Guillemots and the Climate Change Mistake

Its nearly February and the weather persists in being unseasonably mild. A cold snap is forecast in the next few days but, touch wood, it shouldn't go near matching the bitterness of our previous two Irish winters. The consequences of this warm weather, garden bulbs in full bloom, frogs spawning early, may bring delight to us in banishing the darkness of winter from our minds, but they also serve to remind us of the ever present problem of climate change. It is fact that birds are breeding and singing earlier, migrant birds are arriving earlier, butterflies are appearing earlier and plants are shooting earlier (1). This blog has reported on dragonfly species increasing their European range northward into Ireland. The effects of climate change on fish species in the oceans is one of the most worrying, due to its knock on effect on other associated species and on the consequences it holds for commercial fisheries. In the North Sea, cod, anglerfish and snake blenny have all shifted their ranges further northwards (2).
 

Common Guillemots, Uria aalge, during breeding season

However, there is a risk in attributing too much to climate change and not recognising the effect humans activity may have directly in changes to species distribution and behaviour. An example of this is the virtual extinction of the Common Guillemot (Uria aalge) in Atlantic Iberia. This wonderful, chocolate-brown coloured auk numbered c. 20,000 individuals in Atlantic Iberia in the first half of the 20th century, the largest population of any seabird in the area. By 2004 it was considered quasi-extinct, with no no breeding attempts recorded since 2003 (3). Such a dramatic decline was thought to be a result of climate change as the Iberian population was at the southern most limit of the species, and thus prone to extinction under natural conditions. A reexamination of the data from the extinction however, revealed that climate change was not to blame. The largest population crash occurred from 1960 to 1974, when annually there was a decline of 33.3%. This period saw good climate conditions and higher or sustained availability of pelagic prey fish, but also marked a rapid shift away from using vegetal based nets in commercial fishing to those constructed from synthetic materials (3). This points the finger directly at another human-mediated extinction. It also shows how easy it is to attribute much to climate change without assessing the role we have directly in the survival of other species.

References:

1. Walther et al., 2002. Nature 416 pp. 389-395
2. Perry et al., 2005. Science 308 pp. 1912-1915
3. Munilla et al., 2007. Biological Conservation 207 pp. 359-371