Natural Climate Solutions: Why We Need Them
The Intergovernmental Panel on Climate Change (IPCC) has said that we must keep global warming to 1.5˚C to avert the most catastrophic impacts of climate change. Research indicates that we can’t achieve the Paris Agreement goal of limiting warming to 2°C by 2100—let alone 1.5°C—through changes in the energy, industrial and transportation sectors alone. The four pathways the IPCC presented that could hold warming to 1.5°C all depend on removing carbon dioxide from the atmosphere, but technological solutions, such as direct air capture, are still relatively expensive or have not yet been tried on a commercial scale.
Nature itself, however, offers proven ways to combat climate change. During the Leaders Summit on Climate in April, Interior Secretary Deb Haaland declared that “achieving net zero by 2050 will not be possible without nature.”
Protecting, restoring and enhancing nature’s ecosystems can reduce greenhouse gas emissions as well as create resilience to climate change impacts. Trees, coastal habitats, and grasslands absorb and store carbon dioxide from the atmosphere. Natural climate solutions are based on the role these ecosystems play in the carbon cycle: Plants take in carbon dioxide from the atmosphere through their leaves and absorb water through their roots.
During photosynthesis, they form glucose and oxygen. They release oxygen into the atmosphere, but the glucose is incorporated into the plant and deposited into the soil, trapping the carbon used to produce the glucose. Land-based ecosystems currently absorb about 20 percent of all manmade greenhouse gases, but this is offset by changes in land use such as deforestation and agriculture. Implementing natural climate solutions could potentially reverse agricultural, forestry and other land use sector emissions—now almost 25 percent of global greenhouse gas emissions—and turn these sectors into more powerful carbon sinks.
How much can natural climate solutions achieve?
A 2017 study of 20 natural climate solutions showed that they could deliver up to 37 percent of the cut in emissions needed by 2030 to help keep warming below 2 °C, which is 30 percent more than previously thought. The research also found that they could often be much more cost-effective than many emerging technical solutions.
In the U.S., 21 natural climate solutions could potentially prevent or sequester 1.2 gigatons of CO2 by 2025, according to a 2018 Nature Conservancy study. This is more than one-fifth of our current yearly greenhouse gas emissions.
Manishka De Mel, senior staff associate at Columbia University’s Center for Climate Systems Research, leads the portfolio of conservation and development projects for the Climate Impacts Group, primarily looking at climate risk. “The benefit of natural climate solutions is that they provide large benefits in terms of climate change mitigation—reducing emissions—and also in terms of climate change adaptation, because of the ecosystem services they provide.”
Besides storing carbon, natural climate solutions deliver ecosystem benefits such as clean air and water, enhanced soil health, reduced erosion, and habitat and biodiversity conservation. In addition, nature plays an important part in disaster reduction. De Mel said a study of over 500 articles over approximately 20 years found links between nature and the role it plays in reducing specific disasters. “A large portion of those articles focused on urban areas, looking at things like pollution, drought, urban heat island effects, storms, hurricanes,” she said. “So these [nature-based] solutions already have multiple uses—from mitigation to recreation to disaster risk reduction, which are among the biggest challenges we have.”
What are natural climate solutions?
Forests are responsible for about 45 percent of all carbon stored on land and have the potential to store almost a quarter of the carbon needed to avoid 2°C of warming. Each year, 100 mature trees can absorb 53 tons of carbon and 140,000 gallons of rainwater, which is released into the atmosphere to form clouds and precipitation. Of the six trillion trees that once populated Earth, however, only half remain. The rest have been cut down for timber, for development, to make room for agriculture and livestock, and lost through drought, desertification, pests, and wildfires. More than 17 million acres of forest are lost each year, resulting in up to 15 percent of global greenhouse gas emissions.
