Researchers have just calculated the value the community derives from a common but hidden underwater resource and have found that it is much higher than we expected. Seaweed forests have long done so much for humanity as they work by lurking beneath the waves. They cover a third of our coastline, providing food and shelter for most of our coastal seafood. Thus, this vibrant oceanic forest facilitated daring human migrations such as the southward colonization of the Americas 20,000 years ago.

We also eat algae, use it to fertilize crops, add it to medicines and skin care products, and breathe the oxygen it produces. However, kelp forests are declining catastrophically and we do not fully understand the scale, let alone the value of what we have lost. So a research team calculated the services that algae ecosystems provide to all of us.

“For the first time, we have figures that show the significant commercial value of our global kelp forests,” says University of New South Wales marine ecologist Aaron Egger.

“We found that 740 million people live within 50 kilometers of a kelp forest. So these systems play an important role in supporting their livelihoods and vice versa.”

Egger and colleagues used 1,354 studies of fish and invertebrates in six different kelp forests in eight different ocean regions. They also took measures to use nutrients from carbon to phosphorus.

The team reported that the economic value of the algae’s contribution to fish production averages $29,851 and 904 kilograms per hectare per year. Surprisingly, of the 193 animals identified, only 50 species were of prime value for fisheries, primarily invertebrates such as lobster, chestnut and abalone.

These oceanic “trees” not only provide habitat for thousands of marine species, but also play a large role in global nutrient cycles. Kelp is a type of algae that is a protist, not a plant, but like plants, their photosynthesis energizes the living networks they form, removing carbon dioxide from the environment and producing oxygen in the process.

Removing carbon dioxide, in turn, raises the pH level and oxygen supply in nearby areas, helping to mitigate the local effects of ocean acidification. Kelp also absorbs other nutrients such as nitrogen and phosphorus to support their rapid growth, and some species can grow up to 50 centimeters per day. Previous studies have shown that kelp forests are even more productive in terms of growth than intensively grown crops such as rice and wheat.

“Among the three elements, nitrogen removal provided the highest economic value per hectare per year (average = $73,831,620 kilograms), followed by phosphorus removal (average = $4,075.59 kilograms) and finally carbon sequestration (average = $163,720 kilograms) ) followed. ),” write Eger et al.

Algae carbon uptake is not as impressive as nitrogen removal, but still equivalent to terrestrial forests and seagrass.

“Globally, these kelp forests produce an average of $500 billion annually,” the team said. That’s three times the previous best estimates, and it’s just a baseline that should account for other significant contributions to our economy.

“There were many other services we didn’t measure, including tourism, education and learning experiences, and kelp as a food source, so we expect the true value of the world’s kelp forests to be higher,” says Eger.

Kelp also has incredible potential as a sustainable biofuel and helps protect our coasts from erosion.

But like much of the world around us, kelp forests are struggling. In the last few decades, about a third of all kelp forests have suffered major losses. The combination of heat waves and insatiable invasive sea urchins has led to a 95 percent decline in algae off the California coast since 2014. Half a world away, Australia’s kelp forests have been listed as endangered after the same severe decline.

They also suffer from human-made pollution, and as these floating forests shrink, so do lobsters, abalone, fish and all the other life that depends on them.

“Evaluating these systems in dollars is an exercise that will help us understand some measure of their tremendous value,” says Eger. It should not be forgotten that these forests also have their own historical, cultural and social values.

The researchers hope their findings will draw much-needed attention to this long-neglected ecosystem. With the Global Kelp Forest Challenge, they fight to restore and protect millions of hectares. The study was first published in Nature Communications.