Population responses to harvesting in fluctuating environments

Abstract

Achieving sustainable harvesting of natural populations depends on our ability to predict population responses to the combined effects of harvesting and environmental fluctuations while accounting for other internal and external factors that influence population dynamics in time and space. Here, we review recent research showing how spatial patterns and interspecific interactions can influence population responses to harvesting in fluctuating environments. We highlight several pathways through which harvesting can, often inadvertently, influence the dynamics and resilience to environmental fluctuations of both harvested and surrounding non-harvested populations and species. For instance, spatial models have shown that harvesting is expected to influence the spatial synchrony of population fluctuations, both of the harvested species and its competitors, predators and prey, with implications for population extinction risk. Dispersal and interspecific interactions can cause responses to harvesting in areas and species that are not themselves harvested. Harvesting that selectively targets certain groups of individuals, either intentionally or through for example spatially biased harvesting, can amplify environmentally induced population fluctuations by biasing the population structure towards individuals that are more sensitive to environmental variation. On the other hand, harvesting can in some cases buffer populations against the density-dependent effects of harsh climatic conditions, which are probably more common than previously acknowledged. Recent advances in modeling are providing new predictions that are highly relevant under global warming and now need to be tested empirically. We discuss how knowledge of these pathways can be used to increase the sustainability of harvesting.

Predictability of Population Fluctuations

“…This study was inspired by our previous results on spatial population synchrony [31][32][33][34] and motivated by the findings that population fluctuations showed larger predictability than the underlying environmental variables. This was shown to happen for a wide range of systems: primary production in oceans [25], crop yield [26], malaria [27] and fisheries [28].…”

Demographic consequences of harvesting: a case study from a small and isolated moose population

“…An important question is how the effects of harvesting interact with ongoing climate change (Gamelon et al 2019), for instance through age-or sexspecific sensitivities to climate variation (Herfindal et al 2015, Lee et al 2021 in this Special). However, because range shifts or changes in large-scale movement patterns such as seasonal migrations are central mechanisms in animals' responses to climate change (Morrison et al 2021), the study at Vega may be less ideal for generating general results about harvesting under climate change.…”

Experimental evidence of size‐selective harvest and environmental stochasticity effects on population demography, fluctuations and non‐linearity

“…However, age structure and the form of density-dependent mortality among life history stages can also substantially change the stability properties of non-linear models (Liz & Pilarczyk, 2012). In contrast, models and a reindeer case study have also shown that harvesting can dampen population fluctuations due to the specifics of life history and density dependence (Lee et al, 2022;Peeters et al, 2022). Alternatively, fluctuations can be elevated by a shift in demographic parameters that alter how to process noise interacts with non-linear deterministic processes.…”