We compared historical and present-day vegetation plot records from a cultural landscape rich in fishponds, where recent eutrophication and water table manipulations threaten the unique fen diversity. We assess species composition change over the last 50 yr. The historically wide array of fen vegetation has turned into a homogeneous and floristically depauperate set of acidic yet productive flooded fens with a high water level. Rich and quaking fens that were both low in nutrient availability and had a stable water level near the moss layer experienced a large and substantial reduction and have become rare in the landscape. Eutrophication combined with a lack of management has resulted in fen species persisting only in flooded fens. However, fluctuating water levels and high nutrient availability in flooded fens favour productive Sphagnum fens over the other vegetation types, and, importantly, do not support some endangered fen species.