What is the climate mitigation potential of Natural Climate Solutions?
To stop climate change, we must drastically reduce fossil fuel emissions and remove greenhouse gases (GHG) already in the atmosphere. Natural Climate Solutions offer a way to make forests, wetlands, grasslands, farms and ranches part of the solution to climate change. Globally, these conservation, improved land management, and restoration practices could deliver up to a third of the carbon reduction necessary by 2030 to keep global warming in check.
While Natural Climate Solutions alone cannot solve climate change, there is no way to limit global warming to 1.5ºC without integrating these solutions alongside efforts to reduce emissions from the energy, transportation, and industrial sectors. Thankfully, conserving, restoring, and rethinking the way we manage our natural and working lands have multiple payoffs not only for climate, but also for people and our economy, for air and water quality, and for fish and wildlife.
To estimate the climate change mitigation potential of forest, grassland, agricultural, and blue carbon Natural Climate Solutions pathways, U.S. Nature4Climate worked with scientists from both coalition and external organizations in 2023 to incorporate the most up-to-date scientific literature. The results of this effort can be found below:
The 823 million acres of forest lands in the United States are managed by public agencies, Native American Tribes, forestry companies, families, and municipalities. These lands can play a crucial role in our efforts to mitigate climate change by capturing and storing carbon in trees, roots, and soils.
There are many approaches for leveraging this natural climate benefit. Preventing the conversion of forests to agriculture or development keeps more carbon on the landscape and protects the ability of forests to continue capturing carbon. Agroforestry practices, post-fire reforestation, tree planting in urban areas, and forest regrowth in the historically forested lands outside our cities can sequester more carbon as well.
Climate-smart management techniques can keep forests growing faster, healthier, and longer. Not only do these practices help address climate change, but they can also prevent soil erosion and improve water quality, enhance habitat for fish and wildlife habitat, and make our communities healthier and safer.
Each year, approximately 1 million acres of forests in the United States are converted to other uses such as development and cropland. Retaining existing forests that would otherwise be converted to other land uses can prevent the emission of 38 to 48 million metric tons of CO2 per year (Fargione/2018, American Forests IRA Analysis/2022). The lower number comes from counting just the carbon in the trees, whereas the higher number comes from also counting the future carbon sequestration potential of those trees.
GHG Estimate: 38-48 million metric tons of CO2e/year
Acreage: 1 million acres/year (based on historic average forest loss, 2000-2010)
Climate-Smart Management of Existing Forests
A variety of climate-smart (also known as climate-informed) management practices can increase carbon sequestration and storage in forests, aiming to balance forests’ ability to adapt to and mitigate climate change while still providing essential co-benefits like clean water, wood products, and wildlife habitat. These climate-smart practices include optimizing forest stocking at ecologically-appropriate levels, restocking degraded forests, restoring the diversity of species in the forest, extending timber rotations, controlling browsing and grazing by animals, actively managing forest pest and drought impacts, reducing the risk of catastrophic wildfire, and controlling competition from invasive plants.
There are multiple methodologies available for calculating the climate change mitigation impact of these practices. A review of existing literature provides estimates on some practices. One study (Domke et al, 2020) focused specifically on using existing seedling production to increase stocking density in forests in the United States, which would sequester an additional 48 million metric tons of carbon and cover 4 million acres each year. Another study (Robertson et al, 2022) focused on extending timber rotations on half of harvested natural forests in the United States, finding that this would sequester an additional 12 million metric tons of CO2e a year. Combined, these two practices would yield 60 million metric tons of additional CO2e sequestered per year.
Forest Restocking: 48 million metric tons of CO2e/year from fully stocking understocked forestland (Domke et al, 2020)
Forest Restocking Acreage: 4 million acres each year
Extended Timber Rotations: 12 million metric tons of CO2e/year from extending timber rotations (Robertson et al, 2022)
Extended Timber Rotation Acreage: 76.6 million acres
Beyond restocking and extended rotations, there are other climate-smart forest management practices that could be applied across the hundreds of millions of acres of managed forestland nationwide to provide additional climate mitigation. For example, reducing harvest intensity in selectively logged forest can help to boost stand level carbon values (Family Forest Carbon).
Finally, modeling conducted by American Forests in Pennsylvania and Maryland breaks down the climate change mitigation impact of eliminating diameter limit cuts on private lands, controlling deer browse, restocking understocked stands, and extending timber rotations, finding that implementation of these four practices across 19 million acres of forests in those two states would sequester an additional 1.2 million metric tons CO2e a year, including both biomass and soil carbon dynamics. American Forests is conducting similar research in other states, and is working toward providing national estimates.
GHG estimate (Maryland & Pennsylvania only): 1.2 million tons CO2e per year
309,037 metric tons CO2e/year from eliminating diameter limit cuts (high grades) on private lands
307,055 metric tons CO2e/year from controlling deer browse
308,620 metric tons CO2e/year from restocking understocked stands
314,989 metric tons CO2e/year from extending rotations
Acreage: 19 million acres of forested land (Pennsylvania and Maryland only)
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Increasing Urban Tree Cover
Increasing urban tree cover by planting trees in urban open spaces provides another mechanism for sequestering carbon.
According to the Reforestation Hub, reforesting developed open spaces in suburban and surrounding areas can sequester up to 101.6 million metric tons of carbon a year over 26 million acres, an area about the size of Kentucky. While people may not want trees in all those places, increasing tree cover in at least part of the available space can help capture carbon, cool our cities, and create habitat for biodiversity.
There are also opportunities to plant additional trees along streets in highly-developed urban areas. Analysis from American Forests suggests that planting 522 million additional trees in urban areas – allowing every American city to achieve Tree Equity – could sequester and store 8.7-13.7 million metric tons of CO2e/year, including avoided energy emissions from reduced heating and cooling needs. Furthermore, a new, high resolution study suggests that there is room to plant 1.2 billion trees in metro areas (McDonald et al, pre-print). These trees could capture 23.7 million metric tons of carbon and avoid a further 2.1 million metric tons from heating and cooling that would no longer be needed due to trees’ ability to insulate buildings from low and high temperatures.
In addition to planting new trees in urban areas, it is also critical to keep existing tree cover healthy and well maintained so that the trees already in our cities sequester their full potential of carbon.
Reforesting Open Spaces in Suburban-Exurban Areas:
GHG Estimate: 101.6 million metric tons of CO2e per year
Acreage: 26 million acres (full implementation)
Urban Trees
GHG Estimate: 8.7 – 25.8 million metric tons of CO2e per year
Number of Trees: 522 million-1.2 billion
Read More >
Agroforestry on Pastureland (Silvopasture)
The U.S. Department of Agriculture defines agroforestry as “the intentional integration of trees and shrubs into crop and animal farming systems to create environmental, economic, and social benefits”. Agroforestry practices, including silvopasture, windbreaks, and alley cropping, can be implemented on pasture land and cropland, and can yield significant economic, environmental, and climate benefits.
