Forests can no longer carry the climate burden alone

Intact forests once absorbed 7.8 billion tonnes of CO₂ each year, about one-fifth of global emissions. Today, their reliability is fading. Climate change, deforestation, and land degradation now threaten this vast carbon sink.

A new study by the Potsdam Institute for Climate Impact Research (PIK) raises alarms. The experts warn that relying on forests to deliver consistent carbon removal is no longer a safe bet.

Worse still, most climate strategies still assume forests will expand and stay resilient.

Dangerous gamble with carbon storage

Michael G. Windisch, the lead author of the study, highlights the growing risk.

“Our climate strategies bet on forests not only remaining intact, but even expanding,” he said. But with rising wildfires and Amazon deforestation, this is a fragile assumption.

Forests are vulnerable to pests, disease, drought, and other climate-driven changes. If these threats intensify, forests may begin to release more carbon than they store. That would wipe out years of progress.

The risks of depending on forests

The study outlines three key risks. First, we depend on existing forests to stay intact. Second, we rely on them to keep removing carbon each year. Furthermore, we plan to increase forest cover for future carbon removal. If any part fails, the whole plan collapses.

This is why the researchers stress caution. Immediate action is essential to prevent forest disturbances from derailing climate goals. Postponing action by just five years can double the mitigation cost and effort.

Climate models confirm forest risks

The researchers used REMIND-MAgPIE, a climate and land-use model, along with the LPJmL vegetation model. They introduced disturbance rates – events like pest outbreaks, fire, and wind damage – into their scenarios.

Their findings? Even low disturbance rates drastically affect outcomes. Myopic policy responses that delay action lead to steeper emission cuts and higher costs.

The models show that a five-year delay doubles the pressure on all sectors, especially energy and land use.

Climate costs soar as forest sinks shrink

Under immediate action, the carbon price by 2050 rises to $327 per tonne. But with delay, that shoots up to $483. GDP losses also increase from 2.4 to 2.7 percent.

The energy sector suffers more in myopic scenarios. Renewables must scale up much faster. Fossil fuel use must fall more steeply. The industry and transport sectors, especially, bear heavier burdens.

Negative emissions technologies like BECCS and DACCS become essential. But delayed action means building them faster and larger, increasing pressure on land and budgets.

In delayed scenarios, land demand for mitigation jumps to 563 million hectares – larger than the European Union. That’s 149 million hectares more than if action were taken immediately.

Forests need surveillance, not assumptions

Many global climate models ignore natural disturbances or assume forests react positively to rising CO₂. But evidence shows otherwise. Phosphorus limits and shifting ecosystems reduce forests’ ability to absorb carbon.

Some models also underestimate human impact, assuming forest lands are quickly and efficiently reused. In reality, land speculation and mismanagement delay recovery.

“Forests are not an infinite resource,” Florian Humpenöder warns. He urges immediate monitoring and realistic projections. Only then can we act fast when carbon sinks weaken.

The study also shows that myopic responses to small disturbances demand more effort than immediate responses to double those disturbances. Every delay becomes costlier than we expect.

Forests can’t solve the climate crisis

“We must act immediately to safeguard the carbon stored in forests,” said Windisch. Without foresight, future generations may inherit a climate plan full of gaps.

“Alongside protecting forests, it is essential to promote sustainable land use practices,” added study co-author Alexander Popp. This includes conserving biodiversity and avoiding reckless land expansion.

Forests are crucial – but they can’t solve the climate crisis alone. The study leaves no room for wishful thinking. Forests will face more stress in the future. Assuming otherwise puts climate goals at risk.

Instead of hoping forests remain stable, policies must adjust. Immediate, coordinated action across all sectors can still deliver on the Paris targets – but the window is closing.

The study is published in the journal Nature Communications.

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