Is the impact of environmental noise visible in the dynamics of age-structured populations?

Climate change has ignited lively research into its impact on various popul ation-level processes. The research agenda in ecology says that some of the fluctuations in population size are accountable for by the external noise (e.g. weather) modulating the dynamics of populations. We obeyed the agenda by assuming population growth after a resource-limited Leslie matrix model in an age-structured population. The renewal process was disturbed by supe rimposing noise on the development of numbers in one or several age groups. We constructed models for iteroparous and semelparous breeders so that, fo r both categories, the population growth rate was matching. We analysed how the modulated population dynamics correlates with the noise signal with di fferent time-lags. No significant correlations were observed for semelparou s breeders, whereas for iteroparous breeders high correlations were frequen tly observed with time-lags of -1 year or longer. However, the latter occur s under red-coloured noise and for low growth rates when the disturbance is on the youngest age group only. It is laborious to find any clear signs of the (red ) noise- and age group-specific fluctuations if the disturbance i nfluences older age groups only. These results cast doubts on the possibili ty of detecting the signature of external disturbance after it has modulate d temporal fluctuations in age-structured populations.