Deploy Ocean Fertilization

Submitted by Drawdown Admin on
Sector
Nature-Based Carbon Removal
Mode
Remove Carbon
Cluster
Manipulate Biogeochemical Cycles
Image
An aerial view of the Earth with colorful plankton blooms in the ocean off the coast of a landmass
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Summary

Ocean fertilization uses nutrients to enhance photosynthesis by marine phytoplankton, which remove CO₂ and convert it into biomass that can sink to the deep ocean. This practice is a carbon removal technology that could achieve Gt-scale CO₂ removal annually. Potential advantages of ocean fertilization include localized reduction of ocean acidification and low costs. Disadvantages include high and uncertain risks of altering ecosystems both near dispersal sites and farther away, unclear but probably low effectiveness, potentially difficult operational upscaling, and challenges with monitoring and verification. We conclude that Deploy Ocean Fertilization is “Not Recommended” as a climate solution given its likely low effectiveness, technical challenges, and high environmental risks.

Description for Social and Search
Ocean fertilization uses nutrients to enhance photosynthesis by marine phytoplankton, which remove CO₂ and convert it into biomass that can sink to the deep ocean. We conclude that Deploy Ocean Fertilization is “Not Recommended” as a climate solution given its likely low effectiveness, technical challenges, and high environmental risks.
Overview

What is our assessment?

Based on the scientific uncertainties regarding its effectiveness and the potential serious environmental and social risks, we conclude that Deploy Ocean Fertilization is “Not Recommended” as a climate solution.

Plausible Could it work? Yes
Ready Is it ready? No
Evidence Are there data to evaluate it? Limited
Effective Does it consistently work? No
Impact Is it big enough to matter? Yes
Risk Is it risky or harmful? Yes
Cost Is it cheap? ?

What is it?

Ocean fertilization involves adding nutrients, such as iron, to seawater to promote photosynthesis in the surface ocean. As phytoplankton draw in seawater CO₂ and convert it into biomass, the ocean can absorb more CO₂ from the atmosphere. Some of the carbon eventually sinks or is transported to the deep sea or seafloor, where it can be stored for decades or centuries. Most ocean fertilization efforts are focused on adding iron because it is a micronutrient already required in small amounts for photosynthesis and because iron limitation is common in many global ocean regions. The Southern Ocean, in particular, has been highlighted as a potential target due to its widespread iron limitation.

Does it work?

As a carbon removal technique, ocean fertilization requires that the nutrient addition enhances phytoplankton uptake of seawater CO₂ and subsequent absorption of additional CO₂ from the atmosphere, and that the carbon is transported and durably stored in the deep sea. Research since the 1990s has shown that ocean iron fertilization does lead to increased seawater CO₂ uptake due to enhanced photosynthesis. However, the ultimate fate and durability of that carbon are less well understood. To be sequestered, carbon must be transported below water depths where annual mixing occurs, often considered to be ~1,000 m, but research suggests that, on average, 66% of carbon at these depths can be re-exposed to the atmosphere in less than 40 years. Ocean fertilization might also increase production of GHGs, such as nitrous oxide and methane, which could impact the effectiveness of this practice, although these effects remain understudied. In places like the Southern Ocean, sunlight and changes in the availability of other nutrients, such as silicate, can also limit the effects of iron addition. Additionally, nutrients such as iron can have high loss rates, up to 75%, after dispersal into seawater due to conversion into forms inaccessible to phytoplankton, potentially further reducing the effectiveness of nutrient addition.

Why are we excited?

If ocean fertilization were broadly deployed and functioned as intended, its global climate impact could reach 0.1–1.0 Gt CO₂ /yr. Ocean fertilization is expected to increase surface water pH, which could help temporarily reduce ocean acidification locally. However, some studies suggest this benefit will come at the cost of increased acidification of deeper ocean regions. While costs remain highly uncertain, estimates of ocean fertilization costs range between US$80/t CO₂ and US$457/t CO₂, suggesting this practice might also be relatively inexpensive compared to other marine CO₂ removal practices.

Why are we concerned?

Ocean fertilization poses several technical challenges, along with significant environmental and social risks. Tracking the amount of carbon sequestered from ocean fertilization is difficult because carbon export efficiencies – the amount of carbon produced in surface waters that makes its way to the deep sea – can be low and highly variable in time and space. Addressing this will require both field studies and models capable of capturing global and multi-decadal changes in carbon cycling due to fertilization, given the long time scales and large spatial areas involved. Implementing ocean fertilization at globally meaningful carbon removal levels could raise additional feasibility concerns, given the potential difficulty of dispersing sufficiently large quantities of nutrients across vast areas and the need for fertilization to be done continuously to minimize carbon returning to the atmosphere. 

Beyond these technical challenges, ocean fertilization also poses several potentially severe environmental risks. Enhancing primary production could disrupt existing nutrient pools in the ocean, reducing the nutrients available for ecosystems far from dispersal sites. Another consequence of ocean fertilization is that increased organic carbon supply can enhance microbial processes that consume dissolved oxygen, potentially impairing respiration in marine organisms and leading to mortality. Other unintended consequences of nutrient fertilization include promoting harmful algal blooms that can release toxins that negatively impact a wide array of life, from shellfish to marine mammals to humans. Ocean fertilization also carries significant social risks because global-scale modification of marine ecosystems is likely to create inequities in environmental and economic impacts.

Solution in Action

Aumont, O., & Bopp, L. (2006). Globalizing results from ocean in situ iron fertilization studies. Global Biogeochemical Cycles, 20(2). Link to source: https://doi.org/10.1029/2005GB002591

Bakker, D. C. (2004). Storage of carbon dioxide by greening of oceans. In C. B. Field & M. R. Raupach (Eds.), The global carbon cycle: Integrating humans, climate, and the natural world (pp. 453–469). Island Press.

Boettcher, M., Chai, F., Canothan, M., Cooley, S., Keller, D. P., Klinsky, S., ... & Webb, R. M. (2023). A code of conduct for marine carbon dioxide removal research. Aspen Institute. Link to source: https://www.aspeninstitute.org/publications/a-code-of-conduct-for-marine-carbon-dioxide-removal-research/

Boyd, P. W. (2008). Implications of large-scale iron fertilization of the oceans. Marine Ecology Progress Series, 364, 213–218. Link to source: https://www.int-res.com/articles/theme/m364p213.pdf

Boyd, P. W., Jickells, T., Law, C. S., Blain, S., Boyle, E. A., Buesseler, K. O., ... & Watson, A. J. (2007). Mesoscale iron enrichment experiments 1993-2005: synthesis and future directions. Science, 315(5812), 612–617. Link to source: https://doi.org/10.1126/science.1131669

Buesseler, K. O., & Boyd, P. W. (2003). Will ocean fertilization work?. Science, 300(5616), 67–68. Link to source: https://doi.org/10.1126/science.1082959

Cao, L., & Caldeira, K. (2010). Can ocean iron fertilization mitigate ocean acidification? A letter. Climatic Change, 99(1), 303–311. Link to source: https://link.springer.com/article/10.1007/s10584-010-9799-4

Emerson, D., Sofen, L. E., Michaud, A. B., Archer, S. D., & Twining, B. S. (2024). A cost model for ocean iron fertilization as a means of carbon dioxide removal that compares ship‐and aerial‐based delivery, and estimates verification costs. Earth's Future, 12(4), e2023EF003732. Link to source: https://doi.org/10.1029/2023EF003732

Gattuso, J. P., Williamson, P., Duarte, C. M., & Magnan, A. K. (2021). The potential for ocean-based climate action: negative emissions technologies and beyond. Frontiers in Climate, 2, 575716. Link to source: https://doi.org/10.3389/fclim.2020.575716

Harrison, D. P. (2013). A method for estimating the cost to sequester carbon dioxide by delivering iron to the ocean. International Journal of Global Warming, 5(3), 231–254. Link to source: https://doi.org/10.1504/IJGW.2013.055360

Harvey, J. (2020). 30 years: The iron hypothesis is no more. Moss Landing Marine Laboratories Blog. Link to source: https://mlml.sjsu.edu/2020/06/18/30-years-the-iron-hypothesis-is-no-more/

Jin, X., & Gruber, N. (2003). Offsetting the radiative benefit of ocean iron fertilization by enhancing N2O emissions. Geophysical Research Letters, 30(24). Link to source: https://doi.org/10.1029/2003GL018458

Marinov, I., Gnanadesikan, A., Toggweiler, J. R., & Sarmiento, J. L. (2006). The southern ocean biogeochemical divide. Nature, 441(7096), 964–967. Link to source: https://doi.org/10.1038/nature04883