Agroforestry on Pastureland (Silvopasture): Silvopasture involves planting trees in pastures, in locations that were once forested, without removing the land from productive pasture use. Livestock can still graze and benefit from the shade, while the trees can produce nut crops, timber, or fodder for livestock. Silvopasture practices vary widely in tree species and planting densities, so the carbon benefits of the practice vary too (0.1 to 7.0 metric tons CO2 per acre per year). Given the potential for increased market demand of different silvopastoral systems, a recent analysis estimated a potential of 40 million metric tons of CO2 per year if silvopasture were implemented on 68 million acres of pasture, grassland, and marginal croplands in the eastern United States (Greene et al. In Review). The Reforestation Hub estimates that there are an additional 13 million acres of pasture in the western United States, which could provide an additional 7.6 million metric tons CO2 per year if converted to silvopasture .
GHG Estimate: 53 million metric tons of CO2e/year
Acreage: 81 million acres
Agroforestry on Cropland
The U.S. Department of Agriculture defines agroforestry as “the intentional integration of trees and shrubs into crop and animal farming systems to create environmental, economic, and social benefits”. Agroforestry practices, including silvopasture, windbreaks, and alley cropping, can be implemented on pasture land and cropland, and can yield significant economic, environmental, and climate benefits.
Agroforestry on Cropland: A number of agroforestry strategies exist to integrate trees on existing cropland, including planting windbreaks adjacent to cropland, planting fruit and nut trees in alleyways between row crops such as corn and soybeans (alley cropping). According to Udawatta, et al. 2022, converting 5% of U.S. cropland to alley cropping would sequester 13.6 million metric tons CO2e/year, and establishing windbreaks on 5% of U.S. cropland would sequester 91.7 million metric tonsCO2e/year.
Alley Cropping:
GHG mitigation estimates: 13.6 million metric tons CO2e/year
Acreage: 18.4 million acres (5% of U.S. cropland)
Windbreaks:
GHG mitigation estimates: 91.7 million metric tons CO2e/year
Acreage: 18.4 million acres (5% of U.S. cropland)
Landscape Reforestation
Reforesting portions of historically-forested landscapes outside of cities, cropland, and pasture can sequester million tons of CO2 per year. This includes actions like restoring biodiversity corridors and riparian buffers along streams and regrowing trees in frequently flooded landscapes. Taken together, these actions could increase carbon sequestration by 251 million metric tons CO2e across 77 million acres (Reforestation Hub 2023)
GHG Estimate: 251 million tons of CO2e/year
Current Acreage: 77 million acres
Post-Fire Reforestation
Post-fire reforestation is the process of planting ecologically appropriate new trees on a previously forested area impacted by wildfire. An estimate from 2020 suggests that reforesting post-burned landscapes on 4.2 million acres can sequester 6.1 million metric tons of CO2 a year (Cook-Patton 2020). The need for post-fire reforestation is only growing as wildfires become hotter and more frequent, leading to declining natural regeneration rates. Funding in the IIJA and IRA could allow the reforestation of 10.5 million acres resulting in 20.8 million metric tons CO2e per year of additional carbon sequestration (American Forests IRA Analysis/2022).
Practices that help prevent the occurrence of catastrophic wildfire on forested land, such as thinning and prescribed fire, can help prevent the massive release of CO2 that occurs in these fires, providing an important long-term climate mitigation benefit.
Prescribed Fire: Prescribed fire treatments entail restoring frequent, low-severity understory fires in fire-adapted forest ecosystems to reduce the potential for high-severity wildfires which release significantly more carbon than prescribed fires and decrease net sequestration resulting from increased tree mortality.
Thinning: Thinning refers to the practice of removing smaller trees and other vegetation in overgrown forests to reduce the severity of wildfires and reduce tree death – and avoiding the higher carbon emissions that would have resulted from a severe fire.
Thinning and application of prescribed fire can be implemented either alone or together, depending on the ecological and logistical requirements and constraints of the landscape. Note that both practices result in a short-term carbon loss, as living trees are removed from the forest landscape. However, by reducing fire risk and severity, and avoiding the significant carbon emissions associated with catastrophic wildfires, there is a long-term carbon benefit.
Research suggests that these treatments could result in net carbon benefits ranging from 4.8-18 million metric tons of CO2e per year (Fargione/2018, American Forests IRA Analysis/2022); however, given the unpredictable nature of fire behavior and minimal data on the success of wildfire resilience treatments, these estimates comes with a high degree of uncertainty. More research is needed on these topics to refine estimates of carbon benefits from wildfire resilience treatments.
Read More >
Emerging Pathway: Wood Products
Long-lived wood products represent a significant pool of long-term carbon storage. When wood is harvested, a portion of the carbon in that wood remains stored there as long as the wood is still intact. This storage can last for many decades when harvested wood is utilized in buildings and other long-lived structures. The U.S. Environmental Protection Agency estimates that in 2021, nearly 103 million metric tons of CO2e was transferred to and stored in harvested wood products in the United States – equivalent to 13% of the annual U.S. forest carbon sink.
The Inflation Reduction Act and Infrastructure Investment & Jobs Act included $560 million for wood innovation – such as incorporating low-value wood materials produced by wildfire management efforts into greener building materials,increasing wood use in multi-story and commercial buildings, and developing new nanocellulose technologies. A recent American Forests analysis suggests that innovations unlocked by these investments alone could sequester an average of 1.7 million metric tons CO2e per year in wood products.
Recent reports on the impact of climate-smart forestry in Pennsylvania and Maryland suggest that substituting sustainably harvested wood products for emissions-intensive building materials could avoid net emissions of 15 and 2.5 million metric tons CO2e Pennsylvania and Maryland, respectively, over 10 years. More research is necessary to understand the potential trade-offs between management practices that are designed to increase forest ecosystem carbon stocks and provide ecosystem service benefits versus policies and practices that would increase demand for harvested wood product volumes. In addition, further work must be done to ensure sustainable harvesting practices and create markets for sustainably harvested wood building materials.
Read More >
Emerging Pathway: Pest & Pathogen Management
Forest pests and pathogens can reduce a tree’s ability to capture and store carbon in many ways- repeated defoliation, interrupted sap flows, fungal infections, and more- which even may lead to the tree’s premature death. A recent study shows that carbon sequestration in forests experiencing severe insect or disease disturbance was 47 million tons of CO2 lower, per year, compared to sequestration in undisturbed forests (Quirion et al. 2021). Recent research in urban forests estimates that a pest that impacts oak or maple could kill 6.1 million street trees and cost $4.9 billion over the next 30 years (Hudgins et al. 2022). Although it is difficult to quantify the magnitude of the carbon benefit of specific preventative measures, strengthened international trade policies to limit the introduction of new forest pests as well as improved forest management can help reduce this lost sequestration.
