The Silent Extinction: Insect Migration and the Food on Your Plate

Between $235 billion and $577 billion. That is the range the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services put on the annual value of food production directly dependent on animal pollinators in 2016. The number is wide because nobody has pinned it down more precisely. A significant share of that value depends not on managed honeybees trucked between farms, but on wild insects that migrate vast distances each year, pollinating crops and eating pests along the way. These insects have no lobby, no tracking tags, and almost no monitoring infrastructure. They are, in economic terms, an unaudited asset worth hundreds of billions.

The question is not whether this asset is depreciating. It is. The question is how fast, and what the bill looks like when it comes due.

The Trillions Nobody Counts

In 2016, a research team led by Gao Hu at Nanjing Agricultural University, working with colleagues at the University of Exeter, pointed radar antennae at the sky over southern England and counted what flew overhead. The result, published in Science, was staggering: 3.5 trillion insects migrate over the southern United Kingdom every year, carrying a combined biomass of roughly 3,200 tonnes. To put that in perspective, that single airspace corridor moves more animal mass than all the songbirds migrating out of the UK combined.

This was one radar study over one region. Globally, insect migration is one of the largest biomass movements on the planet. Dragonflies cross the Indian Ocean. Painted lady butterflies fly from North Africa to Scandinavia and back. Hoverflies shuttle between continental Europe and Britain in numbers that dwarf most vertebrate migrations.

Yet the monitoring infrastructure for all of this is nearly nonexistent. The Rothamsted Insect Survey, running continuously since 1964, operates a network of suction traps across the UK. It is the world's longest-running standardized insect monitoring system, and it covers one country. A handful of radar entomology stations in China, Australia, and the United States provide intermittent data. Most nations have no systematic insect migration tracking at all. We are managing a multi-hundred-billion-dollar natural asset with the informational equivalent of a napkin sketch.

What a Hoverfly Is Worth

Consider the hoverfly. Syrphidae, to use the family name, are the second most important group of pollinators after bees. They visit flowers for nectar and pollen, and in doing so they pollinate crops ranging from strawberries to oilseed rape. Their larvae, meanwhile, are voracious aphid predators. A single hoverfly larva can consume around 400 aphids during its development.

In 2019, Karl Wotton and colleagues published a study in Current Biology estimating that roughly 4 billion hoverflies migrate into southern Britain each summer. These migrants and their offspring consume approximately 6 trillion aphids per year in the UK alone. Six trillion. That is biological pest control delivered free of charge, every summer, by animals that weigh a fraction of a gram each.

What would it cost to replace this service? Chemical aphid control requires repeated applications across a growing season, and the UK has roughly 6.1 million hectares of croppable land. Even a conservative estimate of additional pesticide applications needed to compensate for lost hoverfly predation runs into hundreds of millions of pounds per year. And that calculation ignores the pollination services these same hoverflies provide while they are eating aphids.

The hoverfly is not charismatic. It does not appear on conservation posters. It does not have a World Wildlife Fund campaign. But it delivers a dual service, pest control and pollination, that commercial alternatives cannot replicate at comparable cost.

The Monarch's Balance Sheet

The monarch butterfly is the one insect migration that the public actually knows. Every autumn, hundreds of millions of eastern North American monarchs fly up to 4,500 kilometres from Canada and the northern United States to overwintering sites in the oyamel fir forests of central Mexico. It is one of the most studied migrations in biology.

It is also one of the most thoroughly documented collapses. The overwintering colony area in Mexico's Monarch Butterfly Biosphere Reserve peaked at 18.19 hectares in the 1996-1997 season. In recent years, the average has hovered around 2.8 hectares. The 2013-2014 season hit a record low of 0.67 hectares. The eastern monarch population has declined by approximately 80% over three decades.

