Marshes on the move

The rate of global sea level rise is increasing as ice from Greenland and Antarctica melts and warmer seawater expands. By 2050, sea levels could surge by 10 to 25 millimeters per year, according to climate modelers, up from just about 3 millimeters per year now. The rising water could drown some 20% to 90% of the world9s coastal wetlands, destroying habitats that are among the most ecologically valuable on Earth. But coastal scientist Matt Kirwan has argued that such forecasts of wetland loss are needlessly bleak. Studies he and his colleagues have conducted suggest some tidal wetlands can keep pace with sea level rise, by building their soils vertically and migrating inland horizontally as water creeps up coastlines. Some coastal wetlands could even expand, if people don9t block their paths with seawalls or other infrastructure. But many researchers are skeptical of Kirwan9s findings, and have begun to challenge his work.