Bees, Biodiversity, and the Future of Food (Ep. 55)

Our ecosystems rely heavily on biodiversity for their proper functioning. Recent research highlights the indispensable role of bee diversity in maintaining ecosystem balance, making it a crucial topic in the discussion of biodiversity and food security.

One of the fascinating discoveries from a recent study by our guest Dr. Natalie Kemanski, is the dynamic nature of bee populations over time. Bees thrive at different times of the year, with turnover in bee communities observed seasonally. This indicates that for consistent pollination across a year, a more diverse array of species is required.

Bee populations tend to fluctuate annually, meaning the most crucial pollinators one year may not hold the same status the next. By fostering plant and pollinator biodiversity, we not only ensure stable pollination services but also contribute to the sustainability of our food systems. 

Dr. Natalie Lemanski is an Assistant Professor of Biology at Ramapo College in New Jersey, USA. The study we discussed was published in Nature Ecology & Evolution.

Good to know

We talk a lot about ecosystem function in this episode. If you’d like a refresher on the importance of bees to ecosystem services, check out Episode 35, From Bees to Biodiversity: Shaping the Future of Ecosystem Services.

Transcript

[00:00:00] Welcome to the Bees Knees. A podcast wild about native bees. Wild and native bees are under threat worldwide. In each episode, we look at actionable things we can do to support these adorable little guys whose pollination work is crucial for maintaining biodiversity. . I’m Jacy Meyer, and I thank you for being here.

We need all bees, every single species, and this isn’t just my opinion, it’s what the research tells us. Today I’m speaking with Dr. Natalie Lemanski, who recently led a study examining bee populations across farms in the US states of New Jersey, Pennsylvania, and California. The findings revealed that far more bee species than anticipated are crucial for pollination, not just within a single season, but over multiple years.

Our conversation starts by exploring key questions about biodiversity [00:01:00] ecosystem function, and why wild bees are indispensable for maintaining balance in our environment. Yeah, so there’s been ongoing debate in ecology about just, you know, how important biodiversity loss is going to be for the functioning of ecosystems.

So on the one hand, especially in experimental studies, we pretty consistently find higher biodiversity associated with higher levels of ecosystem function. So for an example, you know, if you plant a plot with higher plant diversity, you know more plant species, you’re gonna tend to get a higher level of biomass.

You know, just the total amount of plant growth in that plot. And this is something that farmers have actually historically known when it comes to things like planting crops in polyculture. This is a practice that historically has occurred where you plant multiple different crops in the same field, and you’re gonna get greater yields than if you were to plant any one alone like a monoculture.

It’s gonna give you a lower yield than a polyculture. [00:02:00] And you see the same thing in experiments in all sorts of different types of ecosystem function. You see that the function is higher when you have higher levels of biodiversity. So that is very concerning because it suggests that biodiversity is very important to ecosystem function.

On the other hand. When we look at wild communities in particular, you know, I’ve looked at wild bee communities. We find this interesting trend where actually it turns out most of the pollination is being done by just a few species. And you see this with other types of function as well. So if you look at a wild forest, you’ll notice that most of the.

For instance, biomass is accounted for by just a few species, and this mostly has to do with species being really uneven in their abundances in nature. So you tend to find this really common pattern in nature. And bee, communities are are no exception, which is where there are a few species that are really common.

Way more [00:03:00] common than even the next most common species. So often you might find that the most common species is 10 times more abundant than the second most, and then there are a few species that are common, and then most species in ecosystem are actually quite rare, quite uncommon. So when you look at.

The effect of biodiversity on pollination. One of the interesting things that we find is that these common bee species tend to contribute the majority of the pollination, both in natural ecosystems as well as in crop pollination, and most of the rare species. Actually don’t contribute very much in terms of pollination, just because they’re so low in their abundance.

They don’t really contribute a lot to pollination function. A lot of it’s driven by just how you know common you are, but the rare species, they’re the ones that contribute the majority of the biodiversity of the bee community. So if a few common species are doing really most of the pollination, [00:04:00] then that sort of seems like a contradiction because.

If it’s just these few common species that are doing most of the pollination, then why would biodiversity matter for ecosystem function? You know, it seems then that based on that, that you would think that actually losing a lot of biodiversity might have very little impact on ecosystem function. . On the other hand, we have decades of research, which sort of suggests the opposite, that biodiversity, you know, we’ve seen experiments that sort, that biodiversity does impact the ecosystem function.

