SR1 Summary.Indd

SR1 A Systematic Review EviEM Summary 2015 Claes Bernes Kari Anne Bråthen Bruce G. Forbes Impacts of reindeer on James D. M. Speed Jon Moen arctic and alpine vegetation Impacts of reindeer on arctic and alpine vegetation Summary of Systematic Review SR1 EviEM, 2015 Please cite this report as C. Bernes et al. (2015): Impacts of reindeer on arctic and alpine vegetation. Summary of Systematic Review SR1. EviEM, Stockholm. Printed by US-AB, Stockholm, 2015 Cover: Reindeer in Sarek National Park, northern Sweden Photo: Oskar Karlin Impacts of reindeer on arctic and alpine vegetation Summary of Systematic Review SR1 By Claes Bernes, Kari Anne Bråthen, Bruce C. Forbes, James D.M. Speed and Jon Moen SR1 | Impacts of reindeer on arctic and alpine vegetation In alpine parts of the Scandinavian mountains, reindeer are the most numerous large herbivores. Photo: Claes Bernes. Summary The impact of reindeer on vegetation in arctic and trampling, and herbs are also reduced by expos- alpine areas is not fully known. This hampers both ure to reindeer. The occurrence of other kinds of the management of wild and semi-domesticated vegetation, notably mosses, grasses and shrubs, is reindeer populations and the preservation of bio- on average not signifi cantly affected by reindeer diversity. To synthesise the available evidence, we grazing, although individual studies may show have undertaken a systematic review of published signifi cant effects. The species richness of vascular studies that compare vegetation exposed to dif- plants decreases with increasing grazing pressure, ferent levels of reindeer grazing. We found a total at least in cold climates, where the productivity of of 41 studies that fulfi lled all our relevance and vegetation tends to be low. quality criteria. Almost two thirds of these studies had been conducted in Fennoscandia. There is not suffi cient information to explain the considerable variation that we found among Overall, the studies report on large variations in results from different studies and different sites. the response of vegetation to reindeer. Aver age The outcomes are context-dependent, which sug- effects are usually small, but there are also both gests that research and management have to take signifi cantly positive and signifi cantly negative local conditions into account, but the evidence is effects within all vegetation categories considered. too weak and scattered to inform environmental policy or reindeer management in a detailed way. Nevertheless, when we combined data from dif- It is unlikely that further studies can improve the ferent studies using meta-analysis, some patterns evidence base much, unless they adopt standard- emerged. Lichens are vulnerable to grazing and ised ways of quantifying reindeer impacts. 4 Impacts of reindeer on arctic and alpine vegetation | SR1 Reindeer play key role foraging is made diffi cult by ice or deep snow, and in northern ecosystems herd sizes can therefore vary considerably from one decade to another. In Sweden, the number of Reindeer (Rangifer tarandus L.) have a natural reindeer has fl uctuated between about 150,000 range extending over much of northernmost Eur- and 300,000 over the last 125 years. asia and North America. In considerable parts of this region, they are the only large herbivores. Being the most numerous large herbivores in the Wild reindeer representing a subspecies known far north, reindeer often play a key role in their as caribou are still numerous in Canada, Alaska ecosystems. Unlike most other herbivorous spe- and Greenland. Another subspecies, the Sval- cies, they are able to digest lichens, which makes bard reindeer, occurs in the wild on Spitsbergen them highly adapted to the vegetation of the tun- and other islands in the Svalbard archipelago. In dra. Reindeer lichens (Cladonia and Cladina), a northern Europe and Siberia, however, the ma- prominent part of the ground vegetation in many jority of reindeer populations have been domest- polar areas, are a major component of the winter icated or semi-domesticated for several centuries. diet of most reindeer populations. In summer, Here, they are to a large extent being herded by reindeer prefer green, vascular plants such as indigenous peoples. Some large populations of graminoids (grasses, sedges and rushes), herbs, wild reindeer are still present in Russia, but most and leaves of shrubs and deciduous trees. Never- of the Norwegian and Finnish herds and all of the theless, since lichens are sensitive to trampling Swedish ones are semi-domesticated. under snow-free conditions, they can be affected by reindeer in summer pastures too. Over the seasons, many reindeer herds migrate over large distances between summer and winter Many studies of tundra ecosystems have shown pastures. Reindeer in Sweden normally spend the that intensive grazing and trampling by reindeer snow-free season on alpine tundra or in subalpine can cause lichens to be replaced by vegetation birch forests, whereas they spend the winter in dominated by bryophytes (mosses and liver- lowland coniferous forests. During some winters, worts). If the grazing pressure is increased further, Reindeer numbers in Fennoscandia Sweden 300,000 200,000 Norway This diagram shows total 100,000 populations of semi- domesticated reindeer in Finland Sweden, Norway and Fin- land following the autumn slaughter. After calving in spring, herds are signif- 0 icantly larger. 