Climate-Smart Management of Existing Forests
A variety of climate-smart (also known as climate-informed) management practices can increase carbon sequestration and storage in forests, aiming to balance forests’ ability to adapt to and mitigate climate change while still providing essential co-benefits like clean water, wood products, and wildlife habitat. These climate-smart practices include optimizing forest stocking at ecologically-appropriate levels, restocking degraded forests, restoring the diversity of species in the forest, extending timber rotations, controlling browsing and grazing by animals, actively managing forest pest and drought impacts, reducing the risk of catastrophic wildfire, and controlling competition from invasive plants.
There are multiple methodologies available for calculating the climate change mitigation impact of these practices. A review of existing literature provides estimates on some practices. One study (Domke et al, 2020) focused specifically on using existing seedling production to increase stocking density in forests in the United States, which would sequester an additional 48 million metric tons of carbon and cover 4 million acres each year. Another study (Robertson et al, 2022) focused on extending timber rotations on half of harvested natural forests in the United States, finding that this would sequester an additional 12 million metric tons of CO2e a year. Combined, these two practices would yield 60 million metric tons of additional CO2e sequestered per year.
Forest Restocking: 48 million metric tons of CO2e/year from fully stocking understocked forestland (Domke et al, 2020)
Forest Restocking Acreage: 4 million acres each year
Extended Timber Rotations: 12 million metric tons of CO2e/year from extending timber rotations (Robertson et al, 2022)
Extended Timber Rotation Acreage: 76.6 million acres
Beyond restocking and extended rotations, there are other climate-smart forest management practices that could be applied across the hundreds of millions of acres of managed forestland nationwide to provide additional climate mitigation. For example, reducing harvest intensity in selectively logged forest can help to boost stand level carbon values (Family Forest Carbon).
Finally, modeling conducted by American Forests in Pennsylvania and Maryland breaks down the climate change mitigation impact of eliminating diameter limit cuts on private lands, controlling deer browse, restocking understocked stands, and extending timber rotations, finding that implementation of these four practices across 19 million acres of forests in those two states would sequester an additional 1.2 million metric tons CO2e a year, including both biomass and soil carbon dynamics. American Forests is conducting similar research in other states, and is working toward providing national estimates.
GHG estimate (Maryland & Pennsylvania only): 1.2 million tons CO2e per year
309,037 metric tons CO2e/year from eliminating diameter limit cuts (high grades) on private lands
307,055 metric tons CO2e/year from controlling deer browse
308,620 metric tons CO2e/year from restocking understocked stands
314,989 metric tons CO2e/year from extending rotations
Acreage: 19 million acres of forested land (Pennsylvania and Maryland only)
Increasing Urban Tree Cover
Increasing urban tree cover by planting trees in urban open spaces provides another mechanism for sequestering carbon.
According to the Reforestation Hub, reforesting developed open spaces in suburban and surrounding areas can sequester up to 101.6 million metric tons of carbon a year over 26 million acres, an area about the size of Kentucky. While people may not want trees in all those places, increasing tree cover in at least part of the available space can help capture carbon, cool our cities, and create habitat for biodiversity.
There are also opportunities to plant additional trees along streets in highly-developed urban areas. Analysis from American Forests suggests that planting 522 million additional trees in urban areas – allowing every American city to achieve Tree Equity – could sequester and store 8.7-13.7 million metric tons of CO2e/year, including avoided energy emissions from reduced heating and cooling needs. Furthermore, a new, high resolution study suggests that there is room to plant 1.2 billion trees in metro areas (McDonald et al, pre-print). These trees could capture 23.7 million metric tons of carbon and avoid a further 2.1 million metric tons from heating and cooling that would no longer be needed due to trees’ ability to insulate buildings from low and high temperatures.
In addition to planting new trees in urban areas, it is also critical to keep existing tree cover healthy and well maintained so that the trees already in our cities sequester their full potential of carbon.
Reforesting Open Spaces in Suburban-Exurban Areas:
GHG Estimate: 101.6 million metric tons of CO2e per year
Acreage: 26 million acres (full implementation)
Urban Trees
GHG Estimate: 8.7 – 25.8 million metric tons of CO2e per year
Practices that help prevent the occurrence of catastrophic wildfire on forested land, such as thinning and prescribed fire, can help prevent the massive release of CO2 that occurs in these fires, providing an important long-term climate mitigation benefit.
Prescribed Fire: Prescribed fire treatments entail restoring frequent, low-severity understory fires in fire-adapted forest ecosystems to reduce the potential for high-severity wildfires which release significantly more carbon than prescribed fires and decrease net sequestration resulting from increased tree mortality.
Thinning: Thinning refers to the practice of removing smaller trees and other vegetation in overgrown forests to reduce the severity of wildfires and reduce tree death – and avoiding the higher carbon emissions that would have resulted from a severe fire.
Thinning and application of prescribed fire can be implemented either alone or together, depending on the ecological and logistical requirements and constraints of the landscape. Note that both practices result in a short-term carbon loss, as living trees are removed from the forest landscape. However, by reducing fire risk and severity, and avoiding the significant carbon emissions associated with catastrophic wildfires, there is a long-term carbon benefit.
Research suggests that these treatments could result in net carbon benefits ranging from 4.8-18 million metric tons of CO2e per year (Fargione/2018, American Forests IRA Analysis/2022); however, given the unpredictable nature of fire behavior and minimal data on the success of wildfire resilience treatments, these estimates comes with a high degree of uncertainty. More research is needed on these topics to refine estimates of carbon benefits from wildfire resilience treatments.
Emerging Pathway: Wood Products
Long-lived wood products represent a significant pool of long-term carbon storage. When wood is harvested, a portion of the carbon in that wood remains stored there as long as the wood is still intact. This storage can last for many decades when harvested wood is utilized in buildings and other long-lived structures. The U.S. Environmental Protection Agency estimates that in 2021, nearly 103 million metric tons of CO2e was transferred to and stored in harvested wood products in the United States – equivalent to 13% of the annual U.S. forest carbon sink.
The Inflation Reduction Act and Infrastructure Investment & Jobs Act included $560 million for wood innovation – such as incorporating low-value wood materials produced by wildfire management efforts into greener building materials,increasing wood use in multi-story and commercial buildings, and developing new nanocellulose technologies. A recent American Forests analysis suggests that innovations unlocked by these investments alone could sequester an average of 1.7 million metric tons CO2e per year in wood products.
Recent reports on the impact of climate-smart forestry in Pennsylvania and Maryland suggest that substituting sustainably harvested wood products for emissions-intensive building materials could avoid net emissions of 15 and 2.5 million metric tons CO2e Pennsylvania and Maryland, respectively, over 10 years. More research is necessary to understand the potential trade-offs between management practices that are designed to increase forest ecosystem carbon stocks and provide ecosystem service benefits versus policies and practices that would increase demand for harvested wood product volumes. In addition, further work must be done to ensure sustainable harvesting practices and create markets for sustainably harvested wood building materials.
