Relative sea-level rise has a wide range of effects on the natural system; the main effects are summarised in Table 1. Flooding/submergence, ecosystem change and erosion have received significantly more attention than salinisa-tion and rising water tables. Rising sea level alters all coastal processes. The immediate effect is submergence and increased flooding of coastal land, as well as saltwater intrusion into surface waters. Longer term effects also occur as the coast adjusts to the new environmental conditions, including
TABLE 1 The main natural system effects of relative sea-level rise, including climate and non-climate interacting factors
Natural system effect
1. Inundation a. Surge (from the sea) (including flood and storm damage)
Wave/storm Sediment supply, climate, erosion, flood management, sediment supply erosion, land reclamation b. Backwater effect (from rivers)
Catchment management and land use
2. Morphological a. Wetland loss (and Change change)
CO2 fertilisation of Sediment supply, biomass migration space, production, land reclamation sediment supply, (i.e., direct migration space destruction)
b. Erosion (of beaches and soft cliffs)
Sediment supply, wave/storm climate
3. Hydrological a. Saltwater i. Surface change intrusion waters
Catchment management (over extraction), land use
Ground Rainfall water
Land use, aquifer use (over pumping)
b. Rising water tables/ impeded drainage
Rainfall, run off
Land use, aquifer use, catchment management
Some interacting factors (e.g., sediment supply) appear twice as they can be influenced both by climate and non-climate factors.
wetland loss and change in response to higher water tables and increasing salinity, erosion of beaches and soft cliffs and saltwater intrusion into ground-water. These lagged changes interact with the immediate effects of sea-level rise and generally exacerbate them. For instance, coastal erosion will tend to degrade or remove natural protective features (e.g. saltmarshes, mangroves and sand dunes) that in turn increase extreme water levels and hence the risk of coastal flooding.
A rise in mean sea level also has a net effect of intensifying flooding during extreme storm events . Changes in storm characteristics could have also influenced extreme water levels. Increases in tropical cyclone intensity in the North Atlantic over the past three decades are consistent with the observed changes in sea surface temperatures  and wave data in the North Atlantic support this observation . However, it is difficult to prove if this is a systematic change or a component of cyclic variations in the frequency and intensity of tropical storms. Changes in storm tracks might also result from global climate change; in this context, Cyclone Catarina was the first documented hurricane in the South Atlantic, striking the coast of Brazil in March 2004 as a Category 2 storm on the Saffir Simpson Hurricane Scale [37,38]. The cyclone killed at least three people and caused an estimated US $350 x 106 in damage in Brazil, and it is unclear whether this indicates an extremely unusual event, or the beginning of a new trend under global warming.
Changes in the natural system due to sea-level rise have many important direct socio-economic impacts on a range of sectors with the effect being overwhelmingly negative. For instance, flooding can damage key coastal infrastructure, the built environment, and agricultural areas, and in the worst case lead to significant mortality as occurred in 2008 when Cyclone Nargis devastated southern Myanmar. Erosion can lead to losses of the built environment and related infrastructure and have adverse consequences for sectors such as tourism and recreation. In addition to these direct impacts, there are indirect impacts such as negative effects on human health. For example, mental health problems increase after a flood , or the release of toxins from eroded landfills and waste sites which are commonly located in low-lying coastal areas, especially around major cities (e.g. Ref. ). Thus, sea-level rise has the potential to trigger a cascade of direct and indirect human impacts.
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