Grassland accounts for 70% of the UK agricultural land and approximately 32% of agricultural output. This study will aim to investigate the effects of climate change and enhanced atmospheric CO2 levels on grassland systems. The project will be composed of 4 specific objectives outlined as follows, together with ways in which they might be achieved: 1. Investigation of the interactions between enhanced atmospheric CO2 levels and temperature on herbage yields and forage quality for mixed species grassland swards covering lowland and upland sites. Forty-eight well-established monoliths of permanent mixed swards that have already been extracted from Valley, Anglesey, and transferred to Climate Change Solardomes at ITE Bangor, will be exposed to elevated CO2 (ambient + 240 p.p.m. CO2) and temperature (ambient + 3C) to investigate their long-term effects on forage crops. Effects of 2 management regimes that are typical of permanent grassland/upland farms and lowland dairy farms will be investigated; 2. Development of the pre-existing LEGSIL model for examining in detail the effects of projected climate change on lowland and hill systems in the UK, with reference to forage yields, sward composition, length of grazing season, grazing and forage conservation management and livestock output. Initially, the LEGSIL model will be developed so that it can predict in detail a range of sites, climatic and price scenarios. Subsequently, synthesising scenarios will be prepared regarding future climate, future livestock and input prices, and future farming systems; 3. Examination of the possible consequences of climate change on both the viability of livestock farming in the different grassland areas of the UK and on the viability of the industries supplying inputs. Climate change scenarios will be identified in liaison with UKCIP and components of grassland systems will be identified and developed to support development of the model described above. Supporting information on the consequences of possible adaptations to the effects of climate change will be developed through farmer-based focus groups. In addition, economic viability of the farming systems study will be assessed using economic scenarios based on commodity price scenarios produced for MAFF project CC0320 and wider socio-economic scenarios based on those produced by the SPRU study. These data will be translated into a broad assessment of the likely economic impact of climate change on key types of livestock farms in the different farming regions of the UK in order to determine effects of climate change on national livestock output and fertiliser and feed requirements. Secondary effects on associated industries will be derived; and 4. Dissemination of the research findings through a special Forum meeting and through production of both a technical report for a scientific audience and policy makers, and a booklet suitable for farmers. The booklet will provide practical information on the impacts of climate change on UK grass-based livestock systems and on possible coping strategies that are available for farmers to adopt.