Agriculture & Grasslands
In the United States, about 16% of the country’s land area, or 396 million acres, is cultivated to produce crops. Intensive cultivation practices have impacted a large proportion of the original soil carbon in croplands. By changing management of croplands, we can store more carbon in the soil, prevent soil erosion, improve water quality and, in many places, increase the productivity of the land. Increasing productivity, in turn, can ease pressures to convert natural forests and grasslands to food production in the U.S. and abroad. There is also the possibility of adding more trees in agricultural lands. Agroforestry includes four practices that store carbon: alley cropping, silvopasture, windbreaks, and riparian buffers.
Many of these practices, like cover crops, have already been adopted by numerous farmers, though overall adoption rates are still low. At the same time, research is underway to determine the carbon mitigation potential of other agricultural practices, like composting, crop rotations and planting deep rooted crops, and to determine the scalability of innovative practices like biochar and alley cropping. By advancing research and applying a variety of innovative and proven management practices that reduce agricultural emissions and/or enhance carbon sinks, America’s farms can be an important part of the solution to climate change.
Taking action to preserve and improve the management of America’s pasture and rangelands can also help mitigate climate change. In the U.S., pasturelands and rangelands cover about 401 million acres– more than twice the size of Texas. Pasture and rangelands store high levels of carbon in their soils. A significant fraction of that carbon has been lost through conversion to cropland and overgrazing. Taking additional steps to protect and improve grazing practices on pastures and rangelands would provide significant carbon benefits, while also protecting habitat for wildlife and safeguarding our water.
Agriculture & Grasslands
Below we provide the best available evidence-based estimates for a practice to reduce emissions and/or enhance carbon sinks if adopted on all available acres, unless otherwise stated, in the US.
Click Pathway for More Information
Cropland Nutrient Management >
Biochar >
Agroforestry on Pastureland (Silvopasture) >
Agroforestry on Cropland >
Grassland Restoration >
Avoided Grassland Conversion >
Improved Manure Management >
Rangeland & Pasture Plantings >
Cover Crops >
Emerging Pathway: Grazing Optimization >
Emerging Pathway: Long-Rooted Perennial Grains >
Potential Pathway: No-Till/Reduced Till Farming >
Cropland Nutrient Management
Applying the right fertilizer, in the right amount, at the right time and place can significantly reduce the use of fertilizer, while increasing profitability (Sela et al. 2016). Applying such best management practices, such as spring fertilization with side dressing, can reduce fertilizer use by about 20%. Applying this across US cropland would save 52 million tons of CO2e per year (Fargione et al. 2018). A recent report by EDF estimates that an aggressive yet feasible target would be to reduce these emissions by 27 millions tons CO2e.
GHG Estimate: 27-52 million tons of CO2e/year
Acreage: 396 million acres (all U.S. cropland)
Biochar
Biochar is produced from agricultural and forestry waste in a controlled process called pyrolysis, heating in the absence of oxygen so that the majority of biomass carbon is not lost to the atmosphere but transformed to a more stable form, delaying decomposition for decades to centuries. Based on available agricultural waste, amending agricultural soils with biochar could sequester up to 95 million metric tons of CO2 per year (Source: Fargione/2018). In addition to sequestering carbon and reducing nitrous oxide emissions from the soil, biochar amendments may have co-benefits such as increasing the moisture holding capacity of soils. However, the true potential of biochar to mitigate GHG emissions depends on the feedstocks used, how they are produced and transported to biochar production facilities, the energy used in the production process, and other steps that constitute its full life cycle. While this is the best current estimate of biochar’s climate mitigation potential at the national scale, it remains highly uncertain and more research, including full life-cycle assessments, is needed to constrain this estimate.
Current GHG Estimate: 95 million tons of CO2e/year from carbon sequestration.
This estimate is based on the supply of agricultural waste available as feedstock to make biochar; the estimate would increase if forestry waste was included.
Agroforestry on Pastureland (Silvopasture)
The U.S. Department of Agriculture defines agroforestry as “the intentional integration of trees and shrubs into crop and animal farming systems to create environmental, economic, and social benefits”. Agroforestry practices, including silvopasture, windbreaks, and alley cropping, can be implemented on pasture land and cropland, and can yield significant economic, environmental, and climate benefits.
Silvopasture involves planting trees in pastures, in locations that were once forested, without removing the land from productive pasture use. Livestock can still graze and benefit from the shade, while the trees can produce nut crops, timber, or fodder for livestock. Silvopasture practices vary widely in tree species and planting densities, so the carbon benefits of the practice vary too (0.1 to 7.0 metric tons CO2 per acre per year). Given the potential for increased market demand of different silvopastoral systems, a recent analysis estimated a potential of 40 million metric tons of CO2 per year if silvopasture were implemented on 68 million acres of pasture, grassland, and marginal croplands in the eastern United States (Greene et al. In Review). The Reforestation Hub estimates that there are an additional 13 million acres of pasture in the western United States, which could provide an additional 7.6 million metric tons CO2 per year if converted to silvopasture .
GHG Estimate: 53 million metric tons of CO2e/year
Acreage: 81 million acres
Agroforestry on Cropland
The U.S. Department of Agriculture defines agroforestry as “the intentional integration of trees and shrubs into crop and animal farming systems to create environmental, economic, and social benefits”. Agroforestry practices, including silvopasture, windbreaks, and alley cropping, can be implemented on pasture land and cropland, and can yield significant economic, environmental, and climate benefits.
A number of agroforestry strategies exist to integrate trees on existing cropland, including planting windbreaks adjacent to cropland, planting fruit and nut trees in alleyways between row crops such as corn and soybeans (alley cropping). According to Udawatta, et al. 2022, converting 5% of U.S. cropland to alley cropping would sequester 13.6 million metric tons CO2e/year, and establishing windbreaks on 5% of U.S. cropland would sequester 91.7 million metric tons CO2e/year.
Alley Cropping:
GHG mitigation estimates: 13.6 million metric tons CO2e/year
Acreage: 18.4 million acres (5% of U.S. cropland)
Windbreaks:
GHG mitigation estimates: 91.7 million metric tons CO2e/year
Acreage: 18.4 million acres (5% of U.S. cropland)
Grassland Restoration
Restoring 5 million acres of marginal cropland to grasslands to build carbon in soils and root biomass could help sequester an additional 9 million metric tons of CO2 per year. This is equivalent to returning to the 2007 peak in Conservation Reserve Program enrollment. (Source: Fargione/2018)
Current GHG Estimate: 9 million tons of CO2e/year
Current Acreage: 5 million acres (equivalent to peak CRP enrollment)
Avoided Grassland Conversion
Current Language: Retaining grasslands that would otherwise be converted to cropland or other uses could help reduce carbon emissions between 22 million (EDF) and 24 million (Fargione) metric tons CO2e per year, assuming a cost of $10 per ton of carbon. According to the Fargione study, this could rise to up to 107 million metric tons of carbon a year at a cost of $100 per metric ton of CO2e. (Source: Fargione/2018 and EDF 2022)
GHG Mitigation Estimate: 22-24 million metric tons of CO2e/year at a cost of $10/metric ton CO2e. Up to 107 million metric tons of CO2e at a cost of $100/metric ton of CO2e.
