Restoring nature without phasing out fossils ‘only marginally’ reduces global warming

Restoring degraded environments, for example by planting trees, is an important climate solution, but is no substitute for preventing fossil fuel emissions to limit global warming, write University of Melbourne researchers Kate Dooley and Zebedee Nicholls in an article for The Conversation.

Nature-based solutions are often presented as a stand-alone solution to the climate crisis, they write. But in their new search, the two authors calculated the maximum potential of responsible nature restoration to absorb carbon dioxide from the atmosphere. They found that, combined with ending deforestation by 2030, this could reduce global warming by 0.18°C by 2100. In comparison, countries’ current pledges put us on track to warming 1.9-2℃.

This is far from what is needed, Dooley and Nicholls note, to mitigate the catastrophic impacts of climate change, and is well above the Paris Agreement’s 1.5℃ target. And it pours cold water on the idea that we can shift our path out of the ongoing global warming.

The priority remains the rapid phase-out of fossil fuels, which have contributed 86% of all CO2 emissions in the last decade. Deforestation must also stop, along with land use, deforestation and forest degradation contributing 11% global broadcasts.

The hype around nature restoration

Growing commitments to net-zero climate goals have focused on restoring nature to remove CO2 from the atmosphere, based on claims that nature can provide more a third climate change 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 that destroy biodiversity, increase pollution and take land away from food production.

Indeed, the hype around nature restoration tends to overshadow the importance of restoring degraded landscapes and conserving existing forests and other ecosystems already storing carbon.

Dooley and Nicholls therefore applied “responsible development” frame to nature restoration for their study. Broadly, this means that restoration activities should follow ecological principles, respect land rights and minimize land use change.

This requires differentiating between activities that restore degraded lands and forests (such as ending native logging or increasing vegetation in pastures), versus planting new forest.

Distinction matters. Creating new tree plantations means changing the way land is used. This poses risks to biodiversity and has potential trade-offs, such as removal important agricultural land.

On the other hand, restoring degraded land does not displace existing land uses. Restoration enhances, rather than alters, biodiversity and existing agriculture.

The potential of nature restoration

Dooley and Nicholls suggest that this presents the maximum potential for ‘responsible’ land restoration available for climate change mitigation. This would translate to a median of 378 billion tonnes of CO2 removed from the atmosphere between 2020 and 2100.

That may seem like a lot, but, for perspective, global CO2 equivalent emissions were 59 billion tons in 2019 only. So the removals we might expect from nature’s restoration over the rest of the century correspond to just six years of current emissions.

Based on this CO2 removal potential, the two researchers assessed impacts on peak global warming and temperature reduction over a century. They say they found that restoring nature only marginally reduces global warming – and that any climate benefits are dwarfed by the scale of ongoing fossil fuel emissions, which could exceed 2 trillion tonnes of CO2 from by 2100 under current policies.

But let’s say we combine that potential with a deep decarbonization scenario, where renewables expand rapidly and we reach net zero emissions globally by 2050.

Next, Dooley and Nicholls calculated that the planet would briefly exceed a temperature increase of 1.5℃, 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 go hand in hand with ending deforestation. Otherwise, emissions from deforestation will wipe out any gains from carbon removal.

Thus, the study also explored the impact of phasing out land use-related emissions, to achieve 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 only reduce warming by about 0.08℃ over the century. This is largely because the baseline scenario already assumed that governments would take action. Increased deforestation would lead to much greater warming.

Together, restoring nature and halting deforestation, end-of-the-century warming could be reduced by 0.18℃.

Is it enough?

In a low-emissions pathway to limit global warming to 1.5℃ this century, Dooley and Nicholls expect global temperature increase to peak in the next one to two decades.

As their research shows, nature restoration is unlikely to happen fast enough to offset fossil emissions and notably reduce these global maximum temperatures.

So “let’s be clear,” they write. “We are not suggesting that nature restoration is futile or 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 that human health and thriving natural systems are inextricably linked.

In addition, 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 clearly shows, however, is that it is dangerous to rely on the restoration of nature to meet climate goals, rather than the effective and drastic elimination of fossil fuels. We see this dependency in, for example, carbon offset programs.

Retaining the ability to limit 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 countries, like Australia, are expected to reach net zero CO2 emissions sooner than the global average based on their higher historical emissions.

This underlines the need for new international agreements and cooperation to stop the expansion of fossil fuels around the world and for governments to strengthen their national climate commitments under the Paris Agreement ratchet mechanism. Promises of terrestrial carbon dioxide removal cannot justify delays in these necessary actions.

Teresa H. Sadler