Habitats for Bees (Ep. 8)

Researchers are employing various interventions to see if they can, if not stop, at least slow down the worrying decline in bees. Planting pollinator-friendly habitats in agricultural areas is one of these initiatives. Today, we talk about bee diversity and abundance in different habitats and the importance of habitat quality when it comes to intentionally planting spaces for pollinators.

We discussed Dr. Hannah Leverson’s findings on the relationship between flower cover, plant species in bloom, and bee abundance and diversity. She measured flower cover and plant species as low, medium, or high, and found that bee abundance and diversity significantly increased as flower cover and the number of flowers increased. The conclusion? Planting any amount of habitat is better than nothing, but the highest cover and number of plants possible is important for supporting bee communities.

Learn more about Dr. Hannah Leverson and read the North Carolina study we discussed in this episode. She’s part of the North Carolina State University’s Department of Entomology and Plant Pathology, which is doing a lot of exciting work in the entomology field.

Hannah gained further insight into bees using those same pollinator habitats. She looked at pathogen presence within bee communities and evaluated the impact of habitat presence on soybean crop yields.

Did you know?

Hannah said her favorite bees are parasitic, which is quite an interesting and surprising choice! As she explained, parasitic bees don’t forage for food or make nests for themselves. They invade other bee species’ nests and food supplies to provide for their young. She mentioned two examples, the Triepeolus, and the Holcopasites.

Transcript

[00:00:00] Doing whatever you can, wherever you can actually matters and just starting somewhere is what’s important. And then you can always work up and build up from there, but you got to start somewhere.

Welcome to The Bees news. I’m your host, Jacy Meyer. Providing food and homes for bees are two fundamental things we can do to support them. Our living environment can significantly affect our quality of life. So it’s no surprise, the same goes for animals and insects. Today, we’re going to look at one study out of North Carolina in the United States and talk about what the team found when they looked at bee abundance and diversity following an initiative mandating pollinator habitat planting on sites across the state.

I’m happy to welcome Dr. Hannah Levenson, a postdoctoral research scholar at North Carolina State [00:01:00] University. Hannah, thanks so much for joining us. You had an exciting opportunity to gather this data. Could you tell me about the sites you studied? Why were they available to you? Of course. So the sites I used were all North Carolina Department of Agriculture Experimental Research Stations.

So these are established across the state by the state government. And there are about 16 sites that I used for my study and they were available to us because the North Carolina Department of Agriculture started an initiative a few years ago around the end of 2015, early 2016 called Protecting NC Pollinators.

Part of that initiative required that all of these experimental research stations planted pollinator habitat on their property. So, this could be in unused areas on the research station, it could be in fields that they wanted to rotate out of a crop for a year, but [00:02:00] they had to plant it somewhere. And so, my advisor, David Tarpy at North Carolina State University, heard about this when the NCDA was developing this plan.

And saw a really exciting opportunity to see how this conservation effort of adding habitat into agricultural areas truly impacted bee communities by measuring those impacts from the very beginning of this effort. So from 2016 to 2018, we visited 16 of those research stations across the state. There are a couple more that weren’t able to plant

in time to be a part of our study and we documented what happened to show if this could act as a conservation tool for pollinators in agriculture areas. So how did you measure the bee abundance and diversity? Yes. So at all of our sites, all of those 16 research stations we visited, we used something that is called bee bowls.

So these are small plastic cups [00:03:00] that are painted with special paint that reflects UV that attracts bees. So we painted some blue, some yellow, and some white. And at all 16 stations, we had a contact, an employee at the research station, help us out and we put those bee bowls all around the perimeter of the habitat that was established for this study.

So we collected those once a month for four months during peak bloom at the plots for all three years, 2016, 17, and 18. And the way we use that sampling method is our contact at the research station would put the bowls around the perimeter of the habitat early in the morning around 9am, fill it with soapy water.

What that does is the soap breaks the surface tension of the water so that anything that falls in is collected. So it’s a passive sampling tool, you just leave it out across the day. And so in the afternoon, they would go by and pick up anything that was collected and send it back to us to process. So we did that at all [00:04:00] of our stations.

And then at 12 stations, me and other members from the lab went out together and we collected additional samples using hand nets. The main reason we utilize these two different sampling methods is because each of them are known to collect a different portion of bee, of pollinator communities. So, bee bowls tend to collect smaller bees that are harder to see with your eye, but bee bowls can be biased

towards environmental factors. So when there’s more flowers blooming, the bees might not be as attracted to bee bowls. So netting is perhaps less biased to environmental factors because we’re there, we know we need to collect bees, but we might not see the little bees or if something is too quick, it might escape us.

