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composition consistent with responding to recent warming (Umina et al., 2005),
but very few species have been studied in this respect (Hoffmann and Sgro,
2011). But simply assuming that short-lived species will be able to adapt quickly
enough is simplistic. A recent study of 94 species of
Drosophila
, the poster species
of rapid evolution research, found that climate adaptation by the fruit fly was
slower than expected. It is also likely that many species with narrow geographic
limits will have tightly constrained evolutionary limits of thermal tolerance
(Kellermann et al., 2012).
Phenotypic plasticity
Changes in behaviour, especially in relation to the timing of life cycles, have
been the most commonly observed responses to climatic change thus far.
Compilations of hundreds of datasets for Northern Hemisphere species show
consistent advances in the seasonal timing of biological events in all major
taxonomic groups studied. Thackeray et al. (2010), for example, show that the
timing of life cycles of UK species has, on average, advanced 0.39 days per year,
over a period of warming of 0.04-0.05°C per year. While linear extrapolations
from these trends are probably simplistic for most species, they do indicate that
phenological advances in the order of a month or more for a 4°C warming are
possible. Given that phenological responses are already known to be highly
variable even among groups of closely related species, the potential for increas-
ingly decoupled interactions between species (such as between plants and
pollinators) is likely to be an important driver of community-level change.
Observed changes consistent with having a climate change 'signal' are relatively
few in Australia - once again presumably due to the paucity of data rather than
because Australian species are responding differently from those elsewhere.
Those that have been recorded, such as the earlier arrival and later departure of
migratory birds (Beaumont, McAllan and Hughes, 2006), and earlier emergence
of butterflies (Kearney et al.,
2010a), are generally consistent in magnitude and
direction with those elsewhere.
Conclusions: What could we lose?
Current global species extinction rates already exceed the highest rates seen in
the fossil record (Barnosky et al.,
2011). These extinctions are mostly attributed
to habitat loss, invasive species and direct exploitation. However, recent climate
change has already been linked to population-level extinctions and declines in
terrestrial mammals, birds, lizards, butterflies and some plants (e.g. McLaughlin
et al., 2002; Sinervo et al., 2010) and has likely contributed to the extinctions
of about 80 tropical amphibians in Central and South America (Pounds et al.,
2006; McMenamin and Hannah, 2012).
Loss of only those species already considered threatened would constitute a
mass extinction event of a similar magnitude to the five previous extinction
episodes in the earth's history (Barnosky et al., 2011). Most global estimates
