|Author(s):||Ranta, E.; Kaitala, V.; Fowler, M.S.; Lindström, J.;|
|Title:||Environment forcing populations.|
|Book title:||The Impact of Environmental Variability on Ecological Systems|
|Editorial:||Vasseur, D.A.; McCann, K.S.;|
A striking feature for many species is that populations fluctuate in synchrony over vast geographical ranges. Historically synchronicity was attributed to external forcing (like weather) that influences local population renewal. It is now understood that forcing can be due to any agent (dispersal, competition, predator-prey interactions) interfering with local processes. Data show that often synchrony levels off with increasing distance among populations. Such a feature suggests presence of population travelling waves. That is, processes of population highs coinciding in time in limited regions while elsewhere in space population lows coincide and the pattern changes in location over time. A poorly studied feature in this cotext is synchrony across species that is suggested to emerge due to interspecific interaction networks. That external forcing causes populations to fluctuate in step is easy to prove. However, time series of population change do not always necessarily carry any extractable information about the agent that is forcing the population, unless complemented with auxilliary data about the environment and the focal population studied. The fingerprint of the external signal is more easily visible in the noise-modulated population data if the underlying renewal process is undercompensatory.