This summer, several gardeners were out working in our test gardens when they noticed a swarm of honey bees crossing the street. A short investigation revealed a “wild” honey bee hive in a tree near our building. The hive was about 10 feet off the ground, tucked into a split in the trunk of the tree and covered with bees. We’ve enjoyed watching the bees come and go from their hive this season and have a variety of questions about the rarity of this type of hive, the difference between native and non-native bees and what role gardening plays in all of it.
Being plant – not bee – experts, we turned to a rich resource near us, the University of Vermont. Dr. Leif Richardson is an ecologist who studies bees and their interactions with plants and their parasites. He is currently doing a post-doctoral fellowship an the Gund Institute for Ecological Economics.
Dr. Leif Richardson, an ecologist who studies bees, sat down with me to talk about the North American bee population.
Native bees vs. non-native bees: what’s the difference?
Dr. Richardson took the time to sit down with me and discuss the difference between native and non-native bees, the importance of native bees to pollination and what we can do to really help the bee population.
“I study only wild bees,” Dr. Richardson clarifies as we begin our conversation. “I primarily work with bumble bees, but I’ve done some work with other, solitary bees that aren’t social.” He explains that these solitary bees live an independent lifestyle, in stark contrast to the European honey bee, which is the bee that Dr. Richardson says “most people know about.” The European honey bee has been in North America for hundreds of years, but they’re not native. “So it’s sort of like other agricultural animals we’ve brought here because they’re useful, [like] livestock,” he explains.
The hive in action.
Due to naturalization, the European honey bees, like the ones that made our hive, are sometimes found in nature, but generally, because of recent problems with parasites, Dr. Richardson explains that it’s not common. “They occur in hives that humans maintain. So that’s a really different situation from wild bees, which generally live underground or in hollowed twigs, trees and other places,” he says. Native bees are Dr. Richardson’s specialty, and his fondness for them is apparent as he speaks. “What’s interesting about [native bees] is, as you would expect, they are the main pollinators of native plants, wild plants in the woods, wetlands and so on. So they are really important to ecosystem structure and function. But surprisingly, they are, in many cases, the most important pollinators on farms,” he says. “So even though we’re not managing wild bees, native bees … they just happen to be in the natural lands around farms.”
Bees, farms and your food:
Despite being somewhat ignored by humans, native bees still commute to farms to get their food, which is pollen and nectar. Dr. Richardson explains that because of this, we get a huge environmental benefit from these native bees. “They are actually more important to most of our crops that need pollination than our honey bees. So even though we put honey bees in apple orchards and they do some pollination, they don’t do as much pollination, on average, as the native bees,” he says.
Dr. Richardson can’t stress the importance of this enough, “Native bees are really important to people, partly because they help to maintain natural systems, but also because they are very important to the thoroughly human ecosystem that is a farm.” Without the wild bees that we don’t pay much attention to, Dr. Richardson says, we wouldn’t be able to grow many of the crops we rely on.
Pesticides and bees:
It’s apparent that native bees have a huge, positive effect on people, but what Dr. Richardson and his colleagues are trying to find out is what is our effect on them? “We know a lot about how bees affect outcomes for people on farms, but now we’re looking at ways that farms may benefit those wild bees or may actually have detrimental impacts on some of them,” he explains. On a basic level, it’s obvious what good farms do for bees. They provide flowering resources that feed bees, and Dr. Richardson notes that for virtually all bees, pollen is their only source of protein. On a basic level, it’s also obvious that farms can harm bees. Bees are negatively impacted by pesticides and insecticides, which is a big concern for bee decline around the world right now, explains Dr. Richardson. Especially, a class of insecticides called neonicotinoids.
But then there is a whole range of other, less-obvious effects that farms have on bees, which is what scientists like Dr. Richardson are trying to figure out. “One of the things I’m working on now is the effect of the chemistry of the nectar and pollen in one particular plant, which is the blueberry, on the bees that consume them,” explains Dr. Richardson. “So for bumble bees that come to farms, pollinate blueberries, deliver us this benefit, this ecosystem service, what is the effect of the phenolic compounds in the nectar and pollen on bee health, on bee reproduction, what is the effect – if any – on them?” He explains that some chemicals found in the pollen and nectar of agricultural plants can be toxic to bees at the right dose.
Additional threats to bees:
A common false misconception is that Colony Collapse Disorder, a phenomenon that has gotten a lot of media attention lately, can happen to all bees, explains Dr. Richardson. “It’s a phenomenon of the European honey bee and it’s not just one thing, it’s a syndrome that is caused probably by multiple interacting negative effects, of things like mites, fungi and viruses,” he says. Bumble bees and other native bees have their own pathogens and parasites that they can sometimes share with the European honey bee. “In fact, some of the diseases that came here on the backs of honey bees then spread to wild bees, which is a concern to us with the maintenance of healthy populations of native species here,” he says.
