Science1 publisher2 min readPublished
IUCN lists the EU's wild-nesting honeybees as endangered on a modelled 56% decline
The endangered listing rests on a model of what happens to wild-nesting colonies if beekeepers' swarms stop arriving. Its authors put the loss at about 56% over ten years, while some English populations hold steady.
The Scientist · Science desk
What happened
- The IUCN has classified honeybees living in the wild as endangered across the European Union, the first time wild populations of the Western honeybee appear on the Red List.
- The listing follows an estimate from researchers at Hohenheim and Agroscope that EU wild populations would fall by about 56% within ten years without swarms arriving from beekeepers.
- Colonies that nest in tree hollows, rock crevices and hollow walls sustain themselves without human help and account for about one-sixth of Europe's honeybees.
- International collaborations have so far documented more than 1,600 wild nesting sites across 15 countries.
- Rutschmann said the regional spread is stark, with some central European populations under significant threat while stable colonies exist in England.
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Why it matters
- constraint One EU-wide category now covers populations on opposite trajectories, so a member state cannot read its own risk off the listing and would need country-level survival data to act on it.
- capability Selection that happens only where nobody treats for mites is available to breeders for as long as untreated colonies persist, and Kohl argues European beekeeping could draw on that adaptability.
- precedent If the biological line between listed and managed animals cannot be drawn, protection has to attach to nesting places: tree hollows, rock crevices, cavities in walls.
The estimate is the output of a model. The researchers took survival data from wild colonies at nesting sites already under monitoring in several European countries, then calculated how those colonies would fare with no swarms migrating in from beekeeping operations [4]. That immigration is real and continuing, so the 56% describes self-sufficiency under a scenario that switches it off [3][7]. The paper is in Conservation Science and Practice, from the University of Hohenheim in Stuttgart and Agroscope in Zurich [2].
Spread over ten years, that decline is about 7.9% of colonies a year: 0.44 to the power of one tenth is 0.921 [1]. Wild-nesting colonies are about 17% of Europe's honeybees. If managed hive numbers held while the modelled loss ran its course, they would end up near 8% of the European total [2].
What separates a listed colony from a farmed one is where it lives. "This means that, based on current data, a clear biological separation between honeybees in the wild and managed honeybees cannot be sustained," said Patrick Kohl of the Livestock Population Genomics Department at the University of Hohenheim [6]. He described how the two groups mix: "The two groups still intermingle today, for example, when young queen bees from beekeeping operations mate with drones from wild bee colonies during their nuptial flights" [7].
Little has been known about these wild colonies and their ecological, economic and evolutionary importance [17]. The documented nesting sites work out to an average of more than 100 per country [3], and the authors say comprehensive data on distribution, population size and development remain lacking [9]. "Europe has the lowest density of honeybee colonies in the wild in the world," said Benjamin Rutschmann of Agroscope [10].
"Overall, however, many populations in the wild will not be able to survive on their own and are reliant on an influx from beekeeping operations," Rutschmann said [12].
The reason to track a subpopulation of a livestock species is genetic. "Wild honeybees enjoy tremendous genetic diversity," Kohl said [13]. His clearest case for what that produces is American: wild colonies there cope with the Varroa mite, an Asian parasite capable of wiping out entire colonies, because the absence of chemical treatment selected for resistant colonies [14]. For the species' native range he makes a narrower claim, that "the remaining wild populations of honeybees are reservoirs for subspecies that have become rare" [15]. Kohl said beekeeping in Europe could benefit from the genetic adaptability of a wild population to diseases or environmental conditions [16].
What to watch
- Whether monitoring extends from the several countries that supplied survival data to all 15 with documented nesting sites, which would give an observed trend instead of a modelled one.
- Whether any EU member state converts the listing into protection for nest cavities in trees, rock and walls.
- Whether European wild colonies are tested for survival with Varroa in the absence of chemical treatment, as American ones have been.