A major cross-continental analysis published in Nature Communications has quantified what ecologists have long suspected: biological invasions drive a 31% average decline in terrestrial insect abundance — a figure that places invasive species alongside habitat loss and pesticides as a primary driver of the insect decline crisis, not a secondary footnote to it.
Analysis drawing on the published UKCEH and University of Cambridge study, the IPBES Global Assessment Report, and peer-reviewed literature on invasion ecology and insect population dynamics · Updated March 2026
The scientific literature on global insect decline has been accumulating since at least 2017, when a long-term monitoring study from Germany reported a 76% decline in flying insect biomass over 27 years in protected nature reserves — a result striking enough to generate the phrase “insect apocalypse” in mainstream science coverage. Subsequent studies from the United States, Puerto Rico, and across Europe broadly confirmed the direction of the trend, though with significant regional and taxonomic variation that has complicated both the narrative and the policy response.
The established explanatory framework has centred on three drivers: agricultural intensification and habitat loss, pesticide application (particularly neonicotinoids and other systemic insecticides), and climate change. These three factors receive the majority of research funding, policy attention, and conservation intervention.
A study published in Nature Communications by researchers at the UK Centre for Ecology & Hydrology (UKCEH) and the University of Cambridge adds systematic, quantified evidence for a fourth driver that has been present in the ecological literature for years but has not received comparable attention in either research funding or policy frameworks: biological invasions — the introduction of non-native species into ecosystems where they did not previously exist.
The study’s headline figure — a 31% average decline in terrestrial insect abundance in areas affected by biological invasions — is significant not because it supersedes the other drivers but because it establishes invasive species as operating at a scale that demands equivalent treatment in conservation prioritisation, biosecurity investment, and international policy coordination.
The Research Design: What Made This Study Different
Previous work on invasive species and insects had largely been species-specific or region-specific: the impact of the Asian hornet (Vespa velutina) on European honeybee populations, the effect of invasive ant species on native ground-nesting insects in specific habitats, the plant community changes driven by Japanese knotweed. Valuable, but difficult to aggregate into global estimates.
The UKCEH and Cambridge study took a different approach: a cross-continental meta-analysis drawing on standardised ecological monitoring datasets from multiple continents, tracking insect population metrics across sites with and without established invasive species presence. The scale of the dataset — and the use of a consistent methodological framework across geographically diverse sites — is what allows the 31% figure to carry weight as a global estimate rather than a local observation.
Lead author Grace Skinner, a data scientist at UKCEH, described the study’s aim as providing the evidence base needed to move biological invasions from a recognised but underprioritised concern to one that conservation managers can act on with quantified justification: as she put it in the paper, “identifying the insects most vulnerable to biological invasions will support better prioritisation of habitat management and action to prevent and control invasive alien species.”
The study also distinguished between two mechanistically distinct pathways through which biological invasions reduce insect populations — a distinction that matters considerably for understanding which interventions are effective:
Direct predation by invasive animals. Non-native predators — invasive mammals, birds, reptiles, and invertebrates — consume native insect populations at rates that native prey have no evolutionary history of experiencing and no behavioural or population-level adaptation to withstand. Island ecosystems are the most severe cases, but continental ecosystems with historically low predation pressure on specific insect groups show comparable vulnerability.
Habitat and resource displacement by invasive plants. When invasive plant species replace native vegetation — as Japanese knotweed, Himalayan balsam, or kudzu do in various contexts — they remove the specific host plants, nectar sources, and microhabitat structures that native insect communities depend on. This is a slower but no less effective pathway to population decline: insects that require specific native plants for larval development or foraging simply cannot persist when those plants are no longer present.
The relative contribution of these two pathways varies by insect order and invasion type, and the study’s order-level breakdown of decline rates reflects this variation.
The Taxonomic Data: Which Insects Are Most Affected and Why
The study’s breakdown of population decline by insect order reveals a pattern that is ecologically interpretable rather than random — the variation in impact rates maps onto what is known about the ecology and habitat specificity of each group.
| Insect order | Common examples | Average population decline |
|---|---|---|
| Hemiptera | True bugs, aphids, cicadas, plant hoppers | 58% |
| Hymenoptera | Bees, wasps, ants | 37% |
| Orthoptera | Grasshoppers, crickets, katydids | 27% |
| Coleoptera | Beetles | 12% |
Hemiptera — true bugs in the broad sense, including plant-feeding species across a wide range of plant families — show the steepest declines at 58%. This is consistent with the plant displacement pathway: many Hemiptera are highly host-plant specific, and the removal of native vegetation by invasive plants eliminates the resource base for entire assemblages simultaneously. The group’s relatively limited mobility also reduces its capacity to track shifting plant communities across fragmented landscapes.
