The study investigates the impact of past land use on the current diversity of stream invertebrates and fish by comparing watersheds with different land-use histories. The research found that whole watershed land use in the 1950s was the best predictor of present-day diversity, while riparian land use and watershed land use in the 1990s were less effective indicators. The findings suggest that past land-use activities, particularly agriculture, can lead to long-term modifications and reductions in aquatic diversity, even if riparian zones are reforested. The study also indicates that preserving habitat fragments may not be sufficient to maintain natural stream biodiversity, and that conservation efforts may need to focus on protecting much or all of the watershed. The results challenge assumptions about the maintenance and recovery of biodiversity in disturbed stream ecosystems, emphasizing the importance of considering the entire watershed for effective conservation.The study investigates the impact of past land use on the current diversity of stream invertebrates and fish by comparing watersheds with different land-use histories. The research found that whole watershed land use in the 1950s was the best predictor of present-day diversity, while riparian land use and watershed land use in the 1990s were less effective indicators. The findings suggest that past land-use activities, particularly agriculture, can lead to long-term modifications and reductions in aquatic diversity, even if riparian zones are reforested. The study also indicates that preserving habitat fragments may not be sufficient to maintain natural stream biodiversity, and that conservation efforts may need to focus on protecting much or all of the watershed. The results challenge assumptions about the maintenance and recovery of biodiversity in disturbed stream ecosystems, emphasizing the importance of considering the entire watershed for effective conservation.