Fifty years of change in an area of intensive agriculture: plant trait responses to habitat modification and conservation, Bedfordshire, England

We re-surveyed 107 vegetation plots recorded between 1949 and 1951 in Bedfordshire, England, UK to assess (1) the extent of habitat change, (2) quantify overall species trends, (3) relate trends to plant traits in order to identify the main causes of floristic change, and (4) assess the effectiveness of conservation protection. Many more species declined (66%) than increased (34%) indicating an overall decline in species diversity. Vegetation changes were greatest on arable, waste and neutral and acid grassland plots. The composition of woodlands, calcareous grasslands and marshes remained remarkably stable. The main causes were agricultural improvement and succession; other factors, including the spread of invasive alien species, only had very localised impacts. Shifts in plant traits were related to rarity, habitat specificity and nutrient availability with tall nutrient-demanding species increasing at the expense of small habitat specialists. These changes mirror national trends caused by the eutrophication of terrestrial and aquatic ecosystems. The increase of tall species may also reflect the cessation of woodland and grassland management. Greater regenerative abilities did not buffer species from extinction, and rather unexpectedly conservation designation had little effect in reducing habitat change in most cases. Effective conservation of habitat specialists will therefore depend on reduced nutrient enrichment of lowland habitats as well as more effective control of extrinsic factors on designated sites.