Only 150 years after arriving in Southern California, honey bees are dominating the native flowers. European colonizers of North America brought honey bees to the eastern shore in 1622 and to the western shore by 1853. Now distributed widely in the world by humans who wanted to make use of them, honey bees have taken over floral resources. Social lifestyle and good communication skills have allowed this bee species to monopolize flowers worldwide, according to a 2018 study.
In 2019, the same team of researchers published a new study with an alarming title: Non-native honey bees disproportionately dominate the most abundant floral resources in a biodiversity hotspot. The study’s title references its alarming conclusion — honey bees forage primarily on the most abundantly flowering native plant species (I added bold to hint my conclusion) and often account for more than 90 percent of pollinators observed visiting flowers.
In the San Diego area, a biodiversity hotspot with over 600 native bee species, about two-thirds of all the observed pollinators are one non-native species: honey bees.
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The honey bees, that we brought here and treat as an important livestock crop for pollination services in orchards and honey production, are monopolizing floral resources needed by native bees and other native wildlife (e.g., hummingbirds, bats, moths).
“To have a non-native species that removes the lion’s share of pollen and nectar in a diverse ecosystem such as ours is stunning” said [Joshua Kohn of UC San Diego’s Division of Biological Sciences]. “Think about if we had an invasive plant that covered 75 percent of the region’s land area—it’s similar to that level.”
The researchers say that “...honey bees’ monopoly over the most abundantly blooming plant species may strongly affect the ecology and evolution of species that are foundational to the stability of the region’s plant-pollinator interactions.” Honey bees are disproportionately taking the pollen and nectar from plant species that likely support the most diversity and abundance of native pollinators.
The reasons for honey bees success in monopolizing nature is due to humans maintaining them for our own purposes and honey bees’ natural behaviors. They are social animals who live in groups and tell each other where to find abundant pollen and nectar resources (just like us!). Native pollinator insects mostly are solitary and find pollen and nectar individually. Their populations are not supported by human efforts, instead our actions decrease habitat extent and nesting sites.
“Honey bees are thought to have the most sophisticated communication of all invertebrates. They can communicate the distance and direction of a high quality food source,” said Kohn. “Native bumble bees are also social and are thought to communicate that there is a worthwhile floral resource and what it smells like, but they can’t communicate distance and direction the way honey bees can.”
Native pollinators are important for many plants because their foraging behavior is to move from plant to plant, not focus on a single plant. This type of pollen dissemination promotes out-crossing. Honey bees tend to work many flowers on one plant before moving on, thus encouraging self-fertilization, which leads to lower quality seed due to in-breeding. Honey bees also are rowdy visitors who do more damage to flowers than most native pollinators (thus affecting seed set).
“In general, the threats that honey bees may pose to native biodiversity have not been explored very thoroughly, but we are now headed that way,” said Kohn, who first became interested in honey bee dominance while hiking in local wilderness areas. “No matter how far away from agriculture or urbanized areas I was, if something was blooming heavily, it was just swarmed with honey bees. I thought it was odd that there were so many honey bees here.”
Another problem with honey bee dominance of floral resources is reduced crop pollination because native bees increase crop pollination even when honey bee hives are present. This means crops will produce smaller yields (this also includes vegetables like squash and melons as well as orchard fruits and nuts). Some flowers are designed for buzz pollination that comes from bumblebees and honey bees aren’t as effective. Tomatoes and peppers are mostly wind pollinated but the flowers also benefit from buzz pollination, so bumblebees increase plant yields.
According to the researchers, the high biodiversity, coupled with the fact that many plant and pollinator species in the region are threatened by habitat loss and climate change, means that any ecological impact of honey bees on native species could be especially consequential.
The next step for scientists is to examine the plant/crop consequences and other ramifications of honey bee domination. They note it’s difficult to assess the true impact level because we have no data from the period prior to honey bee introduction.
We can help native insect pollinators by protecting and enhancing habitat. Studies found that for certain crops, all the pollination needs can be met if 25 to 30 percent of the landscape is left as natural habitat. We also can manage our gardens and developed areas to support native pollinators. Include native plants that encompass a range of flowering times from early in spring until fall. Allow leaf litter and other debris to accumulate in areas and refrain from or limit insecticide use.
Native bees don’t build the wax or paper structures we associate with honey bees or wasps, but they do need places to nest, which vary depending on the species. Wood-nesting bees are solitary, often nesting in soft-pithed twigs or beetle tunnels in standing dead trees. Learn how to make nest-blocks for wood-nesting native bees and learn how to maintain these and other tunnel nests. Ground-nesting bees include solitary species that construct nest tunnels under bare ground. Cavity-nesting social species–bumble bees–make use of small spaces, such as abandoned rodent burrows, wherever they can find them.
When you create a pond or ditch, you can leave the pile of excavated soil. Ground-nesting bees may build nests in stable, bare areas of this mounded earth. Planting clumps of native flowers will attract more pollinators.
A tidy garden full of non-native plants bordered by manicured lawn may be a snappy Instagram photo, but the message behind that image is the loss of nature. Keep some areas messier. Learn to appreciate leaf litter, twigs, fallen decaying logs, and standing dead trees. Include native plant species (not selected cultivars) in naturalized plantings in addition to your carefully designed display garden. Keep some nature in your yard and promote conservation of natural lands in your communities.
Think about it.
- 600 native bee species
- 1 non-native honey bee
- 2/3rds of all observed pollinators are the one non-native
Give the other 600 a boost.
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