Synchronous effects produce cycles in deer populations and deer‐vehicle collisions

Abstract

Population cycles are fundamentally linked with spatial synchrony, the prevailing paradigm being that populations with cyclic dynamics are easily synchronised. That is, population cycles help give rise to spatial synchrony. Here we demonstrate this process can work in reverse, with synchrony causing population cycles. We show that timescale‐specific environmental effects, by synchronising local population dynamics on certain timescales only, cause major population cycles over large areas in white‐tailed deer. An important aspect of the new mechanism is specificity of synchronising effects to certain timescales, which causes local dynamics to sum across space to a substantial cycle on those timescales. We also demonstrate, to our knowledge for the first time, that synchrony can be transmitted not only from environmental drivers to populations (deer), but also from there to human systems (deer‐vehicle collisions). Because synchrony of drivers may be altered by climate change, changes to population cycles may arise via our mechanism.

Tail‐dependent spatial synchrony arises from nonlinear driver–response relationships

“…Tail‐dependent spatial synchrony represents a new extension of spatial synchrony's general negative implications for the stability of population ensembles (Anderson et al, 2021; Heino et al, 1998; Schindler et al, 2015). Because of the implications of tail‐dependent spatial synchrony for the tendency towards synchronised booms versus synchronised crashes, understanding the nature of tail associations and how they vary spatially can help explain patterns of temporal stability.…”

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Spatial synchrony, the tendency for fluctuations to be correlated across locations, is a ubiquitous population dynamic phenomenon with important consequences for extinction risk and aggregate population variability (Liebhold et al, 2004). All else being equal, a more synchronous ensemble of populations faces higher extinction risk (Heino et al, 1998) and has a regional total population that is more temporally variable (Anderson et al, 2021) than a less synchronous ensemble. Recent studies of spatial synchrony have leveraged methodological advances to reveal new aspects of the phenomenon and strengthen inference into its mechanisms and consequences for ecological and socio-environmental systems (Anderson et al, 2021;Ghosh et al, 2020b;Sheppard et al, 2016Sheppard et al, , 2019Walter et al, 2017).

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“…All else being equal, a more synchronous ensemble of populations faces higher extinction risk (Heino et al, 1998) and has a regional total population that is more temporally variable (Anderson et al, 2021) than a less synchronous ensemble. Recent studies of spatial synchrony have leveraged methodological advances to reveal new aspects of the phenomenon and strengthen inference into its mechanisms and consequences for ecological and socio-environmental systems (Anderson et al, 2021;Ghosh et al, 2020b;Sheppard et al, 2016Sheppard et al, , 2019Walter et al, 2017). For example, "geographies of synchrony" focus on spatial patterns, beyond the historically standard focus on how synchrony declines with increasing distance between locations, to reveal previously overlooked structural patterns and mechanisms that both cause synchrony and modify its strength (Larsen et al, 2021;Walter et al, 2017).…”

The spatial synchrony of species richness and its relationship to ecosystem stability

“…4). The negative relationship between richness synchrony and ecosystem stability was expected due to the known destabilizing effects of synchrony in population spatial (Anderson et al 2021) and community (de Mazancourt et al 2013, Hallett et al 2014 synchrony. However, it remains noteworthy since the relationship between synchrony in species number and aggregate abundance (as in this study) is less direct than the relationship between abundances in component units and aggregate abundance (as in population spatial and community synchrony studies).…”

“…The negative relationship between richness synchrony and ecosystem stability was expected due to the known destabilizing effects of synchrony in population spatial (Anderson et al. 2021 ) and community (de Mazancourt et al. 2013 , Hallett et al.…”