Monarchs and Climate Change

Hello everyone, I'm Tracy McCleaf with the Fish and Wildlife Service at our National Conservation Training Center. I wanted to thank you for joining us today. I see we have people from all over the world today. We want to say hi to Jacqui Knight from Auckland, New Zealand. We have people from Canada, coast to coast in the United States. We've got a great audience today for our topic. So I wanted to thank you for joining us for the first of two webinars we're going to have this month. Today we are talking about monarchs and climate change. Next Tuesday, December 20, at the same time, we're going to be doing a presentation on monarch conservation planning tools. You can register for that one, and you'll follow all the same links and get to where you are right now, next Tuesday at 2 o'clock Eastern Standard Time. And we can see you right back here.

And now I wanted to introduce you to my co-host Wendy Caldwell. She'll introduce us to today's topic and our speakers. Wendy? Hi, everyone. Thanks again for joining us. As Tracy mentioned, my name is Wendy Caldwell, and I'm the coordinator of the Monarch Joint Venture. I'm also joined by Cora Preston, who is our communication specialist. Today, Karen Oberhauser and Kelly Nail are joining us to give a talk about monarchs and climate change. Kelly recently received her PhD in conservation biology from the Monarch Lab at the University of Minnesota. Her work focuses primarily on the effects of climate change on monarchs, in particular how changing temperatures impact the development of immature monarchs. She also uses large citizen science data set to better understand conservation related problems. Kelly now works full time as a biologist for the US Fish and Wildlife Service, and is currently working on the species status assessment for monarchs.

Karen Oberhauser is a professor in the Department of Fisheries, Wildlife, and Conservation Biology at the University of Minnesota, where she and her students conduct research on several aspects of monarch butterfly ecology. In 1996, she and a graduate student, Michelle Prysby, started the Monarch Larva Monitoring Project, which engages hundreds of volunteers throughout North America. In 2013, Karen received a White House Champion of Change award for her work with citizen science. If any questions come up during today's presentation, Cora and I will be monitoring the chat box where you can enter your questions, which we will come back to at the end of Karen and Kelly's presentation. So we encourage you to use that chat box to communicate your questions that come up throughout their talk. With that, I'll now turn it over to Kelly to get us started. Thank you very much Wendy.

So we will be talking today about monarchs and climate change. Although I do want to note that due to time constraints, we're not going to be covering anything about human-caused climate change. Rather– give you a little outline here for where our talk is going to go– we'll first start by focusing on the relationship between monarchs, climate, and temperature, with a focus specifically on what we know about how temperature affects both monarch survival as well as monarch growth. From there, we'll jump in to covering a few different models, specifically models about where monarch habitat niches are now, and how those locations might change with climate change. We'll also mention similar models for associated species. After that, we'll briefly touch on what all of this means for monarchs.

And then we'll end with some unknowns and future research questions. So if you've been following all of these NCT monarch presentations, you know the annual monarch life cycle in North America, and you've seen this graph many times. However, we want to point out here because monarchs, as a migratory organism, need a habitat not just in one place, but they need suitable habitat and suitable climate in all different areas of their range– so in their breeding grounds, in their migratory routes, and in their overwintering sites. We'll organize that accordingly. So we'll start by talking about the importance of climate during monarch breeding and migration, which occurs approximately from March through October. Dream this time, low temperatures and rain can lead to slower monarch development.

This can be detrimental for several reasons. One is that it leads to fewer generations. And another is that by having slower development, monarchs are in the vulnerable immature stages for longer periods of time, making them more vulnerable to predation, as can be seen here in this image. On the other hand, high temperatures and drought can lead to shorter lifespan, higher mortality, and smaller individual monarchs. We'll jump right now into some research that has been done on extreme temperatures and monarchs. And then we'll talk more about how other temperatures, cool and warm temperatures, can impact monarch growth. So to begin with, we started with a study in the University of Minnesota Monarch Lab looking at the lethal impact of cold. We started first by looking at the freezing point of immature monarchs.

In this case, eggs, first instars, and third instars. And that freezing point or supercooling point is shown here with the box and whisker point– box and whisker plot. And you can see that those supercooling points ranged, for the third instars, just about negative 10 degrees Celsius all the way down to eggs for below negative 25 degrees Celsius. However, this measurement of cold tolerance isn't that useful in and of itself, because many insects die at a warmer temperature than what they freeze at. So the next measurement we looked at was the lower lethal temperature at which 50% of monarchs were expected to die. And you can see that represented here by the gold diamond. And you can see that this is a much narrower range here, ranging from about negative 12 degrees Celsius for third instars to just below negative 15 degrees Celsius for eggs. This is much colder than we expected.

