A kelp forest in Santa Barbara, California.

Credit: Douglas Klug / Getty Images

Seaforestation

Call to action:

Restoring and expanding seaweed forests across the oceans will bolster marine health, reverse ocean acidification, prevent coral bleaching, increase fish harvests, and safely store enormous amounts of carbon.

Seaweed forests, made up of large macroalgae such as kelps and rockweeds, are efficient at storing carbon. Some of it is transported to deep ocean sinks, effectively removing it from the atmosphere. A recent study posited that the protection, restoration, and improved management of kelp and seaweed forests globally could provide mitigation benefits in the range of 36 million tons of CO2, equivalent to the CO2-capturing capacity of over a billion trees. Restoring these forests can bring back vital habitats for diverse marine life, boosting local fisheries while drawing down carbon from the atmosphere. These approaches would benefit fisheries, protect coastal communities, and restore marine dead zones while removing billions of tons of carbon from the atmosphere annually.

Nexus Rating System^Beta

Solutions to the climate emergency have unique social and environmental effects, positive and negative. To develop a broader understanding of the solutions in Nexus, we rate each solution on five criteria.

Sources for each Nexus are graded numerically (-3 through 10), and the average is displayed as a letter grade. You can explore each source in depth by clicking “view sources” below. For more information, see our Nexus Ratings page.

Seaforestation

8.70

0.00

9.36

7.00

Social Justice
Culture
Women
Biodiversity
Carbon

Reference	Social Justice	Culture	Women	Biodiversity	Carbon
Kelp Forest Ecosystems: Biodiversity Stability Resilience and Future				10.0
How farming giant seaweed can feed fish and fix the climate	8.0			10.0
By cultivating seaweed Indigenous communities restore connection to the ocean	7.0	9.0		10.0
The Cultural Importance of Kelp for Pacific Northwest Tribes		9.0
Could Our Energy Come from Giant Seaweed Farms in the Ocean?	5.0			5.0
Tribal access to the ocean can help save the kelp	8.0	9.0		10.0
Kelp has protected Samish people for millennia. Now it needs their help	8.0	9.0		10.0
Reclaiming Native Knowledges Through Kelp Farming in Cordova Alaska	7.0	7.0		9.0
Coastal peoples and marine plants on the northwest coast		9.0
Seaforestation: Benefits to the climate the ecosystems and the people of British Columbia	9.0	9.0		10.0
Indigenous knowledge of key ecological processes confers resilience to a small-scale kelp fishery	9.0	9.0		9.0
Preparing for the Worst with a Kelp Seed Bank	9.0	9.0		10.0
The Guardians of the Kelp Forests	8.0	8.0		10.0
Macroalgae Protection and Restoration - Project Drawdown					7.0
	7.8	8.7	0.0	9.4	7.0

Action Items

Individuals

Learn where and why wild kelp forests disappeared so you can help support their restoration. Kelp forests are pound-for-pound among the most productive ecosystems on the planet. Unfortunately, many kelp forests have disappeared. One study found that more than a third of the regions where kelp occurs have seen considerable loss of kelp forests since the 1960s. In Northern California, for example, 95 percent of kelp forests have died off in just the past eight years due to a marine heat wave and a catastrophic outbreak of purple sea urchins. Kelp forests can also suffer directly from warming oceans, as well as from pollution and runoff. Knowing the specific causes of local decline is critical in restoring kelp forests properly. Fortunately, individuals can have a significant impact on reviving kelp forests. Here are some examples of local efforts where individuals can make a difference:

