The Other Vanishing Forests

“Bull kelp is a seaweed that is like trees for the ocean” Michelle George, cultural and technical specialist for Tsleil-Waututh Nation.

Along the Pacific coast, lie forests as intricate and vital as any on land. Towering stalks of kelp sway in the cold currents, sheltering herring, rockfish, and salmon while anchoring entire coastal food webs and contributing to oxygen production and CO2 absorption. However, these underwater forests have thinned and, in some places, vanished altogether in the recent decades.

Over the past seven years, up to 95% of kelp has disappeared from parts of North America’s west coast.[1]

Globally, more than 40% of kelp forests have been depleted in the past five decades.[2]

Warming seas, unchecked sea urchin populations, and pollution have stripped rocky shorelines bare, leaving what scientists call “urchin barrens” where biodiversity once thrived.

Kelp forests experience considerable natural variability, shifting from year to year as storms, seasonal cycles, and upwelling patterns influence their growth and reproduction. Winter swells can strip away canopies, while spring upwelling drives rapid regrowth. Recognizing this inherent dynamism helps distinguish normal ecological cycles from the sustained, human-driven declines now unfolding along the Pacific coast.

photo: Erick Morales Oyola

On the Pacific coast, the two most critical canopy-forming kelp species experiencing decline are bull kelp and giant kelp.

Bull kelp (Nereocystis luetkeana): This species is annual (living only a year), meaning it relies on rapid growth, reproduction, and re-establishment each season.[3]

Giant kelp (Macrocystis pyrifera): This “floating kelp” has a longer lifespan under ideal conditions:4–8 years in some regions, though often shorter in BC. Its deep holdfasts anchor in rocky substrates, but the long stipes and canopy make it especially vulnerable to physical disturbances, overgrazing, and heat stress.[4]

The Importance of Kelp Forests

Kelp forests are among the most productive and dynamic ecosystems in the world, forming dense underwater canopies that rival terrestrial forests in both structure and ecological function. These forests provide critical habitat for a wide range of marine species, from invertebrates like sea stars and abalone to commercially and culturally significant fish such as salmon and rockfish. Juvenile salmon, in particular, rely on kelp understories for shelter and foraging, using the complex tangle of fronds to avoid predators as they prepare for their journey to the open ocean. 

(Read our article The Importance of Pacific Salmon: The Fraser River).

Beyond their role as habitat, kelp forests stabilize coastal environments. Their dense growth dampens wave energy, reducing shoreline erosion, and their extensive holdfast systems anchor sediment, supporting water clarity and benthic habitat health.

Kelp also plays a vital role in carbon sequestration. By capturing carbon dioxide through photosynthesis and transferring organic matter into the deep sea, these forests act as natural carbon sinks, helping to mitigate climate change on a local and global scale.

A 2016 paper estimated that macroalgae sequester 173 million metric tons of carbon every year as they float offshore and eventually sink into the deep sea.[5]

Kelp forests are not only ecologically significant; they are also deeply intertwined with human culture and subsistence. Since time immemorial, coastal Indigenous communities have harvested kelp for food, medicine, and tools, while observing the cycles of growth and decline as indicators of broader environmental health.

Kelp forests were central to Indigenous communities’ lifeways, providing both practical resources and ecological guidance. Strips of kelp were harvested for food, as a source of nutrients and minerals, and used in medicine, weaving, and other daily applications. 

Certain species, like sugar kelp, were carefully collected during specific seasons to ensure ongoing growth, reflecting an understanding of ecological cycles long before formal scientific study. Kelp forests also served as a living indicator of environmental health. Indigenous observers recognized that changes in the density or color of kelp signaled shifts in marine populations, water temperature, or the presence of predators such as sea otters or urchins. These observations informed sustainable harvesting practices, fishing schedules, and broader coastal management, ensuring that human use of the ecosystem did not compromise its resilience.

Coastal nations also incorporated long-standing kelp beds into their navigational systems. In Tlingit oral histories, for instance, several place names and stories point to prominent kelp patches as reference points at sea. The Makah were known to anchor near dense kelp canopies during extended trips offshore, taking advantage of the shelter they provided. Nuu-chah-nulth warriors similarly relied on these kelp-rich areas for strategic positioning, including during their well-known 1852 encounter with the U.S. Pacific Survey near Cape Flattery.[6]

By supporting biodiversity, stabilizing coastlines, and maintaining cultural connections, kelp forests are a foundation for both ecological resilience and human well-being. Understanding their importance is essential to grasping why their restoration has become a focal point for conservation and Indigenous-led stewardship efforts along the Pacific coast.

Photo: Ben Wicks

Why Are Kelp Forests Vanishing?

Kelp forests along the Pacific coast have experienced dramatic declines over the past few decades, as warmer ocean temperatures, particularly during marine heatwaves, disrupt kelp growth and reproduction.

But another important factor is the loss of key predators. Sea otters, once abundant along the coast, are critical regulators of sea urchin populations. Without sufficient predation, purple urchins can overgraze kelp holdfasts, turning once-dense forests into “urchin barrens,” landscapes almost entirely devoid of plant life. In some regions of British Columbia, surveys indicate that urchin density has increased tenfold in areas without otters, directly correlating with kelp loss.

“Two centuries without sea otters, hunted for the fur trade, have left these coasts overrun with the urchins, an otter’s meal of choice. Sea urchins fed voraciously on the holdfasts that keep kelp fixed to the seafloor, decimating Haida Gwaii’s kelp forests.”[7]

Photo: Michael Steinman

Human impacts compound these natural pressures. Coastal development, aquaculture, and industrial activities increase sedimentation and nutrient loading, which can smother young kelp or alter competitive dynamics with invasive species. Pollution from runoff, including heavy metals and microplastics, interferes with kelp’s ability to photosynthesize efficiently.