So both sampling methods have their own biases. And so they portray the pollinator community slightly differently. So we wanted to utilize multiple sampling methods to try to document the entire community as best as we could. So [00:05:00] your study found increases in both bee abundance and diversity, but a lot of it depended on the habitat.

Could you tell me what you found? Yeah, this is really cool. We weren’t totally expecting some of the results that we found. So it was really exciting to see as it developed over time. So one other measurement we took while we were there, the once a month for four months when we were collecting samples, we took a measurement of the habitat at that point in the year.

So the first measurement we took was what percentage of the plot was in bloom. So this is what we’re calling flower cover. We measured it as low, medium, or high. Um, at each sampling event, we also took a measure of the number of different plant species that were in bloom while we were there taking a sample.

We also measured that as low, medium, or high. And that is our two main characteristics that we were measuring as a proxy for habitat quality. Since we’re providing resources for bees, those are two key factors [00:06:00] in resources. So what we found was that the abundance or the number of bees we found was significantly correlated with the percent cover.

Whereas the cover increased, we saw an increase in bee abundance. So, very logical. Bees need flowers. Bees are going to where flowers are. But it was cool to actually document that that was happening in these agricultural areas. And we saw a trend where bee abundance also increased as the number of flower species in bloom increased, but this wasn’t significant.

So similarly, we looked at the bee richness, and that’s just the number of different bee species we found at the habitat, and compared it to these two habitat characteristics. And we also found that the number of bee species significantly increased as the percent cover increased. And this time we also found that the number of bee species increased with the number of flowers.

So that’s telling us these are really important factors for supporting [00:07:00] bee communities, and we are documenting that that does truly influence what bees we’re finding during our samples. So basically this tells us that planting any amount of habitat is better than nothing, you know, as cover increased, bee abundance and bee diversity increased, but to support bees the best, highest cover possible, highest number of plants possible was really important.

So we’re getting more of an idea of what we need to do at these habitats to support bee communities. The other thing I like to add here is that even though we saw that the community overall had a trend where cover and diversity was important, this isn’t going to be a one size fits all. So when we look at specific species within the bee communities, we did see that different species respond slightly differently, depending on their foraging behaviors, what time of year they might be active, since the habitat will also change across the year.

So… In general, supporting general bee [00:08:00] communities, this really did seem to make a difference. But if someone has specific needs or specific goals, that is suggesting that we might want to fine tune this habitat to those specific situations. And every time you establish it, it’s not going to be the same.

That’s a great point. And it brings me perfectly to my next question, which is the research stations covered a variety of landscapes. So were different flowers planted for different environments? This is a great question. And it’s something that in initial conversations, we were hoping to look at and just how things happen in real life,

you can’t do everything you always plan. So that is not what ended up happening, but I think it’s an important point and something that other researchers are looking at and something that I think in this specific context, we would like to look at in the future. So initially, the discussion was centered around planting a region specific mix to the different parts of North Carolina.

So in North Carolina, [00:09:00] we have very distinct regions. We have a coastal region, a Piedmont region, and a mountain region. And those all have different impacts on what environmental conditions organisms will experience in those regions. So logically, it would make sense to have different habitat that we’re adding to support the different bee species that also occur in all those places.

So yes, I agree. That would be great to look at in the future. For now, it was just a really big effort to get this amount of habitat planted at somewhat of the same time to do a standardized research study over several years. So it was already a huge effort. That was something that couldn’t be done at the same time, but I think it’s definitely something people are still looking into.

What worries you about your local bee population? We have concerns for rare species, mostly because they might be rare because we just don’t see them very often, and so we don’t know what’s going on with their populations. Or they could be rare because their numbers are truly low. [00:10:00] So those are definitely species of concerns, and then specialist species are definitely of concern.

And in North Carolina, we do have a bumblebee species, Bombus pennsylvanicus, that is currently under review for potentially being listed on the endangered species list. I found quite a surprisingly large population across North Carolina in agricultural areas. So it seems like this bee might be more common in agricultural areas than people previously realized.

But it definitely has documentation showing that its populations might be of concern. So we did find those in North Carolina. But an alternative example is Bombus affinis, the rusty patch bumblebee, which is listed on the endangered species list. Historically was found in North Carolina in our mountain region, and it has not been found in several decades.

So we’re more concerned with specialist bees or bees that have very small ranges, things like that. [00:11:00] Did anything surprise you about the results from your study? Yeah, there is a few things. So I think the biggest takeaway is that starting where you are at and what you can provide to bees does make an impact on the community.

And these habitats were relatively small, so all of the habitats I sampled at were an acre or less. And to us, even though that seems pretty big, in the grand scheme of bees flying through the landscape, that’s a very small portion of land. And we still saw that adding flowers in an acre or less, over time, supported bee abundance and diversity.

