Regenerative Ocean Farming: How Can Polycultures Help Our Coasts?

Job creation, carbon sequestration, nutrient runoff capture, oxygenation, storm surge protection, ecosystem restoration, food security: just a few of the selling points and ecosystem services promised by the champions of regenerative ocean farming. So what is this type of farming, and what’s so special about it?

Still from an animation of GreenWave’s general ocean regenerative farming set up. Seaweed, like sugar kelp (Saccharina latissima), hangs from long lines attached to buoys along with scallops and mussels; cages with oysters and clams hang on the seafloor beneath. (Credit: The Water Brothers, all rights reserved)


Regenerative ocean farming (ROF) is a “polyculture farming system [that] grows a mix of seaweeds and shellfish…[and] require[s] zero inputs…while sequestering carbon and rebuilding reef ecosystems.” I first heard the term from a friend in SMEA, and then again in a How to Save a Planet episode focused on the ROF nonprofit GreenWave. The ROF system is also called 3D ocean farming because it takes advantage of every depth of water, from the surface to the seafloor. Rather than a “monoculture” as seen on many industrial farms on land, where a single species grows together, this is a “polyculture,” where multiple species grow side by side and intertwined.

The term “regenerative farming” was coined in the 1980s for terrestrial agriculture that regenerates the health of its ecosystem through polycultures, with each species providing an important service such as nitrogen fixing. The concept has been practiced since time immemorial by many Indigenous peoples, perhaps most famously through the Three Sisters system used by Tribes such as those in the Haudenosaunee Confederacy. In regenerative terrestrial farming, the polyculture requires few “inputs,” such as fertilizer, because the species complement each other in providing key services. Regenerative ocean farming also requires no inputs because both seaweeds and shellfish can get the nutrients they need from the water around them. In contrast, the vast majority of farming on land today requires regular fertilizing and watering.

GreenWave, co-founded by Bren Smith and originating from his Thimble Island Ocean Farm in New Haven, Connecticut, is not only one of the most popular faces of the ROF system in the media, but is also working to train and support 10,000 regenerative ocean farmers in the next ten years through its free Farmer-in-Training program. In this way, GreenWave hopes not to be a single farm doing exceptional work alone, but a network of many farms that together can make a much bigger impact. GreenWave’s website includes tools for farmers on topics ranging from permitting, to obtaining baby sugar kelp, to planting kelp, to building a network of buyers for the harvest. Many of these tools are password protected, giving a leg up to small- and medium-scale farmers in the GreenWave training program over big, rich agricultural businesses.

In GreenWave’s setup, seaweed, scallops, and mussels hang down from buoys, while beneath them hang cages with oysters and clams. This efficient use of space allows the system to provide a laundry list of benefits, including decreasing carbon and nitrogen in the water and increasing oxygen to regenerate and restore local habitat. Through photosynthesis, seaweed can take up carbon in the surrounding water, buffering the impacts of varying levels of ocean acidification locally. A collaborative team, led by the Puget Sound Restoration Fund and including SMEA’s Terrie Klinger, is currently investigating these buffering capabilities in sugar kelp (Saccharina latissima), the favored kelp crop of Thimble Island Ocean Farm. Meanwhile, the shellfish in the ROF system are filter feeders that suck up nutrient pollution, like nitrogen from fertilizer runoff. Unchecked, these excess nutrients can cause algal blooms, and when microorganisms decompose that algae, they use up oxygen, creating oxygen-deprived dead zones. Kelp absorbs these excess nutrients too, and also provides oxygen through photosynthesis.

A regenerative ocean farm from above. When a long line covered in kelp is not pulled up, as seen in the foreground, all that is visible from the surface are buoys, as seen in the background. (Photo credit: GreenWave)


Even the structure of kelp provides benefits. Kelp can act as a physical cushion to storm surges, absorbing energy from waves that would otherwise hit coastal communities with full force. A University of Maine project has found that seaweed aquaculture alone can reduce the impact of waves by thirty to fifty percent during storms. It is important to note, however, that the strength of all these ROF benefits depends on growing conditions and species used: for example, one study found that eastern oysters are better able to clean the water of nutrients when exposed to high levels of salinity rather than low, even if both levels are within their natural salinity range.

Of the crops that can be harvested from an ROF system, kelp has proven the most difficult to market in the United States. Globally, seaweed is a $6 billion per year industry, with about eighty-five percent of the products used for food. Beyond products like sushi nori that clearly stem from seaweed, seaweed extracts, like carrageenan, are everywhere in our processed foods and cosmetics. Wild harvest of seaweed is led by Chile, while China leads the way in farmed harvest. The U.S. is the fourth largest importer of seaweed products globally. However, it is not a top producer of seaweed, and many of the types of seaweed used globally are not native to the U.S. or must be grown in tank systems rather than in an ROF setting.

