Press release: Altered research is needed to clarify reindeer grazing effects

NEWS | 2015-02-23

Views on how reindeer affect vegetation in mountain areas have varied over time. EviEM, the Mistra Council for Evidence-Based Environmental Management, has collated existing knowledge in this area. Its review shows that research needs to be more standardised if it is to answer questions about the impacts of reindeer grazing.

Reindeer in Sarek National Park, Sweden. Photo: Oskar Karlin

The Mistra Council for Evidence-Based Environmental Management (EviEM) works to promote environmental management built on a scientific foundation. Using systematic reviews of different issues relating to the environment, its aim is to improve the basis for environmental decision-making in Sweden.

The systematic review method, which sets out to synthesise the results of a large number of existing studies, can be used to bring clarity to issues on which consensus has previously been lacking.

The impacts of reindeer grazing in mountain areas are one such issue. Historically, views on how reindeer affect vegetation have varied, from fears in the 1990s that mountain regions were overexploited to the view in recent years that grazing in fact benefits vegetation. One of the environmental objectives set by the Swedish Parliament calls for a landscape ‘characterised by grazing’ to be preserved in mountain areas, but it remains unclear what mountain vegetation should look like to fit that description.

The main aim of EviEM’s review was to clarify how grazing, browsing and trampling by reindeer affect the vegetation of their ranges in alpine, tundra and subalpine birch-forest areas (but not coniferous forests) the world over. The review was launched in autumn 2012, at the suggestion of the Swedish Environmental Protection Agency.

EviEM’s initial search identified over 6,000 scientific studies, which were whittled down to 40 that were judged to be useful and relevant. Their findings varied widely, however, making it difficult to draw general conclusions about the impacts of reindeer on alpine and Arctic vegetation.

Individual results pointed to everything from positive to negative effects on different kinds of vegetation, or no significant effects at all. Even within a single study, a particular vegetation type could respond positively to reindeer grazing at some sites, but negatively at others.

‘The results tell us that reindeer do affect vegetation, but the data we have had access to don’t allow us to establish why their impacts are so variable. Clearly, there are gaps in the current knowledge base,’ says Jon Moen, chair of the review team and a professor in the Department of Ecology and Environmental Science at Umeå University.

Moen calls for a more standardised way of measuring reindeer impacts on vegetation. In particular, we need more reliable data on densities of reindeer at the sites where vegetation studies are carried out.

Although it is difficult to draw firm conclusions about reindeer grazing, some patterns do emerge from EviEM’s review:

  • Lichens are vulnerable to grazing and trampling by reindeer
  • Bryophytes (mosses etc.) are not sensitive to such pressures
  • Herbs (forbs) are sought after by reindeer, making them vulnerable to grazing
  • No clear and consistent impacts on grasses and shrubs could be seen.


What is a systematic review?

Systematic reviews are based entirely on existing studies and are no different in that respect from ordinary literature reviews of scientific questions. The difference lies, rather, in the procedure adopted, which is more methodical and involves full and open documentation of all the assessments made as the work proceeds.

The methodology is designed to avoid preconceived and biased conclusions and to allow for meta-analysis (quantitative deductions based on data from several different studies).


Jon Moen
Chair of the review team and professor at the Department of Ecology and Environmental Science, Umeå University.
Phone: +46 (0)70 227 15 13+46 (0)70 227 15 13 +46 (0)90 786 96 47+46 (0)90 786 96 47 

Claes Bernes
Project manager for the review, EviEM
Phone: +46 (0)8 673 97 55+46 (0)8 673 97 55 +46 (0)72 246 38 89+46 (0)72 246 38 89

Matilda Miljand
Coordinator, EviEM
Phone: +46 (0)8 673 97 53+46 (0)8 673 97 53+46 (0)72 208 72 59+46 (0)72 208 72 59