So this to me seems like a contradiction. You know, why is biodiversity so important for ecosystem function when it’s just these few common species doing most of the function? You know and as a scientist, of course, I’m attracted to contradictions because contradictions suggest that more research is needed.

You know, that’s a question, right? That’s something that we need to reconcile, and it’s important to reconcile it because we need to know what the consequences of biodiversity loss are going to be for these [00:05:00] functions that we really rely on. So this is, I think this to me is a really important question in ecology.

Thinking about long-term ecosystem function, is that what inspired you to study bee diversity over longer periods of time? One of the interesting things about a lot of previous studies on biodiversity and pollination is that they’ve typically been either, you know, snapshots of a single moment in time, or they’ve sort of aggregated, you know, maybe several different.

Sample points just sort of, uh, lumped together. So they’re kind of a static picture of a pollinator community. So, you know, you might go out and sample the bee community on a given day and look at which species are providing the pollination function. But the thing about bees is that many of them actually have rather short flight seasons, like the time when the adults are active and forging, and that’s when they do all the pollinating, right?

Is when they’re flying and forging for food as adults. So across the season there’s [00:06:00] turnover in the bee community. You have bees that are. Most common early in the year, like in spring for instance, are actually gonna be different from the bees that are common later in the year. So mid-summer or late summer across the season, we see turnover in the bee community, and this is one of the things that we found in our study is that there’s this turnover when we actually sample across multiple times the same fields, the same location across different time points.

We see turnover in the bee community. So why that’s important is because what we found is that different bees are actually providing this crop pollination services at different times throughout the year. And what we found was actually consistent with previous studies. So if you go out in any one day, you find what previous studies have found that a few highly abundant bees tend to be providing most of the pollination function at any given one time.

The thing is it’s a different set of highly abundant bees at different times. So the [00:07:00] result essentially is that if you want consistent pollination throughout the year. You need more species than you would if you just needed it for any one time point, right? So if you actually want to provide this ecosystem function consistently, so you need both the early bees and the late bees, and that’s really what we found.

So if you look at just a snapshot. You find very few species really required for ecosystem function. But then when we expand our view to look at a longer time series, you realize that actually a lot more species are needed if you wanna provide this function over long periods of time, which of course matters because many of our crops are flowering for longer periods of time than any one particular bee species is gonna be active.

We saw the same thing in terms of turnover from year to year as well. So the bees that are most abundant in one year aren’t necessarily the most abundant the following year. And this is actually not that surprising because we know that a lot of wild species, their populations will fluctuate over time.

And so a species that doesn’t seem [00:08:00] to be very important as a pollinator this year might actually be the most important pollinator in some future year. And so having more species of bees ensures, that you get more consistent pollination from year to year, even as individual populations fluctuate. So the way we sort of view it is that it’s kind of like diversifying your stock portfolio, right?

If you invest in a single stock, it can go up or down, but having biodiversity. It’s kinda like having a diversified portfolio, right? You’re gonna have higher yields over time because it’s likely that at least one species is having a good year and is gonna be your abundant pollinator, even as individual species kind of go up and down from time to time.

So let’s talk about the loss of bee species and the effects on biodiversity over the long term. We actually know surprisingly little about long-term trends in bee populations, and most of the studies that have been done long-term studies on bee populations have been done on bumblebees, which are weird in a couple of [00:09:00] ways.

Bumblebees are, for starters, are social, which most bees are not, but the studies that have been done have actually shown pretty alarming declines in a lot of bumblebee species, and so the best studied bee species. Many of them are declining. In fact, a bumblebee species was, I believe, the first invertebrate to be classified as an IUC and red list endangered species.

So it’s hard to say how general that trend is for other bee species. One of the longest studies of bee diversity that I’m familiar with was around six years, which really isn’t very long. And it did show an overall trend of decline in bee diversity during that period. But of course, like I said, populations fluctuate over time.

So a six year period, it’s hard to really say whether this is a general trend or whether that was just, you know, a kind of a, you know, natural fluctuation. Still pretty short timescale, you know. Certainly given that [00:10:00] habitat loss is the biggest driver of biodiversity loss for most species, I think there’s certainly reason to be concerned for bees as well, because bees are experiencing the same habitat loss that a lot of other species are experiencing.

