Current warming and likely future impacts - Climate Change: Biological and Human Aspects - page 273

timing, their results suggest an alteration in the degree of temporal-niche overlap
experienced by amphibian larvae in this community. This puts additional pressure on
both species.
Knowledge of a species' primary requirements is also fundamentally important
given that these requirements may in turn be driven by a climatic dimension or dimen-
sions. These can be complex. Consider the migratory black-tailed godwit ( Limosa
limosa islandica ), a shore bird that winters between Britain and Iberia while breeding
in the summer almost exclusively in Iceland. Breeding pairs exhibit a high degree
of partner fidelity. Whereas most migratory pairs winter together, and so migrate
together, the black-tailed godwit is one of a number of species where males and
females winter in different locations many hundreds of miles apart. Yet breeding
pairs arrive in Iceland typically within about 3 days of each other. The question then
arises as to how this degree of synchrony is maintained when the environmental con-
ditions at the different sexes' wintering sites are dissimilar (Gunnarsson et al., 2004).
The answer will be key in beginning to understand how such species will respond to
future climatic change. Indeed, respond to climatic change they will, for clearly as
little as 15 000 years ago, towards the end of the last glacial, their migratory patterns
would have been most different and so a successful response to glacial-interglacial
climate change must have taken place on a number of occasions.
Today climate change seems to be affecting another migratory bird species, the
pied flycatcher ( Ficedula hypoleuca ). Its migration is timed to the availability of food
for its nestlings. However, phenological changes have meant that in some parts of
The Netherlands the caterpillars that are its food peak early in the season. Here the
flycatcher populations are in decline (Both et al., 2006). Whether such species will
adapt with time in the modern world remains to be seen. As with the earlier amphibian
example, such phenological disruption of ecological relationships is likely to increase,
and for some species probably become critical, as climate change continues.
So what is happening to seasons on the global scale? First of all we need to
remember our school-day geography, that seasons - that is, the cycle of spring,
summer, autumn and winter - only take place outside of the tropics (tropics have their
own seasonal patterns, principally wet and dry). Outside the tropics there is an annual
cycle of change in mean daily temperature driven by a combination of the Sun's
elevation above the horizon and day length. This facilitates the TGS during which
primary producers, mainly algae and plants, grow, drawing down carbon dioxide.
In the autumn, plants begin to die and decompose, and carbon dioxide is released
through the respiration of the decomposer (detritovore) community (including
earthworms, insects, fungi, bacteria and so forth). And so, outside of the tropics
atmospheric carbon dioxide has an annual cycle. This annual cycle is what causes the
ripple seen in the graph of atmospheric carbon dioxide over recent decades (Figure
1.4). Looking at just one year of carbon dioxide change in the northern hemisphere,
there is a sinusoidal-like pattern. Figure 6.1 has two single years half a century apart
superimposed on each other: 1959 and 2010. This shows how the annual pattern of
northern hemisphere atmospheric carbon dioxide concentration has changed. The
first thing to note is that the amplitude of the wave has increased. This means that the
year is seeing more drawing down of carbon dioxide. This drawdown is unlikely to
be the result of abiotic gaseous absorption by the oceans because gas is less soluble