Climate change will affect human settlements. Settlements that depend heavily on commercial fishing, subsistence agriculture and other natural resources are particularly vulnerable. Also at risk are low-lying areas and deltas, large coastal cities, squatter camps located in flood plains and on steep hillsides, settlements in forested areas where seasonal wildfires may increase, and settlements stressed by population growth, poverty and environmental degradation. In all cases, the poorest people will be the most affected. Though climate change will often have less impact on this sector than will economic development, technological change, and other social and environmental forces, it is likely to exacerbate the total stress on settlements.

Infrastructure will become more vulnerable to flooding and landslides. More intense and frequent precipitation events are expected to intensify urban flooding. The flood risks may also increase for settlements along rivers and within flood plains. The risk of more landslides is greatest for hillside areas.

Tropical cyclones are expected to become more destructive in some areas. Also known as hurricanes and typhoons, these massive storm systems combine the effects of heavy rainfall, high winds, and storm surge and sea-level rise. The risk is that warmer oceans will increase the frequency and intensity of such storms.

Warming, dryness and flooding could undermine water supplies. Settlements in regions that are already water-deficient – including much of North Africa, the Middle East, Southwest Asia, portions of western North America and some Pacific islands – can be expected to face still-higher demands for water as the climate warms. There are no obvious low-cost ways in which to obtain increased freshwater supplies in many of these regions. In some regions, repeated flooding could create problems with water quality.

The danger of fire could increase. However, there are many uncertainties about how hotter and drier weather will combine with other factors to affect the risk of fire.

Agriculture and fisheries are sensitive to climate change. In some cases agricultural yields may be reduced by up to several tens of percent as a result of hotter weather, greater evaporation, and lower precipitation, particularly in mid-continental growing regions. However, other regions may benefit and could experience higher yields. Fisheries will be affected because changes in ocean conditions caused by warming can substantially impact the locations and types of target species.

Heat waves would become a greater threat to human health and productivity. Heat waves have their most severe effects on the old, the chronically ill and the very young. The likely effects on the overall death rate are less clear. Stronger urban heat-island effects would further exacerbate the oppressive effects of heat waves by increasing the temperatures experienced in the summer by up to several degrees Centigrade. Meanwhile, as the weather becomes very warm, the economic productivity of unprotected and outdoor populations declines.

Sea-level rise will affect coastal infrastructure and resource-based industries. Many coastlines are highly developed and contain human settlements, industry, ports, and other infrastructure. Many of the most vulnerable regions include some small island nations, low-lying deltas, developing countries and densely populated coasts that currently lack extensive sea and coastal defense systems. Several industries such as tourism and recreation – the principle earners for many island economies – are particularly dependent on coastal resources.

Energy demand is sensitive to climate change. Heating requirements at mid- and high latitudes and altitudes would decline but cooling requirements would increase. The net overall impact of these changes on energy use would depend on local circumstances. For example, if temperature increases take place primarily at night and during the winter months, the demand for heating would be less, as would the demand for cooling and for irrigation. Meanwhile, energy supply systems will be vulnerable to changes resulting from global warming. For example, increased water deficits, less winter snowfall to fill summer streams, and more demand for freshwater supplies would affect hydropower production.

Infrastructure in permafrost regions is vulnerable to warming. Permafrost melting is a threat to infrastructure in these regions because it would increase landslides and reduce the stability of foundations for structures. Other impacts would include greater damage from freeze-thaw cycles. In addition, melting permafrost is thought to be a source of methane and carbon dioxide emissions.

Local capacity is critical to successful adaptation. The capacity of local communities to adapt tends to be strongly correlated with wealth, human capital and institutional strength. The most effective sustainable solutions are those that are strongly supported – and often developed – locally. The role of higher-level bodies is then to provide technical assistance and institutional support. A clear message for policy-makers is to always anticipate the likely future impacts of climate change when they take decisions regarding human settlements and make investments in infrastructure.