Estimating Trends for Antarctic Birds in Relation to Climate Change
The earth’s climate is changing rapidly and these changes are expected to affect the structure and functioning of ecosystems. It is now clearly established that recent climate changes have impacted on living organisms. Several studies have demonstrated ch
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Estimating Trends for Antarctic Birds in Relation to Climate Change A.F. Zuur, C. Barbraud, E.N. Ieno, H. Weimerskirch, G.M. Smith, and N.J. Walker
14.1 Introduction The earth’s climate is changing rapidly and these changes are expected to affect the structure and functioning of ecosystems. It is now clearly established that recent climate changes have impacted on living organisms. Several studies have demonstrated changes in population abundance, geographic distribution, and even microevolutionary changes in relation to climatic fluctuations (Parmesan, 2006). Perhaps the best documented and most spectacular responses of living organisms to climate change are changes in phenology, which is the timing of seasonal activities of biological events such as the sprouting of plants. The vast majority of studies from the Northern Hemisphere that have analysed the relationships between long-term phenological and climate data sets have reported an advance in spring activities. For example, the earlier arrival and reproduction of migratory birds or earlier breaking of leaf buds since the mid-20th century in response to increasing temperatures. Some studies have also reported early onset of autumn activities such as grape-harvesting dates. However, due to the scarcity of long-term data sets, phenological changes are poorly documented in the Southern Hemisphere, particularly in Antarctica. Nevertheless, it is crucial to know whether, and to what extent, phenological changes have also occurred in the Southern Hemisphere for at least two reasons: (i) climatic changes between both hemispheres are different and (ii) we need to understand and eventually predict the impact of future climatic changes on species and ecosystems. Permanent human occupation of the Antarctic continent is very recent compared to the other continents, and the landmark for scientific studies in Antarctica is the International Polar Year 1957–58 when most of the existing permanent research stations were built. In Terre Ad´elie, East Antarctica, the Dumont d’Urville research station was established during the mid 1950s, and since then, ornithologists have over wintered almost every year recording arrival and laying dates of Antarctic seabirds as part of long-term studies on Antarctic marine top predators (Barbraud A.F. Zuur (B) Highland Statistics Ltd., Newburgh, AB41 6FN, United Kingdom A.F. Zuur et al., Mixed Effects Models and Extensions in Ecology with R, Statistics for Biology and Health, DOI 10.1007/978-0-387-87458-6 14, C Springer Science+Business Media, LLC 2009
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Fig. 14.1 Emperor Penguin. The photograph was taken by C. Barbraud
and Weimerskirch, 2006). Fortunately, all but one of the Antarctic seabird species breed close to the research station and records of phenological data have been collected over a 50-year period with quasi-annual frequency. Here, we use arrival and laying dates of three of these bird species to estimate trends and determine the effects of possible explanatory variables. The Emperor Penguin Aptenod
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