On one hand, kelp forests grow on over one third of the world’s coastlines, and over 750 million people live within 50 km of a kelp forest. These highly productive ecosystems generate 500 billion dollars of potential value each year and are some of the most productive ecosystems on the planet¹. Thousands of animals live in or rely on a kelp forest, from iconic sea otters to treasured abalone, from the smallest snail to the largest whale. Humans, too, are inextricably tied to kelp forests and all the benefits they provide.

On the other hand, kelp forests are often overlooked or misunderstood. They are, in many places, our forgotten forests. For such important ecosystems, they are rarely defined or included in national or international policy and regulation². In many countries, kelp forests receive a small (or near zero) fraction of the environmental-spending budget. This funding gap means that there are lower levels of knowledge and protection for kelp forests than there are for their land-based counterparts or even for better-known marine ecosystems like coral reefs or the deep sea.

But the tide is turning, and the number of kelp forest conservation activities (restoration, sustainable management, or protection) is increasing, as dedicated funding is becoming available. There is also an emerging consensus that kelp forests are becoming more visible to the public. This increase in kelp-based awareness and activity coincides with a growing global interest in topics such as “nature positive”, “blue carbon”, and “biodiversity credits”. Putting all of this together means there is an opportunity to ensure that kelp forests are well represented in these emerging international initiatives as well as in the emerging social and market trends.

1.1.1 What is Kelp?

Kelp is both an organism and a habitat. As an organism, kelp is a structurally complex brown seaweed (species list). However, much of the data presented are based on a subset of species: most commonly, species within the taxonomic groupings Laminariales and Fucales. Kelps are attached to the seafloor, grow vertically, create a leafy structure and canopy, produce oxygen, and cycle nutrients. Several kelp together create a kelp forest, yet notably the term ‘kelp forest’ does not have a strict definition. All kelps are a type of seaweed, but not all seaweeds are a type of kelp. Kelps create unique, complex, homes for animals in their blades (“leaves”), stipes (“trunks”), holdfasts (“roots”), and their very presence defines the ecosystem (Figure 1.1).

Figure 1.1 Diagram of Kelp Forest Ecosystems (Differnet Forms)

Simply put, kelp forests are the forests of the sea.

1.1.2 Distribution and Depth

Kelp forests are mostly subtidal (always under water), extending from the water’s edge down to 15–25 metres: within the sunlight’s reach. In particularly clear waters, they live at depths of up to 40–60 metres and, in very rare instances, all the way down to 200 metres. Kelp forests are cold-water (~0-25 °C) ecosystems and are distributed on every continent from the subtropics to the poles. The only kelp forests in the tropics are in very deep waters, and they occupy a small area³.

1.1.3 Meet the Kelp

The many species of kelp come in many different shapes and sizes ranging from centimetres to tens of metres tall.

Canopy species: These species are over 10 metres tall from the seafloor to the surface. They have a strong holdfast gripping them to the seafloor, flexible stipes, and dense canopies that float on the surface, where they can often be seen from shore or by satellite.

Sub-Canopy species: These kelps have stiff, tree-trunk-like stipes that grow upright in the water with leaves growing from the top. They live only beneath the waves and do not break the surface.

Understory group: These kelps have big leafy branches that grow from the top of the stipe down to the seafloor. This creates a dense canopy that you have to brush aside to swim through.

Seafloor species: These kelps straddle the line between land and sea and form dense mats on the seafloor, where they are often exposed to the air at low tide.

Among these species, there are several notable species that have captured public attention, either for their ecological and economic significance or simply because of their impressive aesthetic.

Giant kelp (Macrocystis pyrifera) is one of the most iconic species of kelp, recognised for its dense, towering forests that are vital to marine biodiversity. It is a perennial species, present all year round, and commonly found along the Eastern Pacific from Alaska to Mexico. Further south, it is distributed across the southern coasts of Chile and Argentina, in the waters of South Africa, New Zealand, and Tasmania, and along Australia’s southern coast.

Bull kelp (Nereocystis luetkeana) is found predominantly along the West Coast of North America, beginning in central California and extending to the Aleutian Archipelago. Bull kelp is an annual species with cycles of growth, reproduction, and senescence each year. It gets its common name from its bull-whip-like form and has been a highly regarded cultural component of Indigenous cultures in North America for millennia.

Golden kelp (Ecklonia radiata) forms extensive forests in the Western Pacific and is the key component of the Great Southern Reef on the southern half of Australia.

Bamboo kelp (Ecklonia maxima) is found only off the coast of South Africa, and sharks weave through its towering trunks. It was recently featured in the Oscar-winning documentary, My Octopus Teacher.

