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Plastic bottles defend coastline
The natural erosion of shoreline in Louisiana, USA, threatens homes, livelihoods and wildlife. Local people and government are working hard to protect the land. One novel approach uses recycled plastic bottles to give worn areas new strength.
In the Louisiana parish of Terrebonne, land is slowly washing away. Continuous waves lap against the soft sediment deposited by the Mississippi river. And Gulf of Mexico hurricanes add to the erosion taking place.
Homes close to the sea are increasingly exposed to the force of these storms. So are sensitive ecosystems.
As seawater runs into the fresh-water marshes, salt levels rise, risking the loss of fish, crab, oysters and shrimp – along with the income they provide to local businesses.
Gerald Schouest, 69, has always lived in the area. So did his parents and native American grandparents. “Hunting for fish and waterfowl is a way of life,” he says. But now this is under threat.
In 2009 he heard about artificial islands made from recycled plastic bottles used in golf courses and parks. He saw a way to help strengthen Terrebonne’s defences.
Ed Landgraf, who works with local communities for Shell operations in the Gulf of Mexico, liked the idea. So they contacted the manufacturer, Martin Ecosystems, to test them for the first time in open water.
A new line of defence
The islands are rectangular mats punctured with holes filled with soil and plants common to this region. They measure around 1.5 m (5 ft) by 2.5 m (8 ft) by 20 cm (8 inches). Each mat contains plastic from around 460 recycled polyethylene terephthalate (PET) drinks bottles, just some of the billions discarded each year.
Layers of foam keep the mats afloat. Steel cables secure them to the seabed in shallow water in rows about 1.5 metres (5 feet) apart. Over time the plants grow and their roots extend into the seabed, reinforcing the natural shoreline.
Gerald and Ed helped raise money – with Shell Oil Company as the main contributor – to build a strip of mats stretching over 450 metres (1,500 feet).
Volunteers, including many Shell employees, filled the mats with native grasses.
Four months after the mats were installed most of the plants were thriving. Roots have shot down to over 40 centimetres (16 inches). Above the surface the plants have more than doubled in height and volume.
“We see waterfowl and wading birds, as well as racoons, using the new wetland,” says Gerald.
Now waves lap against the artificial land, relieving pressure from the shore. In September 2012, the islands provided valuable extra protection as hurricane winds and high waves struck the area.
Some islands have since been re-anchored, and more added by local schoolchildren using grants from local non-governmental organisations supported by Shell.