Kelp 101: What Are Kelp Forests, and Why Do They Matter?

May 15, 2025

Cover Image: Giant kelp forest in California © Taylor Griffith

Kelp forests, to those who know and love them, are some of the most majestic places on Earth. But for many others, these magnificent ecosystems remain unknown, out of sight and out of mind beneath the waves. 

Found along 30% of the world’s coastlines in temperate waters, these underwater forests provide critical habitat, biodiversity, and benefits to thousands of marine species, coastal communities and the planet as a whole. 

Despite their importance, kelp forests are often overlooked in high-level conservation by better-known systems like coral reefs or mangroves. But a growing global movement, energized by the global community of kelp lovers and organizations like the Kelp Forest Alliance (KFA) are working to change that, and to help the kelp.

Among Mission Blue’s global Hope Spot network, more than 30 Hope Spots support kelp ecosystems. With support from Mission Blue’s Kelp Initiative, researchers are actively working to protect, conserve and restore kelp forests, with exciting research projects in Hope Spots including Northern Iceland, Chile’s Humboldt Archipelago, and False Bay in South Africa.

First things first: what do we mean when we say ‘kelp’? 

Kelp refers to a group of species of large photosynthetic brown algae in the orders Laminariales and Fucales. They anchor to the rocky ocean floor with a structure called a holdfast, and grow towards the sunlight at the water’s surface. All kelp species can also be referred to as seaweed, but not all seaweed species are considered kelp. Seaweed can belong to one of three groups – red, green, or brown – but only certain types of brown seaweed are classified as kelp. It’s also important to note that while seaweeds (including kelp) are algae, they are not plants, but belong to a different group of organisms called protists.

And next, what do we mean when we talk about a kelp forest (or a kelp bed)? 

Kelp grow in temperate, coastal waters where they can form dense aggregations of individuals, known as kelp beds. A grouping of kelp beds is known as a kelp forest. With canopy forming kelp species like giant kelp (Macrocystis pyrifera) and bull kelp (Nereocystis luetkeana), which can grow to be over 100 feet tall, the forests they create really are the aquatic equivalent of terrestrial forests. Sunlight streams through the kelp canopy into the water underneath, where fish and invertebrates graze, protected from predators, and smaller species of kelp and seaweed grow, creating an understory.

Kelp forests are incredibly productive. They provide food and shelter for hundreds of marine species, including many types of fish, invertebrates, and marine mammals, both resident and migrating. Beyond biodiversity, kelp forests perform ecosystem services such as physically protecting coastlines from storm surges, reducing erosion, and absorbing nutrients from agricultural runoff pollution. Some kelp species can even grow faster than tropical bamboo, drawing down significant amounts of carbon as they grow. 

Kelp forests are among the marine ecosystems most vulnerable to climate change—second only to coral reefs. Rising ocean temperatures, intense marine heatwaves and pollution have triggered declines in kelp ecoregions around the world. 

Warming not only stresses kelp directly but can also tip ecological balances. In Northern California and Southern Australia, marine heatwaves in the 2010s triggered a cascade of events that led to the loss of over 90% of the kelp canopy cover in each area in less than a decade, transforming lush forests into sea urchin barrens or turf reefs that have yet to recover.

How can kelp forests be protected? 

Marine Protected Areas (MPAs) can offer some protection to kelp forests by limiting harvest and development, but they aren’t able to protect kelp from the major threat of warming water temperatures. Today, researchers estimate that 16% of global kelp forest habitat is currently protected by some form of MPA, but effective kelp conservation requires mitigating the major stressor of excess heat from climate change, while also investing in conservation strategies informed by the best available science and traditional knowledge.

Despite the global challenge of warming water, there is hope. South Korea has restored more kelp forest by area than any other country to date through a ‘marine gardening’ approach, and there are small-scale restoration projects underway in places like Chile, Northern California, New Zealand and more. In Wellington, New Zealand, the restoration work even involves freediving “kelpers”—volunteers and school children helping grow, plant, and monitor young kelp in the ocean using breath hold freediving techniques. Scientists and researchers are exploring how thermal-tolerant genetic strains, biodiversity protection, and art and culture can be part of restoration and advocacy to support kelp. 

Around the world, scientists, communities, divers, artists, and ocean lovers are rallying to protect and restore these vital ecosystems. The solutions aren’t simple—but they are growing quickly, just like the kelp. And whether it’s through policy, research, restoration, or simply spreading the word, there’s a role for all of us to help the kelp. 

References:

Eger, Aaron M., McHugh, Tristin A., Eddy, Norah, Vergés, Adriana (Editors). State of the World’s Kelp Forests V1.0. Kelp Forest Alliance, Sydney, Australia. Date Accessed (05/08/2025).

Eger, A., Aguirre, J.D., Altamirano, M. et al. The Kelp Forest Challenge: A collaborative global movement to protect and restore 4 million hectares of kelp forests. J Appl Phycol 36, 951–964 (2024). 

Woods Hole Oceanographic Institution and The Nature Conservancy. (2025). Kelp Report Card 2024.