Potential to Enhance Biodiversity in Intensive Livestock farms -PEBIL
		Simon Potts, Ben Woodcock and Alex Ramsay Most agricultural grassland in lowland UK is species-poor and structurally uniform Management intensification has had a deleterious affect on the biodiversity of invertebrates and the suitability of grassland as feeding and breeding habitat for birds Pilot studies have indicated that significant biodiversity enhancement can be achieved by creating structural variation in field margins. Overall Objective: To quantify the biodiversity benefits, particularly in relation to invertebrate diversity and bird abundance, of imposing different field margin treatments on to intensively managed grasslands. Different field margin treatments are designed to test the effects of increasing amounts of sward structural heterogeneity, in terms of canopy height, architectural complexity and botanical composition, on faunal abundance and diversity, as well as food resources for birds. Specific Objectives: 1. Quantify effects of vegetation attributes (height, structural heterogeneity, and species composition) on invertebrates and birds in the context of managed grassland 2. Evaluate the relative biodiversity gain from different field margin treatments 3. Identify practical options for enhancing biodiversity on intensively managed livestock farms 4. Quantify cost and agronomic implications of field management options for enhancing biodiversity on intensive grassland farms. Methodology Site Management: Following the project start-up in spring 2002, two areas with grassland-dominated landscapes (Devon and Somerset) were selected on the basis that they have shown marked declines in farmland birds. Experimental treatments have been successfully established on 4 farms with intensively managed permanent pastures. Each treatment has been applied to a 10 x 50 m field margin, with 3 replicated blocks of the 9 treatments per farm. Treatment Rationale: The treatments are based upon ecological requirements of the invertebrates, in terms of their taxonomic and phenological diversity and abundance, and as a vital component of the food chain for birds. The treatments are designed to provide a range of habitat structures and test responses of invertebrates to increases in vegetation height and structural complexity along a gradient of decreasing disturbance, as illustrated in Fig 1. Treatment Codes: The treatments range from variations in relatively simple practices, readily adopted on grass fields, through to more radical and interventionist practices (Fig 1.). Treatments 1 to 4 provide a fully factorial design that will enable any effects/interaction between fertilizer nitrogen input, silage stubble height and/or aftermath grazing intensity on invertebrate diversity and abundance and farmland bird usage to be examined. Treatments 5 to 7 will explore the influence of temporal variation in cutting/grazing date and Treatments 8 and 9, which involve establishment of more complex communities, will explore the influence of enhanced canopy architectural complexity. Structural characteristics of treatments: Output: The findings of the project will provide quantification of: Effects of field margin botanical composition and structure on invertebrate diversity and abundance Effects of different field margin treatments, within intensive grassland farms, on food resources for birds Impact of different field margin treatments on agronomic output from intensive livestock farms and implications for agri-environmental support. Together, these will provide an assessment of environmental benefits that may be derived from schemes that incorporate field margin extensification on intensive grassland farms; and provide the basis for developing stewardship agreements for intensive livestock farms with the aim of enhancing biodiversity, particularly the diversity and abundance of invertebrates and farmland birds. Policy Relevance Data from this project will form the basis for developing agri-environment management agreements for intensive livestock farms to improve their value for wildlife. The project complements an existing Defra funded project (BD1435) that is examining the relationships between intensity of grassland management, sward structural state(s) and invertebrate and bird diversity on commercial livestock farms. Information from the two projects will be of value in predicting wider countryside benefits of integrating extensification options with intensive livestock farming systems. The research has a strong relevance to the delivery of objectives in the Habitat Action Plans, of the UK BAP, through the enhancement and protection of such habitats. Research Partners Sponsor