Coastal development and landslides can cover rock reefs in muddy sediments, depriving kelp of substrate for their holdfasts to attach to. By supporting rock reef restoration efforts, such as this one in Southern California, you can restore the conditions that kelp forests need to thrive. This approach may be doubly effective since new research has shown that complex seafloor substrates can create hotspots of resilient kelp that can resist overpopulating sea urchins.
Urchins can overwhelm kelp forests, eating through the holdfasts that link kelp to the ocean floor, overpopulating to the point they become “zombie urchins.” In Southern California, the Bay Foundation is leading an effort on the Palos Verdes Peninsula to cull these urchins, restoring fifty-seven acres of kelp forest.
Also, in Southern California, as well as in Norway and Japan, a small group called Urchinomics harvests zombie urchins so they can be fattened up in “ranches” and sold to sushi restaurants for their roe. Eating sushi at these restaurants, therefore, helps restore kelp forests.
In Norway, kelp forests declined by 80 percent due to urchins but failed to recover even after the urchins suffered mass mortality. In this case, the culprit was turf algae, which outcompeted the kelp for surfaces to attach to.
In Sydney, upgrading a wastewater treatment facility improved local water quality, and small teams are reseeding the healthy kelp through Operation Crayweed. Fighting for better wastewater treatment can help kelp forests grow and reproduce while eliminating marine dead zones.
Changes in ocean currents bringing warmer, less nutrient-rich water to Tasmania (along with urchin herbivory) decimated 95 percent of the island’s giant kelp forests. A recent trial found that growing giant kelp near a Tasmanian salmon farm quadrupled the seaweed’s growth rate, all while helping purify the runoff from the fish pens. Learn more about how kelp can be a critical part of sustainable mariculture in the Seaweed Farming Nexus.
Working to protect sea otters is another step individuals can take to help restore lost kelp forests. In southeast Alaska, the historic overhunting of sea otters for their luxurious pelts caused their extinction in the late nineteenth century, allowing the otters’ favorite prey, sea urchins, to run rampant and decimate the local kelp. The reintroduction of otters in the 1960s led to the recovery of kelp forests, along with a boom in populations of commercially important species like cod, salmon, and rockfish, which more than makes up for the decline in shellfish species that the otters also consume.

Learn about seaforestation. Seaforestation is a portmanteau of “sea” and “afforestation” and involves planting and restoring underwater seaweed forests. There are at least three methods of achieving this being explored. Each technique essentially starts with something like a standard kelp farm, in which the seaweeds are grown on ropes or other substrates running between buoys (see Seaweed Farming Nexus).

The first approach allows the farm to be moved into or established in the huge expanses of the open ocean that are so nutrient-depleted that they are commonly referred to as marine deserts. The Climate Foundation is a leader in developing “irrigation” approaches in which cold, nutrient-rich water is pumped from the ocean depths with solar and wave power to provide the conditions kelp and other macroalgae need to thrive.
The Climate Foundation envisions giant kelp and red algae eventually growing on hundreds of 1-square-kilometer semi-submerged “marine permaculture arrays” and at-sea biorefineries that extract a variety of proteins and useful compounds like omega-3 fatty acids and other food and cosmetic additives before sinking the remaining carbon-rich pulp to the ocean floor, where it will remain for more than a thousand years on average.
The second approach is similar, but rather than bringing the deep water to the kelp farm, it brings the kelp farm to deep water using submersible drones that can physically move the whole farm up and down, alternating between sunlight near the surface during the day and the nutrient-rich waters hundreds of feet down at night. Marine BioEnergy Inc. is at the forefront of this idea, with federal grants from the U.S. Department of Energy’s MARINER (Macroalgae Research Inspiring Novel Energy Resources) program.
The third approach uses biodegradable buoys to allow farms to be grown near shore in nutrient-rich shallow coastal waters before currents carry the farm out to the deep ocean. The buoy eventually degrades, causing the kelp to sink to the ocean depths.

Invest in seaweed. There are a number of ways you can support seaforestation financially or with your time and energy.

Donate or volunteer with groups on the cutting edge of kelp forest restoration or seaforestation. Kelp forest restoration is expensive. Seaforestation needs the resources and investments that any emerging technology does. A number of organizations could use your time and/or financial support (see Key Players below).
Buy seaweed products. See Seaweed Farming Nexus for a long list of seaweed-derived products currently on the market. Supporting ocean farming by buying these products also supports seaforestation because ocean farming and seaforestation share markets and technologies.
Buy Kelp Coin. Kelp Coin is a unique financial instrument for supporting seaforestation. It is a tradable, blockchain-backed security token that represents a forward contract for a ton of kelp in the ocean. The idea is that the buyer of a token in 2022 (current price, $175) would be assured that within forty-eight months of the year of purchase, the Marine Permaculture Alliance will see to it that an extra ton of kelp will be stored safely away in the ocean depths as a carbon onset (see Offsets Nexus and Onsets Nexus).