1880 1900 1920 1940 1960 1980 2000 5 SR1 | Impacts of reindeer on arctic and alpine vegetation bryophytes may be replaced by grasses and other Shifting opinions on the impacts graminoids. Changes of the latter kind have been of reindeer grazing observed in experiments or where reindeer often crowd together along fences and other obstacles to In Sweden, public opinion on how reindeer their migration, but not in studies of range lands grazing affects alpine vegetation has shifted with freely roaming semi-domesticated reindeer. during the last few decades. In the 1990s, several If reindeer ranges are enclosed by fences, grazing and trampling along the fence may become so intense that vegetation is strongly impacted. This picture was taken at Ifjordfjellet in Finnmark, Norway. Photo: Kari Anne Bråthen. 6 Impacts of reindeer on arctic and alpine vegetation | SR1 well-publicised records of vegetation degrada- Moreover, there is still no scientifi c consensus tion in areas grazed by reindeer helped to form on how important reindeer really are for the a widespread perception that some mountain diversity of alpine or arctic vegetation. While areas were overutilised. There was a concern some studies have found the impacts of reindeer that Swedish reindeer husbandry was not sus- grazing to be strong, others suggest that they tainable. In other parts of Fennoscandia, severe are relatively minor, at least in comparison to overexploitation of reindeer ranges was noted those of other grazers (such as voles, lemmings during these years, not least on lichen heaths or insects). in Finnmark in northernmost Norway and in Finnish Lapland. Need for a synthesis of the available evidence More recently, however, the impact of reindeer grazing on alpine vegetation was subject to Since the documented impacts of reindeer on re-evaluation in Sweden. Analyses of reindeer vegetation differ between studies and between numbers and grazing effects indicated that the regions, it is not easy to predict the ecological fears of overgrazing were based on local damage consequences of various forms of management of around a few enclosures and fences. No evidence reindeer populations, whether wild or domestic- of large-scale overutilisation of reindeer ranges ated. This suggests a need to synthesise and as- in the Swedish mountains could be found. The sess all the available evidence on how vegetation current consensus is that overgrazing of Swedish is affected by reindeer, and to identify knowledge reindeer ranges has been temporary and local, gaps that could be fi lled in by further research. and that it has rarely caused permanent damage. Recent evidence from Finnmark’s winter range- In Sweden, the recent re-evaluation of what lands points to a similar conclusion. reindeer grazing means for arctic and alpine vegetation makes an examination of the scientifi c A common view today is that, on the whole, reindeer grazing benefi ts the montane vegeta- What is a systematic review? tion and enhances its species richness. There are indications that even heavy grazing during In this review, we used a systematic ap- a limited period can promote the diversity of proach to synthesise available evidence on alpine vegetation in the long run. Fears have ac- the impacts of reindeer herbivory. System- tually been expressed that parts of the mountain atic reviews are entirely based on existing region will become overgrown with shrubs be- studies – in this respect, they do not differ cause of inadequate grazing pressure, although from ordinary literature reviews of scientifi c the number of reindeer in Sweden is not much questions. The difference lies, instead, in the smaller now than it was around 1990. way of working. A systematic review is characterised by meticulous planning, methodical The current attitude to reindeer grazing is refl ec- procedures and a transparent, objective and ted in an environmental quality objective for the complete documentation of all assessments mountains adopted by the Swedish Parliament. carried out in the course of the work. This One of the specifi cations of this objective de- approach is designed to increase reliability clared that it is essential to preserve ‘a mountain and repeatability, avoid bias and permit landscape characterised by grazing’. However, meta-analysis (quantitative conclusions no details were given on how this was to be in- based on data from several different studies). terpreted in ecological terms. 7 SR1 | Impacts of reindeer on arctic and alpine vegetation support for today’s prevailing opinions on the is- The primary aim of the review was to clarify how sue particularly relevant.

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