However, this doesn't actually represent cooler temperatures, which can have more of an impact for longer periods of time. These temperatures monarchs were just exposed to very briefly. So that was the cold end of extreme temperatures that monarchs can survive. But there's also lethal impact of heat, as you can see here in this study, which was also published at the same time. Here we exposed monarchs to temperatures of 42 degrees Celsius. For those of you who are wanting it converted to Fahrenheit, it's about 108 degrees. And you can see that significant mortality occurred whenever monarchs were exposed to this temperature. For one and two days, we did have some survival. But any time monarchs were exposed to 42 degrees Celsius for more than four days, we had complete mortality. So now that we have the upper and lower thermal limits that cause lethal impacts in monarchs, we can look at how temperatures actually impact monarch development.

And a way that we can do that is by using the concept of growing degree days, or GDD as it will be referred to throughout this talk. So what growing degree days are is they are a measure of how much heat is accumulated by a monarch. And we know from previous laboratory studies how many growing degree days are needed for a monarch to develop from stage to stage or instars to instars. I'll use an example here to show you the concept of growing degree days. First we have a developmental zero, which for monarchs is approximately 12 degrees Celsius. And that's the temperature at which monarchs cannot grow if the temperature goes below that. They'll then grow quicker the warmer it is. And we measure that with this growing degree day concept. So here you can see, for day one, it was 16 degrees all day, obviously a simplified model. We then calculate that it had four degrees above developmental zero, which gives us four growing degree days. We continue to calculate this.

So day two here you see has 10 growing degree days. And we continue to calculate it until we get these certain number of growing degree days that are needed to advance to the next stage for monarchs. As I mentioned, this was previously calculated for monarchs by Myron Zalucki in 1982. And you can see here that we have different developmental zeros for each of the stages of monarch growth, and different growing degree days needed to advance to the next stage or instar. Now growing degree days can be used in several different ways and have been previously, such as this study by Stevens and Frey in 2010. Here, they used growing degree days, as well as milkweed presence, to figure out when the temperatures were right such that we could have monarchs develop that were part of the migratory generation in the West. We can also use average temperatures across continental North America to predict how many generations of monarchs could develop given these temperatures, as you can see here. Now growing degree day calculations are based on a linear model, represented here in this graph by this dashed black line.

And they work really well at modeling monarch growth. And the actual monarch growth curve here is represented by the solid gray line. And they work really well in a majority of temperatures that monarchs experience in the wild, which is kind of this middle ground circled by the red oval here. However, at very high temperatures, monarchs don't just continue to grow linearly, but rather their growth tapers off there. And so the growing degree day calculations overpredicts how fast monarchs will develop at very hot temperatures. Conversely, at very cold temperatures, it actually underpredicts how fast monarchs will develop. And we can see that here in a study that was done last year. You'll see in this graph here that the expected number of days that we thought a monarch would take to develop using those growing degree day calculations was much longer than the actual treatment, which is in the column the left. And this was at a cool temperature. And so you can see here that we expected the monarchs to take 82 days to develop. But the actual number of days, which was 58 days, was 71% of the predicted value.

So it didn't do a great job at predicting it. Monarchs developed quicker than we expected at this cool treatment. But 50 some days is still a very long time for a monarch to develop. Conversely, at the warm temperature treatment, it was much closer to the growing degree day calculation of 25.9 days. Similarly, we can see this with heat. So this is a graph of growing degree days needed for monarchs to develop at 38 degrees Celsius and 40 degrees Celsius. So remember earlier I showed you that 42 degrees was lethal for monarchs. But here, at 38 and 40 degrees, we see that the longer the monarch is exposed to these very warm temperatures, even if it's not lethal, it takes them more growing degree days to develop. So we would expect all of these bars to be the same height. So we see, as they are exposed for more days– so keep going towards that black bar to the right– it takes them more growing degree days to develop. So they're developing more slowly. So here's a summary. Growing degree day models work really well for calculating development times. They work best in the middle range of temperatures.

And development is faster than predicted at low temperatures, as we showed, and then also slower than expected at high temperatures. So primarily the work so far has focused on immature monarchs, primarily eggs and caterpillars. However, in the winter, climate is also very important to the adults. So this overwintering period, which occurs generally from November through March, low temperatures are especially important to monarchs and can cause freezing, particularly if wet. And we'll touch on that more in another slide. Also when it's cold, monarchs start moving around. They're instead clustered in the east here, on oyamel fir trees, and they're vulnerable for predation. On the other hand, high temperatures are also detrimental to monarchs, as it can cause them to deplete their lipids early.

