Bees are disappearing because of several reinforcing threats: habitat loss, pesticides, parasites, climate change, and the stresses of industrial beekeeping. Between April 2024 and April 2025, an estimated 55.6% of managed honeybee colonies in the United States were lost, the highest rate since annual surveys began in 2010. But the problem extends far beyond honeybees. Wild bee species, which do much of the world’s pollination work, are declining in ways that are harder to track and potentially more damaging.
Habitat Loss and the Monoculture Problem
The simplest driver of bee decline is also the most fundamental: there are fewer places for bees to live and eat. Urban development, agricultural expansion, and land clearing have destroyed nesting sites and wiped out the wildflower meadows that bees depend on. But even in areas that remain agricultural, the landscape has become hostile to bees in a subtler way.
Modern farming relies heavily on monocultures, massive plantings of a single crop species that stretch across the landscape. For bees, this creates a brief glut of one type of flower followed by nothing. The nutritional consequences are real. Bees need pollen from a variety of plants to get the full range of proteins, fats, and micronutrients they require. Studies of stored pollen in honeybee hives have found that floral diversity is directly linked to protein and lipid content. When bees forage in monoculture landscapes, they can’t obtain the complete spectrum of nutrients they need. For solitary bees, which provision a single food supply for their larvae, the effects are even more direct: offspring raised on nutritionally incomplete pollen grow poorly and are less likely to survive.
How Pesticides Disrupt Bee Brains
Neonicotinoids, the most widely used class of insecticides in the world, don’t necessarily kill bees outright. What they do is arguably worse for colony survival: they scramble the nervous system at doses far below the lethal threshold.
Neonicotinoids target the same signaling pathway that bees use for learning, memory, and navigation. When these chemicals bind to receptors in the bee’s brain, they block the normal action of a key neurotransmitter. The result is a bee that can’t smell properly, can’t learn which flowers are rewarding, and can’t find its way home. Experiments have shown that after neonicotinoid exposure, the brain’s ability to distinguish between different odors collapses. The neural “maps” that represent different scents become nearly identical, meaning the bee loses the ability to tell one flower from another. Navigation, which relies on related brain structures, is similarly impaired.
A forager that gets lost is a dead forager, and a colony that loses too many foragers starves. This is why neonicotinoid exposure can hollow out a colony without leaving piles of dead bees at the hive entrance, a pattern that initially baffled researchers studying colony collapse.
Varroa Mites and the Viruses They Carry
The parasitic Varroa mite is widely considered the single greatest threat to managed honeybee colonies. These tiny external parasites feed on bee tissue, but the real damage comes from the viruses they inject while feeding. Varroa mites actively replicate at least six viruses inside their own bodies, then transmit them to bees. They aren’t just passive carriers; they’re biological amplifiers of disease.
The most damaging of these is deformed wing virus, which exists in two genetic variants. As mite populations build within a colony, viral loads climb in lockstep, and colony health deteriorates. Heavily infested colonies produce bees with shriveled, useless wings, shortened lifespans, and weakened immune responses. USDA researchers have identified viruses vectored by mites as a likely end-stage cause of colony death, though they note this doesn’t rule out the role of other stressors weakening colonies to the point where viral infections become fatal.
Climate Change and Timing Mismatches
Warming temperatures are creating a timing problem between bees and the flowers they depend on. Plants and bees both use environmental cues to time their seasonal activity, but they don’t respond to warming at the same rate. Flowers generally advance their blooming schedule faster than bees advance their emergence or peak activity.
Research in alpine ecosystems illustrates this clearly. A 1°C increase in temperature with earlier snowmelt advanced peak flowering by nearly 10 days in some plant communities and shortened the overall flowering season by over 9 days. But the peak abundance of worker bumblebees stayed consistent between years, largely independent of temperature. The gap between when flowers bloom and when bees are active to pollinate them widens with each degree of warming. Because bee life cycles are more conservative and slower to shift than flowering schedules, this mismatch is expected to accelerate as global temperatures continue to rise.
