Whether you’re strolling through a garden, wandering a park, or simply enjoying an open space, you’re likely to notice bees buzzing about the flowers. While honeybees, produce honey, are the most recognizable, they aren’t the only bees at work.
If you’re a keen observer, you might spot some of the thousands of less familiar, native bee species that call these spaces home.
Native wild bees play a crucial ecological role, ensuring the survival and reproduction of countless plant species — including many agricultural crops — by spreading pollen as they forage for food. Unfortunately, their numbers seem to be declining, and despite experts suggesting multiple causes, the exact reason remains a mystery.
A new study published in Nature Sustainability sheds light on one potential cause: pesticide use. The research reveals a stark decline in the number of wild bee sightings, with appearances of some species dropping as much as 56% in areas of high pesticide use compared to areas with no pesticide use.
The study points to pesticides as a significant factor in wild bee decline and suggests that alternative pest control methods, could reduce the damage.
Pesticide effects on wild bee populations scrutinized
Loss of wild bees could disrupt entire ecosystems, affecting not just plants but also the wildlife that depend on those plants for food and habitat. The multibillion-dollar agricultural industry could also suffer; wild bees, alongside honeybees, play a crucial role in pollinating three-quarters of food crops and nearly 90% of flowering plant species.
Recognizing the urgent threat posed by bee population declines, an international team of researchers, set out to investigate the impact of pesticides on wild bees. They also examined the effects of agricultural practices and how the presence of honeybee colonies might influence wild bee populations.
The team inspected museum records, ecological surveys and community science data collected between 1996 and 2015 from across the contiguous areas.
We’re ignoring the unique responses of … wild bee species to pesticide exposure.
Using advanced computational methods, they sifted through more than 200,000 unique observations of over 1,000 species — representing one-third of all known bee species to assess how frequently different species were observed in various locations.
In addition, they analyzed data from several government sources. By integrating these resources, the researchers correlated factors such as land use, pesticide application, honeybee colony presence, and types of agricultural crops with wild bee sightings over the past two to three decades.
Pesticides emerge as a top factor harming wild bees
The research provides compelling evidence that pesticide use is a major contributor to the declining numbers of wild bees. The study found a strong correlation between pesticide use and fewer wild bee sightings, suggesting a direct link between pesticide exposure and bee population declines.
Some scientists have speculated that certain crops might adversely affect wild bees. However, the team uncovered evidence to the contrary. Among crops frequented by pollinators, they found just as many wild bees in counties with a lot of agriculture versus a little.
Interestingly, the study hinted that the presence of colonies of honeybees, an invasive species, had almost no effect on wild bee populations, despite some evidence to the contrary. The researchers caution, however, that they need more detailed data and further study to confirm this conclusion.
“While our calculations are sophisticated, much of the spatial and temporal data is coarse,” they said. “We plan to refine our analysis and fill in the gaps as much as possible.”
Wild bees need alternative pest management methods
The researchers view their findings as compelling evidence that alternative pest control strategies, such as integrated pest management, are essential for conserving these crucial pollinators.
Integrated pest management involves controlling pests by using natural predators, modifying practices to reduce pest establishment, and using traps, barriers and other physical means, with pesticide use reserved as a last resort. The team also emphasizes the need for more long-term studies that collect data on more localized bee populations over extended periods.
“We need to combine these large-scale studies that span continents with field experiments that expose bees to chemicals over longer periods and under natural conditions to get a clearer picture of how these chemicals affect bees,” they said.
Beyond bees: Other pollinating species (birds, butterflies, bats)
While bees are by far the most economically important pollinators, other pollinators like butterflies, bats and birds help support wildflower populations and other plants that provide critical ecosystem services, helping to maintain environments from which we derive economic benefits. Maintaining critical ecosystems — including through sustaining wild pollination — has been estimated to avert global economic losses of $2.7 trillion per year by 2030.
The relationships between these pollinators and the plants they fertilize are a focus of NSF (U.S. National Science Foundation investments) to understand how to strengthen the interactions and promote ecosystem health.
Examining the interactions between butterflies and flowering plants researchers found that changes in climate and increases in disturbances from fire and other hazards lead to decreased pollen diversity with the domino effect of harming pollinators and the ecosystems in which they live. Shifting the ecological balance puts pollinators and plants at risk and could harm animals that feed on the insects.
Researchers found that nitrate radicals in the air degrade the scent chemicals released by a common wildflower, drastically reducing the scent-based cues that nighttime pollinators rely on to locate the flower.
There are also changes external to either the plant or the pollinator that can decrease pollination. Researchers at the University of Washington, supported by NSF, found that foul fumes created by nitrate radicals nearly eliminate some scent chemicals produced by the pale evening primrose,
a common wildflower across the western U.S. By blocking these chemicals, the nitrate radicals, which are created by nitrogen oxides released from cars and power plants, make it harder for hawkmoths to find the flower, thus impacting pollination.
While primrose is not a significantly economically important plant, similar impacts on pollination of other plants, including crops, could exist as many pollinators rely on chemical signals.
This type of research across pollinator species is critical as previous studies have shown that without animal pollinators, the viability of plant populations — including some of the ones we depend on to sustain ourselves — will be harmed.
How you can help maintain the pollination-based bioeconomy
While the decline of pollinator populations and interference in plant-pollinator relationships might seem an impossible problem to overcome, minor steps can aid in maintaining these economically important systems.
NSF-supported research has shown that converting vacant urban lots into greenspaces can support native bee populations
The most conducive conditions are created when these new greenspaces are surrounded by 15 or more connected acres of greenspace and flowering prairies with native plants.
Even planting just a few native plant species in a front or back garden and limiting pesticide use can create more pollinator-friendly spaces and support the ecosystem’s health and the economy.
“Diverse networks of plants and pollinator species are essential to maintaining the beneficial interactions we rely on for food, to keep our ecosystems healthy, and to mitigate the impacts of climate change, all of which benefit the bioeconomy. When a plant community declines, all the wildlife that depend on those plants can also suffer, but the reverse can also be true.
Scientists are helping to sustain this key segment of the bioeconomy — the part of the global economy that relies on biological interactions, biotechnologies, biomanufacturing and more — by advancing understanding of the life and role of pollinators and how they interact with the plants they pollinate.