Guest Speaker - Xavier Lambin

Hosted by the Environment Institute

The Environment Institute presented Xavier Lambin from the School of Biological Sciences, The University of Aberdeen, UK on Monday 26th November 2012.

"Continent -wide dampening of population cycles in keystone herbivores; patterns, likely processes and consequences for predators"

In recent years, evidence has emerged that dramatic changes in ecosystem processes and functioning are taking place across Europe under the joint impact of climate change and human-induced shift in land use. One of the most spectacular changes concerns the dampening in the fluctuations of populations of keystone herbivore species such as voles and moths with cyclical dynamics that took place nearly simultaneously in much of Europe in the 1990s. Changes in small herbivore dynamics have the potential to lead to ecosystem re-organisation and therefore represent a challenge for the conservation of biodiversity. However, there remains much uncertainty on what are the processes responsible for multi-annual cycles, how these might be modified by climate and whether the same set of processes operate in all cyclic vole populations. Furthermore, whether cycle dampening is general, or local, and result from extrinsic environmental changes or from intrinsic process stochasticity is currently unknown.

In this talk, Xavier  first presented empirical and modelling developments on the demographic basis for vole cycles based on our long term studies. He then showed how seasonality and the destabilising influences of pathogen host interaction or changes in herbivore-induced changes in plant quality might interact with seasonality in the environment to lead to cyclic dynamics. Next, using the largest compilation of time series of vole abundances yet assembled, Xavier presented new analyses that demonstrate consistent cycle amplitude dampening associated with a reduction in winter vole population growth, and suggesting that regulatory processes responsible for cyclicity have not been lost. The underlying syndrome of change throughout Europe, species and ecosystems suggests a common climatic driver acting over very large scales. Our analyses suggest increasing periods of low amplitude small herbivore population fluctuations are expected in the future, with cascading impacts on trophic webs across ecosystems. Finally, Xavier illustrated the likely impact of changes on prey dynamics on the dynamics of birds of prey using our long terms studies on the demography of Tawny owls.