And so I think that there’s reason for concern, but we just need more data. We need more data on pollinator populations. We really need is long term. Monitoring of pollinator populations, you know, especially bees. And what about food security? As for what it means for global food security? I mean, I think that there’s a very real reason to be concerned.

’cause one of the things that our study suggests is that pollinator diversity can kind of buffer us against these natural fluctuations that are gonna happen just as the environment fluctuates over time. Populations are gonna fluctuate. And so I think what this means for crop production is less diversity is going to result in in greater fluctuations in crop production over time, which obviously is bad for food security when you don’t get consistent pollination [00:11:00] function.

So what practical steps can farmers or policy makers or individuals even take to promote this kind of pollinator biodiversity that is so critical for our food security? One thing that farmers can do, I would say is leave more natural habitat for bees. So when we think of helping the bees, one of the things we often think about is providing food for them in terms of floral resources, and that’s very important.

But bees also need nesting sites. You know, it’s not just about food, it’s also about all of the other things they need for their lifecycle. And a lot of bees nest in the ground and um, in dirt bees nest also in places like sticks and piles of leaves. So leaving some of this natural habitat. You know, leaving open strips, you know, that are un unmanaged, unplanted, leaving these sort of hedgerows and areas and strips of natural habitat that provides nesting sites for bees.

And [00:12:00] so that is, I think, just as important as providing them with food resources for individuals. You can do this as well. So for instance, just leaving leaf piles rather than raking them can actually provide more nesting habitat, not just for bees, but actually for other beneficial insects as well. And then finally, one of the things from the study is that different bees are gonna be active at different times.

So if you wanna protect diversity. Having flowers, that flower at different times of year is going to be helpful for promoting bee diversity. So having a garden that is diverse, not just in terms of species, but in terms of flowering time, having flowers that flower early, and then flowers, that flower late, kind of putting in flowers that bloom at a, at a variety of times is gonna provide resources for a greater variety of bees.

So you mentioned a couple questions that you would still like answered. Uh, what other further research would you like to see in this area? I. [00:13:00] I think the main thing that I’d really like to see is long-term studies monitoring individual bee populations so that we can get a better sense of which bees really are declining.

That’s something that I mentioned. We’ve got a lot of studies of bee communities where we look at the whole community at a single snapshot in time, so now I think doing a deep dive into individual species and monitoring them for long periods of time. I think the research that’s really most needed and um, there’s really, like I mentioned, been very little study of long, long-term study of bee populations.

I would love also to see longer term studies of crop pollination. So in our study we found there was this increased need for biodiversity over longer periods of time, but our study really only looked at three years of crop pollination, which is really remarkably, this is one of the longest. Studies of the role of biodiversity in, in crop pollination that’s been done, which is really remarkable because, you [00:14:00] know, three years really isn’t very long.

So I would love to see this type of research extended over a longer period of time. because one of the things that we found in our study is that you see this increase in the need for bee species over time, but it, it doesn’t level off after three years. And so there’s every reason to think that if you were to measure this over a longer time, you might have found it even stronger effect.

You know, I would guess that. Even more bee species are probably needed over even longer periods of time. And it was just, that was as, as much time as we had data for. So I would love to see this type of study repeated just for longer time. So if you could encourage people to do just one thing to support native bees, what would it be?

If you can do just one thing to support native bees, your average person, if you have a garden, I would say plant native plants. I think that that’s one of the most impactful thing your average person can probably do in terms of supporting the native bees and plant a variety of plants. [00:15:00] Plant plants that bloom early and plants that bloom late have a variety and that’s gonna support bees over their entire season, not just over a short period of time, because many times, many ecosystems, there are periods of dearth.

You know, there’s periods of where a lot of things are blooming, and there are periods of dearth where there’s not as much blooming. So supporting pollinators through that period of scarcity, by having a variety of plants that bloom at a variety of time, that can be really impactful in terms of supporting the bee populations.

Research highlights that while the abundance of a single species is valuable, it’s the diversity of bees that truly make the difference. Different bees take the spotlight at different times, and this variety is what maintains balance throughout a growing season. Across years by creating conditions that support a mix of plant and pollinator species.

Instead of depending on one dominant type, we can foster the biodiversity needed to sustain reliable [00:16:00] ecosystem services. A big thank you to Natalie for such an eye-opening discussion and to you for joining us. Natalie’s actionable advice plant with intention to reduce scarcity. Choose a variety of flowers for spring and another for later in the season.

Until next time, time, your blooms.