Ecosystems Can Curb Global Warming, Increase Resilience
Though his business card says Director of Forest Carbon Science at The Nature Conservancy, Bronson Griscom introduces himself as an ecological accountant. Griscom radiates an optimism somewhat rare in seasoned environmentalists, especially when he discusses the “carbon economy” of nature: the everyday role that trees, grasslands and coastal habitats play in the carbon cycle. Griscom can measure the carbon impact of logging in old growth forests, or how well different forest ecosystems work as sinks for absorbing and storing carbon from the atmosphere. He helps link our economy with the economy of the biosphere.
In recent decades, forest use—Griscom’s area of expertise—has been widely studied for its climate impacts. Forest loss accounts for 8 to 10 percent of carbon emissions globally; tropical rainforests like the Amazon have become almost synonymous with land conservation, largely because they work as massive carbon sinks and are home to many of the world’s indigenous people and endangered species.
But other global ecosystems and managed lands—from farmlands and peatlands to seagrass and tidal marshes—have garnered less attention from climate regulators, both as a source of emissions and a potential mitigation solution. In fact, until recently no one had ever integrated the raw data on all the carbon that all ecosystems were already sequestering, and what the potential was for increasing carbon storage among all these habitats together, as Griscom and his team studied.
“I thought we would review a few papers and take an average to answer the question,” he says. “We were shocked to find that important gaps remained in answering the question: how much can lands contribute to solving climate change? So we took it upon ourselves to convene a large group of scientists across 15 research institutions to take a comprehensive look at this question.”
Answering that question became the highest priority for Bronson’s team, and the foundation for what has become the most comprehensive study on the role that nature can play in keeping global temperature increases to 2°C or below. They found that, with the right management, nature can play a bigger role than we realized.
Natural climate solutions offer up to 37% of the mitigation needed between now and 2030 to keep global temperature rise below 2°C.
The paper offers a comprehensive roadmap for reducing carbon emissions through nature. The study is the culmination of a partnership between the Conservancy and the Doris Duke Charitable Foundation that brought together more than two-dozen leading natural scientists and economists from fifteen research, educational and private institutions around the world.
The land-use sector is currently responsible for a quarter of greenhouse gas emissions. But this new study shows that this could change—and with concerted global action on land use over the next decade, nature can be a significant part of the climate solution.
The analysis found that the total biophysical potential for natural climate solutions while still taking account of food production needs is as much as 23.7 billion tons of carbon dioxide equivalent per year—approximately 30 percent more than previous, less comprehensive estimates.
In addition, the study’s economic analyses show that half of these natural climate solutions (11.3 billion tons CO2e) offer cost-effective mitigation opportunities, because they cost less than the future impacts of climate change, expected to cost society more than $100 per ton of CO2 in the atmosphere. These cost-effective NCS mitigation options offer up to 37 percent of mitigation needed between now and 2030 to keep global temperature rise below 2°C —the widely recognized target of the Paris Climate Agreement.
Pathways to Natural Climate Solutions
To synthesize the research, Griscom and his team developed a framework to distill the world’s “natural climate solutions”—the proven ways of storing and reducing carbon emissions in forests, grasslands (including agricultural and rangelands) and wetlands—into a taxonomy of 20 specific pathways that account for the full climate potential of nature.
In addition to covering three biomes, the pathways also look at different practices across a variety of economic scenarios that mitigate climate change, including the implementation of low-cost opportunities only ($10 per tonne CO2e or less).
Another striking aspect of these pathways is the additional benefits they provide. Most nature climate solutions—if effectively implemented—also offer water filtration, flood buffering, improved soil health, protection of biodiversity habitat, and enhanced climate resilience.
“The approach is synergistic,” says Justin Adams, managing director for Global Lands at the Nature Conservancy. “We can hit multiple targets of the UN Sustainable Development Goals if we get this right.”
There is, however, a catch: The world must act soon.
Assuming current business-as-usual trajectories, increased emissions entering the atmosphere, coupled with continued environmental degradation, will lessen the impact that nature can have. If natural climate solutions are mobilized over the next 10 to 15 years, they could provide 37 percent of the needed mitigation for global climate targets. But if action is delayed until after 2030, that number drops to 33 percent, and drops again to only 22 percent after 2050.
Over the past two years, the world experienced unprecedented global climate momentum. In September 2015, international leaders adopted the UN’s 17 Sustainable Development Goals, which aim to fight poverty, promote sustainability and address climate change. Shortly after, nearly 200 countries came together in Paris to adopt the world’s largest ever international climate treaty.
And despite recent setbacks, including the United States announcing its intention to withdraw from the Paris Agreement, many countries have moved forward implementing voluntary measures to limit emissions. And while natural climate solutions are part of many countries’ pledges, there remains a gap between promised action and realized climate progress.
“Natural climate solutions are available now, are cost effective and greatly benefit communities,” said Justin Adams.
As they are currently written, the Paris Agreement pledges still fall short, likely keeping warming around 4°C. Every five years, international representatives and negotiators will meet to ramp up ambition, but the current timeline for countries to end their reliance on fossil fuels while still maintaining development and economic growth does not align with what is needed to achieve climate stability. Barring a technological miracle, the world likely needs more time than it realistically has to move to full economic decarbonization.
“There’s a growing recognition that to get to below 2°C, we need to actively drawdown carbon from the atmosphere,” Adams says. “And while there’s lots of interest and investment in new technology solutions to capture and store carbon, this is new, experimental technology. Trees and other plants, meanwhile have already perfected this process over hundreds of millions of years of evolution—we’re unlikely to see a better carbon capture and storage technology than that which nature provides.”
This makes the findings from the 20 pathways particularly important: they provide a scalable near-term option that, combined with fossil fuel emission reductions, can put the planet on a 2° path by 2030. If world leaders hold off on concurrently investing in nature now, emerging technology will have to play an exponentially larger role in reducing emissions later on. “That’s a gamble on the future that can be prevented today,” Adams says.
“The rapid deployment of clean energy technologies currently being witnessed is truly inspiring, and we absolutely must press forward with the deployment of renewables, electric cars, energy efficiency and other methods for fossil fuel reduction,” Adams adds. “But we also need to see a similar level of investment in natural solutions, which are available now, are cost effective and greatly benefit communities.”