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South-east Florida, USA

Ross et al., 2000

vegetation changes

Mangrove encroachment into estuarine wetlands due to changing water levels, increased nutrient load, and salt-marsh compaction during drought

1940s-1990s

South-east Australia

Saintilan and Williams,1999; Rogers et al., 2006

1 cm/yr along parts of the Louisiana coast), only part of which is climate-related (Penland et al., 2005). Hurricane Katrina, in August 2005, generated surges over 4 m, with catastrophic consequences (NOAA, 2005). In Venice, Italy, the frequency of surges has averaged around 2 per year since the mid-1960s, compared with only 0.19 surges per year between 1830 and 1930, with land subsidence, which was exacerbated by groundwater pumping between 1930 and 1970 (Carminati et al., 2005), and expanded sea-lagoon interactions (due to channel dredging) playing a greater role than global sea-level rise (Camuffo and Stararo, 2004). Surges have shown a slight decrease in Brittany, France, in recent decades, largely due to changes in wind patterns (Pirazzoli et al., 2004).

Apparent global increases in extreme high water levels since 1975 are related to mean sea-level rise and to large-scale inter-decadal climate variability (Woodworth and Blackman, 2004). Wave height increases have been documented in the north-east Atlantic Ocean (Woolf et al., 2002), along the US Pacific Northwest coast (Allan and Komar, 2006) and in the Maldives (Woodworth and Blackman, 2004), but decreases have been found in some areas of the Mediterranean from 1958 to 2001 (Lionello, 2005; Lionello and Sanna, 2005).

1.33.4 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.

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