6.4.3 Key vulnerabilities and hotspots
A comprehensive assessment of the potential impacts of climate change must consider at least three components of vulnerability: exposure, sensitivity and adaptive capacity (Section 6.6). Significant regional differences in present climate and expected climate change give rise to different exposure among human populations and natural systems to climate stimuli (IPCC, 2001). The previous sections of this chapter broadly characterise the sensitivity and natural adaptive capacity (or resilience) of several major classes of coastal environments to changes in climate and sea-level rise. Differences in geological, oceanographic and biological processes can also lead to substantially different impacts on a single coastal system at different locations. Some global patterns and hotspots of vulnerability are evident, however, and deltas/estuaries (especially populated megadeltas), coral reefs (especially atolls), and ice-dominated coasts appear most vulnerable to either climate change or associated sea-level rise and changes. Low-lying coastal wetlands, small islands, sand and gravel beaches and soft rock cliffs may also experience significant changes.
An acceleration of sea-level rise would directly increase the vulnerability of all of the above systems, but sea-level rise will not occur uniformly around the world (Section 6.3.2). Variability of storms and waves, as well as sediment supply and the ability to migrate landward, also influence the vulnerability of many of these coastal system types. Hence, there is an important element of local to regional variation among coastal system types that must be considered when conducting site-specific vulnerability assessments.
Our understanding of human adaptive capacity is less developed than our understanding of responses by natural systems, which limits the degree to which we can quantify societal vulnerability in the world’s coastal regions. Nonetheless, several key aspects of human vulnerability have emerged. It is also apparent that multiple and concomitant non-climate stresses will exacerbate the impacts of climate change on most natural coastal systems, leading to much larger and detrimental changes in the 21st century than those of the 20th century. Table 6.8 summarises some of the key hotspots of vulnerability that often arise from the combination of natural and societal factors. Note that some examples such as atolls and small islands and deltas/megadeltas recur, stressing their high vulnerability.
Table 6.8. Key hotspots of societal vulnerability in coastal zones.
| Controlling factors | Examples from this Chapter |
|---|
| Coastal areas where there are substantial barriers to adaptation (economic, institutional, environmental, technical, etc.) | Venice, Asian megadeltas, atolls and small islands, New Orleans |
| Coastal areas subject to multiple natural and human-induced stresses, such as subsidence or declining natural defences | Mississippi, Nile and Asian megadeltas, the Netherlands, Mediterranean, Maldives |
| Coastal areas already experiencing adverse effects of temperature rise | Coral reefs, Arctic coasts (USA, Canada, Russia), Antarctic peninsula |
| Coastal areas with significant flood-plain populations that are exposed to significant storm surge hazards | Bay of Bengal, Gulf of Mexico/Caribbean, Rio de la Plata/Parana delta, North Sea |
| Coastal areas where freshwater resources are likely to be reduced by climate change | W. Africa, W. Australia, atolls and small islands |
| Coastal areas with tourist-based economies where major adverse effects on tourism are likely | Caribbean, Mediterranean, Florida, Thailand, Maldives |
| Highly sensitive coastal systems where the scope for inland migration is limited | Many developed estuarine coasts, low small islands, Bangladesh |
While physical exposure is an important aspect of the vulnerability for both human populations and natural systems to both present and future climate variability and change, a lack of adaptive capacity is often the most important factor that creates a hotspot of human vulnerability. Societal vulnerability is largely dependent upon development status (Yohe and Tol, 2002). Developing nations may have the societal will to relocate people who live in low-lying coastal zones but, without the necessary financial resources, their vulnerability is much greater than that of a developed nation in an identical coastal setting. Looking to the scenarios, the A2 SRES world often appears most vulnerable to climate change in coastal areas, again reflecting socio-economic controls in addition to the magnitude of climate change (Nicholls, 2004; Nicholls and Tol, 2006). Hence, development is not only a key consideration in evaluating greenhouse gas emissions and climate change, but is also fundamental in assessing adaptive capacity because greater access to wealth and technology generally increases adaptive capacity, while poverty limits adaptation options (Yohe and Tol, 2002). A lack of risk awareness or institutional capacity can also have an important influence on human vulnerability, as experienced in the United States during Hurricane Katrina.