Assessing potential impacts on biodiversity using critical loads

In many countries there has been much concern over maintaining biodiversity in natural ecosystems in the face of pressures such as changing land use a nd pollution. The 1992 UN Convention on Biodiversity calls upon signatories to develop national strategies for the conservation and sustainable use of biodiversity. In the UK, the potential impacts of sulphur and nitrogen dep osition at the national level are being assessed using national critical lo ads and modelled deposition maps, together with available information on th e occurrence of habitats and plant species. This simple approach gives an i ndication of the areas where atmospheric deposition may have impacts on bio diversity. The results of the analyses are presented and the strengths and weaknesses of the methods used are discussed. This first approach to consid ering the effects on biodiversity shows the importance of including the eff ects of atmospheric deposition in any biodiversity action plan. It also hig hlights those areas where more or improved information is required for the national strategy. With the modelled deposition data available, it would se em that reduced impacts are to be expected by 2010. However, higher resolut ion deposition data, better estimates of ammonium deposition, consideration of temporal aspects and the dynamics of change, and the use of higher reso lution biological data sets are likely to suggest greater impacts than curr ent predictions.