Bees and butterflies help produce our food by pollinating the crops farmers grow. In fact, , including fruits, vegetables, nuts and seeds, depend on pollinators.

But agricultural land is a poor substitute for wild habitat — it often lacks the food and shelter that insect pollinators require. To stay healthy, these creatures need access to pockets of more natural land amid all the agriculture. Currently, pollinators around the world and in Washington , in part because of the loss of their wild habitat.

In a new study, a team of scientists from around the world analyzed a massive dataset of more than 178,000 individual insect pollinators from 19 countries to determine the minimum natural habitat on agricultural land that will allow insect pollinators — including bumble bees, solitary bees, hoverflies and butterflies — to thrive. The results varied between species, from hoverflies needing habitats with at least 6% natural features to butterflies needing at least 37% natural features in their habitats.

The researchers Sept. 25 in Science.

91̽�� News reached out to co-author , 91̽��professor of biology, to learn more about these results and how habitat is important to two types of bees native to Washington.

This paper looks at both habitat “quantity” and habitat “quality.” Why is it important to think about both?

Berry Brosi: When we discuss “natural” habitat in agricultural landscapes, we’re often talking about elements such as semi-wild field margins, small patches of forest or hedgerows between crop fields.

On the quantity side, having more of those kinds of elements tends to benefit many different creatures, including pollinators. But on the quality side, there is a big difference between, say, a field margin planted with a diverse set of flowers that bloom throughout the year that pollinators could visit and benefit from versus a field margin that is mostly non-flowering grasses with only one or two flowering plant species.

The timing of when floral resources are available for pollinators is especially important in agricultural landscapes, because often crop fields are “monocultures” — planted with a single crop species. Even if that crop blooms and provides a lot of resources to pollinators, typically it will only be in bloom for a couple of weeks a year, and that usually isn’t enough to sustain a diverse and abundant set of pollinator species year-round.

How did the research team study habitat quantity and quality?

BB: We analyzed 59 datasets — including one from Costa Rica with data from my doctoral and post-doctoral work — to determine how much natural habitat is enough and how good that habitat needs to be to support pollinator species over the long run.

We found that there are indeed minimum habitat requirements for pollinators, and that these requirements are mostly higher than the targets currently being used by several governments and intergovernmental groups, including the European Union, .

How do these findings affect policies in the U.S.?

BB: We don’t have specific targets here in the U.S., but this research can still inform how we work to conserve our critical pollinator populations in the U.S. and in Washington. For example, the U.S. Department of Agriculture has the that pays farmers to take some of their land out of crop production. It’s been around for decades and was initially used to help prevent erosion. It often makes sense for farmers to stop planting some of their least-productive lands — which they aren’t getting great yields from anyway — and to instead take a payment to manage those in alternative ways. Relatively recently, the USDA added a provision to this program to pay farmers to put in pollinator habitat. Our research findings bolster the support for doing that, and for doing more of it.

This USDA program has a close family element for me. My brother and his family have a pear orchard in Leavenworth and a smaller farm they live on in Cashmere. They would love to enroll in the pollinator program, but it’s oversubscribed in Chelan County. More resources for this program would help pollinators while also helping farmers — it’s a win-win.

Speaking of Washington agriculture, how do these results affect policies here in our state?

BB: Our results also underscore the positive work that the Washington legislature is doing to support pollinators. We have state laws in Washington that are focused on reducing pesticide risks to pollinators. Another state law requires that 25% of the landscaping area of any public works project be made into pollinator habitat. While state-funded public works projects don’t cover a lot of area, that is a great start and well within the minimum habitat amounts we published in our analysis.

Can you give an example of an important insect pollinator here in Washington?

BB: One example is the (Nomia melanderi), which is native to a range of dry areas in the western U.S., including much of central and eastern Washington. This bee is important for alfalfa seed farmers, who grow alfalfa to harvest seed to sell to other alfalfa growers. There are several regions in eastern Washington where growers specialize in alfalfa seed production.

For many crops in our state, growers will bring in honey bees just for the time that their crop is in bloom to pollinate them. That doesn’t work well for alfalfa, because honey bees are very inefficient pollinators for its specialized blooms. Instead, some alfalfa seed producers rely on the alkali bee to pollinate their alfalfa plants, and this helps produce a good seed crop.

What kind of habitat does the alkali bee need to thrive?

BB: This species has very specific nesting requirements. For their nests to be successful, these bees need soil that has a high salt content. Farmers who use them set aside dedicated nesting habitat on their farms — essentially patches of salty mud — that they have developed specific ways of managing to make sure the bees are thriving. For example, many of these nesting habitat patches are carefully irrigated to achieve the ideal soil moisture for the bee nests. Some of these nesting patches have been continuously managed for 50 or more years. There is one large nesting patch of about 5 acres in southeastern Washington that was estimated to contain 5.3 million nesting female bees!

