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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.
On the Isle de Jean Charles 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. Each mat contains plastic from around 460 recycled drinking grade plastic bottles – safe for marine life – 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.
Over 200 volunteers launched 187 “floating islands” in 2011 as a demonstration project. Results exceeded expectations: the islands doubled in vegetative growth over the three months since they were installed. Nine other projects have since been developed, creating more than 900 square metres (10,000 square feet) of floating island shoreline. This includes a project to protect Shell’s pipelines from coastal erosion.
The islands are as healthy as the native marsh they are protecting, sustaining and enhancing coastal protection, fisheries and habitat and establishing new land in open water areas. Above the islands, a protected waterfowl nesting and migratory bird habitat now thrives.
“We see waterfowl and wading birds, as well as racoons, using the new wetland,” says Gerald.
Along with offering protection for the fragile ecosystem, the project has also benefitted the local community. It has given more reliable access to the narrow road leading to Isle de Jean Charles, as well as benefits for people who engage in subsistence fishing.
The Isle de Jean Charles's floating islands project has won multiple awards. In 2013, for example, it came first in the biannual Gulf Guardian Awards run by the US Environment Protection Agency. The project has also given rise to several successful floating islands projects, two of which Shell led in 2013 and 2015.
Terrebonne’s floating islands are an example of “green infrastructure”. This makes use of natural ecosystems to provide a service more common to traditional, man-made engineering solutions.
Shell believes that working with natural ecosystems can help increase resilience of both industrial operations and the environment. For example, using oyster beds to stabilise pipelines and prevent coastal erosion in the Gulf of Mexico, and reed beds to clean industrial water in Oman.
In 2013, we published a white paper together with Dow Chemical Company and The Nature Conservancy, Swiss Re and Unilever. It recommends that green infrastructure solutions become part of the standard toolkit for modern engineers.