Protecting forests can involve planting new trees (reforestation), restoring degraded forests, and avoiding the conversion of forest land for other uses. The Trillion Trees project, which grew out of Nobel Peace Prize Laureate Wangari Maathai’s Billion Tree Campaign, maintains that one trillion trees could be planted without interfering with agriculture or development, and could potentially sequester 488 to 1012 billion tons of CO2, between one-fourth and one-third of all human emissions to date.
Degraded forests can be restored through letting forests regenerate naturally and managing forests more sustainably: preventing logging in old growth forests, lengthening timber harvest cycles, using reduced-impact logging techniques such as directing how a tree falls to reduce impacts on the surrounding forest, minimizing soil damage when moving logs, reducing wood waste, building fewer roads in the forest, and creating watershed protection areas. Forest management also entails wildfire management: conducting prescribed and controlled burns in fire-prone areas to prevent larger conflagrations and creating fire breaks to prevent the spread of fires. Improving agricultural productivity on existing lands would help curtail the need to raze forests for crops in the first place.
Recently, scientists discovered that parts of the Amazon rainforest, an essential carbon sink for the planet, are now emitting more CO2 than they take in due to deforestation and climate change. In 2015 and 2016, extreme drought and wildfires exacerbated by El Niño there killed around 2.5 billion trees, resulting in the emission of 546 million tons of carbon. Reforestation and preventing deforestation could bring back some of the Amazon’s lost ability to store carbon. Because tropical regions like the Amazon have the highest rates of forest loss, they have the most to gain from natural climate solutions. Preventing deforestation, however, requires establishing incentives and regulations to discourage the main reasons for deforestation—cattle ranching and palm oil plantations—as well as providing assistance for rural and Indigenous communities so that they can find alternative livelihoods.
In the U.S., there are 224 million acres of degraded forest that could be restored. And globally, it’s estimated that there are 4.4 billion acres of land, not being used for agricultural or urban development, that could be reforested with the potential to sequester 370 to750 billion tons of CO2. This is equivalent to 17 to 33 percent of manmade emissions since the Industrial Revolution.
At a certain stage of maturity, trees stop capturing and storing carbon, so since older trees store more carbon, preventing deforestation is preferable to replanting or restoring degraded forests. And while trees cannot stop climate change, some research suggests that one trillion more trees could push potential tipping points in the climate system years into the future, buying humanity more time.
Coastal wetlands include mangroves, tidal salt marshes, and seagrass meadows, which absorb carbon dioxide as they grow and transfer it to the soil where it can potentially remain for thousands of years. Also known as “blue carbon,” these three ecosystems, totaling between 86 and 731 million acres globally, store the most carbon per acre, and are responsible for sequestering almost half of all the carbon buried in ocean sediments. Some mangrove forests can shelter up to four times as much carbon per unit area as land-based forests.
Around the world, a third of coastal wetlands have been destroyed over recent decades. They are converted for agriculture, aquaculture or drained for coastal development, resulting in the release of 165 to 1124 million tons of CO2 into the atmosphere yearly, and potentially changing these carbon sinks into carbon emitters. In the U.S., 80,000 acres of wetlands are lost each year to erosion, sea level rise, and development. Today, there are over 14.1 million acres of degraded coastal wetlands in the U.S. that could be restored.
Restoring coastal wetlands entails preventing their destruction, reducing pollution, establishing protected areas, controlling agricultural and stormwater runoff, reestablishing the natural flow of water, and replanting vegetation. Healthy wetlands nurture biodiversity, filter water, and protect against flooding and storm surge—one acre of wetlands can store up to 1.5 million gallons of floodwater. After Hurricane Sandy hit, scientists at Lloyds of London determined that coastal wetlands had reduced storm surge and waves, preventing about $625 million in property damage.
De Mel noted that multiple co-benefits also make a nature-based solution such as mangrove restoration cost-effective. ‘These include improving fish stocks and preventing erosion,” she said. “There’s also employment because tourism and recreation are associated with these coastal ecosystems.”
