Woody or treeless pastures? Effects of EU tree density limitations on biodiversity in woody pastures
2015 (English)Licentiate thesis, comprehensive summary (Other academic)
The high biological and cultural values of traditionally managed rural landscapes are threatened by habitat change and degradation due to homogenisation through modern agricultural practices and abandonment. Woody pastures are important for many different taxa, and hence crucial for biodiversity conservation in these agricultural landscapes. To mitigate biodiversity loss, agricultural policy recommendations and subsidies are important tools, but if not implemented properly they may have the opposite effect. To keep agricultural landscapes open and to preserve biodiversity, the Common Agricultural Policy (CAP) of the European Union (EU) regulates how many trees farmers are allowed to have on their pastures to receive subsidies from the EU. A seemingly arbitrary limit was set to 50 trees/ha in 2003, which changed recently to 100 trees/ha. However, woody pastures are environments where high nature values often arise from the trees themselves, whereas there is little evidence on how biodiversity is directly affected by tree density in woody pastures. In this study, the tree density limit is targeted to investigate the effects on plant and bird diversity in 64 Swedish woody pastures along a gradient from 0 to 200 trees/ha. The results show that tree density is one of the major drivers of plant diversity, by favouring shade tolerant species without having a negative effect on less shade tolerant grassland specialists. Tree density positively affect bird diversity, an effect saturating at medium dense pastures but large species turnover rates along the gradient point at a variety of species found within woody pastures. Woody pastures with high tree densities in this study contribute substantially to biodiversity as heterogeneous environment enables high species richness. This thesis demonstrates a mismatch between subsidy systems and biological values that need to be further scrutinised to preserve biodiversity of agricultural landscapes.
Place, publisher, year, edition, pages
Stockholm: Department of Physical Geography, Stockholm University , 2015. , 31 p.
IdentifiersURN: urn:nbn:se:su:diva-121799OAI: oai:DiVA.org:su-121799DiVA: diva2:861476
2015-11-06, Högbomsalen, Geovetenskapens hus, Svante Arrhenius väg 8, Stockholm, 10:00 (English)
Pärt, Tomas, Professor
Lindborg, Regina, Professor
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