Many seaweed forests have simply completely disappeared, destroyed by pollution, ocean heatwaves and other factors. They used to cover most coastlines in temperate climates. Now, from Antarctica to Australia, Canada and Norway, they are under threat as our planet catapults towards increasingly rapid environmental degradation.
Yet, restoring those forests could be a crucial step to mitigating climate change and limiting the loss of biodiversity in the ocean.
There are already dozens of such efforts under way across the globe – in Australia, Portugal, Korea, California and elsewhere – but much more needs to be done.
Far too little attention is paid to seaweed, yet these plants can reverse acidification in our oceans, build up depleted fish stocks and capture carbon at least five times more efficiently than tropical forests. At the same time the total area along our coasts, in the Northern and Southern Hemispheres where the sea is sufficiently shallow to allow sunlight to penetrate and sustain marine vegetation, is roughly the same as all of the world’s tropical forests combined, about the size of Europe or the United States.
Unlike plants and trees on land, planting seaweed needs no fertilizer or soil. Seaweed species, such as kelp, are among the world’s fastest growing plants, delivering rapid rates of photosynthesis. They can grow many meters in just a few months. In theory, spores can be sprayed under water and there will be a seaweed forest within a year. When it is grown it can sustain about 100 grams of fish per square meter of forest because of the nutrients it contains and the habitat it creates, according to scientific studies. If we take an area of 5,000 square kilometers, which represents just 0.03 percent of our global target coastal zone with shallow water, kelp forests can support 500,000 tons of fish.
All other benefits follow from there, including the ability of seaweed forests to reduce coastal erosion, a service that could become increasingly crucial if we don’t stop rising sea levels soon.
Growing seaweed forests, or restoring ones that have disappeared, is a viable method of helping nature help itself to mitigate climate change.
A crucial task to restore our seaweed forests is data. We do not yet have a complete survey of the world’s seaweed and kelp forests, nor exact information on how much of them and how fast they have disappeared. This is key to know how and where to act with most urgency. With new technologies for monitoring the earth’s surface this should not be impossible. What we do know is that industrial and agricultural waste discharged on our coasts has helped destroy seaweed forests in many coastal regions. Warming seas, sudden extreme water temperature changes and overfishing have also played big parts.
With greater scientific knowledge some of this may be mitigated. There are thousands of seaweed species in the world and they grow in different water temperatures. Different approaches can be used, from seeding on stones and artificial structures, to restore seaweed forests and the huge ecological benefits they bring.
Our ocean accounts for nearly two thirds of the world’s carbon sinks and seaweed forests, along with sea grass and mangroves, are all key ecosystems in that process. They all need urgent attention.
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