Learn more about Asparagopsis. Asparagopsis is a type of seaweed that can reduce the methane released by cattle by 60 percent to 99 percent when it replaces even a tiny fraction of their diet. Even though Asparagopsis is a “red algae” instead of a “brown algae” like kelp, it may still be possible to grow it using seaforestation approaches. See Asparagopsis Nexus.

Speak up. Write an op-ed to a newspaper or social media site promoting kelp forest restoration, marine permaculture, or public investments in seaweed farming (including the streamlining of permitting processes). Here are some examples of specific calls to action:

Petition to allow any diver to remove or cull overabundant sea urchins in California urchin barrens.
Promote support for the passage of the Keep Ecosystems Living and Productive (KELP) Act, which would allocate $50 million through NOAA for kelp forest restoration.
Encourage representatives to pass the Blue Carbon for Our Planet Act.
See Governance below for policy ideas to write to your representatives about.

Follow the latest from seaforesters on social media. Accounts include:

The Climate Foundation on Facebook and X
Operation Crayweed on Facebook

Groups

Scientists

More research is needed to scale up seaforestation and kelp forest restoration. Scientists and research institutions can get involved by directing their efforts to understand some of the following key issues:

Scaling up seaforestation. Many seaforestation approaches exist as proofs of concept, but more engineering, mariculture, and biological research are needed to understand how to increase the scale of seaforestation efforts efficiently.
Spatial planning. More studies are needed to understand where new seaweed farms or kelp forests could maximize benefits like protecting coral reefs and coastlines, cleaning runoff pollution, or benefiting fisheries.
Cost-effective restoration. Most kelp forest restoration efforts run more than one hundred thousand dollars per acre, but researchers are suggesting strategies for bringing those costs down.
Coastal darkening may be slowing down the rate at which kelp forests draw down carbon from the atmosphere by up to 95 percent, but little is known about how this issue will impact seaforestation or kelp forest restoration efforts.

Companies

Use marine permaculture inputs for animal agriculture, fertilizer, cosmetics, and biofuels. One of the most important stepping stones to achieving seaforestation at a large scale is bolstering the growing seaweed farming industry. Robust markets for seaweed products will facilitate the growth of seaforestation efforts. This is particularly true when it comes to animal feeds and biostimulants, bioplastics, and biofuels.

Help develop blue carbon markets that include kelp farms and kelp forest restoration. Carbon markets allow businesses in one part of the world to support projects in other places in their efforts to reduce their greenhouse gas emissions. Blue-carbon markets focus on many ocean settings, recognizing the outsize potential of certain marine environments for sequestering carbon. Companies can play a key role in nurturing and growing initiatives centered on seaweeds by seeking them out as they participate in voluntary carbon markets and make net-zero pledges, as well as by investing in research to measure the carbon being stored by new kelp forests.

The Vancouver-based Ostrom Climate Solutions is working with First Nations in British Columbia to measure carbon stored on the seafloor by kelp forests, opening the door to the sale of blue carbon credits by groups working to restore or farm kelp in the region.

Support seaforestation through private capital. Financial partnerships between investors, nonprofits, private companies, and the public sector are essential in healing the ocean while drawing down carbon. There is a huge diversity of opportunities. Here are some examples for inspiration:

355 investors crowd-funded C-Combinator’s effort to create sustainable products out of the natural Sargassum seaweed bloom in the Atlantic and Caribbean.
GreenMoney dedicated its September 2021 issue to using investments to support ocean and climate sustainability.

Governance

Scale up kelp forest conservation. There are a number of ways businesses, governments, researchers, resource managers, and the general public can get involved in kelp forest conservation. Read Kelp Forest Alliance's road map for scaling up kelp forest conservation.

Kelp Forest Challenge: The global kelp community is calling for the protection and restoration of 4 million hectares of kelp forests by 2040. From snorkelers to CEOs, anyone or any organization can get involved.

Establish restoration priorities for blue carbon, including kelp forests. The Blue Carbon for Our Planet Act references kelp forests as important blue-carbon ecosystems and, among other things, would establish national restoration priorities for blue-carbon ecosystems in the United States. The Japanese Blue Carbon Initiative is the first nationally recognized system for blue carbon in kelp forest ecosystems.

