This paper explores whether the introduction of an agri-environmental scheme has altered the course of long-term trends in plant species abundance in the Somerset Levels and Moors Environmentally Sensitive Area (ESA), UK. A semi-quantitative approach has been taken which integrates disparate but important historical datasets relating to flora and land management with more contemporary digital information. Species datasets from four time periods throughout the 20th century have been collated within a Geographic Information System and analysed with respect to ancillary data relating to elevation, under-drainage and ESA designation. Qualitative reconstruction of the historical ecology of this internationally important area of lowland wet grassland showed that a steady decline in abundance and extent of key components of the flora had already started by 1900. Analysis of historical under-drainage records dating from 1940s to 1980s showed a clear link between the length of time an area had been under-drained and the subsequent diversity of flora recorded in later surveys. In addition, the relative persistence of the rarer components of the wetland flora between surveys in 1980 and 1997 was related to the spatial pattern of under-drainage on the site since 1940. When overall species diversity was compared before and after ESA designation (1980-1997) there was some evidence of an increase in the number of species present and their spatial extent. The historical dataset provided useful contextual information with respect to species trends and allowed the interpretation of contemporary datasets to be placed within a longer timeframe. This pilot study using 18 species gives some evidence that long-established trends in species decline in the Somerset Levels and Moors ESA are starting to be reversed.