Red Listed

The Red List of Threatened Species (https://www.iucnredlist.org/en), produced by the International Union for Conservation of Nature, has become the worlds most comprehensive information source on the global extinction risk of animal, fungus and plant species. The Red List shows where and what actions need to be taken to save the building blocks of nature from extinction. It provides a simple way to factor biodiversity needs into decision making processes by providing a wealth of useful information on species.

The Western Honey Bee (wild population) Apis mellifera has most recently been assessed for the Red List in 2025. The Red List conclusion for the EU 27 regional assessment is that it is ‘Endangered’ (and this is extended to South East England and Switzerland). For the whole European regional assessment a status of ‘Data Deficient’  was given (https://www.iucnredlist.org/species/42463639/277757621), which means that there is insufficient data available to determine if the Western Honey Bee (wild population) is endangered across the whole of the European region.

To understand what this means, we need to consider what has led to this conclusion.

Colonies of the Western Honey Bee (Apis mellifera) can be managed or free-living (or wild-living). The latter are colonies that nest in cavities they choose themselves and are unmanaged by humans. Following IUCN guidelines for the assessment of species composed of both managed and wild subpopulations, wild populations of the Western Honey Bee are here defined as self-sustaining groups of free-living colonies. The concept of self-sustaining is defined as a 10 year period of survival and reproduction without the introduction of swarms from managed colonies.

IUCN estimate that in Europe, managed colonies outnumber free-living ones, making the European region the lowest density of free-living Western Honey Bee colonies worldwide.

Evidence derived from the study of both managed and free-living Western Honey Bee colonies strongly suggests that, if left unaided, Honey Bees face numerous threats that significantly limit their capacity to establish and maintain wild self-sustaining populations. This is supported by a recent analysis based on survival data from free-living Honey Bee populations from seven countries in Europe, estimating a current median population decline of 56% (measured in number of colonies) per decade. The period of ten years is used, as it corresponds to length of three generations (following IUCN guidelines, the average generation length of a Honey Bee colony was calculated as 3.3 years).

Given the current evidence on the threats affecting colony survival and the estimated population decline, wild Western Honey Bee populations in the European Union are therefore assessed as Endangered (and given the classification A2abe). Notably, population decline data also indicated a similar level of threat for the non-EU countries of Switzerland and East of England. At the wider Pan European level, the species is retained as Data Deficient at present, given the paucity of data on the distribution, survival rates, and population trends of free-living colonies in this larger region.

The conclusion from the study is therefore that the Western Honey Bee is at risk of loss in the wild because (classification A2abe is the key) a population reduction has been observed, estimated, inferred, or suspected in the past where the causes of reduction may not have ceased OR may not be understood OR may not be reversible (key A2),  which has been determined by direct observation (key a), on an index of abundance (key b), and effects of introduced taxa, hybridization, pathogens, pollutants, competitors or parasites (key c).

A recent study by Kohl and Rutschmann, synthesised the survival rates of free-living colonies monitored at 698 nest sites in seven European countries (France, Germany, Luxembourg, Poland, Spain, Switzerland, United Kingdom) between 2013–2025, estimating an overall median population decline of 56% over a projected ten-year period. Although additional colonies are being monitored in other countries, such as Ireland, Serbia, and Italy, this survival-rates analysis represents the only synthesis available to date that estimates population decline based on observed survival data. Given the extensive geographical scope of this analysis, covering different types of landscapes and habitats (e.g., forest, semi-natural, agricultural, urban, etc.), this estimate can be considered an indicator of the suspected decline of wild Western Honey Bee populations within countries of the EU27 range, plus Switzerland and southeast England.

At the Pan European scale, the estimated decline might be less pronounced as, for instance, understudied regions (e.g., eastern and far eastern European areas) could contain higher quality habitats that better support wild population. While one could estimate that the honey bee in this area is under the same threats, it is unwise to surmise a similar decline in abundance without further investigation.

Free-living colonies are critically dependent on the availability of suitable nesting sites, such as tree cavities (e.g., cavities resulting from wood decay or excavated by the some woodpecker species. The bees also nest in other structures such as cavities in walls, in the roofs of buildings, and hollow man made posts. High densities of colonies have been observed in cities, as in Belgrade, Serbia, and in Munich, Germany, suggesting that urban environments can also be highly favourable for Honey Bees. Although these conclusions are locally or regionally context-specific, they could be applicable to other cities in Europe. While forests have historically served as a primary nesting habitat for Western Honey Bee, recent research suggests that Honey Bees find a richer foraging environment in open habitats as opposed to managed forests, which suffer from a lack of pollen resources in late summer.

Colonies reproduce by fission when swarms leave with the mated old queen (prime swarm) and with the first virgin daughter queens (afterswarms or casts). From the study of Honey Bee colonies in Germany, the average number of offspring produced was estimated to be around two swarms per colony per year. Mating takes place in the air during a nuptial flight of the virgin queen in the spring and summer months (from as early as March in southern European countries), preferably on sunny days with little wind.

