Buzzkill: Climate Change and the Looming Threat to Pollinators (Ep. 37)

You’ve most likely noticed an increase in extreme weather patterns in recent years, such as hotter summers, unexpected droughts, and unusual weather cycles. These changes are not just uncomfortable for us humans, but also pose significant threats to our environment, especially to vital pollinators like bees. In this episode, we delve into how rising temperatures and growing dry conditions, particularly in regions like New Mexico, are affecting these crucial creatures. 

Bees play a vital role as pollinators, essential for both wild plants and numerous agricultural crops. Our guest, Dr. Melanie Kazenel highlights that a decrease in bee diversity could lead to less efficient pollination, impacting plant reproduction and biodiversity. Identifying the most endangered species enables us to implement strategies to safeguard them and maintain ecosystem stability. Listen now to discover more about the obstacles bees encounter and how we can contribute to securing their future.

Dr. Melanie Kazenel is a Visiting Assistant Professor in Biology at Earlham College in Richmond, Indiana in the US. She’s interested in species interactions and how they shape the structure and function of ecological communities, particularly in the context of climate change. You can learn more about the study we discussed here.

Good to know

Melanie did this study at the Sevilleta National Wildlife Refuge near Socorro, New Mexico. Biology Professor Karen W. Wright established a long-term bee monitoring study as part of the Sevilleta Long-Term Ecological Research Program. Since 2002, each month from March through October, when bees are active, researchers open traps in the fields of the wildlife refuge to collect bees. The bee data collected as part of this long-term program is what Melanie used in her study. 

Transcript

[00:00:00] Welcome to The Bee’s Knees. I’m your host, Jacy Meyer. The Bee’s Knees is 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.

Thanks for being here.

How has your weather been this summer, or winter, depending on your hemisphere? In the northern hemisphere, hot, hot days and heat warnings have been worryingly common. We’ve talked about how different aspects of climate change are impacting pollinators, but today we’re going to talk specifically about the heat.

Dr. Melanie Kazenel used a 16 year bee data set to see how increasing dry conditions and rising temperatures are affecting bee population, in a region that’s already known for being warm and dry, New Mexico in the southwestern part of the United States. [00:01:00] Let’s see what she’s discovered. You’ve been studying bee populations in a region that’s getting hotter and drier.

What are the main takeaways from all the data you’ve reviewed? Especially in terms of how climate change is affecting these bees. Yeah, so I was in my study looking at bees in dryland environments in New Mexico. So in desert grasslands and shrublands, grasslands and shrublands. And what we found in particular was evidence that some bees are doing all right under climate change, but other bees are predicted to do poorly.

So, our study made use of a long term monitoring data set that was established in 2002. And through this data set, we have been able to examine which bee species are likely to be affected. to be all right under climate change and which bee [00:02:00] species are likely to decline. And we found that about half of the species in the system have the potential to decline as climate change progresses.

So that’s reason for very serious concern. On the flip side, certain bee species are predicted to be all right. They’re predicted to be resilient to climate change. So that gives us some reason to be hopeful. There’s some resilience there in the bee community. I don’t think we need to fear that we will lose every single bee species under climate change.

But at the same time, losing nearly half of bee species or kind of seeing declines in nearly half of bee species is very concerning in terms of biodiversity and conservation. And just to clarify, The data that we have relates to whether we predict bees will increase in abundance over time, remain stable in abundance and over time, or decline in abundance.[00:03:00]

We don’t necessarily have data related to whether or not those declining species will stick around in the system at low abundance versus will they become locally extinct. We don’t have the ability to predict that, but we do know we kind of find through our study that future bee communities in this area are likely to be less diverse, more homogenous.

So we, we predict biodiversity loss. So thinking about that, if we do potentially lose half of the bee species, or they decline, let’s say they decline, we’ll probably end up with communities mostly made up of bees that can handle drought. What could this mean for the environment and biodiversity, especially when it comes to pollination?

Yeah, that’s a great question. So one of the main reasons that I’m interested in studying bees is that they’re the most important [00:04:00] pollinators of many plants, both wild plants. Um, growing in the environment and agricultural plants. So in terms of the study system that I work in, if we see declines of bees, we’ll see loss of pollination.

The way that pollination works is a bee visits a flower. Its goal is to collect nectar and pollen, which are its food sources. It will collect those resources from one flower, move on to another flower, and in the process, move pollen grains from one flower to another, which pollinates the plant, um, allows it to produce seeds, and that’s its reproduction.

So without that pollination being provided, that could seriously impact. The reproduction of plants, we could see kind of declines in plant communities because bees are declining with what our results suggest. There’s a lot of [00:05:00] evidence that the more bee species you have, the greater number of plant species can be kind of sustained via pollination in the system.

