Honey bees threaten native pollinators in California

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Full Story: Earth (7/8)

Full Story: Earth (7/8)

07-08-2025

Honey bee invasion: A growing threat to native pollinators

BySanjana Gajbhiye

Earth.com staff writer

Pollinators are vital for the natural world. They help plants reproduce, support food webs, and sustain ecosystems. Among them, honey bees hold a special place.

Honey bees are widely celebrated for their role in agriculture and are often seen as environmental heroes. However, their growing presence in places where they are not native raises new concerns.

Southern California is a well-known biodiversity hotspot. It is home to hundreds of native pollinator species. But this unique region now faces a quiet threat.

Feral honey bees, thriving outside human control, have begun to dominate pollination networks here. Their influence extends far beyond what most people realize.

A new study from University of California San Diego sheds light on this issue. The research uncovers how honey bees, despite their benefits, may unintentionally harm native pollinators. The findings challenge common perceptions and bring attention to a growing ecological conflict.

Honey bees outcompete native pollinators

Honey bees are highly effective pollinators. They have been introduced worldwide to support crop production. In the U.S., they are responsible for pollinating crops that contribute billions of dollars to the economy each year.

Their ability to communicate allows them to locate and exploit floral resources efficiently. They share information about flower locations with their colony mates, which makes them powerful foragers. Unlike most native bees, honey bees live in large colonies that work together to gather resources.

Because of their efficiency, honey bees outcompete many native bees. They can strip flowers of pollen and nectar quickly.

Studies show that in Southern California, honey bees now represent nearly 90% of all bees visiting flowers. This leaves little for the region’s diverse native bee species, which rely on the same resources.

Scale of the honey bee invasion

The study found that honey bees now make up 98% of total bee biomass in Southern California’s scrublands. This is not just about numbers. Honey bees are much larger than most native bees in this region. Their dominance extends both in terms of individuals and body size.

One reason for this imbalance is the honey bees’ remarkable ability to remove pollen. The research showed that honey bees can remove up to 80% of pollen from flowers within just one day.

In experiments, just two visits by honey bees stripped over 60% of pollen from flowers of native plants like black sage, white sage, and distant phacelia.

Such high pollen removal rates mean that other bees have far fewer resources left. Native bees, many of which are solitary and less efficient foragers, simply cannot compete at this scale.

Honey bees and pollen resources

Pollen is critical for bee reproduction. Bees collect pollen to feed their larvae. When honey bees take most of the pollen, native bees struggle to raise their young.

The study estimated the daily impact of honey bees on pollen resources. In one hectare of habitat, honey bees removed enough pollen each day to potentially raise hundreds to thousands of native bees.

Over an entire bloom season, this could result in the loss of tens of thousands of potential native bee offspring.

This finding is alarming. It highlights how honey bees, though often viewed positively, may reduce native bee populations by monopolizing food sources.

Larger bees face greater risks

Interestingly, larger native bees appear to be most affected. The study found that only a tiny fraction of native bees were larger than honey bees. Bumble bees, for instance, made up just 0.1% of all bees observed.

Larger bees generally require more pollen to raise their offspring. When honey bees deplete resources, these species may be pushed out first.

“Although honey bees are rightly considered an indispensable asset to humans, they can also pose a serious ecological threat to natural ecosystems where they are not native,” said Hung.

The loss of large bees could also reduce the effectiveness of pollination. These bees tend to carry more pollen per visit, which benefits many plants.

Honey bees vs. native pollinators

The damage does not stop with bees. The study also highlights that honey bee pollination leads to poorer plant offspring quality compared to native bee pollination.

This happens because honey bees often visit many flowers on the same plant before moving to another. This behavior increases the chances of self-pollination, which can lead to inbreeding depression in plants.

Such effects could ripple through ecosystems. Plants that rely on native bees for effective pollination may see lower reproduction rates. This could further degrade habitats that native bees and other wildlife depend on.

The spread of feral honey bees

Feral honey bee colonies are not just an issue in Southern California. These bees have spread worldwide and often outnumber managed colonies.

They thrive in many ecosystems and are difficult to remove once established. Unlike managed bees, feral colonies are self-sustaining and active year-round.

The study points out that feral honey bees have even replaced native bees in other regions. In the southwestern United States, they are increasingly common on both abundant and rare plants.

Rethinking conservation priorities

Many people remain unaware of the negative effects of honey bees on native wildlife. Public concern tends to focus on protecting honey bees from disease and habitat loss

Yet, the study’s authors warn that in North America, honey bees often act as competitors, not conservation targets.

“The plight of the honey bee is an issue of animal husbandry and livestock management, whereas when it comes to conservation issues here in North America, honey bees are likelier to be part of the problem, not a solution or a target for conservation,” said Hung.

This statement challenges common assumptions. It suggests a need for more balanced conservation strategies that consider native pollinators too.

Steps toward potential solutions

Managing honey bee populations in sensitive areas may help. The researchers suggest limiting commercial beekeeping on public lands after crop blooms end.

“In areas with threatened bee species, natural preserve managers may also want to consider systematic removals or relocations of non-native honey bee colonies to provide wild bees a fighting chance,” said Hung.

Though such measures may seem extreme, they are not unprecedented. Many conservation programs already target invasive species to protect native wildlife.

Honey bees harming native life

The study reveals a hidden layer of the pollination crisis. Honey bees, often seen as ecological heroes, can create serious problems in certain ecosystems.

As more people become aware of this issue, discussions around pollinator conservation may shift. Future efforts must balance the needs of agriculture with the importance of protecting native species.

The story of honey bees in Southern California serves as a reminder. Even well-known species can become a threat when removed from their native contexts.

Protecting biodiversity requires seeing the full picture, even when it challenges popular beliefs.

The study is published in the journal Insect Conservation and Diversity.