The study investigates how past land use affects current stream biodiversity. It compares watersheds with different land-use histories, finding that land use in the 1950s was the best predictor of present-day diversity, while recent land use was less so. Past agricultural activities may lead to long-term changes in aquatic diversity, even with riparian reforestation. Preservation of habitat fragments may not be enough to maintain natural diversity, and maintaining biodiversity may require conserving much of the watershed. The study analyzed 24 watersheds in two river basins, comparing streams draining agricultural and forested land. Invertebrate diversity was higher in forested streams, while fish diversity was higher in agricultural streams. The study found that land use in the 1950s was the best predictor of current diversity, and that land use in the 30-meter riparian zone was a strong predictor of invertebrate diversity. The study also found that invertebrate assemblages in forested streams differed from those in agricultural streams, with some forested streams resembling agricultural ones. These streams were in watersheds that were 92% forested in the 1990s but had a different invertebrate composition. The study suggests that past land use has a lasting impact on stream biodiversity, and that recovery may take decades. The study challenges the assumption that riparian zone restoration is sufficient for stream recovery. It shows that the entire watershed needs to be considered for biodiversity conservation. The study also highlights the importance of past land use in determining current species diversity in streams. The findings suggest that long-term agricultural disturbances can significantly alter stream biodiversity, and that conservation efforts should focus on preserving the entire watershed rather than just riparian zones.The study investigates how past land use affects current stream biodiversity. It compares watersheds with different land-use histories, finding that land use in the 1950s was the best predictor of present-day diversity, while recent land use was less so. Past agricultural activities may lead to long-term changes in aquatic diversity, even with riparian reforestation. Preservation of habitat fragments may not be enough to maintain natural diversity, and maintaining biodiversity may require conserving much of the watershed. The study analyzed 24 watersheds in two river basins, comparing streams draining agricultural and forested land. Invertebrate diversity was higher in forested streams, while fish diversity was higher in agricultural streams. The study found that land use in the 1950s was the best predictor of current diversity, and that land use in the 30-meter riparian zone was a strong predictor of invertebrate diversity. The study also found that invertebrate assemblages in forested streams differed from those in agricultural streams, with some forested streams resembling agricultural ones. These streams were in watersheds that were 92% forested in the 1990s but had a different invertebrate composition. The study suggests that past land use has a lasting impact on stream biodiversity, and that recovery may take decades. The study challenges the assumption that riparian zone restoration is sufficient for stream recovery. It shows that the entire watershed needs to be considered for biodiversity conservation. The study also highlights the importance of past land use in determining current species diversity in streams. The findings suggest that long-term agricultural disturbances can significantly alter stream biodiversity, and that conservation efforts should focus on preserving the entire watershed rather than just riparian zones.