Hymenoptera at 37% reflects the intersection of both pathways. Social bees and wasps are vulnerable to both direct predation (invasive hornets, particularly Vespa velutina in Europe and Vespa mandarinia in North America, have documented significant impacts on honeybee and bumblebee colonies) and to floral resource disruption from invasive plants that displace native flowering species. The Bumblebee Conservation Trust has documented that bumblebee species with narrow floral ranges are disproportionately affected in landscapes where invasive plant species have reduced the availability of their preferred forage plants. The Bee Informed Partnership tracks managed honeybee colony losses in the United States, where multiple invasive threats interact with other stressors in ways that complicate attribution but confirm the scale of pressure on the order.
Orthoptera at 27% shows moderate impact, consistent with a group that is somewhat less host-plant specific than Hemiptera but dependent on open grassland microhabitat structures that invasive grasses and forbs frequently degrade. Many grasshopper species require bare ground patches for thermoregulation and oviposition — habitat features that invasive plants often eliminate through dense ground cover.
Coleoptera at 12% shows the most limited impact of the four orders examined, which aligns with the ecological generalisation that beetles are the most taxonomically and ecologically diverse insect order, with a wider range of resource use strategies that provides some buffering against any single type of disturbance. That said, 12% represents a substantial population-level impact at global scale, and specific beetle families — particularly saproxylic species dependent on native deadwood — show much steeper declines in specific invasion contexts.
The Trade and Climate Amplifiers
The UKCEH study situates its findings within two broader systemic processes that are actively accelerating the rate of biological invasion globally — and that explain why the problem is getting worse rather than stabilising.
Global trade volume as an invasion vector. The IPBES Global Assessment Report on Invasive Alien Species, published in 2023, documents that the number of established invasive alien species globally has increased by 40% since 1980 — a rate directly correlated with growth in international trade and travel. Shipping containers, timber imports, live plant trade, and the horticultural industry are the primary documented pathways for insect and plant introductions. The International Plant Protection Convention (IPPC) sets the international standards for phytosanitary measures, but implementation capacity varies enormously between countries, and the inspection resources devoted to biosecurity have not scaled proportionally to trade volume.
The economic analysis of this gap is stark. The IPBES assessment estimates global economic costs of invasive species at over $400 billion annually — a figure that dwarfs the estimated cost of the prevention and early detection measures that would reduce it. The cost-benefit case for biosecurity investment is compelling in aggregate; the political economy of implementing it is complicated by the fact that prevention costs are immediate and visible while the avoided costs are counterfactual.
Climate change as an entry facilitator. NASA Global Climate Change data documents that range shifts driven by warming temperatures are altering the geographic boundaries of what ecosystems are climatically suitable for which species. Species previously constrained to warmer latitudes or lower elevations by cold winters are establishing in formerly inhospitable regions as temperatures rise. The IPCC’s Sixth Assessment Report identifies climate-driven range shifts as one of the most certain ecological consequences of current warming trajectories, with high confidence that invasive species will disproportionately benefit relative to native cold-adapted species because of their generalist traits and high dispersal capacity.
The interaction between climate change and biological invasion creates a compounding effect: as native insects in warming ecosystems experience thermal stress that reduces their fitness and reproductive capacity, invasive predators and competitors arriving into newly suitable territory encounter prey and competitors that are already physiologically compromised. The two drivers amplify each other’s impacts in ways that linear addition of their individual effects would underestimate.
Why Invasive Species Are Underfunded Relative to Other Drivers
The IPBES Global Assessment notes explicitly that invasive species receive significantly less conservation funding than habitat loss or climate change despite being ranked alongside them as a top-five driver of biodiversity loss. Understanding why this funding gap exists is important for assessing whether it is likely to close.
Several factors contribute. Habitat loss and climate change have clearly identifiable human activities as their proximate causes — land conversion and greenhouse gas emissions — which makes them tractable for policy intervention through regulation and incentive structures. Biological invasion, by contrast, is driven by a diffuse set of pathways (trade, travel, horticulture, deliberate introduction) that are individually minor but collectively large, and that involve actors who have no awareness of the ecological consequences of their actions.
The geography of impact also creates political economy challenges. The ecosystems most severely affected by biological invasions are frequently those with the least political and economic weight in international conservation negotiations — island ecosystems in the Pacific and Indian Oceans, where the IUCN’s Invasive Species Specialist Group has documented the most severe extinction impacts, are disproportionately the territories of small island developing states with limited capacity to fund biosecurity infrastructure.
