A Balance Between Productivity and Biodiversity Conservation in Montane and Subalpine Semi-Natural Grasslands
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A balance between productivity and biodiversity conservation in montane and subalpine semi-natural grasslands Inauguraldissertation der Philosophisch-naturwissenschaftlichen Fakultät der Universität Bern vorgelegt von Malie Lessard-Therrien von Duhamel-Ouest (QC, Canada) Leiter der Arbeit Prof. Dr. Raphaël Arlettaz Conservation Biology, Institut für Ökologie und Evolution, Universität Bern Dr. Jean-Yves Humbert Conservation Biology, Institut für Ökologie und Evolution, Universität Bern Von der Philosophisch-naturwissenschaftlichen Fakultät angenommen. Bern, 25. April 2017 Der Dekan Prof. Dr. Gilberto Colangelo Figures & layout: Malie Lessard-Therrien Photo credits: Thesis beginning: Bärbel Koch Table of content: Nora Rieder Chapter 1: Malie Lessard-Therrien Chapter 2: Malie Lessard-Therrien Chapter 3: Malie Lessard-Therrien Erklärung: Eddy Mottaz Department of Conservation Biology Institute of Ecology and Evolution A balance between productivity and biodiversity conservation in montane and subalpine semi- natural grasslands A thesis presented by Malie Lessard-Therrien Academic dissertation for the Degree of Doctor of Philosophy at Bern University to be publicly defended on Tuesday April 25, 2017 at 10.00 in room D110, Baltzerstrasse 6, 3012 Bern, Switzerland. Thesis supervisors: External examiners: Raphäel Arlettaz Regina Lindborg Jean-Yves Humbert Pascal Vittoz Chair: Catherine Peichel “Biodiversity is not a threat to agriculture; it is the key to its sustainability.” – Perrings et al. 2006 Conserv. Biol., 20(2): 263-264 Contents Abstract 8 General introduction 10 Chapter 1 Experiment-based recommendations for biodiversity-friendly management of mountain hay meadows 23 Chapter 2 Moderate irrigation and fertilisation of mountain hay meadows promotes redatory ground-dwelling arthropod communities 53 Chapter 3 Sustainable biodiversity-productivity management trade-offs in semi-natural mountain grasslands 91 General discussion 124 Acknowledgements 142 Erklärung 146 145 CV Abstract Humans are exploiting a large part of the planet to fulfill their needs. The prevention of further biodiversity loss must involve not only protecting the small pristine areas left of this planet, but by changing the way humans exploit ecosystems and resources. One of the greatest threats to biodiversity comes from the activities surrounding food production: agriculture. The negative impacts of agricultural practices on biodiversity have been widely studied and documented over the last few decades. However, agro-ecosystems, where humans produce their food, have a great potential to provide substitute habitats for biodiversity if managed properly. Thanks to a long history of traditional, low intensity management, some of the most biodiversity-rich agro-ecosystems in Europe are semi-natural grasslands situated in mountainous areas. However, this situation is evolving and, over the last few decades, management practices in mountain grasslands have been intensified in the quest for higher forage production, threatening mountain grassland biodiversity. Preserving the natural value of these semi-natural grasslands is a conservation challenge and evidence-based propositions to preserve biodiversity while ensuring modern farming viability are still lacking. The aim of this thesis was to develop concrete and practical recommendations for a biodiversity conservation-productivity balance in mountain semi-natural grasslands, i.e. a sustainable management that would preserve biodiversity while maintaining acceptable levels of hay production. This aim was addressed by experimentally assessing the effect of six different management treatments applied during five years (2010 to 2015) to existing hay meadows; 1) control receiving no input, 2) irrigation with sprinklers 3) fertilisation with organic slurry, and 3-6) low, medium or high amounts of both irrigation and fertilisation combined. The study took place in eleven species-rich hay meadows in the montane-subalpine belt of the Swiss Alps. The experimental design thus created a four-level intensification gradient, mimicking modern agricultural practices, as well as a 2 x 2 factorial design that allowed disentangling the separate effects of irrigation and fertilisation. To obtain a thorough appraisal of the effects of these management regimes on the mountain semi-natural grassland components, responses of plant diversity (Chapter 1), ground-dwelling arthropod diversity (Chapter 2) and agronomic aspects (Chapter 3) were investigated. 