The causes are well established. Glyphosate-resistant crop varieties, adopted massively across the American Midwest from the late 1990s onward, enabled farmers to eliminate milkweed, the sole host plant for monarch larvae, from agricultural fields. Research by Pleasants, Oberhauser, and colleagues documented that more than 1.3 billion milkweed stems were lost from agricultural land in the US Midwest, with milkweed area in farm fields declining by more than 80% since the 1990s. The monarch's migration corridor was chemically sterilized, not by targeting the butterfly, but by removing the one plant its larvae require.

The IUCN listed the migratory monarch butterfly as Endangered in 2022. The economic footprint is harder to pin down. A 2014 survey-based study estimated that US households would collectively pay $4.78 to $6.64 billion as a one-time sum for monarch conservation, a measure of public willingness to pay rather than actual ecotourism revenue. More important than any single valuation, though, is what the monarch's decline signals about less visible insect migrations that nobody tracks.

Pesticide Corridors

The monarch's milkweed story is a specific case of a general pattern. Agricultural intensification along migration routes creates what might be called pesticide corridors: zones where insects attempting to migrate through encounter lethal or sub-lethal chemical exposure at every stop.

Neonicotinoids illustrate this most starkly. Introduced commercially in the 1990s, neonicotinoids became the most widely used class of insecticides globally within two decades. They are systemic, meaning the plant absorbs them and distributes them through its tissues, including pollen, nectar, and guttation droplets. A migratory pollinator stopping to refuel at a flowering crop treated with neonicotinoids ingests the insecticide with every sip.

The effects are not always immediate death. Multiple studies have shown that sub-lethal neonicotinoid exposure impairs insect navigation, memory, and flight endurance. For a migratory insect that must fly hundreds of kilometres on precise navigational cues, these impairments can be as fatal as a direct kill. A hoverfly that cannot navigate does not arrive. A butterfly that cannot sustain flight does not complete its journey.

The European Union banned three neonicotinoids for outdoor use in 2018. The United States has been slower to restrict them. But even where bans are in place, the broader picture remains: intensive agriculture along migration corridors exposes transiting insects to a cocktail of chemicals that were not designed with migration in mind.

The Krefeld Entomological Society in Germany provided the most cited evidence of the scale of the problem. Over 27 years of standardized trapping in 63 nature reserves across western Germany, the society documented a 75% decline in total flying insect biomass. The study, published by Caspar Hallmann and colleagues in PLOS ONE in 2017, shocked the scientific community. These were protected areas. The insects should have been safe. But reserves are islands in an agricultural sea, and the insects that migrate through the surrounding farmland never arrive.

The Price Tag on Pollination

Roughly three-quarters of the world's food crop types benefit from animal pollination, according to the IPBES assessment, drawing on foundational work by Alexandra-Maria Klein and colleagues. That does not mean 75% of food volume depends on pollinators. Staple grains like wheat, rice, and corn are wind-pollinated. But the crops that pollinators support tend to be the ones that provide dietary diversity, nutritional density, and economic value: fruits, vegetables, nuts, oilseeds, coffee, cocoa.

The IPBES range of $235-577 billion represents the estimated annual market value of crop production directly attributable to pollination. Strip out animal pollination, and yields of these crops drop. How much depends on the crop. Almonds are almost entirely dependent on insect pollination. Apples are highly dependent, with studies showing yield reductions of 45% or more when pollinators are excluded. Insect pollination boosts coffee yields by 16-50% depending on the variety. Blueberries depend on pollinators for 90% or more of their fruit set.

California's almond industry already demonstrates what happens when wild pollinators cannot fill the gap. Each February, roughly 2 million managed honeybee colonies are trucked from across the United States to California's Central Valley to pollinate 600,000 hectares of almond orchards. The pollination fee per colony for almonds has climbed to $200 or more in recent years, with total pollination service payments for the crop reaching into the hundreds of millions annually. Almond pollination alone has become a billion-dollar annual logistics operation.

This is what the early stage of pollination service failure looks like: substitution through managed pollinators at escalating cost. The next stage is visible in Maoxian County in Sichuan Province, China, where apple orchards have relied on hand pollination since the late 1980s after pesticide overuse and habitat destruction eliminated local pollinators. Workers climb trees with small brushes, touching each blossom individually. The labour cost dwarfs what insect pollination delivers for free.

