A decision framework to attribute atmospheric nitrogen deposition as a threat to or cause of unfavourable habitat condition on protected sites

This report describes the development of a decision framework to provide a means of attributing nitrogen deposition as a threat to, or cause of, unfavourable habitat condition on protected sites. The UK’s semi-natural habitats exceed their atmospheric nitrogen (N) deposition critical load ranges across much of their area, and survey data suggests there are adverse impacts of this excess N deposition. However, information from Common Standards Monitoring (CSM) of protected sites does not appear to identify N deposition as a potential cause of unfavourable condition at many sites. A decision framework was developed to provide a means of attributing N deposition as a threat to, or cause of, unfavourable habitat condition on protected sites. The framework provides a practical methodology for assessing the impacts of N deposition on protected sites in an objective way, which was previously lacking. It is based on a sound conceptual approach, and is both robust and flexible enough to cope with additional information. The framework is described in the main report, whilst the detailed methodology is included in the supporting annexes. * Annex 1: Strength of “theoretical/national” evidence (Work Package 1 report) – this describes in detail the scoring of national/theoretical evidence to derive an Exceedance Score. * Annex 2: Strength of site-based evidence (Work Package 2 report) – this describes in detail the site-based evidence used to derive a score for strength of site-based evidence (Factor 2) * Annex 3: Matrix design, testing and recommendations (Work Package 3 report) – this describes the version of the matrix as recommended by the contractors, provides recommendations for future work (the key recommendations from this are summarised in this main report), and briefly describes the testing undertaken as part of Work Package 3. The accompanying zipped folder includes: * Factor 1 spreadsheet (Exceedance Score) – this spreadsheet incorporates the elements of WP1 which generate the exceedance score for each CSM habitat (and sub-habitat) based on a user-defined deposition; guidance for utilising the spreadsheet is given in Annex 1. * Factor 2 spreadsheets (N indicators) – these spreadsheets display the results of a review of all targets for each CSM habitat and the identification of strong and weak N indicators; guidance for the spreadsheets is given in Annex 2. * Final assessment matrix – this Word Document provides a copy of the final assessment matrix.