Abstract

Ecosystem stability and resilience depend fundamentally on the functional diversity of insect and vertebrate communities. This review synthesizes current understanding of how animals sustain ecosystem functioning through pollination, seed dispersal, nutrient cycling, biological control, and trophic regulation. Insects, representing over 80% of animal species, dominate critical functions including decomposition, pollination, and energy flow through food webs. Vertebrates, while less speciose, provide complementary and often irreplaceable roles as ecosystem engineers, apex predators, and mobile links connecting disparate habitats. Functional diversity—the variety of ecological traits within communities—underpins ecosystem stability through three primary mechanisms: functional redundancy buffers against species loss, response diversity enables adaptation to environmental change, and food web complexity regulates population dynamics. Across terrestrial, freshwater, and marine ecosystems, insects and vertebrates contribute distinct but interacting functions: insects excel in micro-scale processing and rapid biomass turnover, whereas vertebrates’ mediate landscape-scale processes and exert top-down control. Biodiversity loss threatens ecosystem functioning through trophic cascades, functional homogenization, and service collapse, with over 65% of functional diversity in some regions contributed by threatened species. Conservation must shift from species-centric approaches toward functional trait-based strategies that preserve ecological roles, maintain redundancy, and protect keystone functional groups across interconnected landscapes.