A growing body of evidence suggests that insect populations worldwide are declining at rates that constitute an ecological emergency. A landmark 2019 meta-analysis — synthesising data from 73 long-term studies — found that approximately 40% of insect species are declining and a third are threatened with extinction, with a total biomass loss of approximately 2.5% per year. A 2017 study in German nature reserves found that flying insect biomass had declined by more than 75% over 27 years. In the United States, monarch butterfly populations at their Mexican overwintering sites declined by approximately 97% between the 1990s and the early 2020s. The drivers of this decline are multiple and interacting: habitat loss, agricultural intensification, pesticide use (particularly insecticides and herbicides), light pollution, invasive species, pathogens, and climate change.
of insect species in decline
biomass loss in German reserves over 27 years
annual insect biomass loss globally
of insect species threatened with extinction
Neonicotinoid insecticides — a class of systemic pesticides that are absorbed by plants and expressed in pollen, nectar, and leaf tissue — have become the most widely used insecticides in the world since their introduction in the 1990s, applied to more than 120 crops in over 120 countries. Their systemic nature means that bees and other pollinators are exposed through foraging on treated plants even when the plants are not directly sprayed. Sub-lethal exposures impair bee navigation (reducing foraging efficiency and homing ability), memory and learning, reproduction (reducing queen production and colony growth), and immune function (increasing susceptibility to pathogens). The European Union banned outdoor use of three key neonicotinoids in 2018 following a comprehensive review by the European Food Safety Authority; their use remains widespread in many other regions.
Research into this field has expanded significantly over the past decade, with studies conducted across six continents revealing both shared patterns and important regional variations. Long-term ecological monitoring programmes — some spanning more than 50 years — have been particularly valuable in distinguishing cyclical variation from directional trends, and in identifying the ecological thresholds beyond which ecosystems shift to alternative states that may be difficult or impossible to reverse.
The application of remote sensing technologies — satellite imagery, LiDAR, acoustic monitoring, and environmental DNA — has transformed the scale and resolution at which ecological patterns can be detected and analysed. Where field surveys once required years of intensive effort to characterise a single site, modern sensor networks and automated analysis pipelines can monitor hundreds of sites simultaneously, providing datasets of unprecedented spatial and temporal coverage.
I've spent a lot of time on my hands and knees in field sites across South Asia and the UK, collecting insects that most people never notice — the mining bees nesting in bare soil patches, the hoverflies hovering over umbellifers, the ground beetles sprinting between grass stems. What strikes me every time is how much ecological complexity is packed into a few square metres of decent habitat. And conversely, how empty the same space can feel in an intensively managed agricultural landscape — the silence where there should be buzzing. The numbers bear this out: flying insect biomass in German nature reserves fell by 75% over 27 years. Those aren't abstract statistics. They represent a real, measurable hollowing out of the countryside.
The good news — if there is any — is that insects can recover remarkably quickly when conditions improve. Studies of restored wildflower strips, reduced pesticide regimes, and reconnected habitat networks consistently show rapid rebounds in pollinator diversity and abundance within two to five years. The science of what works is reasonably clear. What is needed is political will, changes to agricultural subsidy systems, and a shift in how we measure the value of the land — one that accounts for the ecological services insects provide rather than treating their decline as an acceptable cost of food production.
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