This research sought to indicate changes in the area of plant communities designated for protection in part of the middle Vistula river valley. The study concerned the 50-year period 1949-2001, with the changes registered cartographically. The study area (about 905 km2) is located between the Sanna confluence above Annopol and Góra Kalwaria (from km 295 to km 482 of the river course). The analysis of changes determined the general trends of the natural environment transformation in the second half of 20th century that helped to indicate areas that should be protected additionally. Nineteen types of habitats listed in legal statutes (Habitats Directive etc.) were identified in the chosen part of the valley. Over 50 years, grassland communities have undergone the most significant modifications. Vegetation changes reveal a tendency of a lowering of the water level or a change in the horizontal movement of water as well as of aggradation (increased sediment accumulation) in the river-channel. There are indications that two specific areas should be protected additionally because of the definite presence of valuable natural habitats.