The Convention on Biological Diversity’s Kunming-Montreal Global Biodiversity Framework, adopted in 2022, includes Target 6: reducing the introduction and establishment of invasive alien species by at least 50% and controlling or eradicating invasive species in priority sites. The target is specific and measurable. The funding mechanism for achieving it remains substantially underdeveloped.
What Effective Intervention Looks Like
Unlike the diffuse challenge of reducing carbon emissions, biological invasion management offers intervention points that are geographically specific, technically feasible, and in many cases cost-effective relative to the damage they prevent.
Prevention through biosecurity is the highest-value intervention because established invasions are expensive or impossible to reverse. New Zealand’s biosecurity system — widely regarded as among the most rigorous globally — combines pre-border risk assessment of imported goods, border inspection infrastructure, and post-border surveillance to detect new arrivals before they establish. The system’s cost is significant; the counterfactual cost of managing established invasions it has prevented is estimated to be substantially higher. The UK’s Check, Clean, Dry campaign, targeting recreational water users as an inadvertent transport vector for aquatic invasives, demonstrates that individual behaviour change campaigns can be effective at specific high-risk pathways.
Early detection and rapid response systems address the window between initial introduction and establishment, when eradication is still feasible. GBIF (the Global Biodiversity Information Facility) aggregates occurrence data from citizen science platforms including iNaturalist, enabling detection of range expansions and new introductions faster than traditional survey programmes. The European Invasive Alien Species Information Network (EASIN) provides a comparable function for EU member states.
Targeted habitat management for the most affected insect orders — particularly restoring native plant communities in areas where invasive plants have degraded floral and larval resource availability — addresses the plant displacement pathway directly. Plantlife and the Wildlife Trusts in the UK have documented measurable responses in Hymenoptera populations to native wildflower restoration on sites where invasive plants were removed and replaced with diverse native flora.
Biological control — the deliberate introduction of natural enemies of invasive species — is the most technically complex intervention and requires rigorous host-specificity testing to avoid creating new invasive problems. When it works, as in the successful biocontrol of the invasive water hyacinth (Eichhornia crassipes) in some African contexts, it can achieve control at landscape scales that mechanical or chemical methods cannot.
Conclusion: Adding a Fourth Driver to the Framework
The UKCEH and Cambridge study does not overturn the established understanding of insect decline — habitat loss, pesticide use, and climate change remain well-documented and significant drivers. What it does is provide the quantitative basis to add biological invasions to that framework with comparable rigour, rather than treating it as a localised or secondary concern.
The 31% figure is a global average that conceals substantial variation: island ecosystems experience much steeper declines, and specific insect orders and taxonomic groups within orders show impacts that approach or exceed the 58% figure for Hemiptera. The average does not minimise the problem — it establishes a floor.
The policy implication is straightforward even if the implementation is not: biosecurity investment, invasion prevention, and early detection systems need to be funded at a level commensurate with the scale of the ecological and economic damage that invasive species cause. The IPBES estimate of $400 billion in annual economic costs dwarfs the investment in prevention. The gap is not a technical or scientific problem — the interventions are known and in many cases proven. It is a political and prioritisation problem.
The insects most at risk — the Hemiptera and Hymenoptera that provide the pollination and food web functions that underpin terrestrial ecosystem productivity — are also the ones whose loss carries the most direct consequences for agriculture and food security. The connection between insect decline and human food production is not abstract. Making the case for biosecurity funding in those terms, rather than purely in terms of biodiversity value, may be the most effective route to the policy change the research supports.
Sources & Further Reading
- UK Centre for Ecology & Hydrology (UKCEH) — Grace Skinner research profile
- Nature Communications — Biological invasions and insect decline study
- IPBES Global Assessment Report on Invasive Alien Species (2023)
- Convention on Biological Diversity — Kunming-Montreal Global Biodiversity Framework, Target 6
- NASA Global Climate Change — Species range shift data
- IPCC Sixth Assessment Report — Ecological impacts of climate change
- GBIF — Global Biodiversity Information Facility
- iNaturalist — Citizen science species occurrence data
- IUCN Invasive Species Specialist Group
- Bumblebee Conservation Trust — Invasive species impacts on bumblebees
- New Zealand Ministry for Primary Industries — Biosecurity system
- Check, Clean, Dry — UK invasive aquatic species campaign
- Plantlife — Native wildflower restoration and pollinator response
- PLOS ONE — German flying insect biomass study (2017)
- European Invasive Alien Species Information Network (EASIN)