Laminaria and Saccharina are known for the big, broad leaves of many of their species. These species are well known for their use in food (known as kombu in Japan), are often grown for aquaculture, and have many important medical and chemical derivatives. They are widespread across the Pacific and North Atlantic.

Lessonia species are native to the southern Pacific Ocean. As they are often intertidal and subtidal, they provide critical connectivity habitat in coastal zones. Lessonia support one of the largest wild harvests of kelp on the planet.

The Cystoseira and Fucus fucoid kelps create shorter, dense meadows of kelp habitat along rocky seashores but are also found in subtidal regions.

Figure 1.2 Kelp Forest Stressors

1.1.4 Threats and Stressors

On average and across their distribution, kelp forests have been declining at a rate of 1.8% per year. As kelp populations are naturally variable and influenced by many different factors, the scale and direction of these changes varies widely across the globe (Figure 1.2 & Table 1)⁴. However, the overall trend is negative: long-term datasets suggest that ~60% of kelp forests have declined in their abundance⁵.

Declines are most evident at the warm range edges of kelp distribution where marine heatwaves add to regional warming and cause large-scale losses⁶ . In many places, kelps in these areas are naturally replaced by more warm-adapted species of seaweed and fishes, which can limit recovery and restoration efforts⁷.

In temperate, mid-latitude regions, most kelp forests are either decreasing or remaining stable, and which of these occurs often depends on how regional changes in sea temperature, e.g., warming or cooling, interact with other stressors such as kelp over-harvesting or grazing by sea urchins. Notably, these kelps have shown a better ability to persist or recover from extreme heat events compared to warmer-water populations.

Kelp populations tend to be stable or are even increasing in higher latitudes or in areas with cool population refuges, upwelling, cooling trends, or increasing cold spells⁸,⁹. Elsewhere in these regions, cooler-water kelp populations are replaced by more warm-tolerant species. In these instances, there is no net loss in kelp cover, but the functioning of the community can shift considerably¹⁰.

Though limited, the historic data suggest that Arctic kelp forests are generally stable or increasing, with limited local losses¹¹. More recent surveys have also found highly abundant and previously undocumented kelp forests¹², so future warming may indeed result in an increase in Arctic kelp forests¹³. However, retreating ice may lead to increased sedimentation and salinity changes that cause these populations to decline.

Bright spots: Examples of places where kelps forests are stable and healthy.

Alaska – With cooler waters, more nutrients, and recovering food webs, the kelp forests of Alaska are faring well, and canopy kelp cover has increased in the region.

South Africa – The Great African Seaforest is made of four species of kelp, with some taxa like Ecklonia maxima expanding its range into cooler waters and currents that keep kelp healthy.

Patagonia – Home to the largest kelp forests on the planet, these remote waters have been protected from overfishing and pollution and rarely experience marine heatwaves. As a result, these kelp forests have been remarkably persistent over the past 200 years.

Worry spots: Examples of places that have had severe declines in kelp populations.

Tasmania – The waters around Tasmania are warming 4x faster than the global average, and giant kelp has declined steeply by 95%. As waters warm, nutrients decrease, and new sea urchin populations thrive, many solutions must be considered in the race to save these kelps.

Northern California – Perhaps the world’s most famous marine heatwave, “The Blob” (2013-2015) coincided with the 2015-2016 El Niño event and marine disease outbreak which killed the sunflower star, the last remaining urchin predator in the region, subsequently reducing the bull kelp of Northern California by more than 95%.

Japan – At least 40% of Japanese kelp forests declined between 1978 and 2007. The causes of decline vary by region but include warming oceans, urbanization, and increases in sea urchins and herbivorous fish.

1.2 The Race to Help our Kelp

December 2022 marked the launch of the Kunming-Montreal Biodiversity Framework. This landmark agreement was signed by 196 countries and agreed to the effective restoration and protection of 30% of the world's ecosystems and the restoration of 30% of the world's degraded ecosystems by 2030 (often called 30x30)¹⁴. The agreement contains language that specifies that these gains should be representative of the ecosystems in each country’s jurisdiction. As such, national targets for the protection and restoration of coastal ecosystems must be adaptive and ensure that all critical habitats are quantified and represented in these international discussions and target setting. As of 2024, countries only have six more years to achieve these targets, and it is imperative that we ensure that critical habitats such as kelp forests are included in these allocations.

