Underwater seagrass helps fight climate change. These inventors want to stop it vanishing
Vital seagrass meadows off the coast of Britain are under threat - and two inventors have come up with a potential solution to help conserve them: an aquatic ‘lawnmower’ that harvests seeds.
Like coral reefs and rainforests, seagrass meadows are threatened around the world: they provide nutrition for three billion people by supporting fish, and are also vital to the battle against climate change.
Seagrass meadows occupy just 0.2% of the world’s ocean, but are responsible for more than 10% of the carbon absorbed in ocean sediment. This makes them 35 times more efficient than rainforests - with a single hectare of seagrass supporting 80,000 fish
But they are vanishing around the world.
In British waters, an estimated 90% of natural seagrass meadows have disappeared due to climate change, coastal development, pollution and overfishing. The International Union for the Conservation of Nature (IUCN) estimated that seagrasses are declining 7% a year worldwide, making them the fastest-disappearing habitat on the planet.
To tackle the problem, British entrepreneurs Sam Rogers and Ed Towler decided to build a machine to potentially help to regrow Britain's lost seagrass.
How does a ‘mower’ help save seagrass meadows?
About a third of seagrass meadows have vanished globally since the late 19th century and previous projects have used volunteers to manually harvest seed pods and plant them using snorkels (and even body boards) in an attempt to save them.
But the ‘mower’ makes it far easier to harvest seeds, trimming plants with a large blade, and moving along the floor of the sea on skids.
It was developed in partnership with charity Project Seagrass. Towler told Yahoo News: "This form factor allows for adjustable trimming height, and the mower body guides the cut seagrass gently toward the collector funnel at the rear, where it is then sucked up a pipe up to the surface for the seeds to be separated from the seawater and collected.
"Currently Seagrass seeds are harvested by hand by divers, which is very time consuming."
The pair have built small-scale prototypes to test for safety, using metal workers, laser cutters and pipe benders from across Britain.
"This absolutely needs to be robust enough to operate in the seven seas (or at least one of them) again and again without corroding or getting damaged. It’s bright yellow to be easily spotted in the water by operators," said Towler.
"We tested our pump and filter systems with wet hay (seagrass simulant) at reservoirs – our early filter systems couldn’t handle the high volume of seagrass flow, with pumps stalling and blocking and requiring complete strip downs to mend them - not ideal. After many iterations we landed on functioning design.
“The latest device glides along the seabed with an adjustable cutting blade that trims seagrass seed pods at just the right height, no buoyancy required. The seed pods are then pumped up to a tow boat where they are filtered from the seawater.
Towler adds that the test drive of the latest prototype was a scary moment, saying: "We waited in anxious silence once we started towing the mower, waiting to see if the seed sucking systems would work in the real world test. After a long 20 seconds, grass started flying through into the collector."
What other projects are aiming to restore seagrass?
One scientific study suggested that seagrass replanting projects could contribute 1.43% to national efforts to offset carbon dioxide emissions by 2030.
Tidal, a project within Alphabet's X division (the so-called moonshot factory), researched the potential of seagrass to drive an increase in the amount of CO2 absorbed by the ocean.
The moonshot division is a part of Alphabet which is encouraged to pursue technological breakthroughs into humanity’s biggest problem, and which is behind Waymo self-driving cars.
The research focused on seagrass, because it grows rapidly and can absorb carbon dioxide from shallow water: the project aims to develop ways to measure how much carbon seagrass can store, by capturing 3D maps of seagrass beds.
Alphabet hoped to drive a market for carbon credits based on seagrass beds, and drive the use of seagrass to limit climate change.
Tidal general manager Neil Dave told MIT Technology Review, “If we can quantify and measure these systems, we can then drive investment to protect and conserve them.”
What will happen next?
Rogers and Towler now hope to expand their prototype device, which they are working on with charity Project Seagrass.
The first prototype was built in July and has already ‘proven effective’, the pair say. They are now crowdfunding £30,000 to build a new prototype.
The two founded Tandem Ventures, an organisation that helps provide practical solutions to environmental, wildlife, and humanitarian challenges using technology.
“Tools like the underwater seed harvester allow these teams to do more of the essential work they’re already doing and that’s what motivates us," said Towler.
