Underneath the rocking blues of the ocean's surface lie forests of green.

Gently flowing in the currents, these organisms are the trees of the ocean.

Stunning groves that rise up from the depths and shelter thousands of species from the vast void of the sea.

But for us humans, these organisms are so much more, they're food, animal feed, protection from storms, a livelihood, and a possible solution to pulling years of fossil fuel emissions out of the atmosphere.

These wonders are none other than seaweed.

And today we'll discover why these plants (that are not actually plants) may be the key to unlocking a new way of farming that could be an essential tool to building a zero-carbon world.

Over the last decade, entrepreneurs, fisherfolk, and thought leaders have latched onto the promise of seaweed farming with exuberance.

Nonprofits like Greenwave, and for-profit entities like Sea6 Energy, have emerged to encourage and fuel a seaweed farming boom in the United States, and more broadly the Americas and Europe.

What they claim is, on the surface, extremely promising: a thriving seaweed farming system that supports the livelihoods of thousands of coastal communities, restores ocean habitats, and for many, the most important bit, sequesters millions of tons of carbon out of the atmosphere.

This is the promise of the nascent “Blue Carbon” industry.

We'll get into whether seaweed farming lives up to this hype in a little bit, but before we do that, what do seaweed farms actually look like on the ground?

Luckily, countries like China and Indonesia have been farming seaweed for almost 1,700 years, so we can already see what this blue carbon aquaculture looks like at scale.

Most seaweed farming looks like plots of coastal waters with lines of kelp or suitable seaweed species growing vertically down from lines strung across the surface of the water.

Some seaweed varieties can grow as fast as two feet per day, and when fully grown, are then harvested by boat, processed on land and broken down in numerous materials that run the gamut from dried seaweed flakes, to animal feed, to agar for thickening, and even biofuels and bioplastics.

In 2019, the world produced 35.7 million metric tonnes of seaweed, with China and Indonesia responsible for 84.61% of that production.

Needless to say, imperial core countries like the United States are champing at the bit to fill their coastal waters with seaweed farms, especially considering their benefits.

But can these macroalgae actually fulfill their host of proposed promises?

Seaweed farming is growing in popularity across the world for a myriad of reasons.

Some farmers grow them to serve demand for edible seaweed in a wide range of dishes like sushi, while others grow them for animal feed–supposedly aiding the health of livestock guts and drastically reducing the methane emissions of meat as a result.

Still others are spurred on by seaweed's potential to sequester substantial amounts of carbon in ocean sediments and the deep sea.

It's here, with carbon sequestration, that we'll begin to unpack the benefits of seaweed groves.

Looking at wild seaweed, which is an umbrella term for thousands of species of large algae, scientists have discovered their immense capacity to draw carbon dioxide out of the atmosphere and lock it back into the earth or the deep ocean.

One research paper estimates that macroalgae sequester roughly 173 teragrams of carbon per year globally.

To put that in perspective, that's the equivalent of sequestering the emissions of 8.65 million people living in the United States each year.

And looking towards seaweed aquaculture, this paper claims that a square kilometer of seaweed farm could sequester 1,500 tons of CO2 every year, which would be like reversing the footprint of 300 people living in China or 75 people living in the U.S. every single year.

To be clear this is a rough estimate of carbon removal.

The body of research and recording mechanisms are still in their infancy, so it's hard to get exact numbers on how much carbon wild and domesticated seaweed is actually capturing.

That being said, there are a host of other benefits that seaweed provides to coastal ecosystems.

Seaweed farms, when introduced have provided rich habitats for sea life, deacidified their surrounding waters, created storm and flood resilient coast lines by buffering wave energy, as well as provided oxygen-rich oases in oxygen-deprived zones.

These are all exciting prospects.

Along the Chinese coast, for example, seaweed farms introduced near dead zones successfully mitigated deadly toxic algal blooms while farms off the coast of Costa Rica noticed that the cultivated seaweed “rapidly attracted biodiversity.”

But part of the reason seaweed aquaculture is so appealing is that it requires few inputs and seaweed grows incredibly fast.

You don't need fertilizer, herbicides, or pesticides, and seaweed mostly takes care of itself, which means that an ocean farm is comparably easier to start and maintain than its on-land cousin.

In short, seaweed farming, if done right, could potentially sequester millions of metric tons of carbon, all while repairing ecosystems and providing buffer zones for coastal communities.

But emphasis on “if done right” and “potentially” because our knowledge of the effects of seaweed farming on carbon sequestration as well as habitat restoration is still growing.