Effect of Traffic on Caribou in an Arctic Oilfield

An ABR team of Alex Prichard, Brian Lawhead, and Joe Welch recently published a study in which they used data from road and aerial surveys conducted in 2001–03 to examine caribou behavior and distribution in relation to two roads with and without traffic convoying. The data used were first presented in unpublished reports that ABR prepared for mitigation plan monitoring, but the team reanalyzed the data using different statistical techniques in response to increasing interest in traffic convoying as a possible mitigation method to limit the impacts from new oilfield development. When interpreting their results, the team also used regional aerial strip-transect surveys conducted during 1993 and 1995–2017 to provide a long-term context for the distribution of calving caribou. The results of the study suggest that, although convoying may lower the amount of displacement by calving caribou somewhat, maternal caribou still avoided areas near roads for 2-3 weeks during calving, even with very low traffic frequency. There was no evidence of strong effects of inactive infrastructure on caribou distribution during calving.

From the paper:

As oil and gas development expands across Arctic Alaska, understanding and mitigating the associated impacts on wildlife movements, distribution, and behavior are of paramount importance for sustaining wildlife populations. The Arctic Coastal Plain of northern Alaska is used by four herds of barren-ground caribou (Rangifer tarandus granti): the Western Arctic herd, Teshekpuk herd, Central Arctic herd (CAH), and the Porcupine herd (Prichard et al., 2020b). Caribou are the most abundant large terrestrial mammals in the region, currently totaling approximately 500,000 animals among all four herds, providing culturally and economically important subsistence resource values for local communities. The range of the CAH has included oil and gas development for more than four decades (Murphy and Lawhead, 2000; NRC, 2003; Prichard et al., 2020a), but only limited development currently exists on the ranges of the other three herds (Person et al., 2007). With oil development expanding into the range of the Teshekpuk herd and recent lease sales on portions of the summer range of the Porcupine herd, applying the knowledge gained from analysis of historical data collected on the CAH has become increasingly important for impact prediction, planning, and mitigation of development.

Behavioral reactions were stronger closer to roads and declined considerably at greater distances.

One consistently observed impact in northern Alaska is displacement of maternal caribou within 2–5 km of active oilfield roads and gravel pads for a period of 2–3 weeks during and immediately after calving. A potential mitigation measure to address calving displacement is convoying of traffic to reduce traffic frequency and vehicle-related disturbance on roads in calving areas. We conducted frequent road and aerial surveys of caribou near two oilfield roads, one with convoying and one without, over a 3-year period during the precalving, calving, and postcalving periods to evaluate the effectiveness of traffic convoying. Road surveys indicated that caribou closer to the

roads and groups with calves exhibited more frequent and stronger behavioral reactions in response to traffic, and that moderate or strong reactions to traffic, such as standing up and walking or running away, were more frequent near the road with convoying than near the road with unlimited traffic. Aerial survey results indicated some avoidance of areas up to at least 2 km from the road with convoying and 4 km from the road without convoying by caribou groups with calves. This relationship was present even after adjusting for other factors affecting distribution. This avoidance of roads by maternal caribou was limited to the calving period and was not evident during the precalving or postcalving periods. In addition, an inactive elevated terrestrial drilling platform was present on the calving grounds during one year, but we found no evidence of caribou avoidance of that structure during calving at our scale of analysis.