Beyond honeybees: The benefits of pollinator diversity

Carter Farms, based in Virginia, specializes in African and Asian crops such as Nigerian spinach, amaranth, taro, sorghum and okra. But besides their unique lineup of produce, they’ve got another distinct feature — an abundance of native pollinators.

Honeybees usually come to mind for pollination, but there’s a whole host of pollinators across a wide variety of groups in the U.S. — including native bees, moths, butterflies, birds, bats and even spiders. Although honeybees are endemic to Europe, Africa and parts of Asia, they’re favored by American farmers — pollinating $15 billion worth of our crops annually. That’s not an easy job for the bees, which are raised by the billions to be trucked around between fruit and nut orchards, a system that, along with pesticide exposure, leads many colonies to annual collapse.

But while most people have heard cries to “save the bees,” far fewer are aware that native pollinators are also important to the food we eat — and in even more trouble. Threatened by disease, invasive species, pesticide use, climate change, habitat loss, light pollution and even competition from honeybees, native pollinators’ numbers are dropping, and more than one-fifth of North American species are at risk of extinction. Luckily, some farmers are supporting native pollinators — and, in return, harvesting the fruits of a diverse labor force.

Boosting harvests

It’s well-documented that a variety of pollinators boosts crop yield for staples like apples, coffee, almonds and jalapeños. Explains Daniel Katumo, a graduate student at the University of Chinese Academy of Sciences, “When we have diverse pollinators, it is possible to have more pollinators visiting the flowers — that’s the crops — and they are able to overcome pollen limitation.” Pollen limitation — where plants are limited by the amount or quality of pollen — leads to reduced fruit and seed production. “It means that more flowers will be pollinated because of the complementarity effects which come with diverse pollinators. For example, if you only have one type of pollinator and maybe it is affected by environmental conditions, it means that there will be no pollination happening. But diverse pollinators, they complement each other both in temporal scales and also spatial scales.”

Adds Katumo, some pollinators, like moths and bats, are active at night, whereas others, like wild bees and honeybees, are more active during the day. Weather also plays a role in pollination. Honeybees are largely inactive during cold, rainy or windy weather, while native bumble and mason bees continue foraging. Besides foraging at different times, pollinators also prefer various parts of agricultural fields.

“These pollinators, they have different foraging behaviors,” says Katumo. “Some fly at different heights, so they target flowers at a certain height of our crop. So if we have many [pollinators], it means that more flowers again would be also pollinated. … Some even prefer areas where the density of the flowers is high. Such pollinators are likely to focus on those, and others, they will go where we have a lower density of flowers.”

For example, a study found that native bees visited trees evenly across an orchard, while honeybees tended to prefer the most flower-filled apple trees. This may be one reason why adding more honeybees to those apple orchards didn’t improve yields — but increasing the number of wild bee species did.

The pollinator advantage

Besides augmenting yield, multiple pollinator species can also improve crop quality — especially the nutritional content. One study found that loquat fruits visited by a variety of pollinators were sweeter and had more moisture, antioxidants, flavonoids and dietary fiber than those visited only by honeybees. Similarly, when bats were prevented from pollinating pitaya fruits, the fruits were lighter and less sweet, which was attributed to a smaller seed set. One of the mechanisms for this uptick in quality may be increased genetic diversity.

“If we have self-pollination — plants pollinating themselves with their own pollen — the quality [of the crop] may be low because there is lower genetic diversity,” says Katumo.

In general, cross-pollination — or pollination occurring between plants — is preferable. For instance, self-pollinated cotton and sesame crops showed reduced fruit set and quality when honeybees, wild bees and wasps were excluded. And having a variety of pollinators around can promote cross-pollination.

The different foraging distances of different types of pollinators can further amplify this effect, notes Katumo. While some insect and animal species have short foraging distances, others forage over larger areas, potentially transporting pollen from crops less likely to be related.

Promoting pollinator diversity

With this world of benefits fluttering by, it’s fortunate that farmers have a variety of strategies to capture them. One approach is to add native vegetation — like hedgerows and flower strips — to attract a diversity of pollinators. At Carter Farms, they accomplish this by protecting wooded areas and riparian buffers on their property, which provide habitat, food and nesting sites for pollinators.

Likewise, Alsum Farms — growing produce like soybeans, potatoes, corn and pumpkins in Wisconsin — takes native plants seriously. They’ve restored about 50 acres of prairie habitat giving pollinators a source of food and shelter. Consequently, they’ve got a buzzy set of inhabitants.