In the U.S., 106 million acres of interior wetlands—peatlands, marshes, tundra and flood plains—also need to be restored. Like coastal wetlands, they too provide long-term carbon sequestration. Globally, peatlands are often drained for agriculture or palm plantations, and burned, which releases additional carbon dioxide into the atmosphere.
These interior wetlands and peatlands can be revitalized by avoiding conversion, bringing back the natural flow of water, removing invasive species, and minimizing agricultural and stormwater runoff.
Globally, about 4.2 million acres of grasslands and shrub lands are converted for agriculture, pasture, or other uses each year. In North America, over 80 percent of these lands have been converted. Grasslands store about one-third of terrestrial carbon, sometimes for even longer than forests, but when they are disturbed, they can potentially lose more carbon per acre than any other ecosystem.
Soil stores three times as much carbon as is in the atmosphere, and almost four times the amount in all living matter, but many farmed soils have lost up to 70 percent of the organic carbon they once held. When soil is left bare between harvests, the carbon it has stored is released into the atmosphere.
Regenerative agricultural practices improve the overall health of the land by rebuilding the organic matter and biodiversity in soil, which enhances its ability to absorb and hold more carbon as well as water. These practices include rotating crops, planting cover crops or double crops so as not to leave fields fallow, applying compost or crop residue to fields, increasing plant diversity, practicing minimal or no-till farming, planting perennial crops, and managing nutrients by applying only as much fertilizer as plants can use.
Grasslands used for livestock can be protected by using rotational grazing so that grass is allowed to recover. Planting legumes such as alfalfa, peas, and beans in pastures provides food for livestock and enriches the soil with carbon. Legumes also fix nitrogen in the soil so less nitrogen fertilizer is needed. Placing trees in crop land or pastures can shade crops, reduce erosion, and enhance soil quality. Better soil health not only stores more carbon, it increases productivity, promotes biodiversity, and make soils more resilient to drought and floods.
In the U.S., more than 243 million acres of grassland could be restored. According to American University, soil carbon sequestration could be ramped up to store 2 to 5 gigatons of CO2 by 2050, and 104 to 134 gigatons by 2100.
Where natural climate solutions are working
An Indonesian province on Kalimantan Island has over 18 million acres of tropical forest. Covering over half the island, the forest has been seriously degraded and diminished by logging, palm oil production, mining, and wildfires. If these trends aren’t stopped, Indonesia will likely be unable to achieve its Paris Agreement carbon emissions reduction target. But in 2017, the Provincial Government, The Nature Conservancy and other groups launched the East Kalimantan Green Growth Compact. Its goals are to cut deforestation 80 percent by 2025, restore degraded forests, and reduce emissions significantly while increasing economic growth. The compact helps villages with land use planning to protect forests from illegal logging and poaching, replants degraded areas, and develops green jobs. It is working with logging companies to implement reduced impact logging practices and obtain sustainable forest management certifications. It also helps palm oil producers identify the best areas for planting and avoid converting high value forest areas, and funds forest conservation through offsets. These actions not only enhance the well-being of 3.5 million people, they help protect the forests’ biodiversity, including some of the world’s few remaining orangutans.
On the southwest coast of Madagascar, mangroves provide food, lumber, jobs, and protection from sea level rise and storm surges. The mangroves here have been increasingly deforested, mainly for timber. The marine conservation organization Blue Ventures has begun a mangrove preservation project that promotes reforestation, establishes protected mangrove areas, helps strengthen regulations for sustainable use, and creates local jobs that don’t depend on exploiting mangroves.
Women and young people are learning how to help with reforestation and carbon monitoring, and the whole community benefits from the sale of carbon credits based on the capacity of the mangroves to sequester carbon.