It can also potentially lead to early departure from the overwintering sites or premature diapause ending. So monarchs kind of need this Goldilocks microclimate while they're in the overwintering sites, not too hot and not too cold. Now I mentioned earlier that monarchs can freeze, particularly if they're wet. And this is based off of a couple of studies. And one here was done by Anderson and Brower in 1996. And you can see here that when monarchs were wetted, they froze– 50% froze at approximately negative 4 degrees Celsius. Whereas if they were dry, 50% froze at approximately negative 8 degrees Celsius. So when they get wet, they freeze at a warmer temperature. Luckily, the microclimate in Mexico provides microclimatic factors that can protect monarchs while they're there. This is a really interesting graph from Williams and Brower in 2015. You can see that monarchs cluster vertically on trees.

And they're centered around 12 meters in height. If you look to the far right of this graph, you'll see that the temperature is the warmest approximately at 12 meters there. So that helps prevent them from freezing. Also, the overwintering sites in Mexico offer many other microclimatic protections, including blanket like thermal insulation– which can be seen here too by these two different lines. The dense forest is warmer than the thinned out forest– and many other factors, such as umbrella-like shield against precipitation and a windbreak against wind. OK, so this is Karen. We're switching gears. Kelly and I are in the same office and we just had to change chairs. So it's really fun to be talking with you. And I think it's kind of interesting to be talking about climate change when, when I walked into work this morning, it was minus 12 degrees.

That's Fahrenheit. It was so cold that when I got to my first meeting of the day, my computer wouldn't start. So, like Kelly said, we're not really talking about the evidence for climate change today. But we know that the climate can be changing, we'll still get some cold days, as we're experiencing today in Minnesota. But in general, the climate is getting warmer. So I'm going to talk to you about how we're using models to understand what's going on or what could go on with monarchs under a change in climate. So the field of ecology– Kelly and I are both ecologists– and we use a lot of models. So when we think about ecology, we're trying to understand the interactions of many complicated systems and environments. And these interactions are often so complex that we can't just look at the patterns and understand what's going on in the world. So we use models to help us understand that.

So if there are any students in there, this is all based on math. So hurray for math for helping us understand more about how the world works. So there are climate change models. That's how we know how the world is expected to change with increased greenhouse gas emissions. And there are a lot of really smart climatologists who are figuring out what will be the impact of increased carbon dioxide in the air. So we're using those models that have been created by climatologists, but we're not building them. We're simply taking the findings of these models to figure out what might go on with monarchs. So there's a lot of modeling involved here. And we're basing all of our predictions on models that are developed by climatologists. OK, so we're going to first talk about a particular kind of mathematical model, which is called ecological niche modeling. So what an ecological niche model, or what an ecological niche is, is a combination of conditions in which some species can maintain its population. So like monarchs need particular temperatures.

Kelly talked to you about how important temperature was to monarchs. Monarchs need particular temperatures to survive. It can't be too cold or they'll freeze to death, or they'll develop so slowly that it hardly even pays being alive. Or they'll get too hot, it'll be lethally extreme for them. So the conditions, the kind of the Goldilocks for monarchs is the conditions within which they can live. And in order to understand these ecological niches, we use these models that are based on associations between occurrences of a species and environmental conditions. So on this slide– let me get my little arrow here– we have places, hypothetical places where people have collected data and said, on this day, at this location, I saw a monarch egg or a caterpillar. And then what we do with these models is we look all over this map. And we see what are the conditions where monarchs occur in all these places where we know there are monarchs, because people saw them. And where do those conditions exist elsewhere on the map? So maybe there was nobody looking for monarchs right here, but we can infer whether or not monarchs are there by seeing if this particular location is similar to all of the other places where we actually did see models– or monarchs.

Model's on my brain here. So then what we do with that is we determine what are the environmental parameters that promote monarch presence and reproduction? So that's the kind of model I'm going to be talking about here. It's really fun to work with these ecological niche models. So to understand breeding niches, we use the currents data from the Monarch Larva Monitoring Project. And here you can see some of our volunteers collecting data, adults collecting data on their own, adults working with kids to collect data. And we have occurrence data for monarchs from all of these places on the map where there are red dots. And then all of these occurrence data are associated with dates. So we know when and where people saw monarchs. And what we found is that the environmental variables that were important to monarchs– not too surprisingly, especially after you just heard all that from Kelly how important temperature was– temperature is important to monarchs, as is precipitation.

So basically our model said that if we know temperature and precipitation in an area, we can predict whether monarchs will be using that location. All right, now I'm going to show you a series of maps. And these maps are showing you what our model said about where we would expect to see monarchs, where there are the right environmental conditions for monarchs, in different months of the year. And what we learned is that during their breeding season, from March to October, monarchs are basically looking for warm and humid places. So here's March. And where you see red on these maps is going to be the best places for monarchs in March. And the gray is places that they could survive, but they're not going to do quite as well. So red is really good, and gray is so-so, and white is horrible, for monarchs. So here's March. And then we're going to skip into April.