Finance restoration projects. Governments of temperate coastal nations can and should fund efforts to restore lost kelp forests in their territorial waters. The NOAA Restoration Center funded sea urchin control efforts to restore kelp forests in California via the Montrose Settlements Restoration Program. The KELP Act in the US would allocate $50 million through NOAA toward kelp forest restoration efforts. Given the cost of kelp forest restoration, institutional support from government entities is essential for scaling up efforts and needs to be pushed into action.

Adopt kelp forest restoration policies and objectives. Government agencies usually require policies to be enacted before they undertake projects. For example, the U.S. Forest Service conducts restoration work on its land under an Ecosystem Restoration Policy issued in 2016.

Protect kelp forests from further degradation. A number of threats or stressors to kelp forests can be mitigated through relatively straightforward projects or policies, like Sydney’s wastewater treatment, California’s grants for sea urchin removal, Alaska’s sea otter reintroductions, or Tasmania’s rock lobster fisheries closures.

Enter into partnerships with universities, NGOs, and private businesses to facilitate seaforestation work. Multi-stakeholder alliances are often enhanced with governmental partnerships, particularly given that the seascapes that could house marine permaculture arrays or seaweed farms are public resources managed by government entities.

Key Players

Organizations and Companies

Sea Forester (Portugal) is an NGO dedicated to restoring the “forgotten forests” of our oceans.

The Climate Foundation (U.S.) is an international organization working on large-scale climate solutions including seaforestation. They are global leaders in the push to achieve seaforestation using cold, nutrient-rich water pumped up from the ocean depths.

MarineBio Energy (U.S.) is an American company working at the forefront of seaforestation using underwater drones that move kelp farms from the sunny surface to the nutrient-rich ocean depths on a daily cycle.

Ocean Wise (Canada) is a Vancouver-based NGO working to ocean conservation issues, including the intersection of climate change and kelp forests.

Urchinomics (Global) is an international organization that restores kelp forests by removing ravenous sea urchins that are then fattened up and sold to sushi restaurants.

The Kelp Forest Foundation (Netherlands) is a nonprofit working to answer key questions about sequestering carbon in the ocean using kelp.

The U.S. Department of Energy’s ARPA-E (Advanced Research Projects Agency-Energy) is a major funder of research into both scaling seaweed farming and deriving biofuels from seaweeds, particularly through their MARINER (Macroalgae Research Inspiring Novel Energy Resources) initiative.

Fearless Fund is working on creating and harvesting free-floating blooms of Sargassum seaweed in the Atlantic and Caribbean.

Ocean Era (Hawai'i) works with ARPA-E-funded project called Blue Fields Offshore Macroalgae Demonstration Project, which hopes to advance the technology for irrigation of open-ocean macroalgae farms through better mooring and more efficient pumping and deep-water application techniques.

Ocean Rainforest (Faroe Islands) is a company with operations in the Faroe Islands and the U.S. that is at the forefront of developing cost-efficient technology for growing giant kelp.

Kelp Forest Alliance (Global) is a non-profit that advances the preservation and restoration of the world’s kelp forests. They conduct targeted research into how to prevent kelp forest loss and how to bring it back once it is gone.

The Nature Conservancy in California helped launch a Kelp Mapping Guidebook to help users from all backgrounds apply advanced mapping techniques to monitor kelp resources in their respective regions.

The Korean Fisheries Resources Agency (South Korea) fosters marine forestation and the regeneration of ocean ecosystems.

Puget Sound Restoration Fund (U.S.) works to restore marine ecosystems and species, with a focus on bull kelp.

Cascadia Seaweed (Canada) cultivates local species of seaweed on low-impact ocean farms in partnership with coastal Indigenous communities, then harvests it to manufacture products.

Greenwave (U.S. / Canada) helps train and support a global network of regenerative ocean farmers and administers a kelp climate fund that collects data.

Canadian Pacifico Seaweeds, LTD (Canada) is establishing a reliable commercial option for kelp seed in British Columbia.

Individuals

Brian von Herzen is the founder and executive director of the Climate Foundation, which upholds the vision and mission to regenerate life in the ocean using Marine Permaculture technology.

Margaux Filippi uses data science and machine learning for sustainability and oceanography.

Adriana Vergés is a professor of marine ecology at UNSW Sydney and the Sydney Institute of Marine Science.

Tristin Anoush McHugh is a subtidal ecologist and kelp forest restoration practitioner based in Mendocino, California.

Colin Bates is the Senior Research Scientist at Cascadia Seaweed.