Louisiana is one of MANY coastal u.s. states that is bracing itself for the rising sea levels that global warming is predicted to bring. But the phenomenon is far from new, regionally: The National Oceanic and Atmospheric Administration estimates that Grand Isle, La., has already seen waters rise at a mean rate of 9.24mm per year over the period 1947 to 2006. In Louisiana's case, rising waters are compounded by a second problem-subsidence. According to a U.S. Geological Survey (USGS) study, "Widespread nearly simultaneous collapse of marshes across the Mississippi delta plain appears to be unprecedented and not repeated in the geological record of the past 1,000 years." The authors of the study date the highest rate of subsidence in the region to the late 1960s and 1970s, when production of oil and gas in south Louisiana was also at its highest. The study authors find that "rapid subsidence and associated wetland loss were largely induced by extraction of hydrocarbons and associated formation water," although the role of natural processes "cannot be discounted entirely."
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