Sea level has been rising at an average rate of approximately 1.8 mm a year for the past 100 years. Sea level rise has been attributed mainly to an increase in global temperatures and the subsequent thermal expansion, which causes the upper 500 meters (1640 ft.) of the surface of the ocean to expand, with a fraction of this attributed to the melting of ice sheets and glaciers due to global warming. While sea level rise affects both humans and animals, it may have a profound effect on certain animal species which rely on the coastal ecosystems, which are most affected by sea level rise, for breeding and feeding.
Increasing sea levels causes flooding on the coastal ecosystem. The depth of flooding depends on the elevation of the coastal habitat, for example, estuaries, bogs, swamps, mangroves, marshes, mud flats and beaches are the first habitats to be flooded. Many coastal animals are resilient to saltwater inundation, but others require freshwater to survive. Sea level rise threatens to flood many coastal wetlands. Wetlands are biologically diverse ecosystems, hosting a variety of plant and animal species. It has been estimated that sea level rise could exceed one meter (3.2 ft.) in the next one hundred years, leaving the wetland environments of the world extremely vulnerable.
Estuaries are coastal ecosystems with inflows of both fresh water from rivers and streams and salty water from the ocean, making estuaries some of the most productive habitats of the Earth. They provide nursery for many marine animals and harbor a wide diversity of birds and other animal species. Higher sea levels are likely to intrude into the estuary ecosystem, increasing salinity further upstream and affecting the entire habitat. Many animals may adapt to variable salt concentrations, but many other animal species might not be able to adapt to the changes in salinity and may be forced to migrate.
The melting of the ice sheets contributes to increase the levels of the world’s oceans. This is affecting certain animal species in the Arctic. One such species is the polar bear. Polar bears rely on the ice sheets that abound on the Arctic sea to find their prey. Global warming is causing the ice sheets to melt earlier each year, affecting the survival of polar bears. It is predicted that polar bears will not survive total loss of sea-ice cover during the summer. It is estimated that the population of polar bears is of a little more than 20,000 and that this amount could decrease by the year 2050.
Six species of sea turtles are endangered due to sea rising levels and rising temperatures. Rising sea levels will flood and erode beaches along many sand beaches, leaving the nesting beach habitat exposed to predators. The rising temperatures threaten to exceed the temperature limit at which turtle’s eggs incubate. Coral reefs on which some species of turtles feed are being affected by rising temperatures due to global warming. Sea grass on which adult turtles feed is being affected by changing temperatures, as well. Although turtles have adapted to geologic changes in the past, it may take from decades to centuries before they can reestablish new habitable zones.
Rising sea levels due to global warming may have a great impact on the coral reef ecosystem. The coral reef ecosystem is adapted to thrive within certain temperature and sea level range. Corals live in a symbiotic relationship with photosynthetic zooxanthellae. Zooxanthellae need the sunlight in order to produce the nutrients necessary for the coral. Sea level rise may cause a decrease in solar radiation at the sea surface level, affecting the ability of photosynthetic zooxanthellae to produce nutrients for the coral, whereas, a sudden exposure of the coral reef to the atmosphere due to a low tide event may induce coral bleaching.
Sea level rise is predicted to significantly impact the coastal environment in the coming century. Rising sea levels will cause flooding in lowlands; increase the saline content of ground water; and increase erosion of land. It will also intensify storms which are related to warmer ocean water. This will affect animal species thriving in the coastal ecosystem, which will have to migrate. According to the IPCC, rising sea level will have a number of impacts in the coastal environment, including wetland and coastal flooding, erosion, salinization of soil and aquifers and the loss of fish, birds and a wide variety of other animal’s habitats.