Biodiversity increases if neighbouring plant communities differ in species composition

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4 Biodiversity is a relevant measure also at larger spatial scales I Biodiversity increases if neighbouring plant communities differ in species composition 4

5 Biodiversity is a relevant measure also at larger spatial scales II Biodiversity increases if a vegetation type differ in species composition between locations in the landscape

6 Reindeer use habitats in vast landscapes: habitats that are marginal to most other herded animals How do reindeer actually affect biodiversity?

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9 Nutrient rich spots promotes establishment of more productive species [additional faeces] Van der Wal et al 2004

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11 Theory predicts I Effects on biodiversity is largest at intermediate reindeer abundances Species richness Effects of reindeer activities increase with reindeer abundance

12 Theory predicts II Species richness Effects on biodiversity is largest at intermediate reindeer abundances, but what is intermediate depends on resource availability at a given location Low resource availability High resource availability Effects of reindeer activities increase with reindeer abundance

13 In the 90s there was a claim that reindeer do not affect their ecosystems in the long term Jefferies et al 1994 In 2012 they are spoken of as iconic features of northern national parks and Arctic landscapes, key drivers of Arctic biodiversity and ecosystem processes, and central to community culture and land-based lifestyles McLennan et al 2012

14 At the other extreme claims of over-abundance causing ecological disaster Moen & Danell 2003, den Herder et al 2004

15 Different claims for an obvious reason; Reindeer husbandry widespread and with highly variable reindeer abundances, e.g. Norway Reindeer abundance ('000) Western Finnmark Counties south of Finnmark

16 Country and County level patterns may not be very representative at regional and local scales 16 Reindeer abundance ('000) e.g. huge variation at the scale of Reindeer herding districts even within Vest- Finnmark only

17 Reindeer abundance differences between districts somewhat important at the landscape scale Lower reindeer density Higher reindeer density District Landscape Within plots Ravolainen et al 2010

18 Reindeer abundance differences between districts somewhat important at the landscape scale Lower reindeer density Higher reindeer density Highest biodiversity at the smallest scale, indifferent to reindeer abundance District Landscape Within plots Ravolainen et al 2010

19 No clear patterns are maybe to be expected I Reindeer can live in a wide variety of landscapes and vegetation types

20 No clear patterns are maybe to be expected II Dwarf shrubs are the dominant plants in reindeer habitats; reindeer influence may be limited 20

21 14/03/2013 Reindeer abundance is positively associated with abundance of small rodents Small rodents (frequency) [0,0.5] (0.5,1] (1,2] (2,10] Reindeer (frequency) Ims et al. 2007

22 Predator Occupancy Probability of Occupancy Reindeer Abundance Henden et al (manuscript)

23 Predator Richness Species Richness Reindeer Abundance Community-wide response in predator richness to reindeer abundance Henden et al (manuscript)

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25 Climate change effects are evident in circumpolar areas: Encroachment of shrubs Warmer Climate and More Precipitation Plant Succession

26 Climate feedback especially in winter radiance albedo Varanger Peninsula April 2008 Photo Rolf Anker Ims

27 Can reindeer browsing limit encroachment? Warmer Climate and More Precipitation Plant Succession Reindeer activities

28 Reindeer limit encroachment at higher elevations Lower reindeer density Higher reindeer density

29 Reindeer limit tall shrub recruitment Lower reindeer density Higher reindeer density

30 Reindeer limit tall shrub encroachment and keep the landscape open and more

31 Riparian plant community composition Multivariate ordination to structure species composition between different localities Grazing-sensitive Unpalatable, Grazing-tolerant - Three types of communities with different grazing tolerance Palatable, Grazing-tolerant Reindeer increase biodiversity at the landscape scale Ravolainen et al. in review

32 Reindeer husbandry affects biodiversity: Reindeer are key drivers of Arctic biodiversity and ecosystem processes, but how depends on climate depends on reindeer abundances depends on time depends on species pool depends on nutrient availability

33 Reindeer as primary driver of the Arctic savannah Thank you!