Geoscience Reference
In-Depth Information
Impacts on ecosystems in the northern regions, however, are far more speculative
because of the lack of agreement amongst climate models as to the direction and
magnitude of rainfall change (CSIRO and BoM, 2007).
Can Australian species adapt?
The three main options available to species in the face of a rapidly changing
environment are (i) to shift their distribution, and thus evade the change by
moving elsewhere to more suitable conditions, (ii) to undergo genetic change,
and (iii) to stay put and adapt
in situ
(Hughes, 2012). These three options are
not mutually exclusive. Globally, many species are already responding to recent
climate change, and these responses provide some clues as to future adaptive
capacity (see
Table 4.2
; end of this chapter). Unfortunately the general lack
of long-term datasets in Australia limits our understanding of autonomous
adaptation by Australian species, but some general conclusions can be drawn.
Shifting ranges
As climate zones continue to shift across the landscape, a significant deter-
minant of species' ability to cope will be the rate at which their distributions
can 'keep up'. Velocities of climate change over the past 60 years calculated for
the geographic ranges of Australian birds vary from 1-76km per decade, with
mean rates of 7.7 and 7.6km per decade for temperature and rainfall respectively
(Van Der Wal et al., 2012). These rates are commensurate with those observed
for range shifts in some species in recent decades. A global meta-analysis by
Parmesan and Yohe (2003), for example, found that terrestrial species had moved
poleward by an average of 6.1km per decade. More recent estimates, however,
found rates of range shift two to three times higher (16.9km per decade) (Chen
et al.,
2011), suggesting that species shifts may be accelerating. These two compi-
lations, however, are overwhelmingly dominated by species from the Northern
Hemisphere and it remains to be seen if Australian species are able to disperse as
rapidly. Further, most of the species shifts reported are for mobile animals such as
birds, butterflies and pelagic marine species, with few for mammals and reptiles,
and even fewer for plants. As indicated above, the low topographic relief and arid
interior of the continent will present formidable barriers to dispersal, as will the
highly fragmented nature of the landscape. Hard limits to range shifts will also
be particularly acute for species on mountaintops, small islands, or those whose
ranges abut southern coastlines (Hughes, 2012).
Genetic change
Increased thermal stress and drought are likely to impose strong selective pressure
on species. Species with short generation times, high reproductive output and
substantial genetic variability within populations will have the greatest potential
to adapt via natural selection. Some species have undergone changes in genetic
