Thinking about populations

This chapter describes some general ways of thinking about population dynamics as a coherent body of interrelated advances in understanding, as developed in the first eleven chapters. The first generality is that understanding population dynamics depends on the concept of a state variable. It also underscores that dynamics depend on time delays, thus on age, even though demographic rates may ultimately depend more on size than age. Replacement plays a general role in dynamics, influencing both behavior at equilibrium and the time scales at which populations respond to environmental variability. Replacement even retains its importance in spatial models, where it is related to the same replacement threshold as in non-spatial models. Additionally, the way in which the distribution of reproduction (i.e. replacement) over age “filters” environmental variability influences extinction probabilities. The chapter closes by discussing how lessons from this book will guide conservation and management in a changing climate.