Restoring degraded environments, such as by planting trees, is an important climate solution but no substitute for preventing fossil fuel emissions to limit global warming, University of Melbourne researchers Kate Dooley and Zebedee Nicholls write in a post for The Conversation.
Nature-based solutions are often touted as a stand-alone solution to the climate crisis, they write. But in their new research, the two authors calculated the maximum potential for responsible nature restoration to absorb carbon dioxide in the atmosphere. They found that, combined with ending deforestation by 2030, this could reduce global warming 0.18°C by 2100. In comparison, current pledges from countries put us on track for 1.9-2℃ warming.
This is far from what’s needed, Dooley and Nicholls note, to mitigate the catastrophic impacts of climate change, and is well above the 1.5℃ goal of the Paris Agreement. And it pours cold water on the idea we can offset our way out of ongoing global warming.
The priority remains rapidly phasing out fossil fuels, which have contributed 86% of all CO2 emissions in the past decade. Deforestation must also end, with land use, deforestation, and forest degradation contributing 11% of global emissions.
The Hype Around Nature Restoration
Growing commitments to net-zero climate targets have seen an increasing focus on nature restoration to remove CO2 from the atmosphere, based on claims nature can provide over one-third of climate mitigation needed by 2030.
However, the term “nature restoration” often encompasses a wide range of activities, some of which actually degrade nature. This includes monoculture tree plantations which destroy biodiversity, increase pollution, and remove land available for food production.
Indeed, the hype around nature restoration tends to obscure the importance of restoring degraded landscapes, and conserving existing forests and other ecosystems already storing carbon.
So Dooley and Nicholls applied a “responsible development” framework to nature restoration for their study. Broadly, this means restoration activities must follow ecological principles, respect land rights, and minimize changes to land use.
This requires differentiating between activities that restore degraded lands and forests (such as ending native forest harvest or increasing vegetation in grazing lands), compared to planting a new forest.
The distinction matters. Creating new tree plantations means changing the way land is used. This presents risks to biodiversity and has potential trade-offs, such as removing important farmland.
On the other hand, restoring degraded lands does not displace existing land uses. Restoration enhances, rather than changes, biodiversity, and existing agriculture.
The Potential of Nature Restoration
Dooley and Nicholls suggest this presents the maximum “responsible” land restoration potential that’s available for climate mitigation. It would result in a median 378 billion tonnes of CO2 removed from the atmosphere between 2020 and 2100.
That might sound like a lot but, for perspective, global CO2 equivalent emissions were 59 billion tonnes in 2019 alone. So the removals we could expect from nature restoration over the rest of the century is the same as just six years’ worth of current emissions.
Based on this CO2 removal potential, the two researchers assessed the impacts on peak global warming and century-long temperature reduction. They say they found nature restoration only marginally lowers global warming—and any climate benefits are dwarfed by the scale of ongoing fossil fuel emissions, which could be over 2,000 billion tonnes of CO2 between now and 2100 under current policies.
But let’s say we combine this potential with a deep decarbonization scenario, where renewable energy is scaled up rapidly and we reach net-zero emissions globally by 2050.
Then, Dooley and Nicholls calculate the planet would briefly exceed a 1.5℃ temperature rise, before declining to 1.25 to 1.5℃ by 2100.
Of course, they say, phasing out fossil fuels while restoring degraded lands and forests must also be coupled with ending deforestation. Otherwise, the emissions from deforestation will wipe out any gains from carbon removal.
So the study also explored the impact of phasing out ongoing land use emissions, to reach net-zero in the land sector by 2030.
As with restoration, halting deforestation by 2030 has a very small impact on global temperatures, and would reduce warming by only around 0.08℃ over the century. This was largely because the baseline scenario already assumed governments would take some action. Increasing deforestation would lead to much larger warming.
Taken together—nature restoration plus stopping deforestation—end-of-century warming could be reduced by 0.18℃.
Is This enough?
In a low-emissions pathway to limit global warming to 1.5℃ this century, Dooley and Nicholls expect global temperature rise to peak in the next one to two decades.
As their research shows, nature restoration will unlikely be done quickly enough to offset fossil emissions and notably reduce these global peak temperatures.
So “let us be clear,” they write. “We are not suggesting nature restoration is fruitless, nor unimportant. In our urgency to mitigate climate change, every fraction of a degree of warming we can prevent counts.”
Restoring degraded landscapes is also crucial for planetary health—the idea human health and flourishing natural systems are inextricably linked.
What’s more, protecting existing ecosystems—such as intact forests, peatlands and wetlands—has an important immediate climate benefit, as it avoids releasing the carbon they store.
What the research makes clear, however, is that it’s dangerous to rely on restoring nature to meet climate targets, rather than effectively and drastically phasing out fossil fuels. We see this reliance in, for instance, carbon offset schemes.
Retaining the possibility of limiting warming to 1.5℃ requires rapid reductions in fossil fuel emissions before 2030 and global net-zero emissions by 2050, with some studies even calling for 2040. Wealthy nations, such as Australia, should achieve net-zero CO2 emissions earlier than the global average based on their higher historical emissions.
That points to the need for new international cooperation and agreements to stop expansion of fossil fuels globally and for governments to strengthen their national climate pledges under the Paris agreement’s ratcheting mechanism. Promises of carbon dioxide removals via land cannot justify delays in these necessary actions.