Martin, J. H., Gordon, M., & Fitzwater, S. E. (1991). The case for iron. Limnology and Oceanography, 36(8), 1793–1802. Link to source: https://doi.org/10.4319/lo.1991.36.8.1793

National Academies of Sciences, Engineering, and Medicine. (2021). A research strategy for ocean-based carbon dioxide removal and sequestration. National Academies Press. Link to source: https://www.nationalacademies.org/our-work/a-research-strategy-for-ocean-carbon-dioxide-removal-and-sequestration

Ocean Visions. (2023). Microalgae cultivation. Link to source: https://oceanvisions.org/microalgae-cultivation/

Oschlies, A., Koeve, W., Rickels, W., & Rehdanz, K. (2010). Side effects and accounting aspects of hypothetical large-scale Southern Ocean iron fertilization. Biogeosciences, 7(12), 4017–4035. Link to source: https://bg.copernicus.org/articles/7/4017/2010/bg-7-4017-2010.pdf

Oschlies, A., Slomp, C., Altieri, A. H., Gallo, N. D., Grégoire, M., Isensee, K., Levin, L. A., & Wu, J. (2025). Potential impacts of marine carbon dioxide removal on ocean oxygen. Environmental Research Letters, 20(1), 011001. Link to source: https://doi.org/10.1088/1748-9326/ade0d4

Robinson, J., Popova, E. E., Yool, A., Srokosz, M., Lampitt, R. S., & Blundell, J. R. (2014). How deep is deep enough? Ocean iron fertilization and carbon sequestration in the Southern Ocean. Geophysical Research Letters, 41(7), 2489–2495. Link to source: https://doi.org/10.1002/2013GL058799

Sarmiento, J. L., Gruber, N., Brzezinski, M. A., & Dunne, J. P. (2004). High-latitude controls of thermocline nutrients and low latitude biological productivity. Nature, 427(6969), 56–60. Link to source: https://doi.org/10.1038/nature02127

Shepherd, J. G. (2009). Geoengineering the climate: science, governance and uncertainty. The Royal Society. Link to source: https://royalsociety.org/-/media/policy/publications/2009/8693.pdf

Strong, A., Chisholm, S., Miller, C., & Cullen, J. (2009). Ocean fertilization: time to move on. Nature, 461(7262), 347–348. Link to source: https://doi.org/10.1038/461347a

Tagliabue, A., Aumont, O., DeAth, R., Dunne, J. P., Dutkiewicz, S., Galbraith, E., Misumi, K., Moore, J. K., Ridgwell, A., Sherman, E., Stock, C., Vichi, M., Völker, C., & Yool, A. (2016). How well do global ocean biogeochemistry models simulate dissolved iron distributions?. Global Biogeochemical Cycles, 30(2), 149–174. Link to source: https://doi.org/10.1002/2015GB005289

Tagliabue, A., Twining, B. S., Barrier, N., Maury, O., Berger, M., & Bopp, L. (2023). Ocean iron fertilization may amplify climate change pressures on marine animal biomass for limited climate benefit. Global Change Biology, 29(18), 5250–5260. Link to source: https://doi.org/10.1111/gcb.16854

Trick, C. G., Bill, B. D., Cochlan, W. P., Wells, M. L., Trainer, V. L., & Pickell, L. D. (2010). Iron enrichment stimulates toxic diatom production in high-nitrate, low-chlorophyll areas. Proceedings of the National Academy of Sciences, 107(13), 5887–5892. Link to source: https://doi.org/10.1073/pnas.0910579107

Yoon, J. E., Yoo, K. C., Macdonald, A. M., Yoon, H. I., Park, K. T., Yang, E. J., Kim, H. C., Lee, J. I., Lee, M. K., Jung, J., Park, J., Lee, J., Kim, S., Kim, S. S., Kim, K., & Kim, I. N. (2018). Reviews and syntheses: Ocean iron fertilization experiments–past, present, and future looking to a future Korean Iron Fertilization Experiment in the Southern Ocean (KIFES) project. Biogeosciences, 15(19), 5847-5889. Link to source: https://doi.org/10.5194/bg-15-5847-2018

Credits

Lead Fellow

  • Christina Richardson, Ph.D.

Internal Reviewer

  • Christina Swanson, Ph.D.
Speed of Action
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Caveats
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Additional Benefits
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Risks
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Consensus
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Trade-offs
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Action Word
Deploy
Solution Title
Ocean Fertilization
Classification
Not Recommended
Updated Date

Boost Whale Restoration

Submitted by Drawdown Admin on
Sector
Nature-Based Carbon Removal
Mode
Remove Carbon
Cluster
Restore & Manage Ecosystems
Image
Peatland
Coming Soon
On
Description for Social and Search
The Boost Whale Restoration solution is coming soon.
Solution in Action
Speed of Action
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Caveats
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Additional Benefits
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Risks
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Consensus
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Trade-offs
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Action Word
Boost
Solution Title
Whale Restoration
Classification
Worthwhile
Updated Date

Boost Large Herbivore Restoration

Submitted by Drawdown Admin on
Sector
Nature-Based Carbon Removal
Mode
Remove Carbon
Cluster
Restore & Manage Ecosystems
Image
Peatland
Coming Soon
On
Description for Social and Search
The Boost Large Herbivore Restoration solution is coming soon.
Solution in Action
Speed of Action
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Caveats
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Additional Benefits
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Risks
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Consensus
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Trade-offs
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Action Word
Boost
Solution Title
Large Herbivore Restoration
Classification
Worthwhile
Updated Date

Explore Ocean Electrochemistry

Submitted by Drawdown Admin on
Sector
Nature-Based Carbon Removal
Mode
Remove Carbon
Cluster
Manipulate Biogeochemical Cycles
Image
Peatland
Coming Soon
On
Description for Social and Search
The Explore Ocean Electrochemistry solution is coming soon.
Solution in Action
Speed of Action
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Caveats
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Additional Benefits
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Risks
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Consensus
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Trade-offs
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Action Word
Explore
Solution Title
Ocean Electrochemistry
Classification
Keep Watching
Updated Date

Deploy Ocean Alkalinity Enhancement

Submitted by Drawdown Admin on
Sector
Nature-Based Carbon Removal
Mode
Remove Carbon
Cluster
Manipulate Biogeochemical Cycles
Image
An image of the frothy crest of a wave
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Summary

Ocean alkalinity enhancement (OAE) increases the ocean’s natural ability to remove CO₂ from the air by increasing the alkalinity of ocean water. This carbon removal practice could be globally effective at removing CO₂ at the gigaton level annually and is currently being tested in field studies. Advantages of OAE include its ability to mitigate ocean acidification where it’s deployed and its scalability. Disadvantages include uncertainties surrounding OAEs’ global effectiveness and feasibility, potential impacts on marine life and humans, complex monitoring needed for verification, and potentially high costs, all of which need to be more closely studied. We will “Keep Watching” Deploy Ocean Alkalinity Enhancement until the technology advances and its risks, costs, and benefits become clearer.

Description for Social and Search
Ocean alkalinity enhancement (OAE) increases the ocean’s natural ability to remove CO₂ from the air by increasing the alkalinity of ocean water. This carbon removal practice could be globally effective at removing CO₂ at the gigaton level annually and is currently being tested in field studies.
Overview

What is our assessment?

Based on our analysis, OAE could be a promising carbon removal technique, but it is not ready for large-scale deployment until the risks, costs, and effectiveness become clearer. We will “Keep Watching” this potential climate solution.

Plausible Could it work? Yes
Ready Is it ready? No
Evidence Are there data to evaluate it? Limited
Effective Does it consistently work? No
Impact Is it big enough to matter? Yes
Risk Is it risky or harmful? ?
Cost Is it cheap? ?

What is it?

OAE is the practice of adding alkalinity to seawater to increase the ocean’s ability to remove atmospheric CO₂. The addition of alkalinity through OAE mimics the natural process of weathering, or the physical and chemical breakdown of rocks. Rock weathering on land produces alkaline substances that eventually flow into the ocean through rivers and groundwater. This natural supply of alkalinity reduces ocean acidity, which affects the distribution of various carbon forms in the ocean. As alkalinity increases, CO₂ dissolved in seawater shifts toward more stable carbon forms, like bicarbonate and carbonate ions, that cannot exchange with air. This allows the ocean to remove more gaseous CO₂ from the atmosphere because the ocean and the atmosphere maintain a balance of CO₂ through gas movement at the sea surface. Most of the dissolved carbon in the ocean is bicarbonate and carbonate ions, which can persist in seawater for thousands of years. Under natural conditions, the ocean removes nearly 0.5 Gt of CO₂ annually. OAE generally relies on dissolving large amounts of ground-up rocks, either directly in the ocean or indirectly in water that is added to the ocean, to increase alkalinity and remove CO₂. This practice typically requires mining for alkaline rocks, though alkaline materials can also be sourced from waste by-products of other industries (e.g., steel slag, mine tailings) or commercially through human-made substances.