This paper also found that bumble bees need at least 18% natural habitat to thrive. How important are bumble bees to Washington agriculture?

BB: There are 13 bumble bee species native to Washington, and many of them are important agricultural pollinators. Unlike most insects, these bees can actually regulate their body temperature to some degree, and that means they can fly when it’s too cold for many other pollinators. That makes them excellent pollinators of crops that bloom early in the season when it’s still relatively chilly.

These bees can also conduct a behavior called “buzz pollinating” where they’ll grasp a flower, vibrate their wing muscles — making a loud buzzing sound in the process — and shake the pollen off of flowers. That behavior makes them excellent pollinators of tomatoes in particular.

Like many other pollinators, bumble bees couldn’t survive in the long run if they were placed in the middle of a tomato field. They need access to a wide range of different flowers to provide different nutrients for their diet, and access to flowers that bloom at different times in the year. Thus, it’s important to have native habitat around any crop fields that bumble bees are pollinating.

Brosi’s work on this project was funded by the Anne M. and Robert T. Bass Stanford Graduate Fellowship in Science and Engineering, the Koret Foundation, the Moore Family Foundation, Stanford University Field Studies and Human Biology Research Experiences for Undergraduates Programs, the Teresa Heinz Scholarship for Environmental Research and the Winslow Foundation. A full list of co-authors and funding is .

For more information, contact Brosi at bbrosi@uw.edu.

A new study by researchers at the 91̽�� shows that losing a particular group of endangered animals — those that eat fruit and help disperse the seeds of trees and other plants — could severely disrupt seed-dispersal networks in the Atlantic Forest, a shrinking stretch of tropical forest and critical biodiversity hotspot on the coast of Brazil.

The findings, Oct. 12 in the Proceedings of the Royal Society B, indicate that a high number of plant species in today’s Atlantic Forest rely on endangered frugivores — the scientific term for animals that eat primarily fruit — to help disperse their seeds throughout the forest. As a result, losing those endangered frugivores would leave a high proportion of plants without an effective means to disperse and regenerate — endangering these plants, reducing diversity in the Atlantic Forest and crippling critical portions of this ecosystem.

“Tropical forests contain this incredible diversity of trees,” said lead author , a 91̽��postdoctoral researcher in biology. “One of the main processes forests use to maintain this diversity is dispersal. If you’re not dispersed, you’re in a crowd of trees that are just like you – all competing for resources. And there are a lot of plant enemies already in the area or that can be easily recruited, like harmful animals or plant diseases. Your chance of survival is higher when you get transported away from your mother tree to an area without trees like you.”

The Atlantic Forest, which lies east of the rainforests of the Amazon Basin, once encompassed an area twice the size of Texas. Some 85% of it has been lost over the centuries due to deforestation, industrial development and urbanization in eastern Brazil, The Nature Conservancy. The forest is home to a variety of frugivores, from primates to birds, which disperse seeds by regurgitating or excreting them. The seeds of some plant species can’t even germinate until they pass through the gastrointestinal tract of a frugivore.

Lamperty and senior author , a 91̽��associate professor of biology, analyzed a dataset in 2017 that incorporated data on the diet and distribution of fruit-eating vertebrates in the Atlantic Forest. The data, compiled from 166 studies spanning more than half a century, allowed Lamperty and Brosi to paint a comprehensive picture of the interactions between hundreds of frugivore species — 331 total — and 788 tree species.

“For reference, the entire state of Washington only has 25 native tree species,” said Lamperty.

Lamperty and Brosi deduced how important those frugivore species are for the forest by modeling how many tree species would be left without seed-dispersal partners if certain frugivores died out. According to the , only 14% of the frugivore species they analyzed are endangered, but losing them left about 28% of the plant species they analyzed without a means of dispersing seeds. Losing endangered frugivores led to a worse outcome than losing even “generalist” frugivores, which eat fruits and nuts from a variety of species and were previously believed to be the most important group of frugivores for seed dispersal networks.

“A lot of frugivores are generalists. But in the Atlantic Forest, it turns out that a lot of plants are specialists,” said Brosi. “The size and the toughness of their fruit and their distribution in the forest can really limit which animals can perform this important role for them.”

Nearly 55% of the specialist plant species in the dataset relied solely on endangered frugivores to disperse their seeds.

Losing a species — like an endangered frugivore — is bad enough. But this study serves as a reminder that what appears to be one loss has numerous “secondary effects,” said Lamperty. Researchers don’t always know these effects until in-depth studies that span years and incorporate many species linked by different interactions, like this one, are conducted. That can also keep the public unaware about the long-term consequences of losing endangered species.

