Systematic review
1 Mistra Council for Evidence-Based Environmental Management, Royal Swedish Academy of Sciences, Stockholm, SE-104 05, Sweden
2 Department of Arctic and Marine Biology, University of Tromsø, Tromsø, NO-9037, Norway
3 Arctic Centre, University of Lapland, Rovaniemi, FIN-96101, Finland
4 University Museum, Norwegian University of Science and Technology, Trondheim, NO-7491, Norway
5 Department of Ecology and Environmental Science, Umeå University, Umeå, SE-901 87, Sweden
Environmental Evidence 2015, 4:4Â
doi:10.1186/s13750-014-0030-3
Published: 23 February 2015
Abstract (provisional)
Background The reindeer (or caribou, Rangifer tarandus L.) has a natural range extending
over much of Eurasia’s and North America’s arctic, alpine and boreal zones, yet its
impact on vegetation is still unclear. This lack of a common understanding hampers
both the management of wild and semi-domesticated reindeer populations and the preservation
of biodiversity. To achieve a common platform, we have undertaken a systematic review
of published studies that compare vegetation at sites with different reindeer densities.
Besides biodiversity, we focused on effects on major plant growth forms. Methods Searches
for literature were made using online publication databases, search engines, specialist
websites and bibliographies of literature reviews. Search terms were developed in
English, Finnish, Norwegian, Russian and Swedish. Identified articles were screened
for relevance based on titles, abstracts and full text using inclusion criteria set
out in an a priori protocol. Relevant articles were then subject to critical appraisal
of susceptibility to bias. Data on outcomes such as abundance, biomass, cover and
species richness of vegetation were extracted together with metadata on site properties
and other potential effect modifiers. Results Our searches identified more than 6,000
articles. After screening for relevance, 100 of them remained. Critical appraisal
excluded 60 articles, leaving 40 articles with 41 independent studies. Almost two
thirds of these studies had been conducted in Fennoscandia. Meta-analysis could be
made of data from 31 of the studies. Overall, effects of reindeer on species richness
of vascular plants depended on temperature, ranging from negative at low temperature
to positive at high temperature. Effects on forbs, graminoids, woody species, and
bryophytes were weak or non-significant, whereas the effect on lichens was negative.
However, many individual studies showed clear positive or negative effects, but the
available information was insufficient to explain this context dependence. Conclusions
We see two pressing matters emerging from our study. First, there is a lack of research
with which to build a circumpolar understanding of grazing effects, which calls for
more studies using a common protocol to quantify reindeer impacts. Secondly, the highly
context-dependent outcomes suggest that research and management have to consider local
conditions. For instance, predictions of what a management decision would mean for
the effects of reindeer on vegetation will have to take the variation of vegetation
types and dominant growth forms, productivity, and grazing history into account. Policy
and management have to go hand-in-hand with research in individual cases if the dynamics
between plants, animals, and humans are to be sufficiently understood.