that price, operating any major fossil company produces negative value for society, even before land, labor, or political hurdles are added.

Afforestation land is already in use

Much of the land assumed to be available for afforestation is already claimed for food production, housing, or biodiversity preservation.

In many regions, open or unforested land is not “unused” but is crucial for pastoralists, indigenous communities, or native species.

Treating this land as expendable undercuts existing ecosystems and social systems that depend on it.

Global land competition is intensifying as population grows and diets change. Turning millions of square miles into carbon sinks means competing directly with agriculture, which could threaten food security worldwide.

Even if afforestation were technically feasible, the political and ethical tradeoffs make it an unworkable solution at scale.

Emissions reductions must take priority

Offsetting programs have gained popularity among corporations aiming to appear climate-conscious without changing their core operations. But many of these schemes lack transparency, consistency, or verification.

Critics argue they allow continued pollution under the guise of future cleanup, which often never materializes or is exaggerated in impact.

Naef and colleagues warn that relying on afforestation as a main climate tool distracts from the immediate need to reduce fossil fuel use. They emphasize that while trees can help, carbon math alone shows the gap is too wide.

Emission reductions must take priority if there’s any chance of meeting international climate targets.

Direct air‑capture still matters, and real forest restoration still protects wildlife. But the study shows those tools cannot shoulder the job of burying every barrel’s worth of carbon.

Keeping proven reserves in the ground costs nothing, buys time for cleaner energy, and avoids an impossible tree‑planting bill.

The study is published in Communications Earth & Environment.

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