Summary Points
- Despite decades of kelp forest restoration, climate-driven losses outpace gains by 1,000 to 10,000 times, with only a small fraction of forests recovered annually.
- Warming seas significantly reduce kelp growth and carbon sequestration, with a 5°C rise expected to cut carbon export by 37%, undermining restoration efforts.
- Seaweed farming produces some carbon burial but is not a net carbon removal solution due to high emissions and limited scale compared to ocean losses.
- Protecting existing healthy kelp forests is far more cost-effective and impactful than costly restoration, emphasizing prevention and climate action over reactive efforts.
Kelp Restoration Faces Harsh Climate Realities
Restoring kelp forests is good, but it cannot keep up with climate change. During recent decades, about 60% of kelp has disappeared worldwide. Only 5% has regrown. Every year, roughly 4,460 square miles of kelp vanish — around the size of Oregon. Meanwhile, restoration projects have recovered just 7,800 football fields. This shows a huge gap between loss and recovery. While restoring kelp benefits ecosystems, it can’t counteract the rapid climate-driven decline. The scale of damage simply outpaces efforts to rebuild.
The Limits of Using Kelp for Carbon Removal
Kelp naturally pulls in a billion tonnes of carbon every year. Some of this carbon sinks deep into the ocean and stays hidden for decades or centuries. However, when kelp dies or is grazed away, much of its stored carbon is released into the water or air. Warmer waters slow kelp growth, decrease carbon absorption, and increase decay. For example, a 9°F rise could reduce carbon export by 37%. Growing seaweed farms offers some carbon capture, but their impact is limited—covering only a quarter of the ocean area that climate change destroys annually. Thus, farming isn’t enough to offset losses, but it still offers other benefits like food and materials.
Prevention Beats Restoration in Cost and Impact
Protecting existing kelp forests costs far less than trying to restore lost ones. Fully protecting a hectare can cost between $650 and $1,300. In contrast, restoring that same area might cost up to $707,000. Preventing overgrazing from sea urchins proves more effective and economical. In Tasmania, closing areas to fishing and moving lobster populations cut overgrazing for years. These efforts help maintain healthy kelp more efficiently than costly repairs. Still, most kelp forests remain unprotected. To help communities, experts recommend understanding local kelp vulnerabilities and focusing on safeguarding what remains rather than only repairing what’s gone.
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