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'A1 World'

'A2 World'

'B1 World'

'B2 World'

Population (2080s) (billions)3

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.

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.

Table 6.2. Main climate drivers for coastal systems (Figure 6.1), their trends due to climate change, and their main physical and ecosystem effects. (Trend: t increase; ? uncertain; R regional variability).

Climate driver (trend)

Main physical and ecosystem effects on coastal systems (discussed in Section 6.4.1)

CO2 concentration (t)

Increased CO2 fertilisation; decreased seawater pH (or 'ocean acidification') negatively impacting coral reefs and other pH sensitive organisms.

Sea surface temperature (t, R)

Increased stratification/changed circulation; reduced incidence of sea ice at higher latitudes; increased coral bleaching and mortality (see Box 6.1); poleward species migration; increased algal blooms

Sea level (t, R)

Inundation, flood and storm damage (see Box 6.2); erosion; saltwater intrusion; rising water tables/impeded drainage; wetland loss (and change).

Storm intensity (t, R)

Increased extreme water levels and wave heights; increased episodic erosion, storm damage, risk of flooding and defence failure (see Box 6.2).

Storm frequency (?, R) Storm track (?, R)

Altered surges and storm waves and hence risk of storm damage and flooding (see Box 6.2).

Wave climate (?, R)

Altered wave conditions, including swell; altered patterns of erosion and accretion; re-orientation of beach plan form.

Run-off (R)

Altered flood risk in coastal lowlands; altered water quality/salinity; altered fluvial sediment supply; altered circulation and nutrient supply.

Table 6.3. Projected global mean climate parameters relevant to coastal areas at the end of the 21st century for the six SRES marker scenarios (from Meehl et al., 2007).

Climate driver

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