Coastal areas: Erosion, coral bleaching and wetlands inundation
Coastal erosion and property damage
One of the most visible impacts of climate change is the utter devastation that sea level rise can cause in concert with harsh coastal storms. As sea level rises, the potential for sever property damage along the coastline from strong coastal storms, heavy rain, strong winds, and associated storm surge will increase dramatically. In the wake of such storms as Hurricane Andrew and Hurricane Katrina, there is no doubt that large coastal storm systems can result in millions, if not billions, of dollars in property damage.
| || |
But coasts also will be under increasing threat of erosion from climate change and sea level rise, an effect which will be exacerbated by ever increasing human-induced pressures, like poor coastal development practices.
While ocean acidification is expected to harm marine life by making it more difficult for corals and other organisms to form their calcareous shells and skeletons, increases in sea surface temperatures of about 1-3 oC are projected to result in more frequent coral bleaching events and widespread mortality of corals and coral reef systems. Coral bleaching is well documented. The NOAA picture above shows a coral bleaching event at the Flower Garden Banks National Marine Sanctuary, located off the coasts of Texas and Louisiana. Coral bleaching is associated with a variety of stresses, including increased sea surface temperatures, pollution, disease, and coastal sediment runoff. These stresses can cause the coral to expel the symbiotic zooxanthellae (micro-algae) living in their tissues—algae that provides corals with nutrients essential to survival.
Losing their colorful zooxanthellae leaves coral tissues devoid of color, and thus the coral appears to be “bleached.” Sometimes the corals can recover from bleaching events, but prolonged coral bleaching will ultimately lead to coral death.
There is no doubt that as global sea surface temperatures rise, corals are at an increased risk of bleaching. This is particularly true for those coral species that already live near the upper threshold of their biological temperature range, and bad news for corals that are already experiencing drastic decline worldwide.
Coastal wetlands, including salt marshes and mangroves, are under increased threat of inundation as a result of rising water levels from sea level rise. This is especially true in areas where wetlands are constrained on their landward side (usually by coastal property development) or in areas where replenishing sediment supply is low.
A Delaware salt marsh, typical of wetlands found along the eastern seaboard. Salt marshes are extremely productive coastal environments and are sensitive to sea level rise.
The US Geological Survey map below shows major wetland areas across the U.S. Wetlands exist in the transition zone between aquatic and terrestrial environments. These areas are highly productive ecosystems and diverse in animal and plant life.
Source: US Geological Survey
Wetlands are critical because they serve many important environmental functions, such as filtering groundwater, serving as stopovers for migrating birds, and providing spawning and foraging areas for many aquatic and terrestrial species, as well as providing recreational opportunities for the public.
Because of their sensitivity to change, wetlands can be dramatically affected by only slight alterations in hydrology. Typically, natural processes allow wetland areas to adapt to long-term changes in sea level rise through sediment accretion and inland migration. However, as global warming accelerates sea level rise, coastal and estuarine wetland habitats may be destroyed in areas where sea-level rise exceeds the rate of sediment accretion and where inland migration is not possible, which is often the case in areas with heavy coastal development. In addition, freshwater wetland areas may be negatively affected by salt water intrusion.