Uk

4 northern butterflies (1970-2004)

2 species retreating 73 and 80 km north, 1 species retreating 149 m uphill

Franco et al., 2006

Central Spain

16 butterfly species

Upward shift of 210 m in the lower elevational limit between 1967-73 and 2004

Wilson et al., 2005

Britain

37 dragonfly and damselfly species

36 out of 37 species shifted northwards (mean 84 km) from 1960-70 to 1985-95

Hickling et al., 2005

Czech Republic

15 of 120 butterfly species

Uphill shifts in last 40 years

Konvicka et al., 2003

Poland

White stork (Ciconia ciconia)

Range expansions in elevation, 240 m during last 70 years

Tryjanowski et al., 2005

Australia

3 macropods and 4 feral mammal species

Range expansions to higher altitudes

Green and Pickering, 2002

Australia

Grey-headed flying fox

Contraction of southern boundary poleward by 750 km since 1930s

Tidemann et al., 1999

Senegal, West Africa

126 tree and shrub species (1945-1993)

Up to 600 m/yr latitudinal shift of ecological zones due to decrease in precipitation

Gonzalez, 2001

Russia, Bulgaria, Sweden, Spain, New Zealand, USA

Tree line

Advancement towards higher altitudes

Meshinev et al., 2000; Kullman, 2002; PeƱuelas and Boada, 2003; Millar and Herdman, 2004

Canada

Bioclimatic taiga-tundra ecotone indicator

12 km/yr northward shift (NDVI data)

Fillol and Royer, 2003

Alaska

Arctic shrub vegetation

Expansion into previously shrub-free areas

Sturm et al., 2001

European Alps

Alpine summit vegetation

Elevational shift, increased species-richness on mountain tops

Grabherr et al., 2001 ; Pauli et al., 2001; Walther et al., 2005a

Montana, USA

Arctic-alpine species

Decline at the southern margin of range

Lesica and McCune, 2004

Germany, Scandinavia

English holly {Ilex aquifolium)

Poleward shift of northern margin due to increasing winter temperatures

Waltheretal., 2005b

logging or firewood collection can be of considerable relevance. In parts of the European Alps, for example, the tree line is influenced by past and present land-use impacts (Theurillat and Guisan, 2001; Carnelli et al., 2004). A climate warming-induced upward migration of alpine plants in the high Alps (Grabherr et al., 2001; Pauli et al., 2001) was observed to have accelerated towards the beginning of the 21st century (Walther et al., 2005a). Species ranges of alpine plants also have extended to higher altitudes in the Norwegian Scandes (Klanderud and Birks, 2003). Species in alpine regions, which are often endemic and of high importance for plant diversity (Vare et al., 2003), are vulnerable to climate warming, most probably because of often restricted climatic ranges, small isolated populations, and the absence of suitable areas at higher elevations in which to migrate (Pauli et al., 2003).

1.3.53 Climate-linked extinctions and invasions

Key indicators of a species' risk of extinction (global loss of all individuals) or extirpation (loss of a population in a given location) include the size of its range, the density of individuals within the range, and the abundance of its preferred habitat within its range. Decreases in any of these factors (e.g., declining range size with habitat fragmentation) can lower species population size (Wilson et al., 2004). Each of these factors can be directly affected by rapid global warming, but the causes of extinctions/extirpations are most often multifactorial. For example, a recent extinction of around 75 species of frogs, endemic to the American tropics, was most probably due to a pathogenic fungus (Batrachochytrium), outbreaks of which have been greatly enhanced by global warming (Pounds et al., 2006). Other examples of declines in populations and subsequent extinction/extirpation are found in amphibians around the world (Alexander and Eischeid, 2001; Middleton et al., 2001; Ron et al., 2003; Burrowes et al., 2004). Increasing climatic variability, linked to climate change, has been found to have a significant impact on the extinction of the butterfly Euphydryas editha bayensis (McLaughlin et al., 2002a, 2002b). Currently about 20% of bird species (about 1,800) are threatened with extinction, while around 5% are already functionally extinct (e.g., small inbred populations) (Sekercioglu et al., 2004). The pika (Ochotona princeps), a small mammal found in mountains of the western USA, has been extirpated from many slopes (Beever et al., 2003). New evidence suggests that climate-driven extinctions and range retractions are already widespread, which have been poorly reported due, at least partly, to a failure to survey the distributions of species at sufficiently fine resolution to detect declines and to attribute such declines to climate change (Thomas et al., 2006).

A prominent cause of range contraction or loss of preferred habitat within a species range is invasion by non-native species. Fluctuation in resource availability, which can be driven by climate, has been identified as the key factor controlling invasibility (Davis et al., 2000). The clearest evidence for climate variability triggering an invasion occurs where a suite of species with different histories of introduction spread en-masse during periods of climatic amelioration (Walther, 2000; Walther et al., 2002). Climate change will greatly affect indigenous species on sub-Antarctic islands, primarily due to warmer climates allowing exotic species, such as the house mouse (Mus musculus) and springtails (Collembola spp.), to become established and proliferate (Smith, 2002). A prominent example is that of exotic thermophilous plants spreading into the native flora of Spain, Ireland and Switzerland (Pilcher and Hall, 2001; Sobrino et al., 2001). Elevated CO2 might also contribute to the spread of weedy, non-indigenous plants (Hattenschwiler and Korner, 2003).