Does it work?

The science behind OAE is theoretically sound, and OAE is expected to result in durable storage over long time periods (>100 years). At scale, OAE could potentially remove over 1 Gt CO₂ /yr, but additional lab and field-based studies are needed to understand whether this approach is effective and safe. The majority of our understanding of OAE comes from models and laboratory experiments. However, when crushed minerals have been dispersed in field studies, the dissolution has not always occurred as expected. Several large-scale experimental trials are currently underway or planned, which will produce real-world data and inform monitoring and verification tactics needed to help refine and guide future implementation. These tests will also provide critical information on any ecological or community impacts. Various ways of implementing OAE are being developed, including ship-based dispersal, shoreline-based systems, and other approaches that leverage existing industrial waste streams or combine with other marine carbon dioxide removal (mCDR) techniques, such as electrochemical alkalinity generation.

Why are we excited?

OAE removes CO₂ from the atmosphere and stores it in the ocean as bicarbonate and carbonate ions, which are stable over long time periods. This means the CO₂ would be durably stored from the atmosphere for thousands of years. OAE could be scaled globally and can also mitigate local ocean acidification, a growing issue that threatens a range of marine ecosystems. Indeed, adding alkalinity to seawater has already been shown to mitigate ocean acidification in some coral reefs. Mitigating ocean acidification could also benefit fisheries and aquaculture, highlighting the potential for OAE to provide additional local benefits beyond carbon removal.

Why are we concerned?

Several technical, environmental, and social concerns surround OAE. The effectiveness could be limited by real-world conditions that either transport the alkaline materials away from the ocean’s surface before CO₂ can be absorbed or result in unexpected chemical reactions or biological uptake of the added alkalinity. Measuring and verifying the amount of CO₂ permanently stored using OAE is also challenging and will rely on a combination of field data and complex numerical models, which will require significant effort to collect and develop. Beyond these technical challenges, OAE poses potential environmental risks on land and in the ocean. On land, OAE could require an expansion of mining that rivals the cement industry, which could have negative environmental impacts on human and ecosystem health. In the ocean, increased alkalinity and the potential release of metals from the source rocks could negatively affect some marine life, but our understanding of the effects on individual species and food webs is limited. OAE could also interfere with existing ocean uses (e.g., fisheries, recreation) in some places and could have other unintended consequences as well. For instance, research suggests that OAE reduces natural alkalinity production in some ocean areas. In addition, OAE faces several social challenges. To be successful, mCDR approaches, like OAE, will require rapid, meaningful, and just community engagement. Public concerns about OAE have already led to a pilot project cancellation, highlighting the importance of public perception for OAE feasibility. It is also unclear if OAE can be scaled globally at reasonable costs, with current estimates highly variable but generally over US$100/t CO₂. Lastly, acquiring and dispersing sufficient alkaline materials could be challenging at scale, particularly because some materials are currently energy-intensive to source, transport, and/or produce.

Solution in Action

Albright, R., Caldeira, L., Hosfelt, J., Kwiatkowski, L., Maclaren, J. K., Mason, B. M., ... & Caldeira, K. (2016). Reversal of ocean acidification enhances net coral reef calcification. Nature, 531(7594), 362-365. Link to source: https://doi.org/10.1038/nature17155 

Bach, L. T. (2024). The additionality problem of ocean alkalinity enhancement. Biogeosciences, 21(1), 261-277. Link to source: https://doi.org/10.5194/bg-21-261-2024 

Bach, L. T., Gill, S. J., Rickaby, R. E., Gore, S., & Renforth, P. (2019). CO2 removal with enhanced weathering and ocean alkalinity enhancement: potential risks and co-benefits for marine pelagic ecosystems. Frontiers in Climate, 1, 7. Link to source: https://doi.org/10.3389/fclim.2019.00007 

Bertram, C., & Merk, C. (2020). Public perceptions of ocean-based carbon dioxide removal: the nature-engineering divide?. Frontiers in Climate, 2, 594194. Link to source: https://doi.org/10.3389/fclim.2020.594194 

(carbon)plan. Introduction to Ocean Alkalinity Enhancement: Link to source: https://carbonplan.org/research/oae-efficiency-explainer 

Carbon Herald. (2025, April 11). Planetary Technologies cancels its mCDR project in Cornwall. Link to source: https://carbonherald.com/planetary-technologies-cancels-its-mcdr-project-in-cornwall/ 

Doney, S. C., Wolfe, W. H., McKee, D. C., & Fuhrman, J. G. (2024). The science, engineering, and validation of marine carbon dioxide removal and storage. Annual Review of Marine Science, 17. Link to source: https://doi.org/10.1146/annurev-marine-040523-014702 

Doney, S. C., Fabry, V. J., Feely, R. A., & Kleypas, J. A. (2009). Ocean acidification: the other CO2 problem. Annual Review of Marine Science, 1(1), 169-192. Link to source: https://doi.org/10.1146/annurev.marine.010908.163834

EGU Biogeosciences. Special Issue: Environmental impacts of ocean alkalinity enhancement. Link to source: https://bg.copernicus.org/articles/special_issue1246.html 

Gattuso, J. P., Magnan, A. K., Bopp, L., Cheung, W. W., Duarte, C. M., Hinkel, J., ... & Rau, G. H. (2018). Ocean solutions to address climate change and its effects on marine ecosystems. Frontiers in Marine Science, 5, 337. Link to source: https://doi.org/10.3389/fmars.2018.00337 

Oschlies, A., Stevenson, A., Bach, L. T., Fennel, K., Rickaby, R. E. M., Satterfield, T., Webb, R., and Gattuso, J.-P. (2023). Guide to Best Practices in Ocean Alkalinity Enhancement Research, Copernicus Publications, State of the Planet, 2-oae2023. Link to source: https://doi.org/10.5194/sp-2-oae2023 

Hartmann, J., Suitner, N., Lim, C., Schneider, J., Marín-Samper, L., Arístegui, J., ... & Riebesell, U. (2022). Stability of alkalinity in ocean alkalinity enhancement (OAE) approaches–consequences for durability of CO 2 storage. Biogeosciences Discussions, 2022, 1-29. Link to source: https://doi.org/10.5194/bg-20-781-2023

Hartmann, J., West, A. J., Renforth, P., Köhler, P., De La Rocha, C. L., Wolf‐Gladrow, D. A., ... & Scheffran, J. (2013). Enhanced chemical weathering as a geoengineering strategy to reduce atmospheric carbon dioxide, supply nutrients, and mitigate ocean acidification. Reviews of Geophysics, 51(2), 113-149. Link to source: https://doi.org/10.1002/rog.20004

He, J., & Tyka, M. D. (2023). Limits and CO2 equilibration of near-coast alkalinity enhancement. Biogeosciences, 20(1), 27-43. Link to source: https://doi.org/10.5194/bg-20-27-2023

National Academies of Sciences, Engineering, and Medicine; Division on Earth and Life Studies; Ocean Studies Board; Committee on A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration. A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration. Washington (DC): National Academies Press (US); 2021 Dec 8. 7, Ocean Alkalinity Enhancement. Available from: Link to source: https://www.ncbi.nlm.nih.gov/books/NBK580052/ 

Ocean Visions: Link to source: https://oceanvisions.org/ocean-alkalinity-enhancement/ 

Palmiéri, J. and Yool, A., 2024. Global‐scale evaluation of coastal ocean alkalinity enhancement in a fully coupled Earth system model. Earth's Future, 12(3), p.e2023EF004018. Link to source: https://doi.org/10.1029/2023EF004018

Renforth, P., & Henderson, G. (2017). Assessing ocean alkalinity for carbon sequestration. Reviews of Geophysics, 55(3), 636-674. Link to source: https://doi.org/10.1002/2016RG000533 

Satterfield, T., Nawaz, S., & Boettcher, M. (2023). Social considerations and best practices for engaging publics on ocean alkalinity enhancement. State of the Planet Discussions, 2023, 1-39. Link to source: https://doi.org/10.5194/sp-2-oae2023-11-2023 

Webb, R. M., Silverman-Roati, K., & Gerrard, M. B. (2021). Removing Carbon Dioxide Through Ocean Alkalinity Enhancement: Legal Challenges and Opportunities. Available at: Link to source: https://scholarship.law.columbia.edu/faculty_scholarship/2981 

Zhuang, W., Zhu, T., Li, F., Queiroz, H. M., Yan, Q., Zhao, X., & Liu, J. (2025). Potential Environmental Impacts and Management Strategies for Metal Release during Ocean Alkalinity Enhancement Using Olivine. Environmental Science & Technology, 59(2), 1091-1099. Link to source: https://doi.org/10.1021/acs.est.4c10705 

Zhou, M., Tyka, M. D., Ho, D. T., Yankovsky, E., Bachman, S., Nicholas, T., ... & Long, M. C. (2024). Mapping the global variation in the efficiency of ocean alkalinity enhancement for carbon dioxide removal. Nature Climate Change, 15(1), 59-65. Link to source: https://doi.org/10.1038/s41558-024-02179-9 

Credits

Lead Fellow 

  • Christina Richardson, Ph.D.

