Declines in farmland biodiversity during the last century have been widely attributed to the intensification and expansion of modern agricultural practices. This is of particular concern in the United Kingdom where approximately 75% of land is classed as agricultural. The negative effects of agricultural processes on birds has been particularly well documented, with farmland breeding wader populations, especially those in lowland England and Wales, suffering catastrophic long-term population declines. Species such as Redshank and Snipe are effectively no longer birds of the wider agricultural countryside, and in many areas this is now also true for Lapwing. Until relatively recently, the breeding wader community of marginal, upland farmland was thought to have escaped such losses, and Scotland is now critically important in supporting UK populations of breeding waders. However, more recent declines in such marginal upland areas have been identified, with losses of 48% of Lapwings, 55% of Curlews, and 29% of Oystercatchers on Breeding Bird Survey squares since the mid-1990s, and Redshank now too scarce for a trend to be reported. Although there is evidence that agri environment scheme (AES) management directed at waders can reverse population declines at field and farm scales in Scotland, implementation has been far too limited to stem on-going declines nationally. Current AES prescriptions designed to benefit waders on agricultural grasslands are based primarily on manipulation of stocking regimes to limit nest loss by trampling and of water tables to ensure good foraging conditions.
Since 2008, the University of Stirling and the RSPB have been collaborating on a research project to determine the environmental drivers behind unusually high lapwing densities on a livestock farm near Stirling. Management involves a combination of different activities, including planting of a fodder crop (tyfon) and liming, and is undertaken as part of the core farm business rather than under agri-environment support. Fields that have undergone tyfon management support almost 60% more lapwings than other in-bye pasture fields, and densities remain higher than on fields that had not undergone tyfon management for at least a further four years once the field has been returned to grass. High densities of other farmland wader species (notably Curlew and Redshank) at the site indicate that they may also benefit from this farm management. A small-scale experimental trial to test the effects of the separate components of the management, found that invertebrate abundance was highest on the plots which had been limed and that indicators of suitable nesting habitat (e.g. % bare earth) were strongly influenced by treatments involving tillage. These findings suggest that conventional agri-environment management for breeding waders might benefit if grassland re-seeding and pH amendment (delivered sometimes – though perhaps not necessarily by means of fodder crop management) is added to the existing armoury of interventions. We might expect particular benefits on upland marginal agricultural grasslands where high rainfall combined with acidic underlying geologies can result in progressive soil pH reduction over time.
In this PhD we therefore propose to conduct large scale trials to test the temporal and spatial responses of grassland management interventions, on breeding waders, and to assess the economics of new interventions in marginal grassland management.
Specific objectives are to:
- Determine how widespread the use of fodder crop management is in marginal farmland, and whether farms deploying this management support denser breeding wader populations than the surrounding farmland;
- Test the roles of vegetation structure, soil properties, invertebrate diversity and abundance in causing observed wader population responses;
- Assess the economics of different grassland management systems with regard to input costs (e.g. liming), output (yields) and variability of prices in the livestock market; and
- Assess the policy implications of grassland management interventions for the benefit of breeding waders, with respect to agri-environment schemes and farming advisory services.