Coastal wetlands and marshes are based on highly organic soil—from which it is very difficult to remove oil. Oil in the soil can kill existing grasses and prevent new grass from growing. In the instance of the 2010 oil spill in the Gulf, there is more likelihood of oil settling into the coastal soil because of the chemical dispersants being used to thin it. Oil treated with dispersants tends to sink; untreated oil tends to float. Recovery workers cleaning the marshes can also push the oil deeper into the soil with their feet and equipment.
As the grasses of the Gulf Coast are effected by the oil, so too are the wildlife that uses them for cover and for food. The National Wildlife Federation highlights this relationship, saying "Ninety percent of all marine species in the Gulf depend on coastal estuaries at some point in their lives, and most of these estuaries are in Louisiana." Animals that depend on these grasses include river otters, mink, swamp rabbits, turtles and many kinds of birds, including local plovers, pelicans, herons and egrets, plus birds that migrate to or through the area seasonally. Loss of grasses along the coastline also increases the rate of erosion. Without plant roots to bind the soil together, the soil slides into the ocean. In turn, soil erosion slows the rate at which plant communities grow back.
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