22.214.171.124 Summary of coastal processes and zones
In many coastal regions, particularly in subsiding regions, local sea-level rise exceeds the 20th century global trend of 1.7 to 1.8 mm/yr. Sea-level rise, enhanced wave heights, and increased intensity of storms are affecting some coastal regions distant from human modification, e.g., polar areas and barrier beaches, mainly through coastal erosion. Coastal erosion and losses of wetlands are widespread problems today, under current rates of sea-level rise, although these are largely caused by anthropogenic modification of the shoreline.
1.3.4 Marine and freshwater biological systems
The marine pelagic realm occupies 70% of the planetary surface and plays a fundamental role in modulating the global environment via climate regulation and biogeochemical cycling (Legendre and Rivkin, 2002). Perhaps equally important to global climate change, in terms of modifying the biology of the oceans, is the impact of anthropogenic CO2 on the pH of the oceans, which will affect the process of calcification for some marine organisms (Feely et al., 2004), but effects of this are as yet undocumented. Other driving forces of change that are operative in marine and freshwater biological systems are over-fishing and pollution from terrestrial runoff (from deforestation, agriculture and urban development) and atmospheric deposition, and human introduction of non-native species.
Observational changes in marine and freshwater environments associated with climate change should be considered against the background of natural variation on a variety of spatial and temporal scales. While many of the biological responses have been associated with rising temperatures, distinguishing the effects of climate change embedded in natural modes of variability such as ENSO and the NAO is challenging.