So you can see, not surprisingly, that monarchs have more appropriate habitat in April because it's starting to warm up. So they're moving north. There's a lot more habitat available to them in the month of April. Now we're going to skip into July. It's getting less appropriate for them in the South. But here are places where monarchs can survive in July. Now they start moving down. I skipped August. Here's September. So you can see they're out of those northern ranges, the white. Remember, they can't survive at all up here in the white. During September, they can maybe survive some years in the gray, but they're moving down to the South. But here's their great habitat in September. And if we look at October, there's hardly any good habitat left for monarchs anywhere in their range. So they're basically not breeding very much in October because there's not great habitat. There's some of it, a little bit of it in a few places, and some way down here.

OK, so that's their breeding. That's the months during which they're breeding. But then we thought it would be interesting to see, where is their breeding habitat for monarchs in the wintertime? We don't normally think of them breeding in the wintertime, but here we are in December. There's a little bit of breeding habitat, great breeding habitat down here in Central America, some so-so, not great, but OK breeding habitat that is at least not going to kill them in other places here. Here's December. January looks pretty much the same. We have a little bit more area down here. Here's February. It looks a little better for them through Central America. So here's where their breeding niche is. These are the conditions that are good for them for breeding. But here is where monarchs actually are during the wintertime.

So here's the breeding habitat. We don't have a lot of people looking for monarchs down here. There probably are some. But most of our North American monarchs that have come from Canada and the United States are either overwintering in Mexico, where their breeding niche just doesn't exist. Or they're overwintering along the Gulf of Mexico in Texas. And some of them are in Florida. So basically what we're seeing is for the most part, overwintering monarchs aren't in their breeding niche. And this is a phenomenon that we call niche switching. So you can try to say that 10 times fast– kind of hard, niche switching. But they switched. They use a different niche in the wintertime than they do in the summertime. The red is good for them in the summer. Here's where they are in the winter. And just to kind of focus on that those Gulf Coast monarchs, the dots that I showed you on the map there, here's where they actually are.

So we have data from citizen scientists that have recorded data through the Monarch Larva Monitoring Project or Journey North or just sent Kelly and me emails, Kelly's KRN and I'm KFO. And so here is where monarchs actually are breeding. And if you remember back to my other map, this is the gray area. And it's not great for them, but they do stay here and breed. But they develop very, very slowly. So what Kelly found in her thesis is based on the growing degree days that's available for monarchs during these winter months down here where they're breeding, they are taking more than two months to develop, even when we count in that our growing degree day models aren't great. It's taking them a long time to develop when they're down here. So again, it's not ideal, but they can do it. So they're using it. So, now I'm going to kind of jump around. So there I was talking about how monarchs are using habitat now.

But what happens if the climate changes? So here we basically use those same models, the ecological niche models, but we use what our friends in climatology have predicted for how the temperatures over the surface of the Earth will change based on increased greenhouse gas emissions. So we used different– basically climate change depends on us, right, depends on human behavior. And we don't know how people are going to– how much greenhouse gas we're going to continue to emit. So often when people use climate models, they use what we call conservative and less conservative views of climate change. So a conservative view is we kind of start to get our act together, and we stop emitting so much carbon dioxide and we start increasing just by half a percent per year. We're at worse than that right now.

Or maybe a less conservative view is we keep increasing by 1% per year. We want to get these numbers down, but we need to understand what's going to happen if we keep going on kind of business as usual. And we based our results– we said OK, what is the climate going to look like 40 years from now in 2055? And first we asked– actually we did this second, but I'm going to talk about it first– how does their range shift in the summertime? And here let's just think ahead. Hopefully some people listening are still going to be alive in 2055. Maybe not me, I'd have to be really old. But here's March of 2055. And I'm going to walk you through these colors here. So there's a little bit of gray. You can just barely see it right down here, some gray. And then there's some red and some pink. And if we look at the combination of the grays and the red, that's where monarchs are now. And the white dots on here are places where we have data, from March. And so here's what the habitat monarchs can use right now.

And in March 2055, all of this area is going to be newly available for them. So they will increase the amount of habitat available to them 40 years from now in March. So here's June. June, basically this gray area, is what's available for them now. But they are going to lose it. It's not there in their future distribution. So the pink and the red are what they'll have in the future. So they gain all this pink up here. This is going to be climatically suitable for monarchs in June 2055. The red will still be suitable. They'll lose the gray. Now clearly, like Kelly said, we don't know if monarchs are going to be able to move up here. Maybe they will, maybe they won't. It depends on if they'll find milkweed and if they'll actually fly that far. Here's August.

