19.3.3 Regional vulnerabilities
Many of the societal impacts discussed above will be felt within the regions assessed as part of the AR4. At a regional and sub-regional scale, vulnerabilities can vary quite considerably. For example, while mid- and high-latitude areas would have increased crop yields up to about 3°C of warming, low-latitude areas would face decreased yields and increased risks of malnutrition at lower levels of warming (•/*) (Chapter 5 Section 5.4.2; Parry et al., 2004).
Africa is likely to be the continent most vulnerable to climate change. Among the risks the continent faces are reductions in food security and agricultural productivity, particularly regarding subsistence agriculture (Chapter 9 Sections 9.4.4 and 9.6.1; Parry et al., 2004; Elasha et al., 2006), increased water stress (Chapter 9 Section 9.4.1) and, as a result of these and the potential for increased exposure to disease and other health risks, increased risks to human health (Chapter 9 Section 9.4.3). Other regions also face substantial risks from climate change. Approximately 1 billion people in South, South-East, and East Asia would face increased risks from reduced water supplies (•) (Chapter 10 Section 10.4.2), decreased agricultural productivity (•) (Chapter 10 Section 10.4.1.1), and increased risks of floods, droughts and cholera (*) (Chapter 10 Section 10.4.5). Tens of millions to over a hundred million people in Latin America would face increased risk of water stress (•) (Chapter 13 Section 13.4.3). Low-lying, densely populated coastal areas are very likely to face risks from sea-level rise and more intense extreme events (Chapter 13 Section 13.4.4). The combination of land-use changes and climate change is very likely to reduce biodiversity substantially (Chapter 13 Section 126.96.36.199).
There is very high confidence that human settlements in polar regions are already being adversely affected by reduction in ice cover and coastal erosion (Chapter 15 Section 15.2.2). Future climate change is very likely to result in additional disruption of traditional cultures and loss of communities. For example, warming of freshwater sources poses risks to human health because of transmission of disease (*) (Martin et al., 2005). Shifts in ecosystems are very likely to alter traditional use of natural resources, and hence lifestyles.
Small islands, particularly several small island states, are likely to experience large impacts due to the combination of higher exposure, for example to sea-level rise and storm surge, and limited ability to adapt (Chapter 16 Sections 16.ES, 16.2.1 and 16.4). There is very high confidence that many islands are already experiencing some negative effects of climate change (Chapter 1 Section 1.3.3; Chapter 16 Section 16.4). The long-term sustainability of small-island societies is at great risk from climate change, with sea-level rise and extreme events posing particular challenges on account of their limited size, proneness to natural hazards and external shocks combined with limited adaptive capacity and high costs relative to GDP. Subsistence and commercial agriculture on small islands is likely to be adversely affected by climate change and sea-level rise, as a result of inundation, seawater intrusion into freshwater lenses, soil salinisation, decline in water supply and deterioration of water quality (Chapter 16 Executive Summary and Section 16.4). A group of low-lying islands, such as Tarawa and Kiribati, would face average annual damages of 17 to 18% of its economy by 2050 under the SRES A2 and B2 scenarios (•) (Chapter 16 Section 16.4.3).
Even in developed countries, there are many vulnerabilities. Arnell (2004) estimated a 40 to 50% reduction in runoff in southern Europe by the 2080s (associated with a 2 to 3°C increase in global mean temperature). Fires will very likely continue to increase in arid and semi-arid areas such as Australia and the western USA, threatening development in wildland areas (Chapter 4 Section 4.4.4; Chapter 11 Section 11.3.1; Chapter 14 Box 14.1 and Section 14.4.4; Westerling et al., 2006). Climate change is likely to increase the frequency and intensity of extreme heat events, as well as concentrations of air pollutants, such as ozone, which increase mortality and morbidity in urban areas (see Chapters 8, 11, 12 and 14).