“It’s a reminder that we should try to understand better what ecological roles and interactions we lose when endangered animals disappear — not just these seed dispersal networks, but other roles, too,” said Lamperty. “Endangered animals have co-evolved with many species in these ecosystems, and I’m not sure we know enough about the roles they play in the health and well-being of places like the Atlantic Forest.”

“It’s an alarming finding, and a sign that we should pay more attention to these interactions between species when considering conservation and land protections,” said Brosi.

The study was funded by the U.S. Department of Defense, Emory University and the UW.

For more information, contact Lamperty at jtl28@uw.edu and Brosi at bbrosi@uw.edu.

Scientists at the 91̽�� and Emory University report that an antibiotic sprayed on orchard crops to combat bacterial diseases slows the cognition of bumblebees and reduces their foraging efficiency. The , published Feb. 9 in the Proceedings of the Royal Society B, focused on streptomycin, an antibiotic used increasingly in U.S. agriculture during the past decade.

“No one has examined the potential impacts on pollinators of broadcast spraying of antibiotics in agriculture, despite their widespread use,” said lead author Laura Avila, a postdoctoral researcher at Emory University.

The team tested how the common eastern bumblebee, Bombus impatiens, responds when its food is dosed with streptomycin. They fed an experimental group of bees a diet of sugar water dosed with streptomycin, while a control group received sugar water. Research has not established the level of streptomycin wild bumblebees receive when they forage crops sprayed with the antibiotic. But the dose that the team tested — 200 parts per million — is likely the highest that bees receive through their diet of floral nectar, based on estimates of the concentration of streptomycin sprayed on crops and the frequency of spraying.

“This paper is a first step towards understanding whether the use of antibiotics on food crops may be taking a toll on pollinators that benefit agriculture,” said senior author , who began this study while a faculty member at Emory University and has been an associate professor of biology at the 91̽��since 2020.

After two days on this diet, the team presented bees with two construction paper strips — one yellow and one blue. One color was saturated with plain water, and the other was saturated with sugar water. The team measured the number of trials it took for an individual bee to show preference for the colored strip saturated with sugar water. Bees fed streptomycin required roughly three times as many trials to make the association compared to the control group. Streptomycin-fed bees were also more likely to display avoidance behavior toward either strip of paper.

In another experiment, bees that passed a training threshold were given a short-term memory test five minutes later: They presented each bee with both paper strips simultaneously and allowed it to select one. Control bees chose the sugar-saturated strip 87% of the time. For streptomycin-fed bees, the success rate dropped to 55%.

A third experiment tested foraging abilities in a chamber with two types of artificial flowers — blue and yellow — that randomly dispensed either sugar water or plain water. Each bee was outfitted with a tiny, ultra-lightweight radio frequency identifier “backpack” to monitor its movements among the artificial flowers. The team found that antibiotic-exposed bees visited fewer flowers that dispensed sugar water relative to the control bees.

Based on evidence from other studies, the researchers hypothesize that the negative impact of streptomycin on bumblebees may be due to the disruption of the insects’ microbiomes.

“We know that antibiotics can deplete beneficial microbes, along with pathogens,” said Avila. “That’s true whether the consumers of the antibiotics are people, other animals or insects.”

Other studies have shown that the antibiotic tetracycline can alter the gut microbiome of the insects and indirectly increase susceptibility to pathogens and mortality. High doses of the antibiotic oxytetracycline can also disrupt the bumblebee gut microbiome, decreasing their immunity to pathogens. Exposure to high doses of tetracycline have been found to affect honeybee learning, while oxytetracycline slows the onset of foraging in managed colonies.

But during the past decade, the spraying of antibiotics on U.S. crops has increased exponentially as farmers battle a rise in plant bacterial infections. These include “fire blight,” which can blacken the blossoms of apple and pear trees and kill them, as well as “citrus greening,” which turns citrus fruits green and bitter and has devastated millions of acres of crops throughout the United States and abroad.

Approximately 75% of the world’s food crops depend on pollination by at least one of more than 100,000 species of pollinators, including 20,000 species of bees, as well as other insects and vertebrates like birds and bats. Many of the insect pollinator species, particularly bees, face risks of population declines.

“Production of our food, farmer livelihoods and the health of pollinators are all tied together,” said Brosi. “It’s critically important to find ways to maintain agricultural production while also conserving the ecosystem services — including pollination — that a biodiverse ecosystem provides.”

The team will next conduct field studies on experimental fruit orchards sprayed with streptomycin. If they find a detrimental impact on bumblebees, the researchers hope to provide evidence to support recommendations for methods and policies that may better serve farmers.

Co-authors on the paper are Emory alum Elizabeth Dunne and David Hofmann, a former postdoctoral researcher at Emory. The research was funded by the National Institutes of Health, the National Science Foundation, the Eva Crane Trust and Emory University.

For more information, contact Brosi at bbrosi@uw.edu.

Adapted from a by Emory University.