The Lac Saint-Pierre (Québec, Canada) is a wetland of exceptional biodiversity. However, in recent decades, anthropogenic activity has led to the loss or modification of many associated natural habitats, causing sharp declines in populations of wildlife species, including the yellow perch (Perca flavescens), which has most probably suffered from a reduction in breeding habitat. To investigate recent vegetation and land use change in the Lac Saint-Pierre floodplain, aerial photographs from 1950, 1964 and 1997 were interpreted, analysed and compared. Approximately 3,200 ha of wildlife habitat (i.e., natural habitats and perennial crops) have been modified in the portion of the floodplain exhibiting a flood recurrence interval of 0-2 years. The most notable change has been the conversion of approximately 2,500 ha of perennial crops (i.e., pasture and hayfields) to annual crops (e.g., corn and soybean), which are poorly suited to use by wildlife. Natural habitats have also been modified, with the most important being the loss of 350 ha of wet meadow. In addition to yellow perch, other wildlife has also suffered from the observed land use changes, including species of waterfowl and passerines that typically nest in perennial crops and wet meadows. Restoration of essential habitats and changes in farming practices are needed to support the recovery of declining species in the Lac Saint-Pierre and its floodplain.