Internal Reviewer

  • Christina Swanson, Ph.D.
Speed of Action
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Caveats
left_text_column_width
Additional Benefits
left_text_column_width
Risks
left_text_column_width
Consensus
left_text_column_width
Trade-offs
left_text_column_width
Action Word
Deploy
Solution Title
Ocean Alkalinity Enhancement
Classification
Keep Watching
Updated Date

Deploy Enhanced Rock Weathering

Submitted by Drawdown Admin on
Sector
Nature-Based Carbon Removal
Mode
Remove Carbon
Cluster
Manipulate Biogeochemical Cycles
Image
Boreal grassland
Coming Soon
Off
Summary

Enhanced rock weathering removes CO₂ from the air by accelerating the natural chemical and physical breakdown of certain rocks. This carbon removal practice can be effective and has been deployed in pilot and small-scale commercial projects. Advantages include its reliance on a natural process (geological weathering), its potential for large-scale deployment on land or in the ocean, and its potential to improve soil conditions and crop yields. Disadvantages of enhanced rock weathering include unpredictable effectiveness for carbon removal, complex monitoring and measurement requirements, and high costs. We will “Keep Watching” Enhanced Rock Weathering, but it is not yet ready for large-scale deployment as a climate solution.

Description for Social and Search
Enhanced rock weathering removes CO₂ from the air by accelerating the natural chemical and physical breakdown of certain rocks. This carbon removal practice can be effective and has been deployed in pilot and small-scale commercial projects.
Overview

What is our assessment?

Based on our analysis, enhanced rock weathering is a promising carbon removal technique, but it is not ready for large-scale deployment. We will “Keep Watching” this potential climate solution.

Plausible Could it work? Yes
Ready Is it ready? Yes
Evidence Are there data to evaluate it? Yes
Effective Does it consistently work? No
Impact Is it big enough to matter? Yes
Risk Is it risky or harmful? ?
Cost Is it cheap? No

What is it?

Enhanced rock weathering is a practice that removes CO₂ from the atmosphere by accelerating the natural chemical and physical breakdown, or weathering, of rocks such as basalt, olivine, or limestone. This is typically achieved by crushing the rocks into dust or sand-sized particles to increase their surface area before applying them to croplands, beaches, or directly into the ocean, the latter of which is also a form of carbon removal known as ocean alkalinity enhancement. During weathering, the rock surface chemically reacts with atmospheric CO₂ that is dissolved in rain or ocean water. This reaction produces bicarbonate ions containing the carbon from the captured CO₂ and positively charged cations, such as magnesium or calcium, depending on the type of rock. For land-based enhanced rock weathering, the bicarbonate needs to be flushed out to the ocean, where it is stable and can be securely stored for thousands of years.  

Does it work?

The basic idea of enhanced rock weathering is scientifically and geologically sound. Its effectiveness in converting atmospheric CO₂ into bicarbonate has been demonstrated in laboratory and field trials for several rock types and application sites. There are currently numerous research and demonstration projects underway. More than a dozen companies are selling enhanced rock weathering-based carbon removal credits, with nearly 10,000 t CO₂ reported to have been removed as of early 2025.

Why are we excited?

Enhanced rock weathering has several features that improve the likelihood that it can be scaled up to remove and store globally meaningful amounts of atmospheric CO₂ (>0.1 Gt CO₂/yr). Since enhanced rock weathering utilizes a natural process – mineralization – it does not need to be combined with other technologies to capture CO₂ from the air or durably store it. Moreover, it does not require external energy for the carbon capture and storage process, although it does use energy and generate emissions from the mining, crushing, transport, and deployment of the crushed rock. Suitable rock types, such as basalt, which is widely used in construction, paving, and concrete, are common and often locally available. Globally, there are large areas of land and ocean surface on which enhanced rock weathering could be deployed, including on croplands where current agricultural practices often already include regular application of soil amendments. A recent study suggested that extensive deployment of enhanced rock weathering on U.S. agricultural lands could sequester 0.16–0.30 Gt CO₂/yr by 2050. Other studies have shown that the application of crushed rock to croplands for enhanced rock weathering can improve soil pH, provide essential soil nutrients, and improve crop yields.

Why are we concerned?

There are numerous challenges for enhanced rock weathering, as well as potential risks and adverse impacts from its large-scale deployment. Numerous studies on both land- and ocean-based enhanced rock weathering have shown that the amounts of atmospheric CO₂ converted into bicarbonate are highly variable, dependent on rock type, soil type, application rates, and other variables, and are therefore difficult to accurately predict and model. This makes measurement, reporting, and verification of the amount of CO₂ captured and stored, which is essential for the carbon market, reliant on extensive and expensive field measurements and customized models. There are also concerns about the harmful impacts of heavy metals, like nickel or chromium, that can be released during weathering, as well as other ecological impacts and environmental justice concerns, particularly for crushed rock deployed on beaches or in the ocean. Finally, costs for deployment and the purchase of enhanced rock weathering-based carbon credits are relatively high (>US$200–US$500/t CO₂ removed) and will likely remain high if verification continues to depend on large numbers of field measurements and carbon removal cannot be easily modeled. There is a general consensus in the scientific community that the current knowledge base is not sufficient to reliably or accurately quantify the CO₂ captured and stored by most land- or ocean-based enhanced rock weathering deployments.

Bach, L. T., Gill, S. J., Rickaby, R. A., Gore, S., & Renforth, P. (2019). CO2 removal with enhanced weathering and ocean alkalinity enhancement: potential risks and co-benefits for marine pelagic ecosystems. Frontiers in Climate 1(7). Link to source: https://doi.org/10.3389/fclim.2019.00007 

Beerling, D. J. et al. (2025). Transforming US agriculture for carbon removal with enhanced weathering. Nature 638, 425–434. Link to source: https://doi.org/10.1038/s41586-024-08429-2 

CDR.fyi. Leaderboards. (2025). Leaderboards. Retrieved from CDR.fyi website: Link to source: https://www.cdr.fyi/leaderboards 

Cong, L., Lu, S., Jiang, P., Zheng, T., Yu, Z., & Lü, X. (2024). CO₂ sequestration and soil improvement in enhanced rock weathering: A review from an experimental perspective. Greenhouse. Gas. Sci. Technol., 14, 1122–1138. Link to source: https://doi.org/10.1002/ghg.2313 

Geerts, L. J., Hylén, A., & Meysman, F. J. (2025). Review and syntheses: Ocean alkalinity enhancement and carbon dioxide removal through marine enhanced rock weathering using olivine. Biogeosciences 22(2), 355–384. Link to source: https://doi.org/10.5194/bg-22-355-2025 

Höglund, R. (2025). Buyers of Enhanced Rock Weathering credits need to ask for the right type of MRV. Milkywire. Link to source: https://www.milkywire.com/articles/buyers-of-enhanced-rock-weathering-credits-need-to-ask-for-the-right-type-of-mrv 

Jagoutz, O. & Krol, A. (2023). Enhanced Rock Weathering. MIT Climate Portal. Link to source: https://climate.mit.edu/explainers/enhanced-rock-weathering 

Jeswani, H. K., Saharudin, D. M., & Azapagic, A. (2022). Environmental sustainability of negative emissions technologies: A review. Sustainable Production and Consumption 33, 608–635. Link to source: https://doi.org/10.1016/j.spc.2022.06.028 

Jones, W., Bower, G., Pastorek, N., King, B., Larsen, J., Houser, T., Dasari, N., & McCusker, K. (2024). The landscape of carbon dioxide removal and US policies to scale solutions. Link to source: https://rhg.com/wp-content/uploads/2024/04/The-Landscape-of-Carbon-Dioxide-Removal-and-US-Policies-to-Scale-Solutions.pdf 

Morris, A. (2024). Testing limestone’s ability to capture carbon from air. Northwestern Now. Link to source: https://news.northwestern.edu/stories/2024/11/northwestern-scientists-test-limestones-ability-to-capture-carbon-from-air/ 

OPIS & CDR.fyi. (2025). Bridging the gap: Durable CDR market pricing survey. Link to source: https://www.cdr.fyi/reports/pricing-survey-jan-2025.pdf 

Taylor, L. et al. (2016). Enhanced weathering strategies for stabilizing climate and averting ocean acidification. Nature Climate Change 6, 402–406. Link to source: https://doi.org/10.1038/nclimate2882 

Credits

Lead Fellow

  • Christina Swanson, Ph.D.

