Reductions in Aquatic Insect Diversity from Anthropogenic Stressors Occur Across Subtropical and Tropical Islands in East Asia

The subtropical and tropical islands of East Asia host a unique and highly endemic aquatic insect fauna threatened by a variety of anthropogenic stressors (e.g., invasive species, habitat fragmentation, pollution, and climate change). This review synthesizes the impacts of these stressors on aquatic insect diversity across this region based on 206 articles published over the past 40 years (1985–2025) to evaluate the impacts of these stressors on insular aquatic insect diversity. The islands of East Asia include all or parts of China, Japan, Taiwan, and South Korea. The annual number of publications demonstrates a steady upward trend over time and has been accelerating in the last decade. Our systematic analysis reveals a large geographic disparity. Research is heavily concentrated on major islands, with Honshu Island (42%) and Taiwan Island (24%) accounting for two-thirds of the total literature, while small islands (<10,000 km2) comprise only 20%. Furthermore, current research tends to focus on independent impacts of single stressors, largely overlooking the complex additive, synergistic, or antagonistic interactions that characterize stressors on these fragile ecosystems. These research gaps, compounded by a lack of long-term monitoring data (i.e., only ~22% of the studies span more than 3 years), hinder efforts to distinguish natural inter-annual variability from anthropogenic shifts. The extinction of cryptic or endemic species may occur before these species are identified and described. In addition, the disentanglement of these interactive impacts on aquatic insect communities in East Asian islands is critical for predicting ecosystem responses to further local and global changes. Identification of non-linear ecological tipping points through these long-term monitoring networks, coupled with proactive, science-guided habitat restoration, is essential to mitigate imminent extinctions and to rebuild the functional integrity of these imperiled freshwater ecosystems.