Voracious honey bees threaten the food supply of native pollinators

The majority of plant species on the earth, including our cultivated plants, depend on the services of animal pollinators in order to reproduce. Bees and other pollinated insects contribute to billions of dollars to the American economy each year and are responsible for almost a third of the food that is found on our tables.

Our modern agricultural industry depends so much on the bees that humans have introduced them worldwide, and in many cases, they have escaped human management and increased in importance in natural ecosystems as non -native and wild populations. And, like any other non -native organism, wild bees can disrupt indigenous ecosystems when they become sufficiently abundant.

Wild bees have considerably proliferated in southern California, as well as the rest of the southwest of the United States. A new study carried out by biologists of the University of San Diego, Dillon Travis, Joshua Kohn, David Holway and Keng-Lou Hung attracts attention to the threat posed by non-native bees to various native pollinators in San Diego and the wider region of southern California.

These researchers previously estimated that honey bees represented up to 90% of all bees visiting flowers of several native plant species in the region.

The new study, published in the journal Conservation and diversity of insectsbelieves that the impact of honey bees can have on native bee populations in this important global hot spot in the biodiversity of native pollinators.

The researchers found that honey bees remove approximately 80% of pollen during the first day that a flower opens. This finding is important because all the bees in the region – and the vast majority of bees in the world – use pollen to raise their offspring.

The quantity of pollen removed daily by honey bees in a single hectare (2.5 acres) of native vegetation is sufficient to provide thousands of native bees per day during the flowering peak of native shrubs, the researchers revealed.

Because honeys are larger than most species of native bees in southern California, the new study has calculated that honey bees now represent 98% of all bee biomass in this ecosystem. If the pollen and nectar used to create a biomass of honey bees were rather converted into native bees, the populations of native bees should be about 50 times larger than they are currently.

“Although honey bees are rightly considered to be an essential asset for humans, they can also constitute a serious ecological threat to natural ecosystems where they are not from,” said Hung, who obtained his doctorate. from UC San Diego and is now a deputy professor at the University of Oklahoma.

“The fate of the bee is a question of livestock and livestock management, while, with regard to conservation problems here in North America, honey bees are more likely to be part of the problem, not a solution or a target for conservation.”

In another concern, a study published in 2023 by Travis and Kohn showed that plants pollinated by bees produced less quality offspring compared to the offspring of indigenous pollinators.

Although bees in general are threatened by loss of habitat, climate change and chemical pollution, researchers say that such level of exploitation of bee pollen is not well documented and may well represent an additional and important threat for populations of native bees in places where honey bees have become abundant.

Even if the number of managed bee colonies increases in the world due to the commercial beekeeping industry, many species of native pollinators decrease.

“Public concern for bees often does not pay attention to their potential negative effects on indigenous pollinators,” note the authors in their report.

“Honey bees are incredibly effective in extracting resources like pollen and nectar,” said Travis, who obtained his doctorate. at UC San Diego in 2023.

“Unlike the vast majority of species of native bees in the region, honey bees can communicate with their nesting comrades the locations of enriching plants and quickly eliminate most of the pollen, often early in the morning, before native bees begin to seek food.”

The new study used pollen elimination experiences to estimate the amount of pollen extracted by honey bees using three common native plants (black sage, white sage and distant phacelia – also known as the distant bad scorpion grass) as sources of targeted pollen.

The researchers found that only two visits by honey bees have removed more than 60% of the pollen available from flowers of the three species. These prodigious pollen exploitation rates leave little pollen for more than 700 species of native bees in the region.

“The most surprising conclusion was the extraordinarily small number of observed indigenous bees observed which were as large or larger than honey bees,” said professor emeritus Kohn of the department of ecology, behavior and evolution.

“The Bourdons were particularly rare, which only represented 0.1% of all the bees that we observed.”

With the new study which highlighted the imbalance bee bee / native bee in San Diego and in southern California, researchers say that the consumption of resources by bees should receive greater attention as a potential factor in the decline of the pollinator.

A step to approach the situation could be an increased orientation on the question of whether and where large -scale contractual beekeepers are allowed to keep their hives on public land after cultures have flowered, in order to limit the possibilities of honey bees to go beyond indigenous species for rare resources provided by indigenous vegetation.

“In areas with endangered bee species, natural canned managers may also want to consider systematic moves or relocations of non -native bee colonies to provide wild bees with a chance to fight,” said Hung.