“We have a lot of cool bumblebees …” says Seth Olson, a conservation agronomist at Alsum Farms. “There’s 20 species that occur in Wisconsin, and some of them are species of concern. One or two of them are even federally endangered species, and we’ve observed, at least 15 of the species on our prairies and one of the federally endangered ones, which is the rusty patched bumblebee. That one is in steep decline, and, in Wisconsin in particular, it’s pretty heavily reliant on prairie habitat. So, we were very excited to observe it in one of our prairies on the farm.”

They’ve also observed pollinating flies, along with monarch and regal fritillary butterflies — both of which are candidates for the U.S. Endangered Species Act. But the farm hasn’t stopped at prairies alone.

“There’s this patch of woods by the farm, too — maybe five or six acres of oak woods,” says Olson. “We’ve started managing it, too, more actively for the oak savanna-type habitat. … So we do control burns on all of them.”

This native and diverse habitat has declined by 99 percent in the Midwest due to agricultural and urban development. Yet, with a range of flowering plants, oak savannas can benefit pollinators. For instance, North American Midwest oak savanna that was restored through thinning and controlled burning had a greater diversity and abundance of bee species versus unmanaged sites.

Preventing pesticide use

Besides habitat creation, minimizing pesticide use is key — since these chemicals can harm and outright kill pollinators. Carter Farms is predominantly pesticide-free, while Alsum Farms uses them, albeit selectively. For instance, they spray only where needed and use pesticides targeting specific insects.

In addition, both Carter and Alsum Farms use crop rotation: planting various crops on the same plot of land over different growing seasons. Removing host plants reduces pest and disease populations and, consequently, the need for pesticide applications. This works especially well for controlling pests with longer life spans and a limited ability to move from field to field.

Finally, boosting pollinators themselves also reduces pests. As an added perk, some insect and bat pollinators do double duty — by also limiting pest populations in agricultural fields. Plus, Carter points out that having an abundance of insects and pollinators benefits the birds, bats and other wildlife on his farm, since these bugs are a staple in the diets of many animals.

However, despite the overwhelming positives, some pollinators are also pests. For instance, some larvae can attack crops, even while their adult forms pollinate.

“Not all pollinators are good for the farm, as moths and various butterflies can do just as much harm as good,” says Carter. “We love to see a tomato hornworm as a pollinator, but as a hornworm, it’s gonna eat up the tomato plant.”

Changes on the farm

Pollinators can do a lot for farms, but they can’t stop politics. The weeks since January 20^th have seen a whirlwind of changes, especially for farmers. For instance, the new administration has paused funding for agricultural research and programs benefitting voluntary conservation actions on farms, like the Inflation Reduction Act.

“I get various Climate-Smart arrangements and some of those programs were cut …” says Carter. “You don’t have faith and trust in the government because of actions that they pose already. And as a Black American, the government hasn’t been fair to us for a long time, so when you finally start getting fair, there’s an immediate backlash. … We’ve been affected by it in many ways, and, because of our historic reality with this, we can also learn how to adjust to the changes — because it’s not surprising for many of us that this happened, how it happened and when it happened.”

Carter says that they’re adapting by looking for other funding sources, tightening their budget and relying on savings if need be. Other programs funded by the Inflation Reduction Act could also be on the chopping block. These include the USDA Environmental Quality Incentives Program, which provides farmers with financial and technical assistance for creating pollinator habitat and carrying out other conservation practices. Another one is the Conservation Reserve Program, which funds farmers to convert some agricultural land, such as riparian areas, to native vegetation. The overall goal is to protect water and soil while also providing pollinator and wildlife habitat.

In addition, certain conservation rules, like sodbuster and swampbuster, are under threat. These rules discourage farmers from sowing crops on land prone to erosion or wetlands, which can be important pollinator habitat. On the bright side of things, new legislation in several states now bans or restricts the use of certain types of pesticides, including neonicotinoids, which can be lethal to bees and butterflies.

Pollination power

Altogether, pollinators provide 35 percent of our food and help 75 percent of the world’s flowering plants reproduce. Promoting an abundance of native pollinators is well worth the effort — benefitting farmers, consumers and the surrounding ecosystem. Thankfully, some farmers already embrace this holistic viewpoint.

“When things grow, we can ultimately start growing as well as people,” says Carter. “I believe in a very interconnected reality where we’re not separate from our plants, or the ground, or the trees, or the larger atmosphere and the birds that are around. We have to all figure out how to work as a team, but working in unison.”