Weak effects of farming practices corresponding to agricultural greening measures on farmland bird diversity in boreal landscapes

Landscape Ecol (2019) 34:389–402 https://doi.org/10.1007/s10980-019-00779-x (0123456789().,-volV) ( 01234567 89().,-volV) RESEARCH ARTICLE Weak effects of farming practices corresponding to agricultural greening measures on farmland bird diversity in boreal landscapes Johan Ekroos . Juha Tiainen . Tuomas Seimola . Irina Herzon Received: 11 April 2018 / Accepted: 28 January 2019 / Published online: 8 February 2019 Ó The Author(s) 2019 Abstract Context The current Common Agricultural Policy (CAP) of the European Union includes three greening measures, which are partly intended to benefit farmland biodiversity. However, the relative biodiversity effects of the greening measures, including joint effects of landscape context, are not well understood. Objectives We studied the effects of increasing crop diversity, proportions of production grasslands and fallows, corresponding to CAP greening measures, on open farmland bird diversity, whilst controlling for the Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10980-019-00779-x) contains supplementary material, which is available to authorized users. J. Ekroos (&) Centre for Environmental and Climate Research, Lund University, 223 62 Lund, Sweden e-mail: ; J. Tiainen
T. Seimola Natural Resources Institute Finland, P. O. Box 2, 00790 Helsinki, Finland I. Herzon Department of Agricultural Sciences, 00140 Helsinki, Finland I. Herzon Helsinki Institute of Sustainability Science, HELSUS, P. O. 20 Box 65, 00140 Helsinki, Finland effects of distance to forests, field edge density and proportion of built-up areas. Methods We surveyed open farmland birds using territory mapping in Southern Finland. We modelled effects of greening measures and landscape structure on farmland birds (7642 territories) using generalised linear mixed models. Results Increasing proportions of grasslands increased farmland bird species richness and diversity in open farmland, whereas increasing proportions of fallows increased bird diversity. Increasing crop diversity benefited individual species, but not species richness or diversity. Increasing field edge densities consistently increased the species richness of all farmland species, in-field nesters and non-crop nesters, as well as total farmland bird diversity. The relative effect of edge density was much stronger compared to the three greening measures. Conclusions Our results show that promoting fallows and grasslands, in particular grazed grasslands and various types of semi-natural grasslands, has the highest potential to benefit farmland bird diversity. Maintaining or increasing field edge densities, currently not supported, seems to be of even more benefit. In open farmland, with little or no field edges, fallows and grasslands are particularly beneficial. Keywords Agri-environment schemes
Common whitethroat
Greening under Pillar I
Meadow pipit
Skylark
Whinchat 123 390 Introduction The European Union (EU) has set a target of stopping biodiversity declines within the Union’s member states by 2020 (European Commission 2011). In European farmland, the main policy approach to counteract widespread biodiversity declines are agrienvironment schemes funded under Common Agricultural Policy (CAP) (Pe’er et al. 2014). While some targeted agri-environment schemes have been highly successful in reversing declines of red-listed species (Perkins et al. 2011), many widely adopted agrienvironment schemes have been criticised for not being particularly effective (Kleijn et al. 2011). The recent CAP reform introduced so-called greening measures to address challenges related to climate change and the environment, including the decline of biodiversity (Pe’er et al. 2014). The greening measures include establishing ecological focus areas over a certain portion of a farm area, retention of permanent grasslands and enhancing crop diversity (European Commission 2013). It has been argued that the greening measures in their approved form became less biodiversity-friendly than originally intended (Pe’er et al. 2014) and they are not based on solid evidence (Dicks et al. 2014). For example, ecological focus areas were originally suggested to consist of fallows or buffer strips, but later additional options, such as legumes under conventional management, were approved as ecological focus areas though their value for biodiversity can be questioned (Pe’er et al. 2014). Retention rules for permanent grasslands became less strict than originally proposed: a reduction of up to 5% in their net area at national or regional scales is permitted (Pe’er et al. 2014). Finally, the outcome of numerous exemptions resulted in that these measures apply to only 50% of EU farmland (ibid). Because the biodiversity effects of the current greening measures are largely unknown but the imperative of improving environmental performance of the CAP remains strong, there is a clear need for further empirical evidence (Dicks et al. 2014; Pe’er et al. 2017). In addition, the added value of management interventions for farmland biodiversity depends on landscape context (Batáry et al. 2011; Scheper et al. 2013). Implementing greening measures may therefore have a stronger impact on farmland biodiversity in structurally simple landscapes, where wildlife- 123 Landscape Ecol (2019) 34:389–402 friendly management can create a stronger ecological contrast between areas with and without agri-environment schemes (Batáry et al. 2011). Moreover, birds breeding in open farmland avoid settlements and other built-up areas and forest edges, whereas predominantly open field boundaries are particularly beneficial non-crop habitat structures (Vepsäläinen et al. 2010; Tiainen and Seimola 2014). In this context, implementing greening measures can be expected to affect farmland birds differently depending on the availability of field boundaries and distance to forests and settlements across agricultural landscapes. Furthermore, individual species can be expected to respond differently to gradients in land-use intensity and landscape structure depending on contrasting ecological requirements between species (Vepsäläinen et al. 2010; Pickett and Siriwardena 2011). Bird species breeding in fields respond directly to changes in field management practices, particularly in open farmland characterised by large fields and low proportions of non-crop habitats. In contrast, bird species breeding in edge habitats, e.g. in non-crop field boundaries, but feeding at least partially in fields, respond to field management indirectly because of effects of landscape complementation and landscape supplementation (Brotons et al. 2005; Smith et al. 2014; Josefsson et al. 2017). While farmland birds benefit from fallows (van Buskirk and Willi 2004; Herzon et al. 2011) and grasslands in cereal-dominated farmland (Piha et al. 2007), it is less clear whether increasing crop diversity benefits farmland birds (Hiron et al. 2 (...truncated)