Overview
- Between 1995 and 2023, the City of Ann Arbor’s Natural Area Preservation (NAP) division coordinated a continuous butterfly monitoring program using trained community science volunteers. In 2024–2025, Ludovico Behrendt, an environmental data specialist with NAP, conducted a retrospective analysis of this nearly 30-year dataset, which includes over 16,600 butterfly observations collected across city parks. His work represents the most comprehensive analysis to date of long-term insect biodiversity trends in the Ann Arbor area and is one of the most sustained municipal-scale pollinator datasets in Michigan. The project aimed to understand how butterfly communities have changed over time and what those changes reveal about local habitat health, ecological management, and landscape conditions throughout Washtenaw County.
- The analysis found that butterfly abundance and species diversity in Ann Arbor’s natural areas remained relatively stable over the three-decade period. While year-to-year variability was expected, there were no significant long-term declines or increases in overall population levels, suggesting that these parklands have provided relatively stable habitat conditions over time—even as insect populations in other parts of the country have faced serious declines.
- Larger parks and those with greater habitat continuity were found to support higher levels of butterfly biodiversity. Sites with expansive and unfragmented green space—such as Barton Nature Area and Bird Hills—consistently hosted a wider range of species and greater individual abundance. This reinforces the ecological value of conserving large, connected natural areas within urban and suburban landscapes.
- Parks that included a variety of habitat types—such as a combination of prairies, wetlands, woodlands, and edge zones—also showed higher butterfly diversity. These structurally and botanically diverse environments were more likely to support both generalist species and habitat specialists, which often have specific host plant or microclimate requirements.
- Over time, parks that received more intensive ecological management by NAP showed measurable increases in both butterfly abundance and diversity. Practices like prescribed burning, invasive species control, and native plant restoration were associated with more robust pollinator populations, particularly in sites where these activities were applied consistently across multiple seasons.
- Since 2019, several habitat-specialist butterfly species—such as eastern tiger swallowtails, spicebush swallowtails, and monarchs—have shown significant increases across Ann Arbor’s natural areas. These species rely on diverse, high-quality flowering plant communities to reproduce and compete successfully with more aggressive generalist species like cabbage whites. Their increased presence in recent years serves as indirect evidence that flowering plant diversity has also improved, likely due to cumulative restoration efforts led by NAP.
- Although fireflies were not included in this study, the monitoring infrastructure and analytical framework developed through this butterfly program offer a strong foundation for future firefly monitoring efforts. Fireflies are increasingly reported to be declining in Michigan, and they face distinct threats such as habitat degradation, pesticide exposure, and especially artificial light at night. Adapting the community science model to track firefly populations would help establish long-term baselines, identify areas in need of dark-sky protections or wetland restoration, and support broader insect conservation strategies across Washtenaw County.
Transcription
David Fair: This is 89.1 WEMU, and I'm David Fair, and I have a question for you. What does a butterfly mean to you? Well, these creatures have the most fascinating life cycle and, from a community standpoint, can tell us a lot about the health of our environment and ecosystems. Welcome to this week's edition of Issues of the Environment! The Ann Arbor Natural Area Preservation Division has been studying this issue for decades. It has continuously monitored the local butterfly population and recently did an analysis of what was found from 1995 to 2023. Our guest this morning headed up that analysis. Ludovico Behrendt is an environmental data specialist with NAP and thank you so much for the time today! I appreciate it!
Ludovico Behrendt: Thank you for having me on!
David Fair: What about butterflies gives us insight into the ecological and environmental health of a particular area?
Ludovico Behrendt: So, a lot of butterflies, especially in Ann Arbor, tend to be environmental specialists, as in they require specific plant species in order to survive and reproduce into the future. So, as specific butterfly species tend to proliferate, then you can directly infer that the plant species that they're dependent on to survive and reproduce are increasing in presence as well across Ann Arbor. A good example of this would be monarch butterflies that specifically feed on milkweed when they're in their larval form. When milkweed is present within a grassland area, monarchs are present. But if milkweed is not there, then they tend to not survive and reproduce and are absent. And milkweed itself as a plant requires specific environmental conditions in order to survive and produce similar to the butterfly. So, if you record the presence of these specific specialists, such as monarchs, in an area, you can infer that the habitat health of that area, in terms of plant biodiversity, is relatively high as well.
David Fair: This is purely anecdotal and based on personal experience, but it feels like I see less butterflies today than I did as a younger person. Am I just less attentive than I should be?
Ludovico Behrendt: I mean, it depends on the areas you're talking about, but in general, the butterfly abundance and diversity across Ann Arbor on average has remained relatively stable since 1995 into 2023.
