Climate Change

Climate change is causing two important impacts along the world’s coastlines. Sea levels are rising and the chemistry of the oceans is shifting (IPCC 2007 and NRC 2011). The rates at which these impacts are occurring is likely to exceed the ability of mangrove forests and the species that live within them to adapt (Gilman et al. 2008).

In areas with upland coastal development, mangroves cannot retreat landward. Mangroves around the world are adapted to specific tidal regimes. If they spend increasing amounts of time inundated, at some point they will not be able to rid themselves of the ocean salt quickly enough, and will whither and die. They will also not receive the nutrients and sediment from freshwater flowing seaward that they require to survive. Compounding this, as the ocean becomes more acidic, mangrove animals with shells and other hard structures (e.g., oysters, snails, crabs, sea stars) will have an increasingly difficult time taking up calcium carbonate from seawater, leaving them with developmental deformities and thin, less protective shells as adults (Doney et al. 2012). And coral reefs—already stressed by increasing temperatures and bleaching—will likewise be weakened by increasing acidity (Hoegh-Guldberg et al. 2007). Many species—including many commercial fishery species—rely on both mangrove and reef habitats during different parts of their life cycle. Climate change directly threatens these habitats, which are responsible for providing food to billions of people around the world. Mangroves provide the critical nursery and adult habitats for 30-80% of commercial fisheries around the world (Rönnbäck 1999). Finally, mangroves are among the most important carbon sinks on the planet (Donato et al. 2011). Losing them will cause even greater carbon releases (Donato et al. 2011), creating a positive feedback loop that will further exacerbate sea level rise and increased ocean acidity.