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

12.4.6 Biodiversity

Climate change is affecting the physiology, phenology and distribution of European plant and animal species (e.g., Thomas et al., 2001; Warren et al., 2001; van Herk et al., 2002; Walther et al., 2002; Parmesan and Yohe, 2003; Root et al., 2003, 2005; Brommer, 2004; Austin and Rehfisch, 2005; Hickling et al., 2005, 2006; Robinson et al., 2005; Learmonth et al., 2006; Menzel et al., 2006a, b). A Europe-wide assessment of the future distribution of 1,350 plant species (nearly 10% of the European flora) under various SRES scenarios indicated that more than half of the modelled species could become vulnerable, endangered, critically endangered or committed to extinction by 2080 if unable to disperse (Thuiller et al., 2005). Under the most severe climate scenario (A1), and assuming that species could adapt through dispersal, 22% of the species considered would become critically endangered, and 2% committed to extinction. Qualitatively-similar results were obtained by Bakkenes et al. (2002). According to these analyses, the range of plants is very likely to expand northward and contract in southern European mountains and in the Mediterranean Basin. Regional studies (e.g., Theurillat and Guisan, 2001; Walther et al., 2005b) are consistent with Europe-wide projections.

An assessment of European fauna indicated that the majority of amphibian (45% to 69%) and reptile (61% to 89%) species could expand their range under various SRES scenarios if dispersal was unlimited (Araújo et al., 2006). However, if unable to disperse, then the range of most species (>97%) would become smaller, especially in the Iberian Peninsula and France. Species in the UK, south-eastern Europe and southern Scandinavia are projected to benefit from a more suitable climate, although dispersal limitations may prevent them from occupying new suitable areas (Figure 12.2). Consistent with these results, another Europe-wide study of 47 species of plants, insects, birds and mammals found that species would generally shift from the south-west to the north-east (Berry et al., 2006; Harrison et al., 2006). Endemic plants and vertebrates in the Mediterranean Basin are also particularly vulnerable to climate change (Malcolm et al., 2006). Habitat fragmentation is also likely to increase because of both climate and land-use changes (del Barrio et al., 2006).

Figure 12.2

Figure 12.2. Change in combined amphibian and reptile species richness under climate change (A1FI emissions; HadCM3 GCM), assuming unlimited dispersal. Depicted is the change between current and future species richness projected for two 30-year periods (2021 to 2050 and 2051 to 2080), using artificial neural networks. Increasing intensities of purple indicate a decrease in species richness, whereas increasing intensities of green represent an increase in species richness. Black, white and grey cells indicate areas with stable species richness: black grid cells show low species richness in both periods; white cells show high species richness; grey cells show intermediate species richness (Araújo et al., 2006).

Currently, species richness in inland freshwater systems is highest in central Europe declining towards the south and north because of periodic droughts and salinisation (Declerck et al., 2005). Increased projected runoff and lower risk of drought in the north will benefit the fauna of these systems (Lake, 2000; Daufresne et al., 2003), but increased drought in the south will have the opposite effect (Alvarez Cobelas et al., 2005). Higher temperatures are likely to lead to increased species richness in freshwater ecosystems in northern Europe and decreases in parts of south-western Europe (Gutiérrez Teira, 2003). Invasive species may increase in the north (McKee et al., 2002). Woody plants may encroach upon bogs and fens (Weltzin et al., 2003). Cold-adapted species will be forced further north and upstream; some may eventually disappear from Europe (Daufresne et al., 2003; Eisenreich, 2005).

Sea-level rise is likely to have major impacts on biodiversity. Examples include flooding of haul-out sites used for breeding nurseries and resting by seals (Harwood, 2001). Increased sea temperatures may also trigger large scale disease-related mortality events of dolphins in the Mediterranean and of seals in Europe (Geraci and Lounsbury, 2002). Seals that rely on ice for breeding are also likely to suffer considerable habitat loss (Harwood, 2001). Sea-level rise will reduce habitat availability for bird species that nest or forage in low-lying coastal areas. This is particularly important for the populations of shorebirds that breed in the Arctic and then winter on European coasts (Rehfisch and Crick, 2003). Lowered water tables and increased anthropogenic use and abstraction of water from inland wetlands are likely to cause serious problems for the populations of migratory birds and bats that use these areas while on migration within Europe and between Europe and Africa (Robinson et al., 2005).