Responding To Sea Level Rise

General scientific understanding of people's vulnerability and ability to adapt to sea level rise and other climate changes has increased substantially in recent years, though place-based, sector-specific knowledge remains extremely limited. Developing countries are expected to generally face greater challenges in dealing with the impacts of rising sea levels because of large exposed populations and lower adaptive capacity—which is largely a function of economic, technological, and knowledge resources, social capital, and well-functioning institutions (Adger et al., 2007; Nicholls et al., 2007). However, even in developed countries like the United States, significant gaps remain in our understanding of the impacts of sea level rise, especially for specific locations (Moser, 2009a), as well as considerable challenges in translating our greater adaptive capacity into real adaptation action on the ground (Adger et al., 2007, 2009b;

NRC, 2010a; O'Brien et al., 2006; Repetto, 2008). Certain technological options such as seawalls and levees are not feasible in all locations, and in many they could negatively impact the coastal ecology, beach recreation and tourism, and other social values (e.g., aesthetics). At the same time, a wide range of barriers and constraints make "soft" solutions equally challenging—these include changes in land use, planning, and, ultimately, retreat from the shoreline, with the associated costs and social and ecological consequences. Such constraints and limits on adaptation are increasingly recognized and researched (Adger et al., 2009b; Moser and Tribbia, 2006; Moser et al., 2008; NRC, 2010a). While there is extensive research about, and experience dealing with, coastal hazards, significant further research is required to determine the most appropriate, cost-effective, least ecologically damaging, and most socially acceptable adaptation options in the face of significantly faster rates of sea level rise than has been historically experienced. Past coastal hazards management approaches may not be ecologically sustainable or economically affordable in light of some of the high-end sea level rise projections.

While many research questions about managing coastal ecosystems and hazards remain (see, e.g., JSOST, 2007), the fundamental best practices are well known and include building new structures, elevating existing structures above flood elevation, and maintaining dunes as storm buffers. However, these measures are not frequently employed because underlying incentives and self-reinforcing factors favor continued development in at-risk areas, structural protection, and repeated emergency intervention (Burby, 1998; Kunreuther, 2008; Mileti, 1999; Platt, 1996, 1999). An additional challenge is how to evaluate and weigh near-term costs and benefits against long-term costs and benefits, given that neither is known with much precision and such evaluations are inherently place-specific. A critical research topic is how to foster adaptive coastal management actions with a long-term, systemic perspective while avoiding the worst economic, social, and ecological consequences for coastal areas (see also Chapter 4). Finally, little is known about local vulnerability to sea level rise in the context of multiple stresses, such as increased storm surge or rainfall rates, or about the feasibility and acceptability of various adaptation options. These issues are discussed in a recent synthesis of the impacts of climate change and vulnerability of coastal areas of the U.S. mid-Atlantic region (CCSP, 2009a; Najjar et al., 2009; Wu et al., 2009).

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