Internal Reviewer

  • Sarah Gleeson, Ph.D.
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Action Word
Deploy
Solution Title
Enhanced Rock Weathering
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Deploy Biomass Crops on Degraded Land

Submitted by Drawdown Admin on
Sector
Nature-Based Carbon Removal
Mode
Remove Carbon
Cluster
Use Degraded Land
Image
Tree plantation
Coming Soon
On
Description for Social and Search
The Deploy Biomass Crops on Degraded Land solution is coming soon.
Action Word
Deploy
Solution Title
Biomass Crops on Degraded Land
Classification
Highly Recommended
Updated Date

Deploy Silvopasture

Submitted by Drawdown Admin on
Sector
Nature-Based Carbon Removal
Mode
Remove Carbon
Cluster
Shift Agriculture Practices
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Cows grazing among trees
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Summary

We define the Deploy Silvopasture solution as the adoption of agroforestry practices that add trees to grazing land, including planted pastures and natural rangelands. (Note that this solution does NOT include creating forested grazing land by thinning existing forest; this is a form of deforestation and not desirable in terms of climate.) Some silvopastures are open savannas, while others are dense, mature tree plantations. The trees may be planted or managed to naturally regenerate. Some silvopasture systems have been practiced for thousands of years, while others have been recently developed. All provide shade to livestock; in some systems, the trees feed livestock, produce timber or crops for human consumption, or provide other benefits. New adoption is estimated from the 2025 level as a baseline which is therefore set to zero.

Income & work,Food security
Nature protection,Animal well-being,Water quality
Description for Social and Search
Deploy Silvopasture is a Highly Recommended climate solution. It enhances carbon storage by adding trees to grazing land, including planted pastures and natural rangelands.
Overview

In silvopasture systems, trees are planted or allowed to naturally regenerate on existing pasture or rangeland. Tree density is generally less than forest, allowing sunlight through for good forage growth.

Silvopasture has multiple climate impacts, though carbon sequestration is the only one which has been thoroughly studied across all climates and sub-practices.

Silvopasture sequesters carbon in both soil and woody biomass. Carbon sequestration rates are among the highest of any farming system (Toensmeier, 2017). The lifetime accumulation of carbon in both soils and biomass is higher than for managed grazing alone (Montagnini et al., 2019; Nair et al., 2012).

Silvopasture can also reduce GHG emissions, though not in every case. We do not include emissions reductions in this analysis.

Conversion from pasture to silvopasture slightly increases capture and storage of methane in soils (Bentrup and Shi, in press). In addition, in fodder subtypes of silvopasture systems, ruminant livestock consume tree leaves or pods. Many, but not all, of the tree species used in these systems have tannin content that reduces emissions of methane from enteric fermentation (Jacobsen et al., 2019). 

Some subtypes of silvopasture reduce nitrous oxide emissions from manure and urine, as grasses and trees capture nitrogen that microbes would otherwise convert to nitrous oxide. There are also reductions to nitrous oxide emissions from soils: 76–95% in temperate silvopastures and 16–89% in tropical-intensive silvopastures (Ansari et al., 2023; Murguietio et al., 2016).

Many silvopasture systems increase productivity of milk and meat. Yield increases can reduce emissions from deforestation by growing more food on existing farmland, but in some cases can actually worsen emissions if farmers clear forests to adopt the profitable practice (Intergovernmental Panel on Climate Change [IPCC], 2019). The yield impact of silvopasture varies with tree density, climate, system type, and whether the yields of other products (e.g., timber) are counted as well (Rojas et al., 2022). 

Ansari, J., Udawatta, R. P., & Anderson, S. H. (2022). Soil nitrous oxide emission from agroforestry, rowcrop, grassland and forests in North America: a review. Agroforestry Systems, 97(8), 1465–1479. Link to source: https://doi.org/10.1007/s10457-023-00870-y

Basche, A., Tully, K., Álvarez-Berríos, N. L., Reyes, J., Lengnick, L., Brown, T., Moore, J. M., Schattman, R. E., Johnson, L. K., & Roesch-McNally, G. (2020). Evaluating the untapped potential of US conservation investments to improve soil and environmental health. Frontiers in Sustainable Food Systems, 4, 547876. Link to source: https://doi.org/10.3389/fsufs.2020.547876 

Batcheler, M., Smith, M. M., Swanson, M. E., Ostrom, M., & Carpenter-Boggs, L. (2024). Assessing silvopasture management as a strategy to reduce fuel loads and mitigate wildfire risk. Scientific Reports, 14(1), 5954. Link to source: https://doi.org/10.1038/s41598-024-56104-3

Bentrup, G. & Shi, X. (in press). Multifunctional buffers: Design guidelines for buffers, corridors and greenways. USDA Forest Service. 

Bostedt, G., Hörnell, A., & Nyberg, G. (2016). Agroforestry extension and dietary diversity–an analysis of the importance of fruit and vegetable consumption in West Pokot, Kenya. Food Security, 8, 271–284. Link to source: https://doi.org/10.1007/s12571-015-0542-x

Briske, D. D., Vetter, S., Coetsee, C., & Turner, M. D. (2024). Rangeland afforestation is not a natural climate solution. Frontiers in Ecology and the Environment. Link to source: https://doi.org/10.1002/fee.2727

Cadavid, Z., & BE, S. T. (2020). Sistemas silvopastoriles: aspectos teóricos y prácticos. CIPAV. Link to source: https://cipav.org.co/sdm_downloads/sistemas-silvopastoriles-aspectos-teoricos-y-practicos/

Cardinael, R., Umulisa, V., Toudert, A., Olivier, A., Bockel, L., & Bernoux, M. (2019). Revisiting IPCC Tier 1 coefficients for soil organic and biomass carbon storage in agroforestry systems. Environmental Research Letters, 13(12), 124020. Link to source: https://doi.org/10.1088/1748-9326/aaeb5f

Chapman, M., Walker, W.S., Cook-Patton, S.C., Ellis, P.W., Farina, M., Griscom, B.W., & Baccani, A. (2019). Large climate mitigation potential from adding trees to agricultural lands Global Change Biology, 26(80), 4357–4365. https://doi.org/10.1111/gcb.15121

Chatterjee, N., Nair, P. R., Chakraborty, S., & Nair, V. D. (2018). Changes in soil carbon stocks across the forest-agroforest-agriculture/pasture continuum in various agroecological regions: A meta-analysis. Agriculture, ecosystems & environment, 266, 55–67. Link to source: https://doi.org/10.1016/j.agee.2018.07.014

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deStefano, A, & Jacobson, M.G. (2018). Soil carbon sequestration in agroforestry systems: A review. Agroforestry Systems, 92, 285–299. Link to source: https://doi.org/10.1007/s13593-014-0212-y

Dudley, N., Eufemia, L., Fleckenstein, M., Periago, M. E., Petersen, I., & Timmers, J. F. (2020). Grasslands and savannahs in the UN Decade on Ecosystem Restoration. Restoration Ecology, 28(6), 1313–1317 Link to source: https://doi.org/10.1111/rec.13272

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Feliciano, D., Ledo, A., Hillier, J., & Nayak, D. R. (2018). Which agroforestry options give the greatest soil and above ground carbon benefits in different world regions?. Agriculture, ecosystems & environment, 254, 117–129. Link to source: https://doi.org/10.1016/j.agee.2017.11.032

Frelat, R., Lopez-Ridaura, S., Giller, K. E., Herrero, M., Douxchamps, S., Djurfeldt, A. A., Erenstein, O., Henderson, B., Kassie, M., Paul, B. K., Rigolot, C., Ritzema, R. S., Rodriguez, D., Van Asten, P. J. A., & Van Wijk, M. T. (2016). Drivers of household food availability in sub-Saharan Africa based on big data from small farms. Proceedings of the National Academy of Sciences of the United States of America, 113(2), 458–463. Link to source: https://doi.org/10.1073/pnas.1518384112

Garrett, H. E., Kerley, M. S., Ladyman, K. P., Walter, W. D., Godsey, L. D., Van Sambeek, J. W., & Brauer, D. K. (2004). Hardwood silvopasture management in North America. In New Vistas in Agroforestry: A Compendium for 1st World Congress of Agroforestry, 2004 (pp. 21–33). Springer Netherlands. Link to source: https://doi.org/10.1007/978-94-017-2424-1_2

