Insect declines alter nutrient cycling through a web of indirect pathways that extend beyond the immediate loss of biomass. Decomposition slows when populations of detritivores such as litter beetles, springtails, and certain fly larvae fall, because these organisms physically fragment organic matter and stimulate microbial activity. Research by Dave Goulson, University of Sussex, highlights how reductions in detritivore abundance change the rate at which nutrients are released from dead plant and animal material, making less nitrogen and phosphorus available for plant uptake. The effect is often non-linear because microbial communities respond differently to changed substrate delivery and microhabitat conditions.
Changes in plant communities and litter quality
When pollinators and herbivorous insects decline, plant reproductive success and selective herbivory patterns shift, causing alterations in plant community composition. Sandra Díaz, National University of Córdoba, contributed to the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services assessment showing that such community shifts influence the type and chemical quality of litter entering soils. Litter with higher lignin or secondary compounds decomposes more slowly, further reducing nutrient turnover and altering the balance between carbon and nutrient storage. These processes can take years to become apparent at landscape scales.
Soil structure, hydrology and microbial dynamics
Insects also influence soil structure and hydrology through burrowing, aggregation and the redistribution of organic matter. Loss of bioturbating species reduces soil porosity and water infiltration, which affects oxygen availability for microbes and slows mineralization. Tom W. Crowther, ETH Zurich, has linked changes in soil biodiversity with shifts in carbon processing, indicating that altered nutrient cycling can feed back to carbon sequestration dynamics. Moreover, the decline of predatory insects can cause herbivore outbreaks that change litter input rates and spatial nutrient hotspots, redistributing nutrients unevenly across territories.
Consequences cascade to human and environmental systems. Reduced nutrient availability can lower crop yields in vulnerable smallholder systems and change pasture quality for grazing communities, affecting cultural livelihoods. Slower nutrient retention in soils may increase nutrient runoff in some landscapes, contributing to eutrophication downstream and modifying aquatic food webs. The indirect effects of insect declines therefore connect biodiversity loss to food security, water quality, and climate feedbacks across regions.