According to IUCN guidelines about generation length, the Western Honey Bees’ generation length should be calculated as the average age of established colonies, with “established colonies” defined as those that have survived at least one year. By analysing the survival rates of two self-sustaining wild Honey Bee populations living outside of Europe, their generation length has been calculated as 3.3 years.

Strong evidence derived from the direct study of free-living colonies or indirectly through investigations on managed ones indicate that unaided colonies face a multitude of threats that can significantly impact their survival in the wild. From these studies, it has been determined that wild, self-sustaining A. mellifera populations in Europe have been greatly impacted and are now considered rare or locally extinct. The primary threats to the survival of wild Honey Bee populations were assessed as follows:

Habitat loss and malnutrition

Intensive agriculture, loss of pollen and nectar sources,  loss of trees, lack of replacement trees, tidy up of the countryside with loss of nest sites.

Maintaining and increasing semi-natural habitats such as woodlands and shrublands could become a viable strategy for conserving free-living Honey Bee populations.

Pathogens, parasites, and predators

Invasive alien species are among the most devastating biotic threats affecting the survival of Honey Bees colonies, both managed and wild. Varroa destructor (the Varroa Mite), first introduced in Europe in the 1960s, has been identified as the most likely cause of the demise of wild populations across Europe by causing direct damage to the larvae and pupae, reduces body weight of drones and hence their reproduction ability is lowered, and is the vector of several viruses that have a severe effect on the honey bee colony.

The fungal pathogen Nosema ceranae (Nosema disease) was first documented infecting the Honey Bee in Europe in 2004, but it is possible that it arrived earlier. It has been detected in managed colonies all over Europe and has also spread to free-living colonies. N. ceranae infects honey bees’ midgut cells and consumes their contents via phagocytosis. It leads to a reduction of colony vitality and reduction in size.

The Honey Bee predator, the Asian Hornet (Vespa velutina), was first sighted in Europe in southwestern France in 2004, and has since expanded across Western Europe, from southern Portugal to the Netherlands and across the English Channel into Great Britain. In this vast non-native area, the Asian Hornet is causing substantial colony losses in managed apiaries, and it is also likely impacting free-living colonies, as it frequently nests in forest habitats. Not only does V. velutina consume honey bees (by preference) it also amasses around a honey bee colony in late season causing a large reduction in honey bee foraging.

The Small Hive Beetle (Aethina tumida) is an invasive species that infests Honey Bee colonies and causes the collapse of wax combs and destruction of honey stores, as a result of uncontrolled reproduction inside the nest. First sighted in Europe in 2014, in managed colonies in Italy. There were also outbreaks in eastern Sicily in 2014 and 2019. Although eradication has not been achieved, restrictive measures have prevented its spread throughout Europe. Currently, the species is confined to a limited area in Calabria.

Lastly, the invasive ectoparasitic mite (Tropilaelaps mercedesae), a novel and devastating pest for Western Honey Bee, has recently been reported in managed colonies in Europe. Infestation by this mite can lead to drastic losses, as it feeds on brood and can transmit bee viruses. Given its successful spread among managed colonies, the mite is expected to be able to infest free-living colonies too, as in the case of Varroa. Its further spread will therefore represent a significant factor limiting the survival of wild Honey Bees in Europe.

Possible effects of beekeeping practices

Some modern beekeeping practices could impact wild A. mellifera populations, including: the commercial trade in queens (leading to introgression and threatening the genetic integrity of native populations and subspecies) as well as migratory beekeeping and large-scale selective breeding (which can contribute to the loss of genetic diversity, rendering the species more vulnerable to diseases and environmental changes).

The international trade of queens and long-distance migratory beekeeping, the extent of which has increased dramatically over the last century, have promoted the spread of non-local Honey Bee subspecies and those produced through the artificial crossing of multiple subspecies. These practices favour the use and persistence of less viable and locally unsuitable genotypes. Given that Honey Bee mating cannot be fully controlled by beekeepers, and considering the high density of managed colonies in Europe, such maladapted genotypes are likely to have already been introduced into free-living populations, thereby impacting their gene pools and ultimately their survival.

Pesticides, herbicides, and fungicides

Pesticides, herbicides, and fungicides may detrimentally impact the forage availability of A. mellifera as well as Honey Bee health. So far, no specific study has been carried out on the effects of exposure of free-living colonies to pesticides. However, colonies nesting in intensive agricultural areas, where these compounds are intensively used, have been found to have lower winter survival rates than colonies in semi-natural areas.

Suggested actions

1. Undertake further research studies on free-living colonies to expand our understanding of the threats to the colonies and to extend the observed region.
2. Ensure the conservation of natural habitats that have a bounty of nesting cavities.
3. Control the spread of invasive Honey Bee predators and parasites.
4. Promote the use of native and regional subspecies for beekeeping to avoid non-native genotype introductions.