Linking woodland caribou abundance to forestry disturbance in southern British Columbia, Canada

Abstract

The decline of many woodland caribou (Rangifer tarandus caribou) populations is thought to be linked with habitat disturbances resulting from industrial development, including timber harvesting and its network of haul roads. Defining a disturbance-abundance relationship offers a tool to assess and potentially manage for the influence of disturbance on caribou abundance. Defining this relationship is challenged by limited historical land use and abundance data, the choice of a disturbance measure, and variability in the relationship between subpopulations and across core versus matrix habitat. For 12 subpopulations of woodland caribou within the southern mountain population, we linked longitudinal caribou abundance data with historical forestry disturbances simulated from forest harvest data. We compared disturbance measures estimating the proportion of forested area commercially harvested with even-aged, regeneration treatments (cutblocks) and converted to roads for transporting timber within subpopulationspecific core and matrix habitats as predictors of caribou abundance. Non-linear mixed models provided evidence that disturbances in matrix habitats negatively influenced caribou abundance, with the effects in core habitat being variable between subpopulations. Of the disturbance types evaluated, the best predictors included roads buffered by 50 m (R50), cutblocks ≤80 years old, and the cumulation of cutblocks ≤80 years old plus roads buffered by 50 m. The top-ranked model was composed of R50 present in core and in matrix habitats.

Prioritizing populations based on recovery potential

“…Criterion weighting was determined using the authors' professional opinions based on the literature but could be changed by users of the web application (Table SI‐1.1; Prioritization Shiny). For Southern Mountain Caribou, permanent alteration in both core and matrix habitat, especially agricultural land, is associated with caribou population decline, as is forest harvest (Apps et al, 2001, 2013; Apps & McLellan, 2006; Kinley & Apps, 2001; Lochhead et al, 2022; Serrouya et al, 2021; Wittmer et al, 2007). Recent wildfire also has negative effects on caribou, however, due to the lack of direct association with linear features the impact is less severe (Johnson et al, 2020; Stewart et al, 2020; Wittmer et al, 2007), therefore was weighted half that of permanent or harvest alteration.…”

“…Furthermore, increased linear features such as forestry roads and transmission lines have accelerated the ingress of predators and predation rates (Dickie et al, 2017(Dickie et al, , 2022Whittington et al, 2011). Considering only ecological parameters, the recovery of subpopulations in the Southern Group is contingent on (1) the degree and extent of habitat degradation from landscape alteration in core and surrounding matrix habitats which affect the populations of primary prey species and predators (Lochhead et al, 2022;Wittmer et al, 2007); (2) the degree and extent to which habitat alteration is permanent, for example, agricultural areas (Apps & McLellan, 2006);…”

“…Furthermore, increased linear features such as forestry roads and transmission lines have accelerated the ingress of predators and predation rates (Dickie et al, 2017, 2022; Whittington et al, 2011). Considering only ecological parameters, the recovery of subpopulations in the Southern Group is contingent on (1) the degree and extent of habitat degradation from landscape alteration in core and surrounding matrix habitats which affect the populations of primary prey species and predators (Lochhead et al, 2022; Wittmer et al, 2007); (2) the degree and extent to which habitat alteration is permanent, for example, agricultural areas (Apps & McLellan, 2006); (3) the age and extent of non‐permanent or temporary habitat alteration such as forest harvest and wildfire; (4) degree that populations are connected to larger, more stable populations, thereby providing meta‐population function and intermittent demographic or genetic rescue (Charlesworth & Willis, 2009); (5) the current population size and trend (Middleton & Nisbet, 1997; Wittmer et al, 2010); and (6) the latitude of the population reflecting its relative susceptibility to changing climate and associated increase in white‐tailed deer density (Dawe & Boutin, 2016).…”

The effects of maternal penning on the movement ecology of mountain caribou

“…Although elevation is a component of the RSF, in the context of our study, elevation is an important driver of access to resources, anthropogenic disturbance, and risk of predation (Wittmer et al ., 2007; Serrouya, McLellan, et al ., 2017). Elevation is also related to the migratory behavior of caribou and land‐use policies to protect caribou habitat (Williams et al ., 2021; Lochhead, Kleynhans, & Muhly, 2022). We used a mixed effects model with the median seasonal elevation for each individual as the response variable and season and penning status as interacting predictors.…”

Spatializing oil and gas subsidies in endangered caribou habitat: Identifying political‐economic drivers of defaunation

“…There is widespread consensus in the scientific literature that these caribou declines are driven by industrial land‐use change resulting in habitat loss and alteration (Lochhead et al, 2022; Shackelford et al, 2018; Wittmer et al, 2007). Industries such as forestry, coal, and oil & gas fragment existing habitat.…”