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 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.
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The Basics of Seaweed Farming [Clip of seaweed hype]
Over the last decade, entrepreneurs, fisherfolk, and thought leaders have latched onto the promise
of seaweed farming with at times fanatical exuberance. [Play another clip]. 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
1700 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 into 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
chomping 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?
The Promise of Seaweed:
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 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. The authors claim that the high end of this carbon sequestration estimate would be enough
to outpace the carbon capture rates of mangroves, seagrassses, and salt marshes combined. 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. To be clear this is still a rough estimate of
carbon removal. The body of research and recording is in its 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 and reintroduced needed oxygen back into the ecosystem. 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 the 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 the 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.
The Perils of Seaweed: A quick google search of seaweed farming
reveals a lot about the excitement over the potential of this carbon sequestration powerhouse.
Articles like this, or this, feel like 19th century gold rush promoters of the American West.
That much hype raises alarm bells for me. Especially considering this recent scientific
paper that has called into question seaweed’s potential for carbon sequestration. It points out
that previous studies have failed to account for the contribution of the influx of organic material
and plankton that wash into wild seaweed groves providing extra food for sea life and ultimately
leading to significantly more carbon dioxide emissions. The paper claims that as a result,
wild seaweed forests might actually be a net source of carbon. I use this paper not to discount
seaweed sequestration wholesale, but merely to demonstrate that the research on these practices
are extremely new and evolving. We are still in the midst of parsing out exactly how wild seaweed
and seaweed farming contributes to our ecosystems. To be clear, many scientists in the field have
found the research promising, but we have to be careful how we treat and implement these
types of natural sequestration solutions. If it’s used as just another carbon offset scheme–letting
the fossil fuel industry continue generating emissions with impunity–then seaweed farming
could be a dangerous proposition, especially because we aren’t clear how much seaweed farming
sequesters. Expanding seaweed farming then, should not be viewed as an excuse to continue fossil
fueled capitalism, it is instead an exciting tool in a wide ranging toolkit that should be
used for the struggle to build a zero carbon world free of fossil fuels and capitalist extraction.
A World of Seaweed: Seaweed could unlock a whole new mode
of agriculture that would tie humans back to the earth and the sea, but to do so,
seaweed farming must not just be seen as another novelty for a startup to automate. Seaweed
farming is a piece of an amazingly complex web of low-carbon, carbon negative, and justice oriented
actions and ideas that we must integrate to build a better world. Because, at the end of the day,
even if seaweed farms expand to pepper the world’s coastlines and drawdown millions of
tons of carbon from the atmosphere, it will not be enough. Yes, it will certainly help,
but if we continue to grow our emissions footprint as our capitalist system is currently doing right
now, the sequestration of seaweed farming will be trying to fill an ever widening hole. So,
the natural carbon capture mechanisms of seaweed farming have to be combined with political
tendencies, justice oriented ecosocialist degrowth that seek a contraction of production
in the imperial core and an expansion of well-being for the periphery. Seaweed farming
might be a small piece of an exciting new future, but that future has already begun to take shape in
the seaweed harvested along the coastlines of the world. With each harvest of seaweed
we’re bringing food to our plates while repairing the harm of centuries of environmental damage.
But what kinds of seaweed farms are springing up across global coastlines? Are they small or
massive industrial plots? How is the current seaweed boom being managed and where
is all of that seaweed going? Those are some of the questions I answer in the bonus section to
this video I’ve uploaded on Nebula all about the current state of American and European seaweed
farming. If you haven’t heard by now, Nebula is a streaming service a group of creators and I built
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