4.22 - Vulnerability of Estuaries to Climate Change

We examine the likely effects of climate and other long-term drivers of change on estuaries, focusing on three key themes. First, on a time scale relevant to climate change, many other factors influencing estuaries will also change. These include human population, water withdrawals, discharge of sediments and substances, harvest, and species introductions. Changes in climate and these more direct anthropogenic drivers affect estuaries mainly through their joint influences on freshwater flow, sediment budgets, alteration of vegetated beds, eutrophication, and shifts in species composition or distribution. Second, estuaries are heterogeneous, ranging from tiny coastal salt marshes to huge marine bays and river deltas, and from remote locations to the harbors of the world's coastal cities. Regional and local differences in trends of climate and human activities ensure great variation among these systems in their long-term trajectories. Third, because estuaries are connected to both sea and land, they are among the most complex, variable ecosystems on earth, and their responses to myriad changes in external influences are unlikely to simply be related to temperature or other climate conditions. Generalizations about the long-term trajectories of estuaries are unwarranted without consideration of regional to local differences in forcing and responses.