Woodland proximity limits benefits of conservation land management for farmland breeding waders

Abstract

1. Breeding waders have suffered long-term population declines, both in Europe and globally, and are species of high conservation concern in Europe, where populations are associated with farmed land. Negative effects of presence of woodland edge on breeding waders have been demonstrated mainly for coniferous plantations, but it is not known if the same relationship exists for broadleaved woodlands and whether conservation interventions for waders might be compromised by the presence of woodland in the wider landscape. This issue is particularly pertinent given the increased interest in woodland cover expansion for ecological restoration and climate change mitigation. 2. Here we analyse data on four wader species of international conservation concern between 2000 and 2015 in an area of the Scottish uplands targeted by wader conservation interventions. We test for each species: 1) change in density over time at the farm scale; 2) associations between wader density and habitat variables at the field scale; and 3) edge effects of distance to broadleaf and conifer woodland on wader density. 3. Wader densities declined between 2000 and 2015 by >50% for Northern Lapwing and >40% for Common Redshank. Effects of habitat variables varin the ied by species with Eurasian Curlew and Common Snipe densities greater in fields with a higher proportion of rush (to c.40% cover); and Common Redshank and Common Snipe densities higher in wetter fields. Densities of all four waders were greater further from woodland edge, whether coniferous or broadleaved, with modelled wader densities extremely low within 100m of woodland. Additional 100m distance bands resulted in increases in predicted wader density of c.10% extending to 500m for Curlew and 700-900m for Lapwing, Snipe and Redshank. 4. Policy implications: Where grassland breeding wader assemblages may be put at risk by tree planting, buffer zones >500m should be implemented to mitigate the negative effect on wader species, with further distances having greatest benefits. Equally, the benefits of conservation measures for breeding waders will be reduced within similar proximities to existing woodland cover. Fields selected for wader AES management should be in open areas, much further from the woodland edge than the current policy recommendations.