SHORT COMMUNICATION WIDER RIPARIAN BUFFER STRIPS: A COSTEFFECTIVE CONSERVATION MEASURE FOR FRESHWATER PEARL MUSSELS IN IRELAND? D. Ó hUallacháin INTRODUCTION The freshwater pearl mussel Margaritifera margaritifera (FPM) is a long-lived invertebrate that is found in coarse sand or fine gravel in clean, well-oxygenated, fast-flowing and unpolluted freshwater (Moorkens 1999; 2000; Skinner et al. 2003). The species has undergone a dramatic decline in the sizes of most meta-populations and in the size of its range over the twentieth century (Young 1991; Reid et al. 2012), with an estimated reduction of over 90% in the FPM population in central Europe over this time (Bauer 1988). The species is in very serious decline throughout its range and is listed in the IUCN red data book as endangered worldwide (Baillie and Groombridge 1996) and in the most recent IUCN Irish Red List of non-marine molluscs as critically endangered (Byrne et al. 2009). Ireland is considered a stronghold for the FPM and is believed to support approximately 46% of FPM individuals in the EU (DAFF 2008). However, the NPWS (2008; 2013) concluded that recruitment levels were insufficient in all Irish FPM populations, resulting in all FPM populations, including the populations in designated Special Areas of Conservation (SAC), having unfavourable conservation status. A number of factors are believed to be responsible for the decline in European FPM populations, including organic pollution; sedimentation ; a decline in fish stocks; over-exploitation; and habitat degradation (Beasley and Roberts 1999; Cosgrove and Hastie 2001; Englund et al. 2008). Freshwater pearl mussels have a complex life cycle (Moorkens 1999), and in order to successfully recruit juveniles, they require well-oxygenated rivers that are low in nutrients and have riverbeds containing clean gravel and sand (Curtis et al. 2009). They are particularly sensitive to environmental pressures that cause habitat degradation (e.g. sedimentation and pollution). In Ireland, the principal threat to the species is believed to be poor substrate quality as a result of physical siltation/sedimentation and excess growth of algae and macrophytes (due to nutrient enrichment) (NPWS 2008; 2013; DEHLG 2009). As agriculture is the dominant land-use in Ireland, it is unsurprising that it is also one of the predominant pressures on FPM catchments; for example, restructuring of agricultural land holdings and diffuse pollution to surface waters due to agricultural and forestry activities are believed to be among the most significant threats to FPM in Ireland (NPWS 2013). In an effort to halt the continued decline, the FPM has been protected under Irish and international legislation. The species is listed in Annexes II and V of the European Habitats Directive (EEC 1992) and Appendix III of the Bern Convention (Council of Europe 1979). In 2009, the European Communities Environmental Objectives (Freshwater Pearl Mussel) (EC 2009) were established to support the achievement of favourable conservation status for FPMs. In Ireland, the species is also protected under the Wildlife Act 2000. However, designation alone has proven inadequate in ensuring the sustainability of FPM populations in Ireland. The national population of mature FPM declined by approximately 8% between 2006 and 2012 (NPWS 2013), despite the most-densely populated FPM sites being protected. The report concluded that the conservation status of the FPM was ‘unfavourable bad’ and that the overall trend in the conservation status was ‘declining’. The most urgent challenge therefore for the conservation FPM in Ireland is reducing losses of sediment and nutrients from forestry and agriculture through the development and implementation of cost-effective mitigation measures. WHAT ARE RIPARIAN BUFFER STRIPS AND WHAT ROLE DO THEY PLAY IN NUTRIENT/SEDIMENT REMOVAL? The Habitats Directive (Article 6) requires Member States to avoid the deterioration of natural habitats within SACs and establish conservation measures for annexed species. To date, many measures have been proposed in an effort to reduce the catchment pressures on FPM (for example, see DEHLG 2010). Received 5 May 2014. Accepted 5 April 2014. Published 15 October 2014. D. Ó hUallacháin (email: daire.ohuallachain @teagasc.ie) Teagasc, Johnstown Castle Research Centre, Wexford. Cite as follows: D. Ó hUallacháin 2014 Wider riparian buffer strips: A cost-effective conservation measure for freshwater pearl mussels in Ireland? Biology and Environment: Proceedings of the Royal...