Farmer Trey Hill produces wheat, corn, and soybeans employing regenerative agriculture. He plants cover crops— rye, turnips, and clover—in the off season so that fields remain covered all year round. When his corn is planted in spring, he sprays the cover crops to kill them. As they decompose, they store CO2 and provide nutrients to the soil microbes, improving soil health. Hill also uses no-till cultivation to prevent stored carbon from escaping, minimal fertilizer, and rotational grazing for his livestock. His yields are comparable to what they would have been with traditional farming, but the soil is healthier and the crops are more resistant to pests and extreme weather. Hill also earns money through selling carbon credits for the extra carbon he stores through Nori, a private carbon marketplace that pays farmers for their carbon removal. Nori then sells these carbon removal tokens based on Hill’s carbon storage to others to offset their carbon footprints. Each year, Hill makes $15 per 1.1 ton of CO2 sequestered per acre; over the past 5 years, he has earned $210,000 for sequestering over 15,430 tons of carbon.
This project established sustainable timber harvesting strategies and conservation measures to preserve the forest, and to maintain native species, protect habitats for threatened species, and increase stream buffers to improve water quality. Between 2007 to 2014, the project created over 286,000 tons of carbon offsets, which were sold in California’s cap and trade marketplace. From 2015 to 2017, it removed an additional 210,000 tons of CO2 from the atmosphere.
The future of natural climate solutions
“When we talk about natural climate solutions, there are direct benefits of using them for mitigation, because it’s [carbon] sequestration,” said De Mel. “Then there’s the ecosystem service part where the services that these ecosystems provide help with resilience. And then there are all these associated co-benefits, like providing employment, preventing erosion, and stabilizing coastal areas as well. I think it’s important to value and communicate all the co-benefits more strongly, such as the benefits for poorer people, marginalized communities. The economic benefits, like job creation, and the cultural significance of these systems—these co-benefits go beyond just carbon sequestration.”
At the UN 2019 climate summit, 70 governments pledged support for the Nature-based Solutions for Climate Manifesto, but in order for natural climate solutions to fulfill their promise, a number of things need to occur:
-More leaders, governments, and communities need to be educated about all the benefits of natural climate solutions, as well as their effectiveness.
-Much more investment, both public and private, must be directed to natural climate solutions.
-Additional regulation and more persuasive incentives, whether from governments or through carbon offsetting programs, are necessary to motivate farmers and local communities to protect their resources.
-Indigenous Peoples and local communities need support and assistance to find sustainable livelihoods.
-Since measuring carbon sequestration is difficult and imprecise, credible and accurate carbon accounting is critical so that carbon storage can be verified.
-Long-term governance of natural climate projects is needed to make sure that future land use changes don’t undo their effectiveness.
-Consumers should be made aware of which products and brands drive deforestation and other unsustainable activities and boycott them.
In June, the Senate passed the Growing Climate Solutions Act to help connect farmers, ranchers, and forest landowners to carbon markets. A companion bill is being considered by the House of Representatives. The Biden administration has also earmarked $30 billion to create carbon trading markets to incentivize farmers to implement sustainable practices that capture carbon in their soil. McKinsey estimated that by 2030, this market could be worth over $50 billion.
While many natural climate solutions will take time to reduce greenhouse gas emissions, some strategies, such as reducing deforestation and forest degradation, delaying timber harvests, and reducing emissions from agricultural soils, can be deployed immediately. However, these solutions are limited in that land can only absorb so much carbon. In addition, their effectiveness is not guaranteed. If carbon emissions continue on their current trajectory, by 2050 the long-term benefits of natural climate solutions could be undone by hotter temperatures, wildfires, droughts, pests, and land use changes, which could affect photosynthesis and carbon storage.
“It’s a vicious cycle,” said De Mel, “because the more you emit and the warmer the temperatures get, the more our options for adaptation become limited, because it’s very hard to adapt to high-end climate change. So in order to both mitigate and adapt, we need to ensure that nature based solutions are a key component within a portfolio of solutions that combat climate change.”
In other words, in addition to natural climate solutions, we must continue to reduce greenhouse gas emissions across all sectors as well as further the development of carbon removal technologies. We need “all of the above.”