The matter of spatial and temporal scales: a review of reindeer and caribou response to human activity

Research on impacts of human activity and infrastructure development on reindeer and caribou (Rangifer tarandus) is reviewed in the context of spatial (m to many km) and temporal (min to decades) scales. Before the 1980s, most disturbance studies were behavioral studies of individual animals at local scales, reporting few and short-term (min to h) impacts within 0–2 km from human activity. Around the mid 1980s, focus shifted to regional-scale landscape studies, reporting that Rangifer reduced the use of areas within 5 km from infrastructure and human activity by 50–95% for weeks, months or even years and increased use of remaining undisturbed habitat far beyond those distances. The extent could vary with type of disturbance, sex, terrain, season, and sensitivity of herds. Of 85 studies reviewed, 83% of the regional studies concluded that the impacts of human activity were significant, while only 13% of the local studies did the same. Accurate assessment of impacts from human activity requires regional-scale studies, a pattern confirmed in a few long-term (decades) pre- and post-development studies. Such long-term studies are needed to improve understanding of both temporal and spatial patterns.