Application of a grazing model to predict heather moorland utilization and implications for nature conservation

An audit of heather moorland utilization by sheep and an assessment of the implications for nature conservation is developed through the application of a grazing model to the Northern Isles of Scotland. Based on guideline maximum utilization limits, the results suggest a marked variation in utilization patterns, but that based upon sample grazing units some 15% of Orkneyʹs heather moorland is overgrazed with a higher figure of 47% for Shetland. Interpolation of the sample data across the two archipelagos indicates a core-periphery pattern with grazing utilization most pronounced along moorland edges. Grazing utilization is observed to be less in areas with statutory conservation designation and on land owned by conservation charities. Incorporating appropriate heather burning programmes together with reduction in the area ofNardusand reductions in sheep stocking rates to between 0·48 and 0·98 ewes/hectare, it is suggested that conservation management will be required to maintain existing heather moorland.1998 Academic Press