So more diverse bee communities make for more effective pollination of the entire plant community. So, Because we project that some bee species will likely be just fine, we’re not going to lose total pollination services, we think, but we will be losing pollination services to a certain extent. Which we project will impact the plant community.

Sticking with bees and their ability to pollinate, one of the things you found is that the size of the bees is an important factor. Why do bigger bees seem to do better in drier conditions? And how does their size affect their pollination abilities? So in terms of how body size relates to pollination, [00:06:00] The matching of a flower and a bee in terms of size and shape determines or can play a really large role in determining whether successful pollination can happen.

So, if the size and shape of a bee match up, let’s say you have a relatively large flower and a relatively large bee, then the bee can get in there, collect floral resources, and then effectively pollinate. But, on the flip side, The sort of most dramatic alternate scenario is a really tiny flower that a really large bee can’t even land on.

That large bee isn’t going to be able to effectively pollinate that really small flower. So as climate change occurs, if we see a homogenization of the bee community, if we see The bee community shifting toward these large bodied bees, that could mean that [00:07:00] certain plants on the landscape are not going to be able to be pollinated as effectively.

Whereas if we have a diversity of bees that are all kinds of sizes, that enables the pollination of a diversity of plants with different flower sizes as well. So we expected large body size to make bees drought resilient. However, we found that body size did not relate to desiccation tolerance, to tolerance to drying in our study.

So we didn’t find evidence that body size relates to being able to hang on to water better. So we kind of speculate that there are other mechanisms at play. One thing that could be going on. Is larger bodied bees are capable of flying greater distances in the environment and that could be an advantage in drought years when flowers are really scarce on the landscape and [00:08:00] flying a longer distance could mean being able to access resources that smaller bees being able to fly a shorter distance can’t access.

So that is speculation as to what’s going on on our part, because the mechanism that we actually tested, we did not find evidence for. There could be other things at play. So for example, larger bees may be superior competitors to small bees. Sometimes if you’re observing a flower, you’ll see one bee there.

Collecting pollen or nectar and another bee will fly along, kick off the first bee, um, to get at floral resources. So we see these direct competitive interactions and it’s possible that large bodied bees have a competitive advantage that’s somehow magnified through drought conditions. But this is definitely speculation and I think it.

Highlights the fact [00:09:00] that there’s so much we don’t yet know about this system that really lays the groundwork for future study. There’s a lot of future work to be done. Were you able to figure out why some types of bees are better at handling heat and lack of water? Do they have special traits that help them survive and reproduce in tougher conditions?

Yeah, that’s a great question. So we kind of predicted that body size as a trait, like I mentioned before, would relate to which bees are able to cope with these tough conditions and which bees can’t. We did not find evidence, as I said, that body size plays that role. So there could be several things going on.

One relates to physiological adaptations that these bees have. So what we found was that We conducted experiments where we measured the thermal tolerances of bees. So we placed them in a chamber and we measured how [00:10:00] much heat they could withstand. And we also conducted experiments where we measured the desiccation or dryness tolerance of these bees.

So how much drying can they withstand? And from that portion of the study, we found that the bees that are doing the best under climate change are the ones with With high thermal tolerance and high drying tile tolerance, high desiccation tolerance. So we can consider thermal and desiccation tolerance themselves as traits.

And those traits correlate with doing better or worse under climate change. So essentially what this tells us is that is that certain bees are better physiologically adapted to deal with heat and low water conditions. And that relates to cellular processes. So things like water use efficiency, things like the metabolism of bees [00:11:00] and their proteins, their biochemistry, how well is all of that.

Adapted to kind of continue operating in these hot, dry conditions. So where would you like to see the research go? Absolutely, yeah. I think there’s so much to learn. One of the largest reasons that I have been really excited and feel really lucky to get to work on this project is we are just starting to learn how many bee species are coping with climate change.

Some species have been well studied. So things like bumblebees in certain locations, things like honeybees, but in most parts of the world, other bee species have been less studied and there are 20, 000 bee species out there. So for most of them, we kind of [00:12:00] simply don’t know how they’re responding to climate change.

We can speculate but we don’t have good evidence yet. So The data set that I worked on we kind of gained evidence related to around 340 bee species and I I think what we are seeing now is amazing scientists working around the world to study other bee species to document their climate change responses.

I think that’s incredibly needed. I think specifically when you consider responses to climate change, the study that I did looked at direct responses to hot dry conditions. So how is that heat and drought affecting the bees physiologically? And how does that lead to changing population trends? What we didn’t consider explicitly [00:13:00] was how if plant communities are affected by drought, if there are fewer flowers on the landscape.

That could have a negative effect on bees because their food resources are no longer there. And Let’s say you have a bee that’s already stressed out by heat and drought from a physiological perspective and its food resources are going away, that could be even more negative. The other thing we think a lot about as scientists is phenology, which refers to the timing of when organisms go through different life cycle stages during the year.