Acreage: > 1 million (EDF) to up to 2 million acres per year (Fargione)
Improved Manure Management
Avoided methane emissions from dairy and hog manure through improved management practices could reduce emissions by the equivalent of 24 million (Fargione/2018). An EDF report estimated 25 million metric tons CO2e in reduced methane emissions and 4.8 million metric tons CO2e in avoided nitrous oxide emissions per year through improved manure management (EDF/2022).
Current GHG Estimate: 24 million to 29.8 million tons of CO2e/year
Current Acreage: N/A
Rangeland & Pasture Plantings
Replanting degraded rangelands and sowing legumes in planted pastures could sequester an additional 22-44 million metric tons of CO2 in rangeland and pasture soils, based on current estimates of the percentage of U.S. rangeland that is degraded and in need of supplemental planting. (Source: AFT CaRPE/2020).
GHG Estimate: 22-44 million tons of CO2e/year
Acreage: 53-99 million acres
Cover Crops
Growing a cover crop in the fallow season between market crops extends the time of year that there are living plants photosynthesizing, helping prevent soil erosion, and providing carbon substrates to the belowground microbial community. While most of the cover crop biomass carbon is returned to the atmosphere when the cover crops die and decompose, some of this carbon may remain in the soil. A recent meta-analysis of US studies suggests that cover crops, on average, store about one-sixth of a ton of CO2 per acre per year (Blanco-Canquiu 2022) – about one third of previous estimates from older global analyses (Poeplau and Don 2015).
This average masks a wide variation in carbon storage. Essentially, there is more benefit when the cover crops achieve higher biomass. If cover crops are planted too late or otherwise have poor establishment, then they don’t grow much and (unsurprisingly) there is not much carbon benefit. This means that when you plant grasses like cereal rye that accumulate more biomass we see more carbon storage. A grass-legume cover crop mix also tends to sequester more carbon because legumes fix nitrogen, which enables greater carbon storage. It also depends on soil type. So, as with most things agricultural, the devil is in the details. If managed effectively, cover crops will provide roughly 0.6 tons of CO2 per acre per year (this was the average from the subset of studies that found significant carbon storage in Blanco-Canqui 2022). Of course, it never works perfectly, so the average will be lower. The more farmers implement and innovate with cover crops, the more we learn, which could nudge the average up over time.
To determine the total amount of CO2 that cover cropping could store, this rate is multiplied by the amount of land area on which they could be newly adopted. Different assumptions about the available land area produce very different estimates of the potential for cover crops to mitigate climate change.. For example, if we assume that cover crops can be implemented on all cropland growing the five major field crops in the US – about 217 million acres (Fargione et al. 2018) – we expect cover crops could sequester up to about 39 million metric tons of CO2 per year. However, the uncertainty in this number is high; extrapolating the range of observed effects of cover crops across the country finds a range of 0 to 296 metric tons of CO2 per year (Blanco-Canquiu 2022).
An Environmental Defense Fund-led study(Aragon, et al 2024) refines the estimate by using a more conservative estimate of carbon sequestration from cover crops (0.12 Mg C /ha/year) and limiting the assumed land area suitable for cover cropping to those acres not reliant on irrigation and not changing to other land uses (i.e., stable annual croplands). This assessment estimates that cover crops are feasible on about 32% of current U.S. cropland extent, or about 95 million acres. The study estimates that cover cropping on this land has the potential to sequester 19.4 million metric tons of CO2e per year; however, the cost of realizing about half of this potential (10 million metric tons CO2e) could exceed $100 per metric ton, suggesting a need for financial incentives to encourage implementation.
This high uncertainty highlights the need for further research into the carbon sequestration benefit of cover crops and the agricultural practices necessary to maximize soil organic carbon. A remote sensing analysis of cover crops suggests that on average they reduce corn and soybean yields by 5.5% and 3.5%, respectively, across the US Corn Belt (Deines et al. 2022). This corroborates findings by The Nature Conservancy’s AgEvidence database that shows across 461 observations from 40 field studies in the Corn Belt that a 3.1% decline in grain yield occurred and across 33 observations from 5 field studies found an 11% decline in grain quality. However, other work has shown that cover cropping with mixtures that include legumes is likely to have positive effects on subsequent yields (Abdalla et al. 2019; Wang et al. 2021). In addition, positive effects on yields are more common in wetter climates on clay loam soils and when cover crop residue is not removed (Wang et al. 2021). These impacts of cover cropping on crop yields are important, as any negative impacts on yields could lead to conversion of carbon-rich forests or grasslands to agriculture, i.e., leakage. Fortunately, the Inflation Reduction Act includes $300 million to the Natural Resources Conservation Service to set up a national soil measurement network that may help to alleviate some of the data limitations contributing to the large uncertainty around the net GHG mitigation potential of cover crops.
GHG Technical Potential Estimate: *19-30 million metric tons of CO2e/year (0.12 Mg C /ha/year).
Acreage: 95-166 million acres
*Note: Estimate Does not include emissions related to cover crop seed production and distribution, emissions related to cover crop seeding and termination, or possible yield impacts.
Read More >
Emerging Pathway: Grazing Optimization
Grazing optimization on existing rangeland and planted pastures could store additional carbon in the soil, though more research needs to be done to better understand realistic potentials across different systems and under different contexts, in order to quantify a potential carbon benefit nationally.
One specific example of grazing optimization is intensively-managed grazing on the land (i.e., 40% forage removal) at 21-day intervals. A meta analysis by Project Drawdown estimated carbon sequestration rates of 0.27 metric tons of carbon/year per acre for tropical-humid areas, 0.19 metric tons/acre for temperate/boreal humid areas, 0.64 metric tons for tropical semi-arid, and 0.26 metric tons/acre for temperate/boreal semi-arid areas. One hectare equals 2.47 acres.
Emerging Pathway: Long-Rooted Perennial Grains
In the United States, most crops are annual crops that must be re-seeded or re-planted yearly. Perennial crops can grow multiple years, reducing the need to plow the soil and apply herbicide. By establishing extensive, deep root systems in the soil, perennial grain crops better protect soil from erosion, and increase carbon sequestration, retain nutrients, and improve water infiltration. Indeed, a perennial grain developed by The Land Institute, Kernza, has been shown to grow roots that reach up to 10 feet underground. Preliminary research by The Land Institute suggests that intercropping perennial grains with legumes, like alfalfa and Kura clover, for nitrogen fertility can reduce nitrous oxide emissions from agricultural soils. Other perennial crops in development, like perennial rice, have also shown promise in increasing carbon sequestration.
