Global decline of aquatic and terrestrial insects driven by climate change and anthropogenic impacts: The interaction of multiple stressors and disruption of niche conservatism

The global decline of insect populations represents a profound ecological crisis with far-reaching consequences for biodiversity and ecosystem functioning. This review synthesizes the global decline of insect populations and goes beyond traditional-based approaches by exploring the complex interplay of anthropogenic and climate change factors. We emphasize how niche conservatism, along with taxonomic, functional, and phylogenetic traits, contributes to insect population declines and potential extinctions. Niche conservatism refers to the tendency of species to retain their ancestral ecological traits. These significant reductions in insect populations are predominantly driven by anthropogenic activities (e.g., habitat degradation and pollution) and climate change (e.g., extreme weather), which collectively disrupt habitats, alter ecological processes, and exacerbate environmental stressors. Global changes are intensifying insect biodiversity loss and driving many insect species toward extinction due to niche conservatism, where species with narrow ecological tolerances struggle to adapt to rapid environmental shifts. Our review highlights the urgency of addressing the loss of insect biodiversity, as it compromises essential ecosystem services, such as pollination, nutrient cycling, and pest control, and ultimately undermines human well-being. We call for immediate integrated conservation strategies and the adoption of climate-adaptive management practices, as the interaction of these factors worsens biodiversity loss and increases the urgency of addressing the synergistic impacts on insect species, specifically those unable to adapt swiftly due to niche conservatism. Although innovative technologies such as remote sensing, big data analytics, and genomics can enhance monitoring efforts, successful conservation action at local, national, and international levels is crucial to stop the ongoing declines and ensure the resilience of ecosystems.