February 2023 marked the launch of the Kelp Forest Challenge ¹⁵. The Kelp Forest Challenge is intended to ensure that kelp forests are included in local and global marine management decisions, as previously, there were no international targets, policies, or agreements for kelp forests. The Challenge is a collaboratively developed mission to save our kelp forests around the world and is at the intersection of local projects and global initiatives such as 30x30. The Kelp Forest Challenge calls for:

1. The protection of 3 million hectares of kelp forests by 2040
2. The restoration of 1 million hectares of kelp forests by 2040
3. Increased awareness and appreciation of kelp forests
4. Increased funding to support these activities (target pending)

The Challenge provides an open, participatory, pledge-based system to incentivise kelp conservation and awareness raising. The Challenge intentionally encourages any section of society to participate, whether business, government, community, university, or individual. The Kelp Forest Challenge is hosted by the Kelp Forest Alliance, a global home for kelp forests that brings together people and information to help our kelp.

The Kelp Forest Challenge calls for holistic management of kelp forests, which requires a combination of strategies. These can include MPAs (marine protected areas), improved fisheries management, habitat restoration, and controlling invasive or overabundant species. This management will depend on collaborative efforts between local communities, governments, and conservation organizations, and its decisions should be grounded in scientific research, respect cultural contexts, and consider socio-economic activities to ensure sustainable and equitable outcomes for both people and marine ecosystems.

Table 1.1

REGION	SUB REGION	DIRECTION OF CHANGE	KEY REFERENCES
Northeast Pacific	Southern California Bight, Baja California	Variable- Declines northern Baja California. Stable-central Baja California.	Arafeh-Dalmau et al. 2019, Cavanaugh et al. 2019, Bell et al. 2023
	Northern California to Washington State	Variable – Washington, California, OregonDeclines - N. California, South Puget Sound	Pfister et al. 2017, McHugh et al. 2018, Hohman et al. 2019, Rogers-Bennett and Catton 2019, McPherson et al. 2021, Bell et al. 2020, Hamilton et al. 2020, Berry et al. 2021
	Western Canada	Variable, stable	Shroeder et al. 2020, Watson & Estes 2011, Starko et al. 2019, Costa et al. 2020, Mora-Soto et al. 2024
	Aleutian Islands	Declines	Estes et al. 1998
South America	Chile and Argentina	Declines – northern and centralStable – southern Chile and Argentina	Vasquez 2008, Mora-Soto et al. 2020, 2021, Friedlander et al. 2020
Northwest Atlantic	Virginian, Gulf of Maine	Declines	Feehan et al. 2019, Suskiewicz et al. 2024
	Nova Scotia, Gulf of St. Lawrence, Newfoundland	Variable, stable	Krumhansl et al. 2024, Navarez 2019
Northeast Atlantic	Southern European Atlantic Shelf, Celtic Seas, North Sea, Southern Norway	Declines – Northern and Southern Norway, Spain, Portugal, English Channel. Increases – Germany, mid-Norway	Araujo et al. 2016, Filbee-Dexter et al. 2020, Smale 2020, King et al. 2020, Christie et al. 2019
Southern Africa	Western South Africa	Variable, increases	Bolton et al. 2012, Blamey et al. 2015
	Eastern South Africa	Declines	Blamey et al. 2015
Northwest Pacific	Japan and Korea	Declines	Kirihara et al. 2006, Tanaka et al. 2012, Kang & Chung 2015, Jeon et al. 2015, Hong et al. 2021
Oceania	Western Australia - Houtman	Declines	Wernberg et al. 2013, 2016, 2020
	Leeuwin	Stable	Wernberg et al. 2013
	South Australia – South Australia Gulfs, Western Bassian, Cape Howe, Manning-Hawkesbury	Declines	Carnell and Keough 2019, Verges et al. 2016
	Tasmania	Declines	Johnson et al. 2011, Ling & Kean 2018
	New Zealand	Declines	Shears et al. 2008, Thomsen et al. 2019, Glover 2021
Arctic	Canada	Unknown
	US – Beaufort Sea	Stable	Bonsell & Dunton 2018
	Norway (Svalbard)	Increase	Bartsch et al. 2016
	Russia	Increase	Krause-Jensen et al. 2020

1.3 Pledge Spotlight

Although there has been much discussion about the role businesses can play in conservation, real-world examples of such support are often rare. The Kelp Forest Challenge invites a range of businesses to leverage their unique capacities and reach to support kelp forest conservation globally.

One example comes from Google Australia, which has dedicated resources, expertise, and capacity building to advance kelp forest conservation in Australia. Specifically, Google Australia has provided technical and financial support to:

• Use aerial imagery to map giant kelp forests in Southern Australia

• Complete sequencing of the giant kelp genome to understand genetic drivers of heat tolerance

• Raise awareness of kelp forests in Australia and worldwide through marketing, original content, and partner creators

Other potential pledgees are invited to consider how they too may support the Kelp Forest Challenge.