Rangifer within areas of human influence: understanding effects in relation to spatiotemporal scales

Abstract

Depending on the spatial scale, fluctuations in the area use of social, migratory herbivores may be related to changes in population size, season, predation, climatic variation, different types of disturbance, and random animal movement. We present a review and case study highlighting how study design limitations and publication bias have influenced our current knowledge on effects of human disturbance on Rangifer spp. Our case study illustrates how yearly variation may lead to false conclusions about the effects of infrastructure. From 58 analyses presented in 52 reviewed papers, we found that 14 analyses had study designs comparing area use before and after construction of infrastructure, 24 included spatial time series of > 6 years, 21 included spatiotemporal variation in their analyses, and only six contained both static and dynamic habitat variables. Categorizing the 58 analyses into 404 specific outcomes, we found that 64% of the authors focused their conclusions on negative effects and 14% focused on mixed effects but emphasized on negative effects of human activities and infrastructure, while only 53% of the outcomes actually showed negative effects, 34% no effects and 13% positive effects. Our review shows that only one study had a before–after-control–impact (BACI) design, and a majority of publications do not include before–after (BA) designs (76%), have not included spatiotemporal variation (64%), and do not evaluate the effects of spatial fluctuations on Rangifer area use at long enough time intervals (only 8 studies had > 10 years data). Although Rangifer is vulnerable to human disturbances, we have showed how the effects of infrastructure differ among studies and highlight the need for study designs that integrate and account for spatiotemporal variation in future studies, for a better understanding of Rangifer (or wildlife) area use in relation to anthropogenic effects.