8 Abstract The main outcomes of this thesis are that plant species richness and phylogenetic diversity are highest under traditional, very low intensity management, corresponding to the control, and are lowest under high management intensification. Both ground beetle and spider abundance (as proxy for ground-dwelling arthropod diversity) showed curvilinear relationships with the intensification gradient, with spider populations peaking at moderate intensity while ground beetle abundance was highest under high management intensification. No significant changes were detected for neither taxon’s species richness. Phytomass production (a proxy for hay) and nitrogen yield increased with the intensification gradient. In the light of these results, a low intensity management regime consisting of combined irrigation and fertilisation corresponding to one-third of the amount required to achieve maximum hay yield with two hay harvests per year would represent a good trade-off between grassland diversity conservation and hay production. However, as no single management regime favours all diversity or agronomic components investigated here, I suggest heterogeneous management across the mountain agricultural landscape. Various management regimes, ranging from no inputs with one hay harvest per year, to medium inputs of water and fertiliser with two hay harvests per year would contribute to maintaining biodiversity across semi-natural grasslands in the Alps. These managements regimes could be facilitated by the adoption of agricultural policies to take into account the opportunity costs from the potential hay production losses faced by the farming community, and would contribute to meet the conservation goals required of European farmlands. 9 General Introduction TIME FOR CONSERVATION The science of conservation biology emerged in the early 1980s, recognizing and addressing species depletion and disruption of life-supporting systems by human activities (Soulé 1985). It was described as a multidisciplinary science linking basic and applied research, which has the objective to protect and ensure the continuity of entire communities and ecosystems. It was also described as being a “crisis discipline”, calling for action before knowing all the facts, and where tolerating uncertainty is often necessary. By the late 1980s, concerns regarding the unprecedented global extent of contemporary diversity loss started to appear in the scientific literature and the need for global solutions were recognized (Myers 1989). A scientific call-to-arms was put out to develop strategies to reduce the magnitude and impact of global diversity loss. At the Earth Summit in Rio de Janeiro in 1992, the Convention on Biological Diversity was adopted as an international agreement, with the primary goal of conserving biological diversity (Convention on Biological Diversity 2006). Building on this, considerable conservation efforts have been focused on pristine or relatively untouched habitats in order to save the last remnants of the planet’s wild nature (Mittermeier et al. 2003). However, since population exchanges and community dynamics are occurring among areas affected by different levels of human pressure and/ or disturbance, improved preservation of biodiversity outside protected areas must also be considered in conservation targets. In central Europe, truly natural ecosystems are almost absent and most nature reserves or other areas of high nature conservation value are already anthropogenically-influenced and require management (Bignal & McCracken 1996; Gaston et al. 2008). Tscharntke et al. (2005) stated that “Biodiversity conservation will not work without protecting the just 5% remaining pristine habitats, but also not without recognition of the contribution of the ‘rest’.” Whether it is in pristine areas or in the “rest” of the world, the goal of conservation is to provide principles and tools for preserving biological diversity (Soulé et al. 2005). After the first conservation wave for pristine area protection, research and conservation efforts have been focusing on how humans interact with nature in the context of resource exploitation, as well as land-use such as agriculture, and how to render those interactions 10 General Introduction less destructive and even beneficial for biodiversity (Naeem 2009; Nelleman & Corcoran 2010; Rands et al. 2010; Lin et al. 2012; Barnosky et al. 2017). AGRICULTURE SHARE Extended exploitation and intensification of agricultural practices has been one of the major causes of biodiversity loss and ecosystem degradation during recent decades (Vitousek 1997; Tilman et al. 2001; Foley et al. 2005). The massive biodiversity loss in agricultural intensive areas has alarmed scientists as well as the public (Carson 1962; Vitousek 1997; Krebs et al. 1999). In response, some stakeholders have started to put into place measures in an attempt to prevent further loss of biodiversity (Kleijn & Sutherland 2003; EEA 2004; EU 2005). In many cases, restoration actions must be undertaken since sites