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The changing contribution of top-down and bottom-up limitation of mesopredators during 220 years of land use and climate change
Stockholm University, Faculty of Science, Department of Zoology.
Stockholm University, Faculty of Science, Department of Zoology.
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Number of Authors: 7
2017 (English)In: Journal of Animal Ecology, ISSN 0021-8790, E-ISSN 1365-2656, Vol. 86, no 3, 566-576 p.Article in journal (Refereed) Published
Abstract [en]

Apex predators may buffer bottom-up driven ecosystem change, as top-down suppression may dampen herbivore and mesopredator responses to increased resource availability. However, theory suggests that for this buffering capacity to be realized, the equilibrium abundance of apex predators must increase. This raises the question: will apex predators maintain herbivore/mesopredator limitation, if bottom-up change relaxes resource constraints? Here, we explore changes in mesopredator (red fox Vulpes vulpes) abundance over 220years in response to eradication and recovery of an apex predator (Eurasian lynx Lynx lynx), and changes in land use and climate which are linked to resource availability. A three-step approach was used. First, recent data from Finland and Sweden were modelled to estimate linear effects of lynx density, land use and winter temperature on fox density. Second, lynx density, land use and winter temperature was estimated in a 22650km(2) focal area in boreal and boreo-nemoral Sweden in the years 1830, 1920, 2010 and 2050. Third, the models and estimates were used to project historic and future fox densities in the focal area. Projected fox density was lowest in 1830 when lynx density was high, winters cold and the proportion of cropland low. Fox density peaked in 1920 due to lynx eradication, a mesopredator release boosted by favourable bottom-up changes - milder winters and cropland expansion. By 2010, lynx recolonization had reduced fox density, but it remained higher than in 1830, partly due to the bottom-up changes. Comparing 1830 to 2010, the contribution of top-down limitation decreased, while environment enrichment relaxed bottom-up limitation. Future scenarios indicated that by 2050, lynx density would have to increase by 79% to compensate for a projected climate-driven increase in fox density. We highlight that although top-down limitation in theory can buffer bottom-up change, this requires compensatory changes in apex predator abundance. Hence apex predator recolonization/recovery to historical levels would not be sufficient to compensate for widespread changes in climate and land use, which have relaxed the resource constraints for many herbivores and mesopredators. Variation in bottom-up conditions may also contribute to context dependence in apex predator effects.

Place, publisher, year, edition, pages
2017. Vol. 86, no 3, 566-576 p.
Keyword [en]
ecosystem processes, historical ecology, historical maps, intraguild killing, trophic interactions, wildlife monitoring, wildlife restoration
National Category
Environmental Sciences Zoology
Research subject
Animal Ecology
Identifiers
URN: urn:nbn:se:su:diva-143409DOI: 10.1111/1365-2656.12633ISI: 000398826400016PubMedID: 28075011OAI: oai:DiVA.org:su-143409DiVA: diva2:1099705
Available from: 2017-05-29 Created: 2017-05-29 Last updated: 2017-06-29Bibliographically approved
In thesis
1. Anthropogenic impact on predator guilds and ecosystem processes: Apex predator extinctions, land use and climate change
Open this publication in new window or tab >>Anthropogenic impact on predator guilds and ecosystem processes: Apex predator extinctions, land use and climate change
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Humans affect ecosystems by changing species compositions, landscape and climate. This thesis aims to increase our understanding of anthropogenic effects on mesopredator abundance due to changes in apex predator status, landscape and climate. I show that in Eurasia the abundance of a mesopredator, the red fox (Vulpes vulpes), is limited top-down by the Eurasian lynx (Lynx lynx) and bottom-up by winter severity. However, where lynx has been eradicated, fox abundance is instead related to bottom-factors such as cropland (paper I, II). Fox abundance was highest when croplands constituted 25% of the landscape (paper II). I also project red fox abundance in Sweden over the past 200 years and in future scenarios in relation to lynx density, land use and climate change. The projected fox abundance was highest in 1920, when lynx was eradicated and the proportion of cropland was 22%. In 2010, when lynx had recolonised, the projected fox abundance was lower than in 1920, but higher than in 1830. Future scenarios indicated that lynx abundance must increase in respond to climate change to keep fox at the same density as today. The results suggest a mesopredator release when lynx was eradicated, boosted by land use and climate change, and that changes in bottom-up factors can modify the relative strength of top-down factors (paper IV). From 1846-1922, lynx, wolverine (Gulo gulo) and grey wolf (Canis lupus) declined in Scandinavia due to persecution; however I show that the change in wolverine abundance was positively related to the changes in lynx and wolf abundance. This indicates that wolverine is subsidized by carrions from lynx and wolf kills rather than limited top-down by them (paper III). This thesis illustrates how mesopredator abundance is determined by a combination of top-down and bottom-up processes, and how anthropogenic impacts not only can change the structures of predator guilds, but also may modify top-down processes through changes in bottom-up factors.

Place, publisher, year, edition, pages
Stockholm: Department of Zoology, Stockholm University, 2014. 18 p.
Keyword
Mesopredators, apex predators, top-down, bottom-up, interspecific killing, red fox, Eurasian lynx, grey wolf, wolverine, productivity, winter severity, cropland
National Category
Zoology Ecology
Research subject
Animal Ecology
Identifiers
urn:nbn:se:su:diva-100720 (URN)978-91-7447-860-0 (ISBN)
Public defence
2014-03-21, Nordenskiöldsalen, Geovetenskapens hus, Svante Arrhenius väg 12, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 3: Submitted. Paper 4: Manuscript.

 

Available from: 2014-02-27 Created: 2014-02-12 Last updated: 2017-06-29Bibliographically approved

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