Mammal responses to human footprint vary with spatial extent but not with spatial grain

Abstract

Ecological patterns and processes can vary with scale, causing uncertainty when applying small‐scale or single‐scale studies to regional or global management decisions. Conducting research at large extents and across multiple scales can require additional time and effort, but may prove necessary if it uncovers novel patterns or processes. Knowing the degree to which patterns vary between spatial extents and grains can provide insight into the importance of considering scale, particularly in applied research. Across multiple spatial scales, we evaluated variation in the strength and direction of large mammal responses to human footprint, a measure of human infrastructure (e.g., roads, buildings) and landscape change (e.g., agriculture, forestry). We focused on the response of five boreal mammals: gray wolf (Canis lupus), Canada lynx (Lynx canadensis), coyote (Canis latrans), white‐tailed deer (Odocoileus virginianus), and moose (Alces alces). Firstly, we asked how responses measured at the regional extent of the boreal forest of Alberta (approximately 400,000 km2) compared to those measured at a nested subregional extent (40,000 km2) and to those reported in previous studies conducted at smaller spatial extents (median 2400 km2, mean 46,993 km2). Secondly, we tested whether responses differed across three spatial grains of measurement (250 m, 1500 m, or 5000 m radii) at the regional extent. Using the Alberta Biodiversity Monitoring Institute's snowtrack survey data (2001–2013) and human footprint map, we created a set of generalized linear mixed‐effects models for each species, which related relative abundance to individual and cumulative effects of human footprint and compared these using an information theoretic approach. We found variation across spatial extents in both direction and strength of estimated mammal responses to human footprint, suggesting that some patterns are scale‐dependent. This reinforces the need for regional studies to complement those conducted at smaller extents in order to fully understand, and thus manage for, the impacts of human footprint on mammalian biodiversity. By contrast, we found little variation in direction and strength of responses across spatial grains, indicating that analyses across multiple grain sizes may be of less importance than those conducted across multiple spatial extents.

The importance of considering multiple interacting species for conservation of species at risk

“…Thus, we predicted low caribou densities because caribou typically avoid linear features, a prominent footprint in the area, and when linear feature densities are too high to avoid, neonate calf survival declines (DeMars & Boutin 2018). The 3 carnivore species use or respond positively to linear features (Toews et al 2017;; hence, we predicted intermediate densities for predators. We predicted the highest densities for alternative prey because linear features and forest cutblocks can benefit these species (Toews et al 2017;.…”

“…The 3 carnivore species use or respond positively to linear features (Toews et al. ; Fisher & Burton ); hence, we predicted intermediate densities for predators. We predicted the highest densities for alternative prey because linear features and forest cutblocks can benefit these species (Toews et al.…”

“…Nonetheless, predation is the proximate cause of caribou declines, and anthropogenic features bolster alternative prey populations (Toews et al. ) and expedite travel by wolves ( Canis lupus ) (Dickie et al. ).…”

“…We predicted the highest densities for alternative prey because linear features and forest cutblocks can benefit these species (Toews et al. ; Fisher & Burton ).…”

“…Compounding this mature forest loss is the pervasive network of linear features resulting from energy exploration and extraction, which represents a smaller loss in areal extent but plays a disproportionally large role in loss of forest ecosystem function (Pickell et al 2015). Nonetheless, predation is the proximate cause of caribou declines, and anthro-pogenic features bolster alternative prey populations (Toews et al 2017) and expedite travel by wolves (Canis lupus) (Dickie et al 2017). The resulting wolf numerical and functional responses are strongly implicated in caribou declines (Festa-Bianchet et al 2011).…”