Why bees are declining

Two different kinds of bee

Today the western honey bee (Apis mellifera) lives overwhelmingly in beekeepers’ hives. According to FAO data analysed in a 2022 study in Scientific Reports, the number of managed colonies worldwide rose by 85% between 1961 and 2017, while honey production rose by 181%. In 2021 there were around 101.6 million colonies, according to FAO, most of them in Asia. The growth is uneven, though: the same study found that Europe and North America had fewer colonies than in 1961 throughout the period studied. The 2016 IPBES assessment on pollinators likewise noted falling hive numbers in many European and North American countries.

So the total is not falling, but losses are high and beekeepers replace them with new colonies every year. The international COLOSS network collects data with a standard questionnaire: in winter 2019/20 beekeepers in 37 countries lost an average of 18.1% of their colonies (including those with unsolvable queen problems), ranging from 7.4% to 36.5% by country. In Czechia, where the COLOSS survey is run by Palacký University Olomouc, 12.2% of colonies died in winter 2023/24, about 26% in winter 2024/25 – the highest in twelve years, more than 160,000 colonies – and 11.3% in winter 2025/26. In the United States the survey by Auburn University and the Apiary Inspectors of America counts losses over a full year from April to April: 55.1% (2023/24), a record 55.6% (2024/25) and 39.9% (2025/26).

For wild bees the picture is different. The 2014 European Red List of Bees assessed all 1,965 native European species and classed 9.2% of them as threatened with extinction; yet more than half (56.7%) were data deficient, and population trends were unknown for 79%. A new IUCN assessment in October 2025 had far better data – only 14% of species remained data deficient – and counted at least 172 threatened species out of 1,928, roughly one in ten, including 15 bumblebees. The IPBES assessment (2016) documented local declines in the abundance and diversity of wild pollinators; these are best recorded in Europe and North America, while data elsewhere are scarce. It found that regional and national assessments show high levels of threat, particularly for bees and butterflies.

A mystery from 2006–07

In winter 2006/07 beekeepers in the United States reported unusual losses: most worker bees vanished from hives within a short time, leaving the queen, plenty of food and a few nurse bees, but almost no dead bees. The phenomenon was named Colony Collapse Disorder (CCD). Total US winter losses reached 31.8% that year and 35.8% the next, but CCD accounted for only part of them. A 2009 study compared 61 variables and found no single cause; affected colonies simply carried more pathogens. A 2013 USDA and EPA report described an interplay of the varroa mite, viruses, poor nutrition, genetics and pesticides, and named the mite as the most damaging pest. According to the EPA, reports of CCD have fallen sharply since: the share of losses attributed to it dropped from about 60% in 2008 to 31.1% in 2013, and it was not mentioned in early reports on winter 2014/15.

Several causes at once

Scientists now regard the varroa mite (Varroa destructor) as the honey bee’s chief enemy. It was originally a parasite of the Asian honey bee (Apis cerana), moved to the western honey bee in the 20th century and, through the trade in bees, spread almost worldwide; it reached Czechia in 1978 and had infested the whole country by 1999. A 2019 study showed that the mite feeds on the bees’ fat body – an organ that stores nutrients, helps break down toxins and supports immunity. Above all, it spreads viruses: an analysis in Science (2016) showed that deformed wing virus spread around the world only recently, driven by the mite and by the movement of colonies.

Beekeepers therefore control the mite regularly, but it can develop resistance to treatments. When commercial beekeepers in the United States lost more than 60% of their colonies – about 1.7 million – in early 2025, USDA scientists found high levels of deformed wing virus and acute bee paralysis virus in samples, and resistance to amitraz, a common miticide, in virtually all the mites tested; they did not rule out other contributing causes. In Czechia, researchers at Palacký University attributed the heavy losses of winter 2024/25 mainly to varroosis, which built up about three weeks earlier than in previous years because of an exceptionally warm spring.

For wild bees, the IUCN identifies habitat loss as the main threat, linked above all to the intensification of farming and forestry. A review in Science (2015) points out that the 20th century saw the loss of flower-rich land and of nesting sites; a landscape of large single-crop fields without flowering margins offers a less varied diet. The authors stress that the pressures add up and reinforce one another: a hungry bee, or one exposed to pesticides, is less able to cope with parasites and disease.

Among pesticides, neonicotinoids have drawn the most attention; residues of these insecticides also end up in pollen and nectar. In 2013 the EU restricted three of them – clothianidin, imidacloprid and thiamethoxam – on crops attractive to bees. In February 2018 the European Food Safety Authority (EFSA) confirmed that most of their uses pose a risk to honey bees, bumblebees and solitary bees, and in April 2018 member states voted to ban their outdoor use, leaving them permitted only in permanent greenhouses. A large field trial in the UK, Hungary and Germany (Science, 2017) found that treated oilseed rape harmed bees in the UK and Hungary but not in Germany; the authors suggested the outcome may have depended partly on how much other forage was available nearby.

Climate change plays a part too. A study of 66 bumblebee species (Science, 2020) found that, compared with 1901–1974, the likelihood of a bumblebee species occurring at a given site had fallen by an average of 46% in North America and 17% in Europe, most sharply where extreme heat had become more frequent. A newer problem for Europe is the Asian hornet (Vespa velutina) from eastern Asia. It reached south-west France shortly before 2004 – probably, according to genetic studies, as a single female – and has since spread to Spain, Portugal, Italy, Germany, Belgium and Britain, among others. It hunts bees right in front of their hives, weakening colonies. In Czechia it was first confirmed in October 2023 in Plzeň, where the nest that was found was destroyed.

What helps

Research also shows what works. A synthesis in Ecology Letters (2020) confirmed that flower strips beside fields improve pollination in neighbouring crops most when they are perennial, well established and rich in plant species; their effect fades quickly with distance from the strip. The authors of the 2015 review in Science recommend more flowering plants in the landscape, a rethink of the prophylactic use of insecticides, quarantine measures against newly introduced parasites, and systematic monitoring of bees. For honey bees, much depends on responsible beekeeping – above all, regular checks for varroa and timely treatment; a new project at Palacký University, for example, focuses on monitoring varroosis throughout the year. The European Union adopted its Pollinators Initiative in 2018 and revised it in January 2023, with the aim of reversing the decline of wild pollinators by 2030.

Two different kinds of bee

A mystery from 2006–07

Several causes at once

What helps

Sources