Now this is kind of depressing to me because here's where I live right here. And 40 years from now in August, It's probably going to be too hot for monarchs where I am in St. Paul, Minnesota. A lot of places where there are monarchs now in August will be too high. They'll still have this red area. They'll gain the pink area if they can move into these pink areas. This will be climatically suitable. So that's how we can think about how monarchs might react to climate change in the summertime. Now let's think about the wintertime. And I'm actually going to talk about this slightly differently. You'll see. So first of all, we did– I worked with Town Peterson, who's a professor at the University of Kansas. For those of you who know Chip Taylor, he's a colleague of Chip Taylor's. And we did ecological niche modeling. And we looked at where monarchs are now. So you can clearly see on these little white dots, these are the places where they're overwintering sites in Mexico. This is the state of Michoacan where monarchs are. This is the state of Mexico where there are monarchs.

And the darker areas are areas that Town's and my model predict that it would be great for monarchs in the wintertime. So you can see they are where they should be. The lighter gray areas are less suitable. And the white areas are not suitable at all. So we have a good model to predict the conditions that are conducive to monarchs in the wintertime. And what do those conditions look like? So here's where I said I'm going to show it to you a little differently. Instead of a map, I'm going to show you a graph. These purple dots on this map are the January precipitation and temperature where we saw monarchs. Here's where monarchs, where a pretty narrow range of precipitation and temperatures from about 2.5 to about 13 degrees Celsius. And the green dots on here are random. These are just random areas, random locations in that overwintering area. And you can see they're using this narrow band of climatic conditions. So this is what's suitable for them now.

Now, what the climate models predict is that the future climate in this area is going to be wetter, for monarchs. And these two yellow triangles that I made really big, so you can really see them well, this is what's predicted for the future. And we can't go into a lot of detail. We can't have a whole bunch of that. But on average where monarchs are now, the January temperature isn't predicted to change very much. But there's going to be more precipitation. You can see we're higher up here on the precipitation map. And it's really interesting to think about why that is. But I'm not going to talk about that now. So, what this means is– you probably all thought about some of the storms that happened in Mexico. And like the storm we had last winter that killed a lot of monarchs, that temperature wasn't the big problem for monarchs during that storm. It was that cold temperatures were accompanied by precipitation.

And Kelly showed you a graph, how monarchs are more vulnerable to freezing to death if they're wet. So this isn't good. There's going to be higher precipitation. So remember, I'm talking about just January here. That's what we found was really important to monarchs, the temperature for them in January. But one thing that's going to happen is that the overall overwintering site conditions– so this is a really similar graph, just that the axes are switched. Here's temperature. Here's precipitation, precipitation on the x-axis. But this is annual. OK, so I just learned how to use this. I'm going to draw this. Here we go. So I just drew these circles for you. This is really important to remember.

These are annual precipitation and temperature, not just January. And what we see that in 2090, all these plots up here, it's going to be hotter, temperatures higher, and it's going to be drier. And the people that did this study, our colleague Isabel Ramirez and several of her colleagues in Mexico, modeled where oyamel trees were. And this is not good for oyamel fir trees. This is going out more into the future, 2090. This is where we are now. These are the conditions down here in the yellow. And the red is where we're going in the future. So speaking of oyamel firs, I want to transition here and just end by talking about all the other species, or some of the other species, that might be important to monarchs. Because monarchs aren't out there all by themselves in the world. And the way that climate affects other species could have an impact on monarchs. All right, so all these species that are associated with monarchs– we talked about the roosting trees, the oyamel fir trees in Mexico, the roosting trees for them along the coast of California for the western population. But we also need to think about milkweed.

Where will there be milkweed? We need to think about the phenology or the quality of the milkweed, not just where it is, but when it blooms and when it's available to monarchs, and nectar plants. And we also need to think about the things that are harmful to monarchs, their natural enemies, their predators and their parasites and their parasitoids. So while monarchs themselves might be able to survive in conditions like in this picture, in Texas, this photo that was taken by Lincoln Brower, this isn't very good for nectar plants. So we're just going to spend a couple of minutes here thinking about this. This was a really interesting paper that was published last year by a guy named Nate Lemoine who looked at the potential impacts of climate change on milkweed. And these maps are showing just milkweed during the breeding season. This isn't the whole year. So don't feel badly if you live in Texas or you're watching this in Texas, or out here.