Goracci, J., & Camilli, F. (2024). Agroforestry and animal husbandry. IntechOpen. Link to source: https://doi.org/10.5772/intechopen.1006711

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Greene, H., Kazanski, C. E., Kaufman, J., Steinberg, E., Johnson, K., Cook-Patton, S. C., & Fargione, J. (2023). Silvopasture offers climate change mitigation and profit potential for farmers in the eastern United States. Frontiers in Sustainable Food Systems, 7, 1158459. Link to source: https://doi.org/10.3389/fsufs.2023.1158459

Hart, D.R.T, Yeo, S, Almaraz, M, Beillouin, D, Cardinael, R, Garcia, E, Kay, S, Lovell, S.T., Rosenstock, T.S., Sprenkle-Hyppolite, S, Stolle, F, Suber, M, Thapa, B, Wood, S & Cook-Patton, S.C (2023). “Priority science can accelerate agroforestry as a natural climate solution”. Nature Climate Change. Link to source: https://doi.org/10.5281/zenodo.8209212

Husak, A. L., & Grado, S. C. (2002). Monetary benefits in a southern silvopastoral system. Southern Journal of Applied Forestry, 26(3), 159–164 Link to source: https://doi.org/10.1093/sjaf/26.3.159

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Jacobsen (2019). Secondary metabolites in leaf hay as a mitigation option for enteric methane production in ruminants. Aarhus University. Link to source: https://pure.au.dk/ws/portalfiles/portal/197235590/Secondary_Metabolites_in_Leaf_Hay_as_a_Mitigation_Option_for_Enteric_Methane_Production_in_Ruminants.pdf

Jose, S., & Dollinger, J. (2019). Silvopasture: a sustainable livestock production system. Agroforestry systems, 93, 1-9. Link to source: https://doi.org/10.1007/s10457-019-00366-8

Lal, R., Smith, P., Jungkunst, H. F., Mitsch, W. J., Lehmann, J., Nair, P. R., & Ravindranath, N. H. (2018). The carbon sequestration potential of terrestrial ecosystems. Journal of soil and water conservation, 73(6), 145A–152A. Link to source: https://doi.org/10.2489/jswc.73.6.145A

Lee, S., Bonatti, M, Löhe, K, Palacios, V., Lana, M.A., and Sieber, S (2020). Adoption potentials and barriers of silvopastoral systems in Colombia: Case of Cundinamarca region. Cogent Environmental Science 6(1). Link to source: https://doi.org/10.1080/23311843.2020.1823632

Lemes, A. P., Garcia, A. R., Pezzopane, J. R. M., Brandão, F. Z., Watanabe, Y. F., Cooke, R. F., Sponchiado, M., Paz, C. C. P., Camplesi, A. C., Binelli, M., & Gimenes, L. U. (2021). Silvopastoral system is an alternative to improve animal welfare and productive performance in meat production systems. Scientific Reports, 11(1), 14092. Link to source: https://doi.org/10.1038/s41598-021-93609-7

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Toensmeier, E. (2017). Perennial staple crops and agroforestry for climate change mitigation. Integrating landscapes: Agroforestry for biodiversity conservation and food sovereignty, 439-451. Link to source: https://doi.org/10.1007/978-3-319-69371-2_18

U.S. Department of Agriculture Natural Resources Conservation Service [USDA NRCS]. (2025). Conservation Practice Physical Effects [Dataset]. Link to source: https://www.nrcs.usda.gov/resources/guides-and-instructions/conservation-practice-physical-effects

Udawatta, R. P., Walter, D., & Jose, S. (2022). Carbon sequestration by forests and agroforests: A reality check for the United States. Carbon footprints, 1(8). Link to source: https://doi.org/10.20517/cf.2022.06 

Zeppetello, L. R. V., Cook-Patton, S. C., Parsons, L. A., Wolff, N. H., Kroeger, T., Battisti, D. S., Bettles, J., Spector, J. T., Balakumar, A., & Masuda, Y. J. (2022). Consistent cooling benefits of silvopasture in the tropics. Nature communications, 13(1), 708. Link to source: https://doi.org/10.1038/s41467-022-28388-4

Zhu, X., Liu, W., Chen, J., Bruijnzeel, L. A., Mao, Z., Yang, X., Cardinael, R., Meng, F.-R., Sidle, R. C., Seitz, S., Nair, V. D., Nanko, K., Zou, X., Chen, C., & Jiang, X. J. (2020). Reductions in water, soil and nutrient losses and pesticide pollution in agroforestry practices: A review of evidence and processes. Plant and Soil, 453(1–2), 45–86. Link to source: https://doi.org/10.1007/s11104-019-04377-3

Credits

Lead Fellow

  • Eric Toensmeier

Contributors

  • Ruthie Burrows, Ph.D.

  • Yusuf Jameel, Ph.D.

  • Daniel Jasper

Internal Reviewers

  • Aiyana Bodi

  • Hannah Henkin

  • Ted Otte

  • Paul C. West, Ph.D.

Effectiveness

We found a median carbon sequestration rate of 9.81 t CO₂‑eq /ha/yr (Table 1). This is based on an above-ground biomass (tree trunks and branches) accumulation rate of 6.43 t CO₂‑eq /ha/yr and a below-ground biomass (roots) accumulation rate of 1.61 t CO₂‑eq /ha/yr using a root-to-shoot ratio of 0.25 (Cardinael et al., 2019). These are added to the soil organic carbon sequestration rate of 1.76 t CO₂‑eq /ha/yr to create the combined total.

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Table 1. Effectiveness at carbon sequestration.

Unit: t CO₂-eq/ha/yr, 100-yr basis

25th percentile 4.91
mean 14.70
median (50th percentile) 9.81
75th percentile 20.45

100-yr basis

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Reductions in nitrous oxide and methane and sustainable intensification impacts are not yet quantifiable to the degree that they can be used in climate mitigation projections.

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Cost

Because baseline grazing systems are already extensive and well established, we assumed there is no cost to establish new baseline grazing land. In the absence of global data sets on costs and revenues of grazing systems, we used a global average profit per hectare of grazing land of US$6.28 from Damania et al. (2023).

Establishment costs of silvopasture vary widely. We found the cost to establish one hectare of silvopasture to be US$1.06–4,825 (Dupraz & Liagre, 2011; Lee et al., 2011). Reasons for this wide range include the low cost of natural regeneration and the broad range in tree density depending on the type of system. We collected costs by region and used a weighted average to obtain a global net net cost value of US$424.20.

Cost and revenue data for silvopasture were insufficient. However, data on the impact on revenues per hectare are abundant. Our analysis found a median 8.7% increase in per-hectare profits from silvopasture compared with conventional grazing, which we applied to the average grazing value to obtain a net profit of US$6.82/ha. This does not reflect the very high revenues of silvopasture systems in some countries.

We calculated cost per t CO₂‑eq sequestered by dividing net net cost/ha by total CO₂‑eq sequestered/ha.

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Table 2. Cost per unit of climate impact.

Unit: 2023 US$/t CO₂-eq

median $43.25

100-yr basis & 20-yr basis are the same.

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Learning Curve

There is not enough information available to determine a learning curve for silvopasture. However, anecdotal evidence showed establishment costs decreasing as techniques for broadscale mechanized establishment were developed in Australia and Colombia (Murguietio et al., 2016; Shelton et al., 2021).

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Speed of Action

Speed of action refers to how quickly a climate solution physically affects the atmosphere after it is deployed. This is different from speed of deployment, which is the pace at which solutions are adopted.

At Project Drawdown, we define the speed of action for each climate solution as emergency brake, gradual, or delayed.

Deploy Silvopasture is a DELAYED climate solution. It works more slowly than gradual or emergency brake solutions. Delayed solutions can be robust climate solutions, but it’s important to recognize that they may not realize their full potential for some time.

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Caveats

Permanence

Living biomass and soil organic matter only temporarily hold carbon (decades to centuries for soil organic matter, and for the life of the tree or any long-lived products made from its wood in the case of woody biomass). Sequestered carbon in both soils and biomass is vulnerable to fire, drought, long-term shifts to a drier precipitation regime, and other climate change impacts, as well as to a return to the previous farming or grazing practices. Such disturbances can cause carbon to be re-emitted to the atmosphere (Lorenz & Lal, 2018). 

Saturation

Like all upland, terrestrial agricultural systems, over the course of decades, silvopastures reach saturation and net sequestration slows to nearly nothing (Lorenz & Lal, 2018). 

