Drivers of demography: past challenges and a promise for a changed future

There is an urgent need to understand how populations and metapopulations respond to shifts in the environment to mitigate the consequences of human actions and global change. Identifying environmental variables/factors affecting population dynamics and the nature of their impacts is fundamental to improve projections and predictions. This chapter examines how environmental drivers, both continuous (stress) and episodic (disturbance), are incorporated in demographic modelling across many types of organisms and environments, using both observational and experimental approaches to characterise drivers. It critically summarises examples of the main approaches and identifies major accomplishments, challenges, and limitations. The chapter points to promising approaches and possible future developments. In the initial sections, models in closed systems without migration among populations are considered. The chapter then focuses on metapopulation models, emphasising the importance of understanding drivers affecting migration and differential extinction among populations. Finally, it concludes with a discussion of some important and general problems associated with assessing how population dynamics may be affected by environmental drivers that are dynamic, nonlinear, and with indirect and/or interacting effects with other drivers..