Nusa Lembongan, Bali, Indonesia (August 16, 2009) – Woman harvesting elkhorn sea moss (Kappaphycus alvarezii), to be used in carrageenan production. (Photo credit: Jean-Marie Hullot, shared under a Creative Commons license)


GreenWave is developing a diverse buyer network to break into the seaweed market, pitching kelp not just as food, but as bioplastics, fertilizer, animal feed, and compost. By removing kelp from the ocean rather than letting it decompose, the ROF system prevents the carbon sequestered in the kelp itself from returning to the water. If the kelp’s end use is as a food, for example, then that carbon will return to the atmosphere through respiration when it is consumed; however, while the kelp is still growing, GreenWave farmers can sell carbon offsets. Another virtual crop for GreenWave farmers, in addition to the tangible crops of shellfish and kelp, is sensor data; GreenWave uses sensors within its polycultures to track water and weather conditions and sells this data to government agencies as well as tech and insurance companies

There are major hurdles for new regenerative ocean farmers. At the ground floor, there can be difficulty getting permits to lease the public coastal waters necessary for a farm. In New York State, there is a bill that would allow kelp farmers in Peconic and Gardiners’ Bays to harvest their kelp, which was planted as part of a Stony Brook University feasibility study. If the bill does not pass, the farmers cannot use the kelp. For farmers on this side of the country, GreenWave provides a nine-page document laying out the time-consuming and expensive process of leasing waters for ocean farming in California.

Beyond these costs, farmers need equipment. Altogether, GreenWave estimates that a farmer requires access to about twenty acres of coastal water, a boat, and $20,000 to $50,000 to start their own regenerative ocean farm. Once the kelp is harvested, it can be expensive to process, presenting another financial hurdle. Finally, a critical component is that buyers must match the demand for seaweed products to the supply provided by farmers; GreenWave hopes to achieve this by targeting a multitude of industries with kelp products.

In Alaska, the non-profit Native Conservancy has been empowering Native Alaskans to start their own GreenWave ROF operations, bringing Native communities into the ROF conversation while providing financial assistance through the Native Regenerative Fund. Dune Lankard, founder of Native Conservancy, board member of GreenWave, and an Eyak Athabaskan Native of the Eagle Clan, hopes that the ROF system will provide an additional benefit to those identified by GreenWave. Lankard hopes that this system will help recover herring, which naturally lay their eggs, or roe, on kelp fronds. For many Native peoples in the Pacific Northwest, both herring and their roe are key cultural and subsistence foods. First Nations, like the Heiltsuk, continue to fight for their management rights to herring populations. After the 1989 Exxon Valdez oil spill, herring catch dropped dramatically in the homelands of the Eyak. By providing offshore kelp farms away from the still-contaminated intertidal, Lankard hopes that ROF systems can yield healthy herring.

Nanaimo, British Columbia, Canada (March 7, 2010) ̶ Herring roe on seaweed. (Photo credit: Greg Schechter, shared under a Creative Commons license)


Although Native Conservancy has been able to protect over a million acres of kelp forest habitat, primarily with salmon in mind, Lankard emphasizes that preservation is not enough: restoration is necessary for food, cultural, and economic security, and regenerative ocean farming can be the answer. Native Conservancy is also planning to co-write an Indigenous Kelp Farmers Bill of Rights with Alaska Tribes, who have been harvesting and managing coastal species for thousands of years, and who now are fighting for their right to that management. The Sitka Tribe, for example, has been challenging the Alaska Department of Fish and Game in court for prioritizing the commercial herring roe fishery over the tribe’s subsistence harvest.

By developing an Indigenous Kelp Farmers Bill of Rights, Lankard intends to stymie the potential for the budding West Coast ROF industry to be a new kind of land claims, with non-tribal farmers encroaching on traditional tribal harvest sites. By giving Indigenous peoples financial and organizational support to develop their own ROF operations, Native Conservancy is proactively working against a new kind of colonization of coastal waters. (For more about Native Conservancy’s ROF work, check out this seminar talk by Dune Lankard.)

Regenerative ocean farming is no silver bullet for our environmental problems, although it seems increasingly unlikely that such a bullet exists. As the environmentalist Bill McKibben has put it, “There are no silver bullets, only silver buckshot.” Yet the GreenWave model of regenerative ocean farming, which so emphatically integrates a network of group action into the solution rather than relying on individual exceptionalism to save the day, provides hope that small climate solutions can have critical results.

Author’s notes:

 This article was inspired by a conversation with fellow SMEA student Jessi Florendo, as well as by an episode of the podcast “How to Save a Planet.” If you are interested in regenerative farming on land, check out this episode of the podcast. If you are interested in learning more about the seaweed farming process in Washington, Washington Sea Grant has recorded an introductory webinar.

 Contact Currents’ Editor-in-Chief for access to:

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