Long-term impacts of extensive grazing and abandonment on the species composition, richness, diversity and productivity of agricultural grassland

Extensification of grassland management has been put forward as a method of redressing the biodiversity losses seen in agricultural landscapes as a result of increases in production. However, there is little evidence for its success, particularly in upland areas. Two long-term (16 year) experiments at different sites compared extensive grazing, abandonment and continued intensive grazing, assessing impacts on productivity, species composition and plant diversity. Extensive grazing led to slow but continual changes in composition, with some increase in diversity compared to intensive grazing and a broad indication that productivity did not decline with time. At the drier of the two sites it appeared that extensive grazing was better than intensive grazing at buffering the impacts on productivity of year-to-year variations in the weather. Abandonment led to rapid changes in composition followed by stabilisation, as there were no late-successional species to invade and lead to further changes. However, abandonment did not affect diversity. Extensive grazing produced only gradual changes in the diversity of plant species present, indicating that biodiversity gains from extensification within productive landscapes may be a slow process.