Habitats plants and invertebrates as tools for rapid identification of high nature value farmland
Hayes nee fitzpatrick, Margaret
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The EU, in recognition that low intensity farming plays an important role in conserving biodiversity, is committed to identifying and protecting High Nature Value (HNV) farming. Most methods used to date to delineate areas of HNV have been undertaken at a landscape scale. However, an indicator at the farm level would be more useful for implementing policy incentives, given that monies to protect agrobiodiversity are generally paid to individual landowners. This provided the incentive for the first part of this study, the aim of which was to develop a nature value index for pastoral farmland in the west of Ireland. This index could then be used by the Irish government as a first step to determining those farms which are HNV, thereby ensuring that payments for protecting biodiversity could be targeted at these farms. Using data from 30 farms, a simple 10 point nature value index was developed following a five step statistical process (1. Non-metric Multidimensional Scaling (NMS); 2. Cluster Analysis; 3. Principle Components Regression; 4. Index development; 5. Index validation using data from 60 additional farms in the west of Ireland). This index is based on three easily accessible datasets i.e. a) percentage improved agricultural land; b) stocking density (Livestock Units / ha of the Utilisable Agricultural Area), both of which are already recorded by the Department of Agriculture; and c) length of linear habitats per ha on a farm which can be easily calculated using aerial photographs. Based on this research, farms scoring greater than 4.5 using this index could be classed as HNV farms with the advantage that the datasets used to determine this index can be accessed without visiting the farm, thereby providing a rapid method in the first step to determining HNV farms. The second part of this study deals with assessing the biodiversity value of farm habitats at a local scale given that certain parts of the farm will have greater biodiversity value than others. Since farmland in the west of Ireland is predominantly pasture based, the ecological status of grasslands is of great importance for biodiversity. Given that previous research has indicated that wet grasslands in the west of Ireland are particularly important for biodiversity, these were selected for further study. As it is not possible to undertake an investigation of the diversity of all animal and plant groups, the purpose of this investigation was to determine whether a single taxon or group of taxa could be used with confidence to rapidly assess the biodiversity of wet grasslands. Grasses (Poaceae), sedges (Cyperaceae), rushes (Juncaceae), ground beetles (Coleoptera) and marsh flies (Diptera) were identified to species and Diptera to parataxonomic units (PTUs) on 17 farms. Sedge species richness was the most significantly correlated taxon with overall species richness of the remaining taxa in that it was able to predict 46% of the richness of the other six taxa examined. In addition, the species richness of sedges and carabids as a pair could predict 55% of the richness of the remaining taxa. While it can be argued that using a single taxon or pair of taxa does not reflect fully the total species richness of the remaining taxa, they can be used (while cognisant of their limitations) to make basic essential assessments of wet grasslands for the purposes of monitoring in the context of farm payments. To wait until comprehensive surveys are undertaken, unlikely given the significant costs involved, would be to risk loss of biodiversity of these sites due to agricultural improvement or abandonment. The third and final part of this study investigates those factors which affect plant, carabid and Diptera assemblages in wet grasslands with a view to determining appropriate land management practices for HNV wet grassland. The results indicate that basing HNV wet grassland management strategies on plant species alone (a common occurrence in habitat management due, in part, to limited resources) would not take into account the requirements of the carabid and Diptera fauna. While grazing was found to be important for all taxa studied, of particular importance to the invertebrate groups is percentage cover of bare ground and dead vegetation in addition to the presence of ruderal plants and Ellenberg salt. These features play key roles in the life-cycles of a range of invertebrate species and recommendations from this study are that these elements be incorporated in the management prescriptions for HNV wet grasslands in the future.
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