135.4 Changes in morphology and reproduction

A change in fecundity is one of the mechanisms altering species distributions (see Section 1.3.5.2). Temperature can affect butterfly egg-laying rate and microhabitat selection; recent warming has been shown to increase egg-laying and thus population size for one species (Davies et al., 2006). The egg sizes of many bird species are changing with increasing regional temperatures, but the direction of change varies by species and location. For example, in Europe, the egg size of pied flycatchers increased with regional warming (Jarvinen, 1994, 1996). In southern Poland, the size of red-backed shrikes' eggs has decreased, probably due to decreasing female body size, which is also associated with increasing temperatures (Tryjanowski et al., 2004). The eggs of European barn swallows are getting larger with increasing temperatures and their breeding season is occurring earlier. Additionally, in the eggs, concentrations of certain maternally supplied nutrients, such as those affecting hatchability, viability and parasite defence, have also increased with warming (Saino et al., 2004). Studies from eastern Poland, Asia, Europe and Japan have found that various birds and mammals exhibit trends toward larger body size, probably due to increasing food availability, with regionally increasing temperatures (Nowakowski, 2002; Yom-Tov, 2003; Kanuscak et al., 2004; Yom-Tov and Yom-Tov, 2004). Reproductive success in polar bears has declined, resulting in a drop in body condition, which in turn is due to melting Arctic Sea ice. Without ice, polar bears cannot hunt seals, their favourite prey (Derocher et al., 2004).

These types of changes are also found in insects and plants. The evolutionary lengthening and strengthening of the wings of some European Orthoptera and butterflies has facilitated their northward range expansion but has decreased reproductive output (Hill et al., 1999a; Thomas et al., 2001a; Hughes et al., 2003a; Simmons and Thomas, 2004). The timing and duration of the pollen season, as well as the amount of pollen produced (Beggs, 2004), have been found to be affected by regional warming (see Section 1.3.7.4).

135.5 Species community changes and ecosystem processes

In many parts of the world, species composition has changed

(Walther et al., 2002), partly due to invasions and distributional changes. The assemblages of species in ecological communities reflect interactions among organisms as well as between organisms and the abiotic environment. Climate change, extreme climatic events or other processes can alter the composition of species in an ecosystem because species differentially track their climate tolerances. As species in a natural community do not respond in synchrony to such external pressures, ecological communities existing today could easily be disaggregated (Root and Schneider, 2002).

Species diversity in various regions is changing due to the number of species shifting, invading or receding (Tamis et al., 2001; EEA, 2004) (see Sections 1.3.5.2 and 1.3.5.3). Average species richness of butterflies per 20 km grid cell in the UK increased between 1970-1982 and 1995-1999, but less rapidly than would have been expected had all species been able to keep up with climate change (Menendez et al., 2006). In non-fragmented Amazon forests, direct effects of CO2 on photosynthesis, as well as faster forest turnover rates, may have caused a substantial increase in the density of lianas over the last two decades (Phillips et al., 2004). Although many species-community changes are also attributable to landscape fragmentation, habitat modification and other non-climate drivers, many studies show a high correlation between changes in species composition and recent climate change, also via the frequency of weather-based disturbances (Hughes, 2000; Pauli et al., 2001; Parmesan and Yohe, 2003). Examples of altered or stable synchrony in ecosystems via multi-species interactions, e.g., the pedunculate oak-winter moth-tit food chain, are still fairly rare (van Noordwijk et al., 1995; Buse et al., 1999).

1.35.6 Species evolutionary processes

Recent evolutionary responses to climate change have been addressed in reviews (Thomas, 2005; Bradshaw and Holzapfel, 2006). Changes have taken place in the plants preferred for egg-laying and feeding of butterflies, e.g., a broadened diet facilitated the colonisation of new habitats during range extension in the UK (Thomas et al., 2001a). The pitcher-plant mosquito in the USA has prolonged development time in late summer by the evolution of changed responses to day length (Bradshaw and Holzapfel, 2001; Bradshaw et al., 2003). The blackcap warbler has recently extended its overwintering range northwards in Europe by evolving a change in migration direction (Berthold et al., 2003). Insects expanding their ranges have undertaken genetically-based changes in dispersal morphology, behaviour and other life-history traits, as 'good colonists' have been at a selective advantage (Hill et al., 1999a; Thomas et al., 2001b; Hughes et al., 2003a; Simmons and Thomas, 2004). Genetic changes in Drosophila melanogaster in eastern coastal Australia over 20 years are likely to reflect increasingly warmer and drier conditions (Umina et al., 2005). Evolutionary processes are also demonstrated in the timing of reproduction associated with climate change in North American red squirrels (Berteaux et al., 2004). There is no evidence so far that the temperature response rates of plants have changed over the last century (Menzel et al., 2005a).

1.35.7 Summary of terrestrial biological systems

The vast majority of studies of terrestrial biological systems reveal notable impacts of global warming over the last three to five decades, which are consistent across plant and animal taxa: earlier spring and summer phenology and longer growing seasons in mid- and higher latitudes, production range expansions at higher elevations and latitudes, some evidence for population declines at lower elevational or latitudinal limits to species ranges, and vulnerability of species with restricted ranges, leading to local extinctions. Non-climate synergistic factors can significantly limit migration and acclimatisation capacities.

While a variety of methods have been used that provide evidence of biological change over many ecosystems, there remains a notable absence of studies on some ecosystems, particularly those in tropical regions, due to a significant lack of long-term data. Furthermore, not all processes influenced by warming have yet been studied. Nevertheless, in the large majority of studies, the observed trends found in species correspond to predicted changes in response to regional warming in terms of magnitude and direction. Analyses of regional differences in trends reveal that spatio-temporal patterns of both phenological and range changes are consistent with spatiotemporal patterns expected from observed climate change.

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