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

6.4.2 Consequences for human society

Since the TAR, global and regional studies on the impacts of climate change are increasingly available, but few distinguish the socio-economic implications for the coastal zone (see also Section 6.5). Within these limits, Table 6.4 provides a qualitative overview of climate-related changes on the various socio-economic sectors of the coastal zone discussed in this section.

The socio-economic impacts in Table 6.4 are generally a product of the physical changes outlined in Table 6.2. For instance, extensive low-lying (often deltaic) areas, e.g., the Netherlands, Guyana and Bangladesh (Box 6.3), and oceanic islands are especially threatened by a rising sea level and all its resulting impacts, whereas coral reef systems and polar regions are already affected by rising temperatures (Sections 6.2.5 and 6.4.1). Socio-economic impacts are also influenced by the magnitude and frequency of existing processes and extreme events, e.g., the densely populated coasts of East, South and South-east Asia are already exposed to frequent cyclones, and this will compound the impacts of other climate changes (see Chapter 10). Coastal ecosystems are particularly at risk from climate change (CBD, 2003; Section 6.4.1), with serious implications for the services that they provide to human society (see Section 6.2.2; Box 6.4 and Chapter 4, Section 4.4.9).

Table 6.4. Summary of climate-related impacts on socio-economic sectors in coastal zones.

 Climate-related impacts (and their climate drivers in Figure 6.1
Coastal socio-economic sector Temperature rise (air and seawater) Extreme events (storms, waves) Floods (sea level, runoff) Rising water tables (sea level) Erosion (sea level, storms, waves) Salt water intrusion (sea level, runoff) Biological effects (all climate drivers) 
Freshwater resources X X X X  X 
Agriculture and forestry X X X X  X 
Fisheries and aquaculture X X  X X 
Health X X X  X X 
Recreation and tourism X X  X  X 
Biodiversity X X X X X X X 
Settlements/ infrastructure X X X X X X  

X = strong; x= weak; – = negligible or not established.

Since the TAR, some important observations on the impacts and consequences of climate change on human society at coasts have emerged. First, significant regional differences in climate change and local variability of the coast, including human development patterns, result in variable impacts and adjustments along the coast, with implications for adaptation responses (Section 6.6). Second, human vulnerability to sea-level rise and climate change is strongly influenced by the characteristics of socio-economic development (Section 6.6.3). There are large differences in coastal impacts when comparing the different SRES worlds which cannot be attributed solely to the magnitude of climate change (Nicholls and Lowe, 2006; Nicholls and Tol, 2006). Third, although the future magnitude of sea-level rise will be reduced by mitigation, the long timescales of ocean response (Box 6.6) mean that it is unclear what coastal impacts are avoided and what impacts are simply delayed by the stabilisation of greenhouse gas concentration in the atmosphere (Nicholls and Lowe, 2006). Fourth, vulnerability to the impacts of climate change, including the higher socio-economic burden imposed by present climate-related hazards and disasters, is very likely to be greater on coastal communities of developing countries than in developed countries due to inequalities in adaptive capacity (Defra, 2004; Section 6.5). For example, one quarter of Africa’s population is located in resource-rich coastal zones and a high proportion of GDP is exposed to climate-influenced coastal risks (Nyong and Niang-Diop, 2006; Chapter 9). In Guyana, 90% of its population and important economic activities are located within the coastal zone and are threatened by sea-level rise and climate change (Khan, 2001). Low-lying densely populated areas in India, China and Bangladesh (see Chapter 10) and other deltaic areas are highly exposed, as are the economies of small islands (see Chapter 16).

Box 6.4. Hurricane Katrina and coastal ecosystem services in the Mississippi delta

Whereas an individual hurricane event cannot be attributed to climate change, it can serve to illustrate the consequences for ecosystem services if the intensity and/or frequency of such events were to increase in the future. One result of Hurricane Katrina, which made landfall in coastal Louisiana on 29th August 2005, was the loss of 388 km2 of coastal wetlands, levees and islands that flank New Orleans in the Mississippi River deltaic plain (Barras, 2006) (Figure 6.7). (Hurricane Rita, which struck in September 2005, had relatively minor effects on this part of the Louisiana coast which are included in this estimate.) The Chandeleur Islands, which lie south-east of the city, were reduced to roughly half of their former extent as a direct result of Hurricane Katrina. Collectively, these natural systems serve as the first line of defence against storm surge in this highly populated region. While some habitat recovery is expected, it is likely to be minimal compared to the scale of the losses. The Chandeleur Islands serve as an important wintering ground for migratory waterfowl and neo-tropical birds; a large population of North American redhead ducks, for example, feed on the rhizomes of sheltered sea grasses leeward of the Chandeleur Islands (Michot, 2000). Historically the region has ranked second only to Alaska in U.S. commercial fisheries production, and this high productivity has been attributed to the extent of coastal marshes and sheltered estuaries of the Mississippi River delta. Over 1800 people lost their lives (Graumann et al., 2005) during Hurricane Katrina and the economic losses totalled more than US$100 billion (NOAA, 2007). Roughly 300,000 homes and over 1,000 historical and cultural sites were destroyed along the Louisiana and Mississippi coasts (the loss of oil production and refinery capacity helped to raise global oil prices in the short term). Post-Katrina, some major changes to the delta’s management are being advocated, most notably abandonment of the “bird-foot delta” where artificial levees channel valuable sediments into deep water (EFGC, 2006; NRC, 2006). The aim is to restore large-scale delta building processes and hence sustain the ecosystem services in the long term. Hurricane Katrina is further discussed in Box 7.4 (Chapter 7) and Chapter 14.

Figure 6.7

Figure 6.7. The Mississippi delta, including the Chandeleur Islands. Areas in red were converted to open water during the hurricane. Yellow lines on index map of Louisiana show tracks of Hurricane Katrina on right and Hurricane Rita on left. (Figure source: U.S. Geological Survey, modified from Barras, 2006.)