Moreover, bottom trawling, which involves dragging heavy nets across the seafloor to harvest fish or shellfish, is a practice that physically disturbs the substrate on which kelp holdfasts attach. Even in rocky areas where kelp anchors securely, the passage of trawl gear resuspends sediments, smothers juvenile sporophytes, and reduces the light available for photosynthesis, all of which limit kelp regeneration. Trawling disrupts benthic communities, removing predators and grazers that normally help maintain balanced ecosystems. Without this natural control, opportunistic species like sea urchins can thrive, compounding pressure on kelp forests

The Kelp Rescue Initiative

Efforts to restore kelp forests along the Pacific coast now rely on a blend of field experimentation, ecological modeling, and community-driven action.

The Kelp Rescue Initiative is a non-profit organization based in British Columbia and dedicated to restoring and protecting BC’s kelp forests.

Traditional knowledge is central to many restoration and monitoring efforts of the KRI. Guardian programs and community-led marine stewardship teams rely on Indigenous observation techniques alongside scientific tools such as diver surveys, remote sensing, and biodiversity monitoring. In some regions, restoration projects incorporate traditional harvesting methods, tidal calendars, and culturally grounded governance principles to guide reseeding and urchin removal. By bringing together ancestral knowledge and contemporary research, Indigenous-led initiatives offer models of restoration that are not only ecologically effective but rooted in cultural continuity and long-term responsibility to place.

One of their key projects centers on urchin control as in many parts of BC, sea urchin populations (particularly red Strongylocentrotus franciscanus, purple S. purpuratus, and green S. droebachiensis urchins) have exploded in the absence of their natural predators.

On the restoration front, KRI is testing novel seeding methods by growing juvenile kelp on ceramic tiles or “green gravel” (small rocks seeded with kelp spores) which are then outplanted to the seafloor. This technique helps ensure that young kelp can establish themselves on stable substrates rather than being washed away. In one pilot program in partnership with the Tsleil-Waututh Nation in Burrard Inlet territory, they found that kelp seeded on larger cobbles reached the surface by June and even developed reproductive tissue.

“This method worked really well, seeing kelp grow and reach its reproductive stage, at which point, the seaweed releases spores into the area, opening the door for natural growth.” Jasmin Schuster, program manager of the Kelp Rescue Initiative.

Read about it here.

And read about the q̓am̓ Restoration in səlilwət: Collaborative Bull Kelp Restoration at Whey-ah-Wichen (Cates Park) and New Brighton Park here.

KRI also engages in deep ecological research and conducts experiments to evaluate kelp thermal tolerance, use species-distribution modeling to predict future shifts in kelp habitat, and sequence the genomes of kelp populations to understand genetic diversity and local adaptation.

Kelp forests are far more than underwater vegetation; they are foundational ecosystems, cultural pillars, and climate allies whose loss signals deep imbalance along the Pacific coast. Their decline is driven by the cumulative weight of warming seas, predator loss, industrial disturbance, and pollution, all of which unravel ecological relationships that once sustained thriving coastal food webs. Yet the growing movement to restore these forests demonstrates what is possible when science, Indigenous knowledge, and community stewardship work together. From selective urchin management to innovative reseeding projects and the revival of culturally rooted harvesting practices, the efforts emerging today reflect both urgency and optimism.

Protecting kelp is ultimately about safeguarding the broader systems that depend on their resilience. Restoring these vanishing underwater forests is a commitment to future generations and to the long-standing relationships between coastal peoples and the living ocean that sustains them.

About the Author

Kimberley has a M.Sc from the University of Montreal. She is passionate about biodiversity and Indigenous peoples' land rights. Kimberley has been working with NGOs for over five years as a researcher, writer, and translator.

[1] The Kelp Rescue Initiative. “The Kelp Rescue Initiative – Science-Backed Solutions to Kelp Restoration.” Kelp Rescue, www.kelprescue.org/.

[2] Ecodrive. “British Columbia Kelp Forest Cultivation.” Ecodrive Community, www.ecodrive.community/updates/british-columbia-kelp-forest-cultivation

[3] Monterey Bay Aquarium’s Seafood Watch. “Kelp, Bull and Giant (British Columbia, Canada).” Seafood Watch, 2024, www.seafoodwatch.org/globalassets/sfw/pdf/expert-review/2024/110424/seafood-watch-kelp-bull-giant-bc-28332.pdf

[4] ibid

[5] Krause-Jensen, Dorte, and Carlos M. Duarte. “Substantial Role of Macroalgae in Marine Carbon Sequestration.” Nature Geoscience, vol. 9, 2016, pp. 737–742. DOI: 10.1038/ngeo2790.

[6] Naar, Nicole. Appendix B: The Cultural Importance of Kelp for Pacific Northwest Tribes. Puget Sound Kelp Conservation and Recovery Plan, Northwest Straits Commission, NOAA NMFS, May 2020. NW Straits, nwstraits.org/media/2925/appendix_b_the-cultural-importance-of-kelp-for-pacific-northwest-tribes.pdf

[7] Geib, Claudia. “By Cultivating Seaweed, Indigenous Communities Restore Connection to the Ocean.” Mongabay, 14 Jan. 2022, news.mongabay.com/2022/01/by-cultivating-seaweed-indigenous-communities-restore-connection-to-the-ocean/