There might be milkweed available, but not during the summer. There's not very much. So here, the areas circled in red on this map are areas where there's a better than a 50% chance that there will be milkweed. So this is now, this map that is on the left. This is where there's milkweed now. And this map over here on the right is where milkweed is predicted to be under a moderate climate change scenario. So this is a more conservative view of climate change. The climate people call this the B1 scenario. So you can see, milkweed has moved a little bit. We're not really losing that much milkweed, except for those of you in the southern part of the United States. There's no red lines down here anymore, moved north a little bit. But there's a lot more habitat for milkweed up in Canada.

So this is under kind of moderate climate change conditions. But Nate also looked at a more severe scenario. So this is what the climate people call the A2 scenario. So here's the same map I showed you before on the left. Here's the one on the right. And here you can see that milkweed has moved quite a ways north, that this whole area in the yellow and orange is predicted to have very little milkweed available under a climate change scenario. So that's milkweed. Now, we're going to think about natural enemies. These are the predators and the parasites and the parasitoids. How might climate affect those? So this hasn't actually been modeled. But I'm going to show you how climate affects the distribution of some predators and parasites right now. And this was another paper that was just published this year, led by a guy named Shaun McCoshum and several people in my lab.

And he was then at the University of Oklahoma with his adviser Kristen Baum. And we looked at a whole bunch of monarch predators and parasitoids. So here's the tachinid flies. You're probably familiar with these. This is another ecological niche model. So all these dots on this map– here, let me point to the data. So all these white dots here are where we had data, where people had reported to the Monarch Larva Monitoring Project that they were finding tachinid flies. So we used these occurrence data to build a model. The red areas on this map are places that are really great for tachinid flies. All right, so there's the flies. Here's this very cool, interesting monarch parasitoid called Pteromalus cassotis It's a wasp that we're studying in our lab.

The white dots on this map are places where people have reported Pteromalus . cassotis And again, the redder areas are places that are good for Pteromalus cassotis. So under climate change, these areas could change. Here's a few other ones. I think I'll show you fire ants. Every time I go to Texas I'm happy I do not live where there are fire ants. I live up here, no fire ants here yet. But you can see where fire ants are. And fire ants are a real problem for monarchs. So they're driven by temperature as well. So then what we did is we put together a map that's basically overall predator risk. I didn't show you all of the pictures, or all of the maps from all the different predators.

But here are all the predators that we studied for this paper that we published this year. And this is the number– this isn't the parasitoids. It's just the predators. So we studied several different predators. And this is the number of those predators that are predicted to be in different areas. So the dark red here is where we predict that six different predator species would be present. The more orange color is five. And then we get up to here to areas where there are four or three or two. Or one is this really– let's see where the other one is. Oh right in here is some area where we only predict there would be one predator species. And then in the yellow, we don't predict that there will be a lot of monarch predators. So we can use these ecological niche models to say where monarch predators are more likely to be found. And you can see on this map that there are more predators in warmer areas. So climate change could affect how this map will look in the future. We might have the high areas of high predator risk moving north. So there are a lot of different ways we can think about how climate will affect monarchs.

And I'm going to turn it back over to Kelly who's going to kind of sum up. Great. Thank you Karen. So what does this mean for monarchs? As you've seen in the graphs that Karen just presented and the map that Karen just presented, it can mean a changed summer habitat. However, whether monarchs are able to go up into the North where there is potentially going to be more suitable habitat depends on their ability to get up there, but also the ability of milkweed to disperse up further north. And if this does happen, it will potentially mean a longer migration. However, we should note too that monarchs, using these ecological niche models, don't use the entire climate space or the entire temperature space that they can withstand. So monarchs are resilient with temperatures up to 40 degrees Celsius. And so they may be able to continue using some of that habitat that we thought might be lost, that gray area in those maps that Karen was showing earlier. There also may be a changed predator distribution which may affect monarch distribution and abundance.

And then of course current overwintering sites may no longer be suitable for monarchs, either for the monarchs themselves, or as Karen showed in the studies earlier, for the oyamel fir trees at the overwintering sites in Mexico. So, how should we respond? Of course the first line of action is to prevent and mitigate climate change. However, knowing that the climate is changing and that that is currently ongoing, what can we do besides prevention? And we can adapt. There's several different ways to do this. One, of course, is resistance. We want to manage habitat such that monarchs are able to persist. And I guess I should mention too that when I say adapt there, I mean we want to make sure that the monarchs are able to adapt. So we can resist– resistance, like I said. We can manage the habitat such that monarchs are able to persist. And this includes intensive management of invasive species, herbivores, and disturbance.