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Current Adoption

Lack of data on the current adoption of silvopasture is a major gap in our understanding of the potential of this solution. One satellite imaging study found 156 million ha of grazing land with more than 10 t C/ha in above-ground biomass, which is the amount that indicates more than grass alone (Chapman et al., 2019). However, this area includes natural savannas, which are not necessarily silvopastures, and undercounts the existing 15.1 million ha of silvopasture known to be present in Europe (den Herder et al., 2017).

Sprenkle-Hippolite et al. (2024) estimated a current adoption of 141.4 Mha, or 6.0% of grazing land (Table 3). We have chosen this more recent figure as the best available estimate of current adoption. Note that in Solution Basics in the dashboard above we set current adoption at zero. This is a conservative assumption to avoid counting carbon sequestration from land that has already ceased to sequester net carbon due to saturation, which takes place after 20–50 years (Lal et al., 2018).

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Table 3. Current (2023) adoption level.

Unit: million ha

mean 141.4
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Adoption Trend

There is little quantifiable information reported about silvopasture adoption trends.

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Adoption Ceiling

Grazing is the world’s largest land use at 2,986 Mha (Mehrabi et al., 2024). Much grazing land is too dry for trees, while other grasslands that were not historically forest or savanna should not be planted with trees in order to minimize water use and protect grassland habitat (Dudley et al., 2020). Three studies estimated the total potential area suitable for silvopasture (including current adoption). 

Lal et al. (2018) estimated the technical potential for silvopasture adoption at 550 Mha.

Chapman et al. (2019) estimated the suitable area for increased woody biomass on grazing land as 1,890 Mha. 

Sprenkle-Hippolite (2024) assessed the maximum area of grazing land to which trees could be added without reducing livestock productivity. They calculated a total of 1,589 Mha, or 67% of global grazing land (Table 4). To our knowledge, this is the most accurate estimate available. 

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Table 4. Adoption ceiling.

Unit: ha converted

25th percentile 1069000000
mean 1343000000
median (50th percentile) 1588000000
75th percentile 1739000000

Unit: % of grazing land

25th percentile 45
mean 36
median (50th percentile) 53
75th percentile 58
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Achievable Adoption

In our Achievable – High scenario, global silvopasture starts at 141.4 Mha and grows at the Colombian Nationally Determined Contribution growth rate of 6.5%/yr. This would provide the high end of the achievable potential at 206.3 Mha by 2030, of which 64.9 million ha are newly adopted (Table 5). For the Achievable – Low scenario, we chose 1/10 of Colombia’s projected growth rate. This would provide 147.0 Mha of adoption by 2030, of which 5.6 Mha are new.

Few estimates of the global adoption potential of silvopasture are available, and even those for the broader category of agroforestry are rare due to the lack of solid data on current adoption and growth rates (Shi et al., 2018; Hart et al., 2023). The IPCC estimates that, for agroforestry overall, 19.5% of the technical potential is economically achievable (IPCC AR6 WG3, 2022). Applying this rate to Sprenkle-Hippolite’s estimated 1,588 Mha technical potential yields an achievable potential of 310 Mha of convertible grazing land.

Our high adoption rate reaches 13% of the adoption ceiling by 2030. This suggests that silvopasture represents a large but relatively untapped potential that will require aggressive policy action and other incentives to spur scaling.

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Table 5. Range of achievable adoption levels.

Unit: Mha

Current Adoption 141.4
Achievable – Low 147.0
Achievable – High 206.3
Adoption Ceiling 1,588.0

Unit: Mha

Current Adoption 0.00
Achievable – Low 5.6
Achievable – High 64.9
Adoption Ceiling 1,447.4
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Carbon sequestration continues only for a period of decades; because silvopasture is an ancient practice with some plantings centuries old, we could not assume that previously adopted hectares continue to sequester carbon indefinitely. Much of the current adoption of silvopasture has been in place for centuries and sequestration there has presumably already slowed down to almost zero. We apply an adoption adjustment factor of 0.25 to current adoption (see Methodology) to reflect that most current adoption is no longer sequestering significant carbon, yet there is substantial new adoption within the past 20–50 years.

For new adoption the calculation is effectiveness * new adoption = climate impact.

For current adoption the calculation is effectiveness * 0.25 * current adoption = climate impact

Climate impacts shown in Table 6 are the sum of current and new adoption impacts. Carbon sequestration impact is 0.35 Gt CO₂‑eq/yr for current adoption, 0.40 Gt CO₂‑eq/yr for Achievable – Low, 0.98 Gt CO₂‑eq/yr for Achievable – High, and 14.54 Gt CO₂‑eq/yr for our Adoption Ceiling. 

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Table 6. Climate impact at different levels of adoption.

Unit: Gt CO₂‑eq/yr

Current Adoption 0.35
Achievable – Low 0.40
Achievable – High 0.98
Adoption Ceiling 14.54

100-yr basis, New adoption only 

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Lal et al. (2018) estimated a technical global carbon sequestration potential of 0.3–1.0 Gt CO₂‑eq/yr. Sprenkle-Hyppolite et al. (2024) estimated a silvopasture technical potential of 1.4 Gt CO₂‑eq/yr ; this assumes a tree density of 2–6 trees/ha, which is substantially lower than typical silvopasture. For agroforestry overall (including silvopasture and other practices), the IPCC (2022) estimates an achievable potential of 0.8 Gt CO₂‑eq/yr and a technical potential of 4.0 Gt CO₂‑eq/yr.

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Additional Benefits

Income and Work 

Silvopasture can also increase and diversify farmer income. Tree fruit and timber often provide income for ranchers. A study in the southern United States showed that silvopasture systems generated 10% more income than standalone cattle production (Husak & Grado, 2002). A more comprehensive analysis across the eastern United States (Greene et al., 2023) found that virtually all silvopasture systems assessed had a positive 20- and 30-yr internal rate of return (IRR). For some systems, the 30-yr IRR can be >15% (Greene et al., 2023).

Food Security

While evidence on the impact of silvopasture on yields is mixed, this practice can improve food security by diversifying food production and income sources (Bostedt et al., 2016; Smith et al., 2022). In pastoralists in Kenya, Bostedt et al. (2016) found that agroforestry practices were associated with increased dietary diversity, an important aspect of food and nutrition security. Diverse income streams can mediate household food security during adverse conditions, such as droughts or floods, especially in low- and middle-income countries (de Sherbinin et al., 2008; Di Prima et al., 2022; Frelat et al., 2016). 

Nature Protection

Trees boost habitat availability, enhance landscape connectivity, and aid in forest regeneration and restoration. In most climates they provide a major boost to biodiversity compared with pasture alone (Smith et al., 2022; Pezo et al., 2018). 

Animal Well-being

By providing shade, silvopasture systems reduce heat stress experienced by livestock. Heat stress for cattle begins at 30 °C or even lower in some circumstances (Garrett et al., 2004). In the tropics, the cooling effect of integrating trees into a pastoral system is 0.32–2.4 °C/t of woody carbon added/ha (Zeppetello et al., 2022). Heifers raised in silvopasture systems had higher body mass and more optimal body temperature than those raised in intensive rotational grazing systems (Lemes et al., 2021). Improvement in livestock physiological conditions probably results from access to additional forage, increased livestock comfort, and reduced heat stress in silvopastoral systems. Silvopasture is highly desirable for its improvements to animal welfare (Goracci & Camilli, 2024).

Land Resources

Silvopasture and agroforestry are important for ensuring soil health (Basche et al., 2020). These practices improve soil health by reducing erosion and may also contribute to soil organic matter retention (U.S. Department of Agriculture Natural Resource Conservation Service ([USDA NRCS], 2025). There is evidence that silvopasture may improve soil biodiversity by preventing soil organism habitat loss and degradation (USDA NRCS, 2025).

Water Quality

Perennials in silvopasture systems could reduce runoff and increase water infiltration rates relative to open rangelands (Smith et al., 2022; Pezo et al., 2018). This increases the resilience of the system during drought and high heat. Silvopasture can improve water quality by retaining soil sediments and filtering pollutants found in runoff (USDA NRCS, 2025). On average, silvopasture and agroforestry practices can reduce runoff of sediments and excess nutrients into water 42–47% (Zhu et al., 2020). The filtering benefits of silvopasture can also mitigate pollution of antibiotics from livestock operations from entering waterways (Moreno & Rolo, 2019). 

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Risks

Some of the tree and forage species used in silvopastures are invasive in certain contexts. For example, river tamarind (Leucaena leucocephala) is a centerpiece in intensive silvopasture in Latin America, where it is native, but also in Australia, where it is not. Australian producers have developed practices to limit or prevent its spread (Shelton et al., 2021).

Livestock can damage or kill young trees during establishment. Protecting trees or excluding grazing animals during this period increases costs (Smith et al., 2022).