In general, we found increasing abundance and increasing number of species detected across the three years across North Carolina. So each year we found a new genera of bee in these habitats. So that was the biggest thing that was surprising is just showing that doing whatever you can, wherever you can actually matters.

And just starting somewhere is what’s important and [00:12:00] then you can always work up and build up from there, but you got to start somewhere. So that was really great to see. Another thing that was more logistics and I think may help people when they’re thinking about how to establish the habitat themselves is that this is still a man made object in the landscape.

So I think a lot of people’s gut reaction would be, I’m putting out plants, they just grow in the environment, I just need to do it, and then it’ll be there forever. But what we found is that over the season, we saw a decrease in plant cover and plant diversity, which we just found was very important for supporting bee communities.

So that is concerning that these habitat characteristics that were crucial for supporting our pollinator communities were decreasing across the season. And then the other thing that we ended up finding was that some of the research stations had quite a bit of trouble maintaining the quality of this habitat. So, there was a lot of invasive weed issues across the state, [00:13:00] and then several research stations have soil seed banks of unwanted invasive plants that because this habitat was no longer being managed with high inputs, it was being, you know, kind of left to grow however it wanted.

Those soil seed banks then became active again. So this is still going to require maintenance. It’s not something you should put out once and leave and never come back. If we want to change our landscape and we’re still, you know, having human impacts on the environment let’s make sure we’re maintaining it over time so that we’re providing the best quality habitat for bees without causing other issues for other systems like invasive weeds.

So those were two big things that we were happy and also interested to find. Do you have a favorite bee? I have a favorite type of bee, I guess. So, I really like parasitic bees, which at first might seem weird, but I think they’re very cool. They will [00:14:00] sneak into the nest of other bee species that they are parasitic on, so those are their hosts.

They sneak into their nest, they lay their own egg, and then the host bee raises the parasitic bee’s egg instead of its own egg, unknowingly. So, I think that’s just so crazy that, you know, that’s happening. But also, the parasitic bees, I think, are really beautiful. They sometimes look more like wasps and can be confused for wasps, but they have really interesting patterns and colors.

Two of my favorites, if anyone wants to look them up, are Hulcopasites, spelled H O L C O P A S I T E S, and it has this really beautiful kind of faded magenta butt, and it has little white polka dots all over and I think what a crazy pattern to have and it’s so cool. And then the other one is Triepeolus, which is spelled T R I E P E O L U S.

And it’s common name is the zebra bee because it’s striped all black and white [00:15:00] all over and I just think that they have very cool patterns. So those are some of my favorites. Thank you for that. I’m going to look for pictures and I will include those in our show notes. What do you believe is the biggest threat to bees and what can we do about it?

So there’s a lot of discussions about all the different stressors that are impacting bees and a really big question is which is the one that we can focus on? And I think that they all matter, and they all play a role, and they can work synergistically together. So some of the ones that people commonly talk about are pesticide use, pathogens and diseases, habitat loss and fragmentation, introduction of new species, which could then introduce even more pathogens and diseases.

But I think that the factors… that we can focus on right now, make immediate changes and have immediate impacts are adding habitat back into the environment. So as we continue to [00:16:00] develop, we continue to fragment our landscapes we’re taking away the resources that bees need to live. Those are floral resources so they can collect food and nesting resources so that they have a place to lay their eggs, raise their young and live.

Without those, we can’t have bees. So, evidence from my research, but as well as research really around the world, adding these back into the environment can have immediate impacts. So, I think those are really big things for us to focus on now, and we can make a big difference now. And then, of course, all those other factors still play a role and can be integrated into these issues of habitat loss, but without the habitat, we can’t even focus on those other issues.

So, I think that’s the biggest one, in my opinion. But, there’s still a lot of questions about… when we’re adding this habitat back into the landscape, how do we do that in the best way to support bees? So there’s still a lot of work to be done, but like I’ve been saying, starting where you are, where you can, doing whatever you can, [00:17:00] even if it’s a very small space, it’s better than nothing.

Land use change is one of the biggest threats to wild bees. Enhancing pollinator habitats is one tool researchers are investigating to see if manipulating bees environment can combat some of the stress in their lives. Hannah’s work found that introducing pollinator habitats can have positive effects, but it’s not just enough to have more habitats

those environments must be of high quality and maintained to truly make a difference in bees lives. Thanks so much for listening. I appreciate your time. In upcoming episodes, we will keep looking at initiatives hoping to help bees in the face of continued land use change. One of those is wildflower strips.

I’ll see you again in two weeks. Until then, keep buzzing.