When the Service Contract Breaks

The economic transmission from insect decline to consumer prices is not theoretical. It is already measurable in specific markets.

A 2020 study by James Reilly and colleagues, published in Proceedings of the Royal Society B, analysed crop production data across the United States and estimated the value of wild pollinator contributions at roughly $1.5 billion per year across six key crops alone. The largest share came from apples, at $1.06 billion, followed by watermelon, sweet cherry, pumpkin, blueberry, and tart cherry. The value was highest in regions where wild pollinator populations remained relatively healthy, underscoring what stands to be lost where they do not.

Coffee provides another data point. While coffee plants can self-pollinate, insect pollination boosts yields by 16-50% depending on the variety and growing conditions. In regions of Latin America and East Africa where pollinator populations are declining, those yield gains are eroding. When it disappears, per-unit production costs rise, and those costs eventually reach the consumer.

The mechanism is straightforward. When free ecosystem services decline, farmers face three options: accept lower yields, pay for substitutes, or switch to less pollinator-dependent crops. All three raise food costs. Lower yields mean higher prices. Managed pollinators cost money. Crop switching reduces diversity and may increase dependence on subsidized staples.

None of this registers as "insect migration collapse" in economic reporting. It shows up as "higher input costs," "reduced yields," or "supply constraints." The cause is invisible because nobody is tracking the migratory insects that used to deliver the service for free.

The Monitoring Gap

The disparity between what insect migration is worth and what we spend tracking it is extraordinary. Global spending on bird migration research runs into hundreds of millions of dollars annually, supported by satellite tracking, citizen science platforms like eBird with its more than 2 billion observations, banding programs, and dedicated flyway monitoring systems. Marine mammal migration receives comparable attention.

Insect migration gets almost nothing. Radar entomology, the primary tool for tracking high-altitude insect movement, operates from a handful of stations worldwide. There is no global insect migration monitoring network. There is no eBird equivalent for migratory insects. The EU Pollinator Monitoring Scheme, proposed in 2020 and still being rolled out across member states with a full implementation deadline of December 2026, tracks pollinator abundance but does not specifically monitor migration routes or patterns.

The consequence is a dangerous informational void. Without baseline data on insect migration volumes, routes, and timing, it is impossible to measure decline accurately, set conservation targets, or evaluate whether policy interventions are working. We know flying insect biomass has declined dramatically in parts of Europe because the Krefeld Society happened to collect data for 27 years. We have almost no comparable data for most of the world's insect migration systems.

From a risk management perspective, this is indefensible. No financial regulator would accept a multi-hundred-billion-dollar asset class with no reporting requirements, no auditing, and no baseline valuation. Yet that is precisely the status of insect pollination and pest control services globally.

What Filling the Gap Would Cost

The cost of building adequate insect migration monitoring is, by any reasonable comparison, trivial. The Rothamsted Insect Survey has produced over 60 years of continuous data on a research budget that rarely exceeds a few million pounds per year. A continental-scale insect radar network for Europe, capable of tracking migration volumes and routes in real time, would cost in the range of tens of millions of euros annually. New technologies including environmental DNA sampling and lidar-based insect detection could supplement radar at lower per-unit costs.

Compare that to the asset at risk. Even the low end of the IPBES pollination estimate, $235 billion annually, dwarfs any plausible monitoring investment by a factor of roughly 10,000 to 1. Spending $50 million per year to monitor an asset worth $235 billion is not conservation charity. It is basic due diligence.

The CMS COP15 agenda includes items on invertebrate conservation, but the commitments remain largely voluntary and non-binding. Insect migration sits at the intersection of agriculture, trade, and environment ministries, which in practice means it sits in nobody's portfolio. The insects keep migrating, or they stop, and the economic consequences accumulate in spreadsheets labelled "unexplained yield variation."

Three and a half trillion insects cross southern England every year, carrying an economy on their wings. We know this because a few scientists pointed a radar at the sky and counted. Almost nobody else is counting.