Poorly designed tree layout can make herding, haying, fencing, and other management activities more difficult. Tree densities that are too high can reduce livestock productivity (Cadavid et al., 2020).

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Interactions with Other Solutions

Reinforcing

Silvopasture represents a way to produce some ruminant meat and dairy in a more climate-friendly way. This impact can contribute to addressing emissions from ruminant production, but only as part of a program that strongly emphasizes diet change and food waste reduction.

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Forms of silvopasture that increase milk and meat yields can reduce pressure to convert undeveloped land to agriculture.

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Silvopasture is a technique for restoring farmland.

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Silvopasture is a form of savanna restoration.

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Competing

Silvopasture and forest restoration can compete for the same land. 

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Silvopasture is a kind of agroforestry, though in this iteration of Project Drawdown “Deploy Agroforestry” refers to crop production systems only. With that said, some agroforestry systems integrate both crops and livestock with the trees, such as the widespread parkland systems of the African Sahel.

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Dashboard

Solution Basics

ha converted from grazing land to silvopasture

t CO₂-eq (100-yr)/unit/yr
04.919.81
units
Current 1.414×10⁸ 01.47×10⁸2.063×10⁸
Achievable (Low to High)

Climate Impact

Gt CO₂-eq (100-yr)/yr
Current 0.35 0.40.98
US$ per t CO₂-eq
43
Delayed

CO₂

Trade-offs

Solutions that improve ruminant production could undermine the argument for reducing ruminant protein consumption in wealthy countries. 

Certain silvopasture systems reduce per-hectare productivity of meat and milk, even if overall productivity increases when the yields of timber or food from the tree component are included. For example, silvopasture systems that are primarily focused on timber production, with high tree densities, will have lower livestock yields than pasture alone - though they will have high timber yields.

The costs of establishment are much higher than those of managed grazing. There is also a longer payback period (Smith et al., 2022). These limitations mean that secure land tenure is even more important than usual, to make adoption worthwhile (Poudel et al., 2024).

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Maps Introduction

Silvopasture is primarily appropriate for grazing land that receives sufficient rainfall to support tree growth. While it can be implemented on both cropland and grassland, if adopted on cropland, it will reduce food yield because livestock produce much less food per hectare than crops. In the humid tropics, a particularly productive and high-carbon variation called intensive silvopasture is an option. Ideally, graziers will have secure land tenure, though pastoralist commons have been used successfully.

Areas too dry to establish trees (<450 mm annual precipitation) are not suitable for silvopasture by tree planting, but regions that can support natural savanna may be suitable for managed natural regeneration.

Most silvopasture today appears in sub-Saharan Africa (Chapman et al., 2019), though this may reflect grazed natural savannas rather than intentional silvopasture. This finding neglects well-known systems in Latin America and Southern Europe. 

Chapman et al. (2019) listed world grasslands by their potential to add woody biomass. According to their analysis, the countries with the greatest potential to increase woody biomass carbon in grazing land are, in order: Australia, Kazakhstan, China, the United States, Mongolia, Iran, Argentina, South Africa, Sudan, Afghanistan, Russia, and Mexico. Tropical grazing land accounts for 73% of the potential in one study. Brazil, China, and Australia have the highest areas, collectively accounting for 37% of the potential area (Sprenkle-Hippolite 2024).

We do not present any maps for the silvopasture solution due to the uncertainties in identifying current areas where silvopasture is practiced, and in identifying current grasslands that were historically forest or savanna. 

Action Word
Deploy
Solution Title
Silvopasture
Classification
Highly Recommended
Lawmakers and Policymakers
  • Lower the risk for farmers transitioning from other pastoral systems.
  • Increase understanding of silvopasture.
  • Reduce technical and bureaucratic complexity.
  • Establish or expand technical assistance programs.
  • Simplify incentive programs.
  • Ensure an appropriate and adequate selection of tree species are eligible for incentives.
  • Establish a silvopasture certification program.
  • Create demonstration farms.
  • Strengthen land tenure laws.
  • Incentivize lease structures to facilitate silvopasture transitions on rented land.

Further information:

Practitioners
  • Seek support from technical assistance programs and extension services.
  • Seek out networks of adopters to share information, resources, best practices, and collective marketing.
  • If available, leverage incentive programs such as subsidies, tax rebates, grants, and carbon credits.
  • Negotiate new lease agreements to accommodate silvopasture techniques or advocate for public incentives to reform lease structures.

Further information:

Business Leaders
  • Prioritize suppliers and source from farmers who use silvopasture.
  • Provide innovative financial mechanisms to encourage adoption.
  • Participate in and help create high-quality carbon credit programs.
  • Incentivize silvopasture transitions in lease agreements.
  • Support the creation of a certification system to increase the marketability of silvopasture products.
  • Join coalitions with other purchasers to grow demand.
  • Collaborate with public and private agricultural organizations on education and training programs. 

Further information:

Nonprofit Leaders
  • Educate farmers and those who work in the food industry about the benefits of silvopasture.
  • Communicate any government incentives for farmers to transition to silvopasture.
  • Explain how to take advantage of incentives.
  • Provide training material and/or work with extension services to support farmers transitioning to silvopasture, such as administering certification programs.
  • Advocate to policymakers for improved incentives for farmers, stronger land tenure laws, and flexible lease agreements.

Further information:

Investors
  • Use capital like low-interest or favorable loans to support farmers and farmer cooperatives exploring silvopasture projects.
  • Invest in credible, high-quality carbon reduction silvopasture projects.
  • Invest in silvopasture products (e.g., fruits, berries, and other tree products)
  • Encourage favorable lease agreements between landowners or offer favorable costs and benefit-sharing structures.
  • Consider banking through community development financial institutions or other institutions that support farmers. 

Further information:

Philanthropists and International Aid Agencies
  • Provide grants and loans for establishing silvopasture and support farmland restoration projects that include silvopasture.
  • Support capacity-building, market access, education, and training opportunities for smallholder farmers – especially those historically underserved – through activities like farmer cooperatives, demonstration farms, and communal tree nurseries.
  • Consider banking through Community Development Financial Institutions or other institutions that support farmers. 

Further information:

Thought Leaders
  • Use your platform to build awareness of silvopasture and its benefits, incentive programs, and regulatory standards.
  • Provide technical information to practitioners.
  • Host community dialogues such as Edible Connections to engage the public about silvopasture and other climate-friendly farming practices.

Further information:

Technologists and Researchers
  • Improve the affordability and equipment needed to plant and manage trees.
  • Refine satellite tools to improve silvopasture detection.
  • Develop ways to monitor changes in soil and biomass.
  • Standardize data collection protocols.
  • Create a framework for transparent reporting and reliable verification.
  • Fill gaps in data, such as quantifying the global adoption potential of silvopasture and regional analysis of revenue and operating costs/hectare. 

Further information:

Communities, Households, and Individuals
  • Purchase silvopasture products and support farmers who use the practice.
  • Request silvopasture products at local markets.
  • Encourage policymakers to help farmers transition.
  • Encourage livestock farmers to adopt the practice.
  • Host community dialogues such as Edible Connections to engage the public about silvopasture and other climate-friendly farming practices.

Further information:

Sources
Evidence Base

Consensus of effectiveness in sequestering carbon: Mixed to High 

There is a high level of consensus about the carbon biosequestration impacts of silvopasture, including for the higher per-hectare sequestration rates relative to improved grazing systems alone. A handful of reviews, expert estimations, and meta-analyses have been published on the subject. These include:

Cardinael et al. (2018) assembled data by climate and region for use in the national calculations and reporting. 

Chatterjee et al. (2018) found that converting from pasture to silvopasture increases carbon stocks. 

Lal et al. ( 2018) estimated the technical adoption and mitigation potential of silvopasture and other practices.

Udawatta et al. (2022) provided an up-to-date meta-analysis for temperate North America. 

The results presented in this document summarize findings from two reviews, two meta-analyses, one expert opinion and three original studies reflecting current evidence from a global scale. We recognize this limited geographic scope creates bias, and hope this work inspires research and data sharing on this topic in underrepresented regions.

Consensus regarding other climate impacts: Low

There is low consensus on the reduction of methane from enteric emissions, nitrous oxide from manure, and CO₂ from avoided deforestation due to increased productivity. We do not include these climate impacts in our calculations.

Consensus regarding adoption potential: Low

Until recently there was little understanding of the current adoption of silvopasture. Sprenkle-Hyppolite et al. (2024) used Delphi expert estimation to determine current adoption and technical potential. Rates of adoption and achievable potential are still largely unreported or uninvestigated. See the Adoption section for details.

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Updated Date
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