While perennial grain crops show significant promise, more research and development are needed before they can be grown at scales large enough to impact atmospheric CO2. Some perennial grain crops, like Kernza, currently have significantly lower yields than annual wheat crops. If grown as a replacement for conventional wheat, more land would be needed to produce the same amount of food. However, as plant breeding improves yields, Kernza can be grown in dual-use forage and grain production systems to help improve on-farm nutrient cycling, efficient water use, and soil health. Other perennial grains, like perennial rice, already produce yields similar to annual rice on comparable acreage.
Potential Pathway: No-Till/Reduced Till Farming
Some research indicates that implementing no-till or reduced-till farming practices on farmland, which entails limiting disturbance of soil to manage plant residue on the soil surface year round, could be a potential natural climate solution. There is consensus that no-till and reduced till farming has many benefits, including preventing soil erosion and improved overall soil health, and the U.S. Department of Agriculture’s COMET Planner tool suggests a significant climate change mitigation benefit from implementing no-till.
However, some recent studies have made the case that the potential climate change mitigation potential of no-till has been overstated for several reasons. No-till has been found in many cases to redistribute the carbon in the soil profile, resulting in higher SOC concentrations in the topsoil and lower SOC concentrations in the subsoil (i.e. below the tillage depth), with little to no change in total SOC stocks in the full profile (shallow sampling schemes, which are common, miss the redistribution and overestimates SOC gains). Further, no-till has the potential to increase nitrous oxide emissions, which can counteract gains in SOC when considering net GHG emissions. And because no-till is often practiced together with other climate-smart practices, it can be difficult to segregate out the climate benefits that can be directly attributed directly to no-till on working farms. As a result of these uncertainties, more research is necessary to better understand under what conditions no-till and reduced-till lead to lower net GHG emissions. Finally, 60-70% of U.S. farmland is already under no-till or reduced-till management, so there is limited potential to implement this practice at a larger scale.
Growing a cover crop in the fallow season between market crops extends the time of year that there are living plants photosynthesizing, helping prevent soil erosion, and providing carbon substrates to the belowground microbial community. While most of the cover crop biomass carbon is returned to the atmosphere when the cover crops die and decompose, some of this carbon may remain in the soil. A recent meta-analysis of US studies suggests that cover crops, on average, store about one-sixth of a ton of CO2 per acre per year (Blanco-Canquiu 2022) – about one third of previous estimates from older global analyses (Poeplau and Don 2015).
This average masks a wide variation in carbon storage. Essentially, there is more benefit when the cover crops achieve higher biomass. If cover crops are planted too late or otherwise have poor establishment, then they don’t grow much and (unsurprisingly) there is not much carbon benefit. This means that when you plant grasses like cereal rye that accumulate more biomass we see more carbon storage. A grass-legume cover crop mix also tends to sequester more carbon because legumes fix nitrogen, which enables greater carbon storage. It also depends on soil type. So, as with most things agricultural, the devil is in the details. If managed effectively, cover crops will provide roughly 0.6 tons of CO2 per acre per year (this was the average from the subset of studies that found significant carbon storage in Blanco-Canqui 2022). Of course, it never works perfectly, so the average will be lower. The more farmers implement and innovate with cover crops, the more we learn, which could nudge the average up over time.
To determine the total amount of CO2 that cover cropping could store, this rate is multiplied by the amount of land area on which they could be newly adopted. Different assumptions about the available land area produce very different estimates of the potential for cover crops to mitigate climate change.. For example, if we assume that cover crops can be implemented on all cropland growing the five major field crops in the US – about 217 million acres (Fargione et al. 2018) – we expect cover crops could sequester up to about 39 million metric tons of CO2 per year. However, the uncertainty in this number is high; extrapolating the range of observed effects of cover crops across the country finds a range of 0 to 296 metric tons of CO2 per year (Blanco-Canquiu 2022).
An Environmental Defense Fund-led study(Aragon, et al 2024) refines the estimate by using a more conservative estimate of carbon sequestration from cover crops (0.12 Mg C /ha/year) and limiting the assumed land area suitable for cover cropping to those acres not reliant on irrigation and not changing to other land uses (i.e., stable annual croplands). This assessment estimates that cover crops are feasible on about 32% of current U.S. cropland extent, or about 95 million acres. The study estimates that cover cropping on this land has the potential to sequester 19.4 million metric tons of CO2e per year; however, the cost of realizing about half of this potential (10 million metric tons CO2e) could exceed $100 per metric ton, suggesting a need for financial incentives to encourage implementation.
This high uncertainty highlights the need for further research into the carbon sequestration benefit of cover crops and the agricultural practices necessary to maximize soil organic carbon. A remote sensing analysis of cover crops suggests that on average they reduce corn and soybean yields by 5.5% and 3.5%, respectively, across the US Corn Belt (Deines et al. 2022). This corroborates findings by The Nature Conservancy’s AgEvidence database that shows across 461 observations from 40 field studies in the Corn Belt that a 3.1% decline in grain yield occurred and across 33 observations from 5 field studies found an 11% decline in grain quality. However, other work has shown that cover cropping with mixtures that include legumes is likely to have positive effects on subsequent yields (Abdalla et al. 2019; Wang et al. 2021). In addition, positive effects on yields are more common in wetter climates on clay loam soils and when cover crop residue is not removed (Wang et al. 2021). These impacts of cover cropping on crop yields are important, as any negative impacts on yields could lead to conversion of carbon-rich forests or grasslands to agriculture, i.e., leakage. Fortunately, the Inflation Reduction Act includes $300 million to the Natural Resources Conservation Service to set up a national soil measurement network that may help to alleviate some of the data limitations contributing to the large uncertainty around the net GHG mitigation potential of cover crops.
GHG Technical Potential Estimate: *19-30 million metric tons of CO2e/year (0.12 Mg C /ha/year).
Acreage: 95-166 million acres
*Note: Estimate Does not include emissions related to cover crop seed production and distribution, emissions related to cover crop seeding and termination, or possible yield impacts.
Potential Pathway: No-Till/Reduced Till Farming
Some research indicates that implementing no-till or reduced-till farming practices on farmland, which entails limiting disturbance of soil to manage plant residue on the soil surface year round, could be a potential natural climate solution. There is consensus that no-till and reduced till farming has many benefits, including preventing soil erosion and improved overall soil health, and the U.S. Department of Agriculture’s COMET Planner tool suggests a significant climate change mitigation benefit from implementing no-till.
However, some recent studies have made the case that the potential climate change mitigation potential of no-till has been overstated for several reasons. No-till has been found in many cases to redistribute the carbon in the soil profile, resulting in higher SOC concentrations in the topsoil and lower SOC concentrations in the subsoil (i.e. below the tillage depth), with little to no change in total SOC stocks in the full profile (shallow sampling schemes, which are common, miss the redistribution and overestimates SOC gains). Further, no-till has the potential to increase nitrous oxide emissions, which can counteract gains in SOC when considering net GHG emissions. And because no-till is often practiced together with other climate-smart practices, it can be difficult to segregate out the climate benefits that can be directly attributed directly to no-till on working farms. As a result of these uncertainties, more research is necessary to better understand under what conditions no-till and reduced-till lead to lower net GHG emissions. Finally, 60-70% of U.S. farmland is already under no-till or reduced-till management, so there is limited potential to implement this practice at a larger scale.
