Countries are cheating their way to net zero by overrelying on forests

Countries are taking a shortcut to net-zero emissions by including forests and other “passive” carbon sinks in their climate plans, in a tactic that will thwart global efforts to halt climate change, leading researchers have warned.

Relying on natural carbon sinks to soak up ongoing carbon emissions from human activity will condemn the world to continued warming. That is according to the researchers who first developed the science behind net-zero emissions, and who have today launched a highly unusual intervention to call out nations and companies for misusing the concept.

“This paper is a call to clarify to people what was originally meant by net zero,” Myles Allen at the University of Oxford told a press briefing on 14 November.

Natural sinks such as forests and peat bogs play a vital role in Earth’s natural carbon cycle by absorbing some of the carbon in the atmosphere. But existing sinks cannot be relied upon to offset ongoing greenhouse gas emissions.

If they are used in this way, global atmospheric concentrations of carbon dioxide will remain stable once “net zero” is reached, and warming will continue for centuries because of the way the oceans absorb heat, Allen warned. “You could think you are on a path of 1.5°C, and end up with warming of well over 2°C,” he said. “This ambiguity could, in effect, cost us the goals of the Paris Agreement.”

To stop global temperatures rising, emissions need to reach net zero without relying on passive uptake by the land and oceans. This allows existing natural sinks to continue absorbing excess CO2, bringing down atmospheric concentrations of the gas and offsetting ongoing warming from the deep ocean.

However, many countries already count passive land sinks such as forests as greenhouse gas removal in their national carbon accounts. Some, including Bhutan, Gabon and Suriname, have even declared themselves to be already net zero, thanks to their existing extensive forest cover.

Others have set long-term net-zero targets based on this approach. Russia, for example, has promised to reach net-zero emissions by 2060, but the plan relies heavily on using its existing forests to absorb ongoing carbon emissions.

“Maybe you will get some countries deliberately using this in a mischievous way,” Glen Peters at the CICERO Center for International Climate Research in Oslo, Norway, told the briefing. “This is going to be more problematic in countries with large forest areas as a share of their total land.”

The team fears this issue will become more acute as carbon markets develop and the pressure on nations to decarbonise intensifies. “As carbon becomes more valuable, the pressure to define any removal you can as a negative emission, in order potentially to be able to sell it on the carbon offset markets, will become much stronger,” said Allen.

Nations and companies with net-zero targets in place should revise their approach to exclude passive carbon uptake from their account, the team says.

Natural sinks can count as carbon removal if they are additional to what already exists: for example, a new forest is planted or a peat bog is rewetted. However, these kinds of natural carbon sinks are vulnerable to climate impacts such as wildfires, droughts and the spread of invasive species, making them unreliable for long-term sequestration.

This hasn’t stopped nations from leaning heavily on these natural sinks in their net-zero strategies. One 2022 study found many countries, including the US, France, Cambodia and Costa Rica, plan to rely on forest carbon or other nature-based removal to balance out ongoing emissions. “Many national strategies ‘bet’ on the increase of carbon sinks in forests and soils as a means of achieving long-term targets,” the study’s authors wrote.

Natural carbon sinks must be preserved, but should not be relied on to balance out ongoing emissions, stressed Allen. Instead, he urges nations to aim for “geological net zero”, which would ensure that all ongoing carbon emissions are balanced with long-term carbon sequestration in underground stores.

“Countries need to acknowledge the need for geological net zero,” he said. “Which means if you are still generating carbon dioxide from burning fossil fuels by mid-century, you need to have a plan to put the carbon dioxide they generate back into the ground.”

“Geological net zero seems a sensible global goal for countries to aim for,” says Harry Smith at the University of East Anglia, UK. “It helps clarify a lot of the ambiguity that plagues the way countries currently account for removals on land.”

But that could have knock-on consequences for climate ambition, he warns. “What might the new politics of geological net zero be? How might this impact the climate ambitions of governments if geological net zero moves the goalposts on their climate strategy?”