EVER been to Long Beach in Barbados? It’s a mile of pure white sand and crashing waves, just south of Grantley Adams airport.
Long Beach has lost 30 metres of its width since the sargassum invasion started.
Thick mats of stinking sargassum seaweed from the tropical mid-Atlantic have periodically swamped Caribbean beaches and coastal waters since 2011, reaching from Tobago, north to Florida and west to Belize and Mexico.
Flying across the Caribbean, teardrop-shaped, brown stains of sargassum can be seen in the blue waters, up to 20 kilometres across. Some smaller clumps of sargassum double in size every 11 days.
Last year’s influx was the worst ever.
The damage extends below the sea surface. When nearshore seas are swamped by mats of sargassum, wave energy is concentrated in the waters trapped below. Powerful currents erode the beach sand.
A few miles east of Long Beach is the glitzy Crane Resort. A glass-fronted cliffside lift drops visitors to startlingly beautiful Crane Beach, voted best in the Caribbean in 2015 by readers of USA Today.
That beach has since lost 15 metres in width, according to Sonia Foster, permanent secretary of the Blue Economy division of Barbados’ environment ministry. She spoke eight days ago in Barbados, at the opening session of The UWI’s third Sargassum Symposium.
Catch the day’s proceedings if you can—they’re on YouTube.
The symposium heard that the Crane sometimes has to transport visitors across Barbados to the west coast when its adjoining beach is choked with sargassum.
Sonia Foster is every inch the solid Barbadian public servant. She’s no wild-eyed alarmist. She asks whether the Barbados tourist economy can survive another decade of sargassum.
Accra and Hastings beaches on the south coast were choked this month. Even the west coast is not immune.
The symposium heard that so far this year, Tobago and Trinidad has got off lightly. The big damage has been further north. That’s for now.
It is not just the beaches that suffer. Decaying seaweed offshore reduces the oxygen supply for coral reefs and marine life, and releases toxic hydrogen sulphide.
At sea, floating sargassum provides a habitat for greedy amberjacks, which gobble up young flying fish. That’s a disaster for Barbados and Tobago fisheries, although amberjacks are now caught as a substitute. That’s when sargassum doesn’t block fishers from even reaching their boats.
Why the sudden surge since 2011? Some blame rainforest clearance in Brazil.
When trees are replaced by cattle pasture and soybean cultivation, fertiliser residues are washed into the Amazon and then the mid-Atlantic. Increased nutrient content promotes seaweed growth.
Can the problem be tackled?
The first step is forecasting. Here, there’s been real progress. Drones and satellite data are used to monitor the problem. Hazard maps identify the shorelines most at risk. Barbados-based SargAdapt researchers now issue a multi-island forecast every two months.
But there are limitations. Some monitoring efforts struggle with images from Google Maps, which may be years out of date. High-resolution satellite imaging in real time costs money.
With more cash, Mexican forecasters produce a sharper picture.
When sargassum hits shore, the Barbados government pays teams of up to 100 workers to rake it up by hand. At first, they tried clearing with heavy machinery, but that scraped up beach sand along with the seaweed.
The sargassum can be trucked away. But there’s a shortage of dumping sites which won’t contaminate the water supply or stink out nearby residents.
In a big sargassum event, one kilometre of beach can produce up to 18 truckloads of seaweed in 24 hours. A major islandwide infestation might theoretically need over 1,600 trucks— massively more than available capacity.
Using satellite-based estimates, there were around 24 million tonnes of sargassum in the Atlantic and Caribbean last July.
Sargassum is rich in proteins, sugars and micronutrients. But, no, don’t eat it. It is also laced with arsenic and other heavy metals.
There are bright ideas for using sargassum to make fertilisers, soap, building blocks and other stuff. In St Lucia, some make a fertilising plant tonic for export, with a process which removes the arsenic. But so far, these and other uses absorb only the tiniest fraction of what’s out there.
Using sargassum as fuel for electricity generation sounds promising. Just one tonne of seaweed can generate 800 kWh of electricity—that’s around one month’s power for a couple of households. Scale that up, it could be a useful power source.
Scooping up sargassum while it’s still at sea would reduce shoreline damage. And the weed could be sunk to the ocean floor.
Fronds of sargassum have a bubbly surface. They contain air pockets, which keep them afloat. If they’re submerged to more than 30 metres, the air pockets burst and the sargassum sinks. That takes the carbon content of the seaweed to sunless depths where it will not add to the carbon dioxide in the atmosphere.
But catching multi-tonnes of seaweed and sinking it to 30 metres would be a massive challenge for marine engineering and logistics.
Who is going to develop an operational plan to handle that? And who is going to pay? As always, those are the big questions.
—Mark Wilson is an international journalist based in Port of Spain.
