Changing environmental conditions are evident around the globe. Understanding how ecological communities are structured and how they might respond to these changes is of critical importance. However, ecological studies are often forced to consider a small subset of potentially relevant metrics in any given system. Indicator species and surrogate metrics are commonplace, though are often used without properly understanding the degree to which these are indicative of broader ecological dynamics.
In an effort to assess community responses to environmental change, we examined both long-term and year-to-year responses of a community of six Antarctic seabirds from 1980-2016. We investigated whether environmental forcing might be driving demographic processes and assessed the strength of synchronized dynamics across the community.
Results/Conclusions
We found a surprising discordance between abundance and breeding success within this seabird community. Long-term trends indicate increasing abundance as breeding success declines – there was little evidence of density dependence. Short-term fluctuations further confirm only weak relationships between breeding success and overall abundance. Additionally, we found little evidence for synchrony in breeding productivity among species. Exceptionally poor years of breeding productivity (‘extreme years’) across the community are rare, though large drops in productivity are not uncommon for single species.
These results demonstrate an uncoupling between abundance and breeding success, indicating that breeding success (a commonly monitored metric in seabird populations) may be a relatively poor measure for population health. Furthermore, dynamics of any given species may not be an effective surrogate for community-level responses or ecosystem health, despite the ubiquitous usage of seabirds as ecological indicators. The independent responses of these species to environmental conditions highlight the challenges in finding effective proxies of ecological change. More accurate assessments of responses to global change may require an evaluation of several parameters, aggregated over a number of species.