Protecting and restoring coastal ecosystems, such as mangroves, tidal marshes and seagrass beds, that capture and store “blue carbon,” can sequester significantly more carbon per acre than terrestrial forests, and if left undisturbed, can store this carbon for a millenia. Most of the carbon is stored in underlying sediments, and these carbon stocks can be thousands of years old. Beyond carbon sequestration, protecting and restoring coastal wetlands provides significant benefits to society: protecting coastal communities, supporting recreational and commercial fisheries, enhancing tourism, and improving water quality that can be worth many thousands of dollars per acre per year. For example, scientists estimate that US coastal wetlands provide $23.2 billion in storm protection services each year. In addition to coastal blue carbon efforts, research is underway on oceanic blue carbon strategies for addressing climate change, including kelp farming and protection of certain fish populations.
Blue Carbon
Click Pathway for More Information
Coastal Wetland Protection and Restoration: Reconnecting Tidal Wetlands >
Coastal Wetland Protection and Restoration: Avoided Tidal Wetland Loss >
Coastal Wetland Protection and Restoration: Other Coastal Blue Carbon Strategies >
Seagrass Restoration >
Avoided Seagrass Loss >
Emerging Pathway: Seaweed/Kelp >
Emerging Pathway: Oceanic Blue Carbon >
Coastal Wetland Protection and Restoration: Reconnecting Tidal Wetlands
Reconnecting Tidal Wetlands:
Roughly 27% of U.S. tidal marshes have been disconnected from the ocean through coastal development such as the construction of sea walls or dikes. These “impounded wetlands” become less salty and are vulnerable to invasive species, resulting in the increased production of methane – a potent greenhouse gas. Removing barriers to tidal flows, as well as other efforts to restore tidal marshes and mangroves, has the potential to remove the equivalent of 12 million metric tons of carbon from the atmosphere by reducing methane emissions. (Source: Fargione/2018)
Current GHG Estimate: 12 million tons of CO2e/year
Current Acreage: 1.2 million acres
Coastal Wetland Protection and Restoration: Avoided Tidal Wetland Loss
Avoided Tidal Wetland Loss:
In addition to restoring tidal wetlands, ensuring that existing tidal wetlands remain intact is also important. A recent brief by the Pew Charitable Trusts notes that, according to the Environmental Protection Agency’s 2021 greenhouse gas inventory, coastal wetlands in the lower 48 states sequestered 4.8 million metric tons of CO2 equivalent—and held a total of about 2.9 billion metric tons in their soils—as of 2019. A “no net loss” policy for wetlands in the United States, first established by President George H.W. Bush in response to significant rates of wetland loss, confers some degree of protection, though destructive impacts may still be permitted if “compensatory mitigation” (e.g., creation of a new wetland) takes place. Compensatory measures like wetland creation are often not tracked to see if they are successful, and also does not account for loss of ecosystem functions like carbon sequestration and storage. As a result, despite the no net loss policy, the U.S. is still losing its coastal wetlands due to continued development, as well as from sea level rise and subsidence, which together “drown” coastal wetlands.
Management options to help prevent tidal wetland loss include closing permitting loopholes, shifting from a net loss to net ecological gain policy, and building resilience in existing tidal wetlands from sea level rise, such as adding sediment or creating space for wetlands to migrate inland and away from rising seas. There is a need to assess the carbon impact of measures that protect existing tidal wetlands from loss.
Read More >
Coastal Wetland Protection and Restoration: Other Coastal Blue Carbon Strategies
Other Coastal Blue Carbon Strategies:
In addition to reconnecting former saltwater wetlands to their tidal source, other forms of coastal restoration, such as restoring native plants to salt marshes, restoring forested coastal wetlands, and removing invasive species, has the potential to restore carbon sequestration in blue carbon habitats. Work is ongoing to quantify the carbon sequestration benefits of these activities; however, a recent analysis in the Pacific Northwest indicated that for every 1,000 acres of forested tidal wetland restored in the region, 212,500 metric tons of CO2e could be sequestered by 2050 – though this restoration work comes at a higher cost than avoiding the conversion of existing wetlands. As this study shows, it is necessary to carefully choose locations for restoration, carefully monitor recovery progress, and implement effective post-restoration management practices to ensure success.
Seagrass Restoration
Seagrass, which includes eelgrass meadows found in temperate waters, as well as other seagrasses like shoalgrass and widgeongrass, is a flowering plant with roots that exists in shallow bays and estuaries in the U.S. and around the world. Seagrasses can store more than twice as much carbon per square kilometer as terrestrial forest, and just 5 acres of eelgrass can offset the yearly emissions of 15,000 cars. Seagrass is distinct from kelp or seaweed, which is a form of algae and does not have roots. Nationwide, up to 6 million metric tons of CO2 could be sequestered by restoring the estimated 29 to 52% of historic seagrass extent that has been lost and could be restored (Fargione et al, 2018). Extensive work is underway in North Carolina, Virginia, California and other states to map existing seagrasses and better understand the climate mitigation benefits of protecting and restoring seagrass.
GHG Estimate: 6 million tons of CO2e/year
Acreage: 5 million acres
Avoided Seagrass Loss
In addition to restoring seagrass, protecting existing beds of seagrass that exist on coastlines around the United States ensures that the carbon currently stored in the underlying soils remains there, and is not emitted back into the atmosphere. By protecting existing beds of seagrass we can avoid up to 7 million metric tons of CO2 emissions (Fargione et al, 2018). Extensive work is being done in North Carolina, Virginia, California and other states to map existing seagrasses and better understand the climate mitigation benefits of protecting and restoring seagrass.
GHG Estimate: 7 million tons of CO2e/year
Acreage: 0.05 million acres per year
Emerging Pathway: Seaweed/Kelp
A 2022 report issued by the Environmental Defense Fund explores the role that kelp and other seaweeds can play as a Natural Climate Solution, summarizing the existing literature on carbon sequestration by seaweed, and evaluating the potential for interventions to increase carbon sequestration, such as conserving and restoring existing kelp forests, increasing productivity of seaweed farms, and expanding seaweed farming to offshore waters while creating conditions to incentivize increased carbon sequestration. The report reveals that, while the processes that influence carbon sequestration by seaweed are understood, there are significant gaps in existing data, as well as the need for new policy and accounting frameworks to govern these activities, which often cross jurisdictional boundaries.
As noted above, carbon sequestration provided by kelp and other forms of seaweed can occur through efforts to protect and restore wild seaweed, as well as efforts to cultivate seaweed through farming activities – which could be undertaken for the purposes of creating food and energy products, or for the carbon benefit alone. Moreover, it is important not to replace existing natural seaweed stands with cultivated seaweed. Potential avoided emissions from protecting kelp forests has been estimated at 42.9 million metric tons of CO2e a year globally (calculated from several studies 1,2,3,4).
