Exploring the consequences of climate change on ecological communities with stochastic population models

Chris Wilmers - UCSC, Environmental Studies
Monday, November 30, 2009, 4:00 pm, Engineering 2 Building, Room 180
Hosted by Assistant Professor Pascale Garaud
Applied Mathematics & Statistics

Abstract

While it is widely appreciated that climate and predation can affect the
population dynamics of various species, a mechanistic understanding of how
climate and predation interact with life history traits to influence
population fluctuations is currently lacking.  Here we develop a general
density-dependent age-structured model that accounts for differential
responses in life history traits to increasing density.  We show that the
greater the year-to-year correlation in environmental conditions, the more
widely a population fluctuates.  As good years accumulate and the number of
individuals grow, successive life history traits become vulnerable to
density dependence once a return to unfavorable conditions prevails.  The
stronger this ratcheting of density dependence in life history traits by
climate, the larger and steeper the population fluctuations become and the
more vulnerable the population becomes to extinction.  We explore the
effects of a large scale atmospheric phenomena, the North Atlantic
Oscillation (NAO), on model dynamics and discuss how its persistence in one
extreme phase during much of the 1980's and early 1990's may have led to the
crash of the Isle Royale moose population.  Lastly, we model climate as a
Markov process and explore the consequences of future changes in climactic
correlation for population dynamics.  We show that the presence of healthy
predator populations will be particularly important in dampening prey
population fluctuations if climatic correlation increases in the future.