A forest the size of North America would be needed to offset Big Oil's reserves, study finds

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The world would need to plant a forest the size of North America in order to offset planet-warming emissions from the 200 largest oil and gas companies, new research has found.
A study published Thursday in the journal Communications Earth & Environment analyzed the economic and ecological benefits of planting trees as a means of balancing potential carbon dioxide emissions from the projected burning of oil reserves held by the fossil fuel industry. Many experts consider planting trees to be one of the best means of balancing CO2 because the plants absorb and store carbon that otherwise would enter the atmosphere and heat the planet.
But researchers in England and France found that the tree-planting process, known as afforestation, faces insurmountable land use and financial challenges.
"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," said Nina Friggens, a research fellow in plant soil ecology at the University of Exeter and one of the study's authors. "The picture on that is increasingly looking very unviable."
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The world's 200 largest fossil-fuel companies hold about 200 billion tons of carbon in their reserves, which would generate as much as 742 billion tons of CO2 if burned, according to the study. That's far more than the budget required to limit global warming to 2.7 degrees Fahrenheit, or 1.5 degrees Celsius — an internationally agreed-upon target intended to prevent the worst effects of climate change.
The burning of fossil fuels represents about 90% of planet-warming emissions. Most experts and governments agree that rapid action is needed, including a combination of offsetting emissions and reducing them altogether.
But, as the paper notes, "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 researchers set out to calculate how much land area of afforestation would be needed to compensate for these emissions by 2050. The number they came up with was 9.5 million square miles of new trees — more land area than North America and part of South America.
"That would displace all infrastructure, agriculture and preexisting habitats," Friggens said. "It's not something that we are at all suggesting that we do — it's just to illustrate the size of the problem."
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The economic viability of such a project for oil and gas companies is even less realistic. Most estimates suggest that afforestation is the "cheapest" means of offsetting carbon emissions — the international Organization for Economic Cooperation and Development estimates it will cost more than $14.5 per ton of carbon offset.
At that rate, afforestation offsets would cost the 200 largest fossil fuel companies around $10.8 trillion — or roughly 11% of global GDP, according to the study.
By comparison, the price of direct air capture — a newer field of technology that draws CO2 from the air and stores it underground or in industrial products — would be about $908 per ton, costing the companies $673.7 trillion, or about 700% of global GDP, according to the study.
That said, even the more affordable afforestation approach would cause nearly all fossil fuel companies to lose value, according to the researchers — they referred to this as "negative net environmental valuation."
The companies "would be worth less than what they would have to pay for their offsetting," said Alain Naef, an assistant professor of environmental economics at the ESSEC Business School in Paris and another of the study's authors.
Lucy Hutyra, a distinguished professor of earth and environment at Boston University who was not involved in the study, said the paper is an "interesting thought experiment, underscoring the immense social and economic costs associated with burning fossil fuels."
She said the economic findings are noteworthy, although nuanced, as monetary estimates of the economic damages that result from emitting CO2 into the atmosphere — sometimes referred to as "the social cost of carbon" — can fluctuate widely. She noted that the Trump administration recently ordered federal agencies to stop considering such damages when writing regulations, "effectively making it $0."
"[The study] clearly supports the argument that these reserves are best left unexploited," Hutyra said. "However, the authors adopt a maximalist approach, assuming that all emissions must be offset solely through afforestation, which unsurprisingly leads to extreme land requirements. Afforestation alone is clearly insufficient to address this scale of the problem."
Indeed, the researchers acknowledged that the study has limitations as it relies on broad assumptions, including that all existing fossil fuel reserves will be sold and burned. In addition, by focusing on afforestation, it does not account for other approaches that are central to tackling climate change, such as preventing deforestation and restoring existing forests.
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Still, the findings come as the world moves further from its climate goals. Last year was Earth's hottest on record with a global average surface temperature about 1.46 degrees Celsius above the preindustrial baseline — closer than ever to the 1.5 degree threshold.
What's more, the Trump administration has shifted the United States away from decarbonization efforts, including canceling funding for dozens of decarbonization projects in recent weeks and ramping up efforts to increase oil and gas production.
President Trump in January also withdrew the U.S. from the Paris climate agreement, the treaty signed by about 200 nations from which the 1.5 degree Celsius goal stems.
The researchers said their findings should not suggest afforestation and carbon offsetting are futile. "It can work — it can have valuable climate benefits, cultural benefits, social benefits, biodiversity benefits," Friggens said.
Naef said carbon offsetting remains an important tool but cannot be used to compensate for all emissions. "While offsetting can be useful at the margin, the key change will not be offsetting — it will be a reduction of carbon emissions," he said.
The main message from the paper, he added, is that "oil and gas should remain in the ground."
This story originally appeared in Los Angeles Times.