Who’s Eating all the Kelp: the sea urchin problem and how we solve it

Sea urchins have been around for millions of years, helping keep ocean ecosystems balanced by munching on algae. 

But something has shifted. Sea urchins have two main natural predators, the adorable sea otter and the striking sunflower sea star. But human activity during the 18^th and 19^th centuries caused a massive decline in sea otter numbers. And while some populations have recovered, many are still struggling, and the impacts of the ecosystem imbalance haven’t disappeared.

With fewer predators around, urchin numbers have exploded. And this army of spiky invertebrates are turning some of our lushest kelp forests into underwater wastelands.  

What Are Urchin Barrens? 

You might be thinking, “How much damage can urchins possibly do?” But when allowed to overgraze, they create urchin barrens: vast stretches of seafloor stripped completely of kelp. 

And while devouring their entire food source doesn’t seem like the smartest move for long term survival, urchins have a unique trick up their sleeves. Once they have eaten all the kelp in their surroundings, they enter a state of hibernation. This allows them to stay alive until a food source returns without starving. 

In other words, they can destroy a forest and then just wait it out. 

Why Urchins Eating Kelp is a Problem? 

Kelp forests are vital for life both below and above water. Beneath the waves, they provide food, shelter, and nursery grounds for thousands of marine species. These incredible algae are also powerful allies in mitigating the impacts of climate change by absorbing carbon from the atmosphere and buffering coastlines from intense storms. 

However, when sea urchins overgraze and turn vibrant kelp forests into barren patches, it does more than destroy beautiful underwater habitats. It affects all life that depends on them, including us. 

How do we solve the problem of urchin barrens? 

Work is already being done to increase the presence of sea urchins’ natural predators in the ocean. And while this helps, more intervention is needed to quell the urchin takeover.  

Studies in New Zealand, California, and Haida Gwaii show that targeted urchin removal can give kelp forests the breathing room they need to recover from overgrazing. In 2026, we’ll be applying those learnings in Barkley Sound with our partners, the Tseshaht First Nation and the Pacific Urchin Harvesters Association (PUHA). Together, we’re building a community-led urchin removal program that brings together science, technology, Traditional Knowledge, and local expertise. 

As part of this work, Tseshaht community members will be trained to harvest urchins sustainably. Urchins are a traditional food source, so harvested urchins can be shared within the community, with any extra available for sale. This creates economic opportunities while actively reducing pressure on kelp forests. 

By blending Traditional Knowledge with science, we hope to create a model that delivers both ecological and economic benefits, ensuring that these underwater forests can thrive for generations to come. 

Learn more about our kelp restoration work here.

Thank you to RBC Foundation, Scotiabank’s Climate Action Research Fund, the Peter Gilgan Foundation, and HCLTech Grant for Climate Action for your generous investment to help restore vital kelp forests, strengthen coastal ecosystems, and advance community-led climate solutions.