There's of course resilience. For example, that's making sure that we have buffers and that we protect existing habitat, making sure that areas that might be suitable for monarchs remain intact and available as the climate changes. And then as a last resort, there is facilitation. And that's helping move species. Monarchs themselves are migratory and are likely to be able to move. But we may have to help move other species, including milkweed, nectar plants, and the oyamel fir trees that monarchs roost on at their overwintering sites in Mexico. There's a lot of remaining questions that are left. And we just came up with a few here. But this is just a short list. And we're looking forward to hearing your questions here at the end of this talk. But some of the questions that we came up with is, what is the impact of climate change on nectar plant distribution and phenology? So phenology being, when in the year are the nectar plants actually available for monarchs? What is the full impact of a changing climate on monarch migration? So we thought that the monarch migration may go longer, potentially.

And there's many other ways that climate change may end up impacting monarch migration and monarch diapause induction. Karen mentioned the breeding that's occurring in the winter. And we still haven't figured out whether this is due to climate change or having more suitable climates in the winter along the Gulf Coast and in Florida, or if it's due completely to host plant availability. And then of course we think that many of the studies that we presented on apply to monarchs in the West and throughout the world. However, we would like to confirm that and have more research on how climate stressors impact monarchs in the Western US. So with that, we have a few acknowledgments. We'd really like to thank the citizen scientists and other researchers who have provided vital information on monarchs and climate, particularly the location data that was used for a lot of the studies presented here. And we'd really like to thank our funding sources as well. And with that, we're excited to answer any questions that you guys may have on monarchs and climate change.

Thank you so much. We'll turn it back over to Wendy and Tracy. Thanks Kelly and Karen. That was really fascinating. You kept people's attention. They didn't ask a ton of questions this time, but I expect that they'll come in as we get into some of the questions that they have. So I'm going to start with a question for Karen and Kelly. Chime in if you want to as well. Karen, you presented a series of maps on breeding habitat and movement for eastern monarchs. And we're wondering if similar data exists for the West. Well that's a really great question. And we're just starting to build these models in the West. So there are a lot of people working on this right now. There have been some really interesting previously published research on the impacts of climate in the West. It's been a little different than the way that we do it.

But a study published by Dennis Frey and his student Stevens looked at how the climate in different areas in the West was correlated with the numbers of monarchs at the breeding sites. So we do have some indication of the importance of climate to the numbers of monarchs in the West. And in terms of developing ecological niche models, none of those are published at this point. But it would be really great. One of the problems is, like I said, we need to have occurrence data. We need monarch occurrence data to build these models, and there are just fewer citizen scientists spread all over the West. So we don't have– but we're starting to get. But back when we did this project, we decided that there just weren't enough data available to build the model for the West. But now we do have more data available. So I bet it will happen soon.

Thanks Karen. This next question is one that I'm asking for your professional opinion. I know you said that this is a future research question. But since so much of Canada will become suitable for monarchs and milkweed if climate continues to change, what do you think that this mean for monarch conservation? Do you feel like monarchs will be able to undergo a longer migration? Well, that's the $50,000 question, isn't it? In some ways, what we're doing to the world with climate change is we're conducting this big, giant science experiment with a sample size of one. And any good scientist is nervous about doing an experiment with a sample size of one. We don't have another Earth where we're not changing the climate. So you know, there are just a lot of things we don't know. There isn't milkweed available in a lot of the areas that will become climatically suitable for monarchs. So they obviously need milkweed to breed. There's a lot of concern, rightly so, among ecologists about moving plant species around because we've had so much trouble with invasive species.

So that's a very controversial action to facilitate the movement of species. So in my professional opinion, I think monarchs probably won't move into that whole pink area that I showed on the map for various reasons. Certainly they'll– or I would guess, if I were a betting woman, which I'm not– but if I were, they might move a little bit north. I think we've seen in some years monarchs do move a lot further north than they do in most years. So they can respond to years that are particularly warm. So yeah, they probably will move at least into part of that pink, but probably not all of it. That was a long way to say I don't know. Fair enough. Another quick one– well, not another quick one. This one is a quick one. Were the maps that you showed for milkweed suitability specific to a particular milkweed species? No, they weren't a particular species.

It was milkweed in general, milkweed availability in general. And one of the reasons for that is a lot of the data that were used for that were from Journey North, a really great citizen science project. And people don't always report the species of milkweed. So you built that model just on milkweed in general. OK, thanks. Do you think we'll see new predator species? You talked some about the existing predators with monarchs. Do you think that as climate conditions change and that impacts ecosystems and the food chain, do you think that we'll see new predator species start to emerge? Kelly and I are looking at each other. You know, I think most predators of monarchs are insects. And insects, there are a lot of specialist insect species. So certainly all the time predator-prey interactions are evolving and changing. I doubt that that would happen very quickly.

