Conservation of wildlife populations: factoring in incremental disturbance

Abstract

Progressive anthropogenic disturbance can alter ecosystem organization potentially causing shifts from one stable state to another. This potential for ecosystem shifts must be considered when establishing targets and objectives for conservation. We ask whether a predator-prey system response to incremental anthropogenic disturbance might shift along a disturbance gradient and, if it does, whether any disturbance thresholds are evident for this system. Development of linear corridors in forested areas increases wolf predation effectiveness, while high density of development provides a safe-haven for their prey. If wolves limit moose population growth, then wolves and moose should respond inversely to land cover disturbance. Using general linear model analysis, we test how the rate of change in moose (Alces alces) density and wolf (Canis lupus) harvest density are influenced by the rate of change in land cover and proportion of land cover disturbed within a 300,000 km 2 area in the boreal forest of Alberta, Canada. Using logistic regression, we test how the direction of change in moose density is influenced by measures of land cover change. In response to incremental land cover disturbance, moose declines occurred where <43% of land cover was disturbed; in such landscapes, there were high rates of increase in linear disturbance and wolf density increased. By contrast, moose increases occurred where >43% of land cover was disturbed and wolf density declined. Wolves and moose appeared to respond inversely to incremental disturbance with the balance between moose decline and wolf increase shifting at about 43% of land cover disturbed. Conservation decisions require quantification of disturbance rates and their relationships to predator-prey systems because ecosystem responses to anthropogenic disturbance shift across disturbance gradients.

Use and selection at two spatial scales by female moose (alces alces) across central British Columbia following a mountain pine beetle outbreak

“…Anthropogenic changes to natural landscapes are often studied to determine if highpriority megafauna are negatively affected by these changes (Scheffer et al 2001, Courbin et al 2014, Ehlers et al 2014, Johnson and Russell 2014, Cristescu et al 2016, Lamb et al 2017). The transition of landscapes from heterogeneous mosaics to homogeneous stands of regenerating coniferous forests or other monoculture plots can have negative consequences for wildlife (Gill et al 1996, Arlettaz et al 2015, MacNearney et al 2016, Wilson 2016, Stewart and Komers 2017. Biological diversity is lost when heterogeneous landscapes are altered to homogenous ones (Hanski 2005), and the loss of megafauna has been observed through such landscape changes (Johnson 2002).…”

“…Anthropogenic disturbance can have negative impacts on wildlife (Gill et al 1996, Arlettaz et al 2015, Wilson 2016, Stewart and Komers 2017 and is a contributing factor for species decline worldwide (Vors and Boyce 2009). Frequently, habitat for wildlife is reduced with expansion of forest clearing and other resource-extraction industries (MacNearney et al 2016).…”

“…Landscape change is often regarded negatively when there is associated loss of biological diversity (Hanski 2005), and loss of megafauna (Johnson 2002). Anthropogenic disturbances to landscapes and negative effects on wildlife include the loss of intact forests due to forestry practices, agriculture, mining and other natural resource developments (Gill et al 1996, Arlettaz et al 2015, MacNearney et al 2016, Wilson 2016, Stewart and Komers 2017. Progressive landscape change due to forest harvesting can alter ecosystems from a heterogenous state to a more homogenous one (Scheffer et al 2001).…”