1.3.5.6 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).

1.3.5.7 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 spatio-temporal patterns expected from observed climate change.