So you know, anything is possible. I think that might– yeah, it's really hard to predict that. One would have to go to these areas and really understand the predator community there to really make a smart prediction about that. Lots of unknowns with climate change. OK, if the ideal summer range become smaller for monarchs, will they become more dense in that area if there's enough milkweed? Do they have parameters of breeding density? That's another really excellent question. We do know from Monarch Larva Monitoring Project data, and actually a paper that Kelly was the first author on last year that– and we've done this in other ways with MLMP data– that when monarchs are found in more dense populations as eggs and caterpillars, they have lower survival rates. So it's possible that they would condense into these areas, but it would probably be not that good for them.

We kind of have seen that a little bit as the monarch population has become smaller. We have fewer monarchs now because there's less habitat available for them. And we're not really seeing– what they have not done is kept their population the same. They don't have the same size of population as they always did and they just squeezed themselves into the remaining habitat as they lost all the agricultural land. So we did not see that when monarchs lost habitat just due to habitat loss, not climate change. So you know, if we can use that as any indication, they might not. We probably will just have fewer monarchs, as has happened when they lost habitat up here because of habitat loss. Great. What do we know about the changing climate and how that affects OE parasites? Is there a cold temperature that will actually kill the parasite? Well, OE is super tolerant to cold temperatures.

It is like the master of surviving under extreme environmental conditions. So monarchs are a lot more sensitive to temperature than OE. So probably not. But it would be interesting to talk to Sonia Altizer and her students about that. And Yapta Rhoda might have some ideas about that too. But I would doubt that there'll be much of an impact on OE. I guess the one way that it may impact OE rates is by having increased winter breeding. And Dara Setterfield and Karen and others did an MPTC webinar on that earlier that's archived right now on the Monarch Joint Venture website where if we have increased winter breeding, such as that that was shown along the Gulf Coast and along the coast of Florida. We also see increased rates of OE. So that's another way that temperature changes may in fact increase the prevalence of OE, or change the prevalence of OE. Yeah, that's a really good point Kelly. Yeah, thanks. Just looking through some questions here, so temperature is a big factor for monarchs. But does milkweed germinate in response to temperature? Is changing climate a concern for how milkweed germinate? I guess and milkweeds likewise, other plants as well.

Actually that's a super interesting question. And people are looking at this. I don't know if anyone's looking at this specifically for milkweed, but certainly other plants. And those of you that grow plants, and if you live in the North, you know that you have to cold stratify the seeds, that the seeds won't germinate in the spring unless they've experienced winter conditions. So that's why we don't have– species up here don't grow unless you freeze them. So it's possible that some of our cold adaptive species will– and that's probably one of the things that drove the models that Nate Lemoine did. And I think Kelly put that map back up again. So you're looking at it. So that probably is at least partly driven by germination of the seed. But I'm not sure that people have studied that specifically with milkweed. If anyone out there knows about studies, if they could let us know. Karen, I know you kind of covered this a little bit in an earlier answer.

But we're curious about how climate change is going to affect conservation prioritization. Is the changing climate factored into how we prioritize where the most important effort for monarch conservation– is that a major factor in the analyses that are being done? So I'm going to give an answer, but then I bet Kelly has a really great answer to that too because Kelly works for the Fish and Wildlife Service, and a lot of federal agencies are really working hard on how they respond to climate change. But you know personally, I've been in this business of conservation biology for a long time. And I've seen our change when we talk about climate change. We have changed from talking about mitigation. That used to be the focus when I was young. We talked a lot about how we're going to prevent climate change. And now the conversation among conservation biologists is really focused on how we help species adapt and survive under climate change. So that was really kind of depressing for me when we had that shift. But we've shifted, and we think about adaptation now.

And Kelly, do you want to say something about how you as an agency are working on that? I won't speak for the entire agency, but I will definitely say that when looking at monarchs, that is one of the main threats that we are looking at in the different ways that we outlined here in this talk, how climate change can impact monarchs. And we are considering that right up there with other threats that impact monarchs that have been covered in previous MPTC webinars. Great. Well I think I'm going to– we might have a few questions that I missed, and I apologize to anyone if I missed your questions. But I think I'm going to take the last few minutes here to just do a few housekeeping things. Thanks again Karen and Kelly for sharing your expertise and telling us where we go from here in terms of monarchs and climate. So we did record today's webinar, as with all of the webinars in our series. So if you want to share this with your friends or come back and watch it again, it will be available online.

And we will send you the details about that in an email following up if you registered for the webinar. We'll also follow up with a short survey. We'd love to hear from you on topics that you'd like to see us cover or any feedback about the technology that we're using. We'd love to hear from you. So with that, thanks again to everyone for joining us. And Karen and Kelly, if you have any closing thoughts, follow up now. Otherwise, we will see you all hopefully next Tuesday. Just thanks to everyone for listening. It was fun to have your questions. Thank you very much. [MUSIC PLAYING] .