Dr. Richardson says that out of the approximately 50 species of bumble bees found in North America; roughly 33 percent are threatened and have declined steeply in the past 50 years. “Although we’re not certain of all the reasons that bumble bees could be declining, use of insecticides or other pesticides is probably one of the factors,” he explains. Land use change and climate are two other big hypotheses. “The home range in bumble bee species, in both North America and Europe, is shrinking in response to a warming world,” says Dr. Richardson. “So bees are retreating from the hottest, Southern most part of the area where they were naturally found, but they’re not expanding their range northward as the climate warms to the North of them.” This results in a shrinking area of habitat in which native bumble bees occur. Dr. Richardson points out that not all bee species are in decline, but there is “great concern” that some of the species integral to us functionally are declining.
How we can help our bees:
I ask Dr. Richardson if there are ways for us to help the bees. “Yes!” he says, enthusiastically. “There are big things that people can do and there are little things people can do. It’s not a hopeless situation and if people care about this, I encourage them to get involved in solving the problems,” he says.
Dr. Richardson’s big and little things you can do to help the bees:
- Help slow down global warming and climate change. Yes, I know that’s a huge one. But Dr. Richardson says that climate change is one of the biggest threats to bee species, just as it is for other organisms. “If we want to protect bees, we need to do something to halt the increase in warming that’s caused by [humans] – greenhouse gas emissions,” he says.
- Reduce or eliminate the amount of insecticides, pesticides, herbicides and fungicides used in your garden. All of these can be harmful to bees, even if they aren’t necessarily targeting insects.
- Buy organic. “Shop like you mean it, and [don’t] support agriculture that uses chemicals,” says Dr. Richardson.
Bumble Bee Watch is developing a scaled map of where's bees occur, which Dr. Richardson says is very important data.
Another thing we can do to help is to join a citizen science project. Dr. Richardson suggests bumblebeewatch.org, which is a project of the Xerces Society. Anyone can go to the website and upload a photo of a bumble bee, or any bee species, with information on the date the photo was taken and the location. “They are developing this scaled map of where bees occur and it’s very important data. It’s a nice thing – a lot of people get involved and learn something about identification of bees,” explains Dr. Richardson. “Its personally gratifying for a lot of participants, but there are many thousands of records that have been submitted that are helping scientists understand where bees currently exist.” Scientists can then compare those data to historic records, helping to determine whether bee populations have shifted with time. “Are bees shifting northward as the climate warms, or are they disappearing from urban areas? You can think of lots of different questions we can actually address with this data collected by people who aren’t specialists, who may not know anything about bees,” says Dr. Richardson.
Native bees and native plants:
The most surprising point Dr. Richardson made in my conversation with him was that “bees aren’t botanists,” meaning they don’t really care if a plant is native or not, as long as it has pollen. “Bumble bees and many other species of bees avidly collect pollen and nectar from non-native and native plants,” he says. But these species differ from specialist bees that only collect their pollen from a certain type of plant, which is almost always native. “So a loss of that native plant results in loss of the bee,” explains Dr. Richardson. “There, obviously supporting populations of native plants is critical to both the plant and the bee.”
Dr. Richardson says that he doesn’t want to diminish the importance of native plants. “But in general, non-native plants are not directly threatening native bees.” He suggests planting native and locally adapted plants, especially native wildflowers. Although he says the absolute solution to bee decline isn’t in our backyards, Dr. Richardson still stresses the importance of gardening. “It definitely makes a positive difference if you do something in your own tiny little backyard if it’s the only land you manage yourself. It’s a very good idea,” he says.
At the end of our conversation, I asked Dr. Richardson if he had anything to add. He paused, and then reiterated his point from earlier. “I’ve said it, but I’ll say it again. I think it’s important that people come to understand better how important native and wild bees are to agriculture,” he says. “A lot of people who are well educated and well versed in the world don’t realize there are so many types of bees.” There are more than 20,000 species globally and nearly 5,000 bee species in North America. “And the European honey bee is just one of those 5,000,” he says.
Dr. Richardson is concerned that our population thinks of farms from the perspective of consumers and eaters, not necessarily as growers. He says that when many people describe what a farm is, they talk about planting the seeds, watering them, adding fertilizer, controlling pests and so on. “All of those things have to do with the location and what’s on the farm, especially what we put in and take out, and pollination is a key aspect of farming for many plants,” explains Dr. Richardson. He says the revelation that has come in the past decade, that a majority of crops are primarily pollinated by wild animals, hasn’t fully “hit us as a culture yet.”
“So much of what we eat, so much of what sustains us, is mediated by unmanaged animals that are threatened by our behavior,” he concludes. “If you were to think of an analogy from another part of human life, we’d probably be doing a whole lot more about it, because of this very direct, important link and threat.”
Although our test gardens are a small solution to a huge problem, it’s possible that the wild honey bee hive tucked into the tree across the street could be benefiting greatly from them. And despite seeing a decline in the bee population in the hive as the summer progressed, we’ll keep gardening – amongst many other things – to help be a part of the solution to the disappearing bee population.
Further Resources from Dr. Richardson:
- Bumblebeewatch.org, a citizen science project where you can upload photos you’ve taken of bees in your area.
- Xerces Society, a nonprofit organization that projects wildlife through the conservation of invertebrates and their habitat.
- BugGuide.net, a community where people submit photos of bees and ask for identifications. Specialists arrange the photos and give info on them.
- DiscoverLife.org, a place to find nature identification guides, including a thorough guide for bees.