So if you’re thinking about A plant, um, in a temperate environment that has seasons at what time of year does it open its leaves at what time of year does it open its buds? How long are flowers open? So what we’re thinking about with climate change is as springs get warmer, for example, in many parts of the [00:14:00] world, we’re seeing the blooming of flowering shift earlier.

We’re also seeing the timing of bee activity shift earlier too, but are those shifts happening in concordance with one another? Are they happening together or are they happening disjointly such that you could have mismatches between when the flowers are open and when the bees are active, which again could cause problems for both organisms.

So that’s a whole other piece of the puzzle. When we’re thinking about how bees are responding to climate change, there are many different factors to consider, both solely thinking about the bees and thinking about their interactions with plants. And I think what we need and what many scientists are working on is pulling together all these different pieces of the puzzle to try to gain a better understanding.[00:15:00]

So based on what you’ve discovered, what kind of conservation efforts would you suggest to help protect bee diversity and make sure we don’t lose out on pollination services as the climate continues to change? So as listeners of your podcast are likely aware, habitat loss is a huge threat to bees. So

loss of land that was previously natural, particularly loss of land previously providing bountiful floral resources and nesting habitat for bees. If we lose that habitat, that is going to not only Stress out bees under any conditions, but if the climate is becoming warmer and drier and bees are already under climate stress, losing habitat

could be additional stress for them, so I think one of the main conservation implications [00:16:00] of this paper is emphasizing just how important that habitat conservation is, and especially thinking about how in regions that are becoming hotter and drier, we can either conserve or plant flowering plants that provide good food sources for bees and that are resilient to these hot, dry conditions.

 I think as well, if bees are under physiological stress in a given location, what that means is if we want to preserve bee diversity, we’re going to have to think about what locations on the landscape provide good habitat for them in the face of climate change. So despite these changing conditions, and how can we conserve that land?

[00:17:00] So identifying that, and then I think we as a scientific community are doing a lot of thinking about Range shifts of organisms, so as climate change occurs, some organisms might try to move into cooler regions so that they’re more buffered. And we can think about how those range shifts are occurring, where bees are shifting their ranges to, and we can implement conservation strategies related to that.

One thing that’s We know as scientists now that’s well documented is that there are multiple stressors that bee populations are experiencing right now in many parts of the world. So one is habitat loss, like we’ve been talking about. One is climate change, but we also know that many bees are being affected by agricultural activities, specifically [00:18:00] pesticides, agricultural chemicals.

And then disease is also really negatively affecting bees. And there’s potential for interactions among all of these factors. So if bees are stressed out by habitat loss, if they’re stressed out by disease, if they’re stressed out by agricultural chemicals, that could make them more susceptible to the impacts of climate change.

So I think my work, um, highlights As well that we need to reduce pesticide application, we need to take seriously bee disease, especially thinking about how honeybee colonies can transmit diseases to wild bees. In the face of climate change, those threats could be magnified. So why do you do what you do?

Why bees? Why bees? Yeah. So [00:19:00] I got my start. As a plant community ecologist, I worked as an undergraduate student studying plant diversity and how it’s affected by soil properties. And that really gave me a love of thinking about the complexity of the natural world and how different factors impact one another.

And from considering plants, I gained a real interest in thinking about all of the Organisms that they’re interacting with, and that really creates this complex web to consider. And bees are a really key part of that. I gained a really strong interest in pollination as this foundational interaction that not only sustains plant diversity in natural ecosystems, but also sustains us, provides us with food.

So that really got me interested in the field, but I also think [00:20:00] bees are just incredibly fascinating. They come in so many shapes and sizes and colors. Observing bee behavior is really interesting. You get to know bee species and their different sort of personalities or behavioral traits. One thing related to studying bees, the typical way to identify bees to species is to look at them under the microscope.

And you’re really paying attention to these fine scale characteristics and also seeing what they look like up close. They’re really fascinating organisms. And I’ve really loved working with them and especially thinking about how they interact with so many different plant species and are so fundamental to the natural world.

What I appreciate about Melanie’s work overall, and especially this study, is that she really narrowed in on an understudied area of bees and climate change. Bees play a vital role [00:21:00] in pollinating a wide variety of wild plants and agricultural crops, making them essential for maintaining natural ecosystems and supporting our food supply.

 High heat and drought can affect bees directly, but also their environment. A lack of floral resources due to hot, dry conditions can lead to a lack of bee diversity and abundance. Thanks again to Melanie for sharing her work and insights. Don’t forget to visit the website, thebeesknees. website, and please share The Bee’s Knees with your bee and flower loving friends.

Until next time, be cool.