IPCC Fourth Assessment Report: Climate Change 2007
Climate Change 2007: Working Group II: Impacts, Adaptation and Vulnerability

6.3.1 Environmental and socio-economic trends

In the SRES, four families of socio-economic scenarios (A1, A2, B1 and B2) represent different world futures in two distinct dimensions: a focus on economic versus environmental concerns, and global versus regional development patterns. In all four cases, global gross domestic product (GDP) increases substantially and there is economic convergence at differing rates. Global population also increases to 2050 but, in the A1/B1 futures, the population subsequently declines, while in A2/B2 it continues to grow throughout the 21st century (see Chapter 2, Box 2.2). Relevant trends for coastal areas under the SRES scenarios are described in Table 6.1.

Table 6.1. Selected global non-climatic environmental and socio-economic trends relevant to coastal areas for the SRES storylines. Regional and local deviations are expected.

Environmental and socio-economic factors Non-climatic changes and trends for coastal and low-lying areas (by SRES Future) 
 ‘A1 World’ ‘A2 World’ ‘B1 World’ ‘B2 World’ 
Population (2080s) (billions)a 1.8 to 2.4 3.2 to 5.2 1.8 to 2.4 2.3 to 3.4 
Coastward migration Most likely Less likely More likely Least likely 
Human-induced subsidenceb More likely Less likely 
Terrestrial freshwater/sediment supply (due to catchment management) Greatest reduction Large reduction Smallest reduction Smaller reduction 
Aquaculture growth Large increase Smaller increase 
Infrastructure growth Largest Large Smaller Smallest 
Extractive industries Larger Smaller 
Adaptation response More reactive More proactive 
Hazard risk management Lower priority Higher priority 
Habitat conservation Low priority High priority 
Tourism growth Highest High High Lowest 

a Population living both below 100 m elevation above sea level and within 100 km distance of the coast – uncertainty depends on assumptions about coastward migration (Nicholls, 2004).

b Subsidence due to sub-surface fluid withdrawal and drainage of organic soils in susceptible coastal lowlands.

National coastal socio-economic scenarios have also been developed for policy analysis, including links to appropriate climate change scenarios. Examples include the UK Foresight Flood and Coastal Defence analysis (Evans et al., 2004a,b; Thorne et al., 2006), and the US National Assessment (NAST, 2000), while model-based methods have been applied to socio-economic futures in the Ebro delta, Spain (Otter, 2000; Otter et al., 2001). However, socio-economic scenarios of coastal areas are underdeveloped relative to climate and sea-level scenarios.