Impacts of small-scale engineering projects on Neotropical freshwater fishes

Neotropical freshwater ecosystems harbor some of the world’s most diverse fish communities, playing a fundamental role in ecosystem functionality and providing essential and free services to human societies. However, this exceptional biodiversity faces escalating threats from multiple and widespread anthropogenic pressures, particularly small-scale engineering activities such as channelization, damming, road crossings, water extraction, and mining, which remain insufficiently assessed despite their cumulative and synergistic impacts. This Special Issue, Impacts of Small-Scale Engineering Projects on Neotropical Freshwater Fish Diversity compiles eleven studies to assess how small-scale interventions affect fish diversity and ecosystem processes. Collectively, these studies consistently demonstrate ecological trends including habitat simplification, loss of sensitive species, predominance of tolerant or generalist taxa, and disturbances on reproductive and trophic dynamics. Hydrological alterations and reduced habitat heterogeneity are key drivers of biotic homogenization and simplification of functional diversity. Overall, these publications emphasize that both local and regional disturbances synergistically compromise the structural and functional integrity of fish assemblages. Maintaining ecological connectivity and functional diversity is essential for maintaining integrity and resilience of Neotropical freshwater ecosystems, and findings underscore the urgent need to integrate small-scale impacts into basin management and conservation, recognizing their cumulative and often underestimated influence on biodiversity and ecosystem functioning.

Keywords:
Biodiversity; Conservation; Environmental; Human activities; Special Issue