Abstract <p>Wetlands in Western Europe are undergoing severe degradation due to drainage, agricultural intensification, climate change, and biological invasions, with cascading effects on trophic networks. Large dytiscid diving beetles (<i>Dytiscus</i>, <i>Cybister</i>) are apex invertebrate predators that contribute to nutrient cycling and ecosystem stability, yet their populations remain poorly monitored. Observed declines were evaluated through site-by-site comparisons between historical (1980–2020) and recent (2021–2025) surveys in Latium, central Italy. We found that 88.6% of dytiscid populations exhibited apparent declining abundance, with 77.1% considered certainly extirpated or suspected extirpated, and nearly half of populations that were previously abundant now absent. Using a generalized linear mixed model (GLMM) with binomial error distribution, we found that population persistence was strongly influenced by habitat type, species identity, and temporal factors, with significantly higher persistence in natural lotic habitats and historically common populations, and markedly lower persistence in artificial and temporary water bodies.</p> Implications for conservation <p>Population declines were consistently associated with wetland infilling and drainage for agriculture, excessive irrigation water abstraction, channel maintenance and riparian vegetation removal, diffuse agricultural pollution, hydrological alteration, and the presence of invasive species such as alien fish and <i>Procambarus clarkii</i>. Concurrent declines in <i>Pelophylax</i> frogs further highlight severe disruption of wetland food webs. Conservation priorities should focus on wetland hydrological restoration, invasive species control, long-term monitoring, and legal protection of key habitats.</p>