Cultivated macroalgae (kelp farming) also has the potential to increase carbon mitigation – with an estimated increase in carbon burial of 1.4 tons of CO2e per hectare per year. However, the climate benefits of farming kelp to make products for human use would have a variable climate benefit depending on the product and its lifespan. Using kelp for food or short-lived products such as nutraceuticals offers lower climate benefits than long-lasting seaweed products because that carbon is released or transferred up the food chain (Scown 2022). Climate benefits from short-lived products stem from reduced production of their fossil fuel-intensive counterparts (DeAngelo et al. 2023).
Read More >
Emerging Pathway: Oceanic Blue Carbon
A 2022 report by the Environmental Defense Fund points to several potential open-ocean blue carbon strategies that could have climate change mitigation benefits, including efforts to rebuild epipelagic fish populations (fish that live in near the ocean surface at depths of less than 660 feet), avoiding greenhouse gas emissions by limiting or prohibiting harvest of mesopelagic fish (fish that live at depths between 660 and 3,330 feet), and limiting or prohibiting activities such as deep-sea mining and trawling that disturb carbon currently sequestered in seafloor sediments. Significant research is needed to better understand the climate mitigation potential of these oceanic pathways, and then to develop practices and financing mechanisms to ensure their safe implementation at scale.
Coastal Wetland Protection and Restoration: Avoided Tidal Wetland Loss
Avoided Tidal Wetland Loss:
In addition to restoring tidal wetlands, ensuring that existing tidal wetlands remain intact is also important. A recent brief by the Pew Charitable Trusts notes that, according to the Environmental Protection Agency’s 2021 greenhouse gas inventory, coastal wetlands in the lower 48 states sequestered 4.8 million metric tons of CO2 equivalent—and held a total of about 2.9 billion metric tons in their soils—as of 2019. A “no net loss” policy for wetlands in the United States, first established by President George H.W. Bush in response to significant rates of wetland loss, confers some degree of protection, though destructive impacts may still be permitted if “compensatory mitigation” (e.g., creation of a new wetland) takes place. Compensatory measures like wetland creation are often not tracked to see if they are successful, and also does not account for loss of ecosystem functions like carbon sequestration and storage. As a result, despite the no net loss policy, the U.S. is still losing its coastal wetlands due to continued development, as well as from sea level rise and subsidence, which together “drown” coastal wetlands.
Management options to help prevent tidal wetland loss include closing permitting loopholes, shifting from a net loss to net ecological gain policy, and building resilience in existing tidal wetlands from sea level rise, such as adding sediment or creating space for wetlands to migrate inland and away from rising seas. There is a need to assess the carbon impact of measures that protect existing tidal wetlands from loss.
Emerging Pathway: Seaweed/Kelp
A 2022 report issued by the Environmental Defense Fund explores the role that kelp and other seaweeds can play as a Natural Climate Solution, summarizing the existing literature on carbon sequestration by seaweed, and evaluating the potential for interventions to increase carbon sequestration, such as conserving and restoring existing kelp forests, increasing productivity of seaweed farms, and expanding seaweed farming to offshore waters while creating conditions to incentivize increased carbon sequestration. The report reveals that, while the processes that influence carbon sequestration by seaweed are understood, there are significant gaps in existing data, as well as the need for new policy and accounting frameworks to govern these activities, which often cross jurisdictional boundaries.
As noted above, carbon sequestration provided by kelp and other forms of seaweed can occur through efforts to protect and restore wild seaweed, as well as efforts to cultivate seaweed through farming activities – which could be undertaken for the purposes of creating food and energy products, or for the carbon benefit alone. Moreover, it is important not to replace existing natural seaweed stands with cultivated seaweed. Potential avoided emissions from protecting kelp forests has been estimated at 42.9 million metric tons of CO2e a year globally (calculated from several studies 1,2,3,4).
Cultivated macroalgae (kelp farming) also has the potential to increase carbon mitigation – with an estimated increase in carbon burial of 1.4 tons of CO2e per hectare per year. However, the climate benefits of farming kelp to make products for human use would have a variable climate benefit depending on the product and its lifespan. Using kelp for food or short-lived products such as nutraceuticals offers lower climate benefits than long-lasting seaweed products because that carbon is released or transferred up the food chain (Scown 2022). Climate benefits from short-lived products stem from reduced production of their fossil fuel-intensive counterparts (DeAngelo et al. 2023).
Peatlands
The Science: Peatlands are known by many names (e.g., mire, marsh, swamp, fen, bog, pocosin), but can simply be defined as a class of wetlands with a naturally accumulated layer of peat. Peat is formed when organic matter accumulates faster than it decomposes due to the lack of oxygen in waterlogged conditions. Even though peatlands cover only 3% of Earth’s surface, they store more than twice as much carbon as the world’s forests. Protecting existing peatlands can help keep carbon sequestered in these ecosystems, and restoring degraded peatlands can help increase carbon sequestration and reduce emissions, while also reducing wildfire risk.
Peatland Restoration
Vast amounts of peat wetlands in the United States have been drained or otherwise damaged. For example, since the early 1800s, the Sacramento Delta has lost about 140 million metric tons of carbon due to diking and draining of the region’s peat wetlands. Damaged peatlands are a major source of greenhouse gas emissions, annually releasing almost 6% of global anthropogenic CO2 emissions (IUCN 2017).
Peatland restoration in the U.S. can therefore bring significant emissions reductions. Restoring peatlands could avoid 9 million metric tons of CO2 emissions (Fargione et al, 2018). Recent research led by Duke University’s Nicholas Institute for Energy, Environment, and Sustainability suggests that an effort to rewet between 111,000 and 190,000 acres of drained pocosin peatlands in Southeastern states can by itself provide up to 2.4% of the U.S. national CO2 reduction target of 180 million metric tons of CO2e a year. Restoring degraded peatlands can also help mitigate the impacts of wildfire.
GHG Estimate: 9 million tons of CO2e/year
Acreage: 7.4 million acres
In addition to restoring degraded peatlands, keeping carbon sequestered in existing peatlands is also important. While there is not yet an existing national estimate of the avoided GHG emissions that would result from a national effort to prevent the conversion of existing peatlands to other uses such as mining, a study in Alaska indicates that the state’s 177,000-acre Kenai Peninsula, 26,376,665 metric tons of CO2e are sequestered. When one considers that peatlands cover over 26.45 million acres (see text under table 13A.6) in Alaska alone, and millions more acres in the lower-48 states, the need to protect these significant carbon sinks is clear.
The Decision-Makers Guide to Natural Climate Solutions Science
is designed to serve as a hub of information to help decision-makers in the public policy, corporate, and non-profit sectors better understand the science supporting a broad array of Natural Climate Solutions strategies, and apply that science to planning, policy making and corporate practices.
