Climate goals overestimate forests’ carbon absorption capacity: Study

Postponing action to reduce emissions and to protect and monitor forests could jeopardise climate targets

Forests are the key to decarbonising the earth. Most global climate plans depend on that. But there’s a critical assumption that the world’s forests will stay healthy, undisturbed, and productive. Is that too optimistic an outlook?

That’s one of the key questions that a new study from the Potsdam Institute for Climate Impact Research (PIK) looks into. Titled ‘Hedging our bet on forest permanence for the economic viability of climate targets’, the study finds that a misaccounting of the potentially decreasing ability of forests to absorb carbon dioxide can make global climate goals unreachable, and definitely, much more costly.

In other words, postponing action to reduce emissions and to protect and monitor forests could jeopardise climate targets. 

Then vs now

Earlier, intact pristine forests had the capacity to absorb 7.8 billion tonnes of CO₂ annually—about a fifth of all human emissions. But now, with climate change and destructive human activities like deforestation, their carbon storage capacity is increasingly at risk, finds the study published in Nature Communications,

“Delaying action leads to disproportionately higher costs. Right now, our climate strategies bet on forests not only remaining intact, but even expanding. However, with escalating wildfires like in California, and continued deforestation in the Amazon, that’s a gamble. Climate change itself puts forests’ immense carbon stores at risk,” says Michael Windisch, lead author of the study, and PIK guest scientist. 

Today, forests are an important decarbonisation tool in removing more than 13 billion tonnes of CO2 from the atmosphere annually—a third of all anthropogenic emissions. 

But to limit the earth’s warming to well below 2 °C requires additional Carbon Dioxide Removal (CDR). One of the low-cost ways to achieve that is regenerating forests to enable CDR at a large-scale, finds the study.

“We must act immediately to safeguard the carbon stored in forests. Otherwise, compensating for potential forest carbon losses through steeper emissions cuts in key emission sectors like energy, industry and transport will become increasingly expensive and possibly unattainable,” says Windisch.

Human activities pose major threat

Like everything else on the earth, forests too, are vulnerable to environmental changes and human activities like deforestation and degradation. 

According to the study, current climate models may have missed certain key factors. 

• Models neglect natural disturbances from windfall, pests, drought, and disease19 that make up the bulk of current forest damage and show the most pronounced increasing trends in many regions
• Models might overestimate the positive influence of indirect human disturbances of warmer temperatures and CO2 fertilization 
• Direct human disturbance like deforestation and degradation are likely underestimated in scenario-building models that currently assume perfect efficiency in replacing forest land with agriculture

Rising temperatures decrease the carbon absorption capacities of temperate forests, while only 45% to 65% of deforested land for agriculture was used within a few years after clearance due to mismanagement, land speculation, and uncontrolled fire clearings, according to the study.

“Staying below critical warming thresholds requires more than just hoping forests will remain intact. Alongside protecting forests, it is essential to promote sustainable land use practices– not only to preserve biodiversity but also to avoid drastic economic consequences and to secure our climate future,” says Alexander Popp, head of PIK’s Land Use Transition lab and author of the study.

The future of the planet depends on not only protecting and preserving the remaining forests, but enabling mechanisms to enable their regrowth so that forest stocks remain intact.

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