Industrial Beekeeping Stress
Managed honeybees face an additional set of pressures that wild bees don’t: the demands of commercial pollination. Colonies are loaded onto trucks and shipped hundreds or thousands of miles to pollinate crops like almonds, blueberries, and apples in sequence. The transport itself is stressful, but the real toll comes from the diet that follows.
Between pollination contracts, commercial colonies are often fed sugar syrup as a substitute for natural nectar and pollen. Bees kept on these low-protein diets show higher mortality and increased viral loads compared to bees with access to diverse pollen. Homemade sugar syrups can also contain toxic byproducts that further harm bee health. When poor nutrition is combined with pesticide exposure, the effects multiply: one study found that the combination reduced bee survival by 50%, cut food consumption by nearly half, and dramatically lowered blood sugar levels. Nutritional deficiencies don’t just weaken individual bees. They increase pathogen loads across the colony and shorten adult lifespans.
Wild Bees Face a Different Crisis
Most public attention focuses on honeybees, which are a managed agricultural species. But there are roughly 20,000 wild bee species worldwide, and many of them are in deeper trouble. Wild bees often have specialized habitat or dietary requirements that make them more vulnerable to landscape changes. They don’t have beekeepers replacing lost colonies each spring.
Ironically, the popularity of urban beekeeping may be making things worse for wild bees. In Montréal, the number of managed honeybee colonies surged from 238 in 2013 to nearly 3,000 by 2020. Over that same period, wild bee species richness declined significantly at sites where honeybee numbers increased the most. Small-bodied wild bee species, which have limited foraging ranges and can’t travel far to find food, were hit hardest. Their richness and abundance both dropped as honeybee populations grew. Honeybees comprised almost 40% of all bees detected in the study area, dominating the urban landscape and competing directly with native species for nectar and pollen.
Wild bee diversity increased with the richness and density of flowering plants, suggesting that the core issue is competition for a limited food supply. Adding more honeybee colonies to an area without increasing floral resources puts wild bees at a disadvantage.
Why It Matters for Food
Pollinators contribute more than $235 billion in value to global crop production each year. In the United States alone, insect pollination adds over $34 billion to agricultural output. The crops at stake aren’t obscure specialty items. Almonds, apples, blueberries, cherries, avocados, cucumbers, pumpkins, squash, watermelons, peppers, raspberries, cranberries, pears, peaches, kiwi fruit, and canola all require bee pollination to produce harvestable yields. Even tomatoes, often grown in greenhouses, rely on bumblebees for pollination.
These aren’t crops that would simply produce a little less without bees. They require bees, either specific species or bees in general, to set fruit at all. The loss of pollination services would reshape the human diet, eliminating or drastically reducing the availability of most fruits, many vegetables, and several major oilseed crops. The staple grains that make up the caloric backbone of the global diet (wheat, rice, corn) are wind-pollinated and wouldn’t be directly affected, but the nutritional diversity of what people eat would narrow considerably.
No Single Cause, No Simple Fix
Early coverage of bee declines focused heavily on Colony Collapse Disorder, a specific phenomenon where worker bees abandoned their hives. That framing suggested a single mystery cause waiting to be identified. The scientific picture that has emerged over the past two decades is more complicated. Bees face a web of interacting stressors: a malnourished bee exposed to low levels of neonicotinoids is more susceptible to viruses carried by Varroa mites, and a colony weakened by all three is less likely to survive a bad winter or a long truck ride to a pollination contract.
The 55.6% annual loss rate in managed U.S. colonies is sustained only because beekeepers aggressively split surviving colonies and buy replacement queens each year. This masks the severity of the problem for honeybees and does nothing for the thousands of wild species that have no such safety net. Winter losses alone hit 40.2% in the 2024-2025 season, and state-level losses ranged from 34% to over 90%, reflecting how much local conditions matter.