Environmental Engineering Reference
In-Depth Information
Contrary to what has been found for spring phenology, trends in autumn
phenologies are not as clear. In the spring, animals are getting ready to breed
and are driven to breed as earlier as possible. Therefore, these species ar-
rive earlier as the springtime warms, which in turn means they need earlier
availability of required resources such as food. If a needed resource is not
shifting in concert with a species exhibiting shifts, this could cause some
decline in breeding success, for example. In the autumn some leaf fall is
delayed, and some migrating animals move their southern migration date
earlier than it was before, while others migrate south at roughly the same
time that they always have migrated, and some stay longer before migrating
(Miholcsa et al., 2009; Schummer et al., 2010).
Mismatch in Timing
Over evolutionary time species have formed predator-prey relationships
that are being disrupted because the predator and prey do not necessar-
ily respond to warming by shifting in concert. For example, the common
cuckoo (
Cuculus canorus
), a migrant, is a brood parasite laying its eggs in
the nests of other birds that migrate either short or long distances. With
climate change the short-distance migrants are arriving significantly earlier
now than in the past and they are nesting before the cuckoo has arrived.
Consequently, the short-distant migrants have reduced brood parasitism
(Saino et al., 2009). This is an example where there are both winners and
losers with climate change—the short-distance migrants winning and the
cuckoo losing. What is “better” or “worse” is of course a value judgment,
yet if one species is aided whereas others are disadvantaged to the point of
population collapses and perhaps extinction, then the net effect could mean
a local loss of species.
Range Shifts
As the climate has changed species have shifted their range because
they are attempting to stay in areas where they are exposed to the same
regional ambient temperatures. For terrestrial species this means moving
toward the pole and up in elevation. From 1914 to 1920, Joseph Grinnell
systematically surveyed a 60 to 3,300 m elevation gradient in Yosemite Na-
tional Park. He kept meticulous field notebooks, and these have been valu-
able in studying changes in species over a century, because the same area
was resurveyed from 2003-2006. Roughly half of the 28 mammals surveyed
moved up in elevation by an average of around 500 m. For example, one of
the species shifting up in elevation in response to climatic warming is the
