PARIS (AFP) - The Mississippi Delta is sinking fast, posing a challenge for the rebuilding of coastal Louisiana after the devastation wrought in 2005 by Hurricane Katrina, a study released Sunday confirmed. Across large swathes of southern Louisiana, average annual subsidence of five-to-10 millimetres (0.2 to 0.4 inches) have contributed to sea-level rise, shoreline erosion and wetland loss, they said. The findings have implications for delta regions around the world -- home to tens of millions of people -- already threatened by rising sea levels caused by global warming, the researchers told AFP. But the study, published in Nature, also...