A vast swath of the coastal lands around New Orleans will be underwater by the dawn of the next century because the rate of sediment deposit in the Mississippi delta can not keep up with rising sea levels, according to a new study published in Nature Geoscience. Between 10,000 and 13,500 square kilometres of coastal lands will drown due to rising sea levels and subsidence by 2100, a far greater loss than previous estimates. The findings revive the debate about the long-term sustainability of New Orleans and other low-lying areas. Scientists say New Orleans and the barrier islands to the south will be severely affected by climate change by the end of this century, with sea level rise and growing intensity of hurricanes. Much of the land mass of the barrier island chain sheltering New Orleans was lost in the 2005 storm. Efforts to keep pace with the accelerated rate of sea level rise due to global warming are compromised by the Mississippi's declining ability to bear sediments downstream into the delta. The authors used sediment data from the Mississippi flood plain to estimate the amount of sediment deposited on the river delta during the past 12,000 years. They then compared this with sediment deposition today.