David Fair: Our Issues of the Environment conversation with Ludovico Behrendt from the Ann Arbor Natural Area Preservation Division continues on 89.1 WEMU. Are there areas that you studied that you found to be in decline for a particular reason?
Ludovico Behrendt: There were no specific areas that had in particular declines. There were areas that showed general stagnation, in terms of population numbers in the sense that there were no particular increases across the 30-year time period, despite management efforts by NAP. However, this can be indicative of the fact that, despite environmental degradation may be occurring, that NAP's management efforts are sort of staying ahead of it, such that the butterfly populations aren't suffering, but rather remaining relatively stable across time. So, even though you don't see increases in specific areas, it still can be considered a conservation success in the sense that you're preserving the butterflies that are currently there and making sure they aren't decreasing across time and that the presence of butterflies remains relatively constant across Ann Arbor across the survey period.
David Fair: You had such a large data set from which to call this information. Did you come to any conclusions about how it can be used in city planning and design with further protections and habitat suitability in mind?
Ludovico Behrendt: Oh, of course! There's a lot of conclusions that can be made. But generally, the types of analysis we ran on the dataset allowed us to sort of correlate specific environmental variables with butterfly survivability. For example, one of the main findings we found with that a park that had a greater degree of habitat diversity that included woodlands and grasslands within their perimeter versus a park that only had one habitat represented within the border had much greater butterfly diversity and that areas that, in general, had a greater degree of management activity by NAP--that includes invasive species removal events and prescribed burns--tended to also have increased butterfly diversity and abundance relative to areas that did not. So overall, we used this to tie into our management recommendations, such that parks that had a greater habitat diversity should be the ones that are most focused on by NAP. But we also included a caveat saying that specific parks, despite not having this high habitat diversity or high management effort, still were valuable in the sense that they had representative populations of these rare indicator species we were talking about before, such as Eastern Tigers, Fault Hills, and Monarchs. So overall, we found that, in general, as management increases and as park habitat diversity increases, butterfly diversity tends to increase as well. So, these are sort of the general environmental variables that should be considered most important when implementing management efforts to try to increase that habitat diversity and increase the usage of management efforts, such as prescribed burns and invasive species removal.
David Fair: Once again, this is 89.1 WEMU, and we're talking with Ann Arbor Natural Area Preservation Division data analyst Ludovico Behrendt on this week's Issues of the Environment. Another casual observation is that I see far less fireflies than I used to. And when I was a kid, that was an evening's worth of entertainment: going out and seeing which of us could catch the most in a jar and then watch in wonder as you release them back to nature and taillights are flashing. Are fireflies a concern when it comes to conservation efforts?
Ludovico Behrendt: Fireflies are a concern in the sense that they are an indicator species, such as the monarchs I was talking about before, that they require specific habitat conditions in order to survive and reproduce. And generally speaking, as invasive plant species presence increases in certain parts of America and the Midwest, firefly populations tend to suffer. However, it's important to note that this is sort of anecdotal evidence on my part because within the NAP survey dataset, we did not look at firefly populations. It was purely focused on butterflies and other sort of wildlife species of concern, such as birds and salamanders and turtles.
David Fair: Well, let me ask you this. Could the Butterfly Monitoring Program methodology be applied to fireflies and other species of concern?
Ludovico Behrendt: Oh, of course! It's very important that citizens of Ann Arbor and of other cities actually get out and start observing the wildlife that they see and record it and submit it to their sort of Parks and Rec Department, their city, because having that data available of those sort of firefly population numbers is incredibly important in determining whether they survive, what areas they survive in, and if there has been like a significant decrease at all. Generally, when it comes to the fireflies, as far as I'm aware, within Michigan, there has been no major firefly population survey. It's just been anecdotal evidence of people saying that they observe less fireflies across time. So, I think it's very important that in order to create these more concrete management recommendations of fireflies, that data be collected and that further research be promoted, in terms of actually analyzing these population numbers and determining what exactly is causing the decline because, as of now, we only have hypotheses, at least within Michigan.
David Fair: The Butterfly Monitoring Program over the decades has been volunteer-driven. And how valuable is that for potential studies of fireflies and other species? And how important is it in community education efforts in utilizing citizen science as a tool for a healthier future?
Ludovico Behrendt: So, citizen science itself is an incredibly helpful tool when it comes to research. It has been found that, if you have enough citizen science observations to work with, it can be as sort of concrete for statistical analyzes as academically collected research by experts in the field, because you can correct for survey or bias if you a large enough sample of people that are observing butterflies or observing fireflies. And generally, more data on the environment is better in terms of in determining what management efforts are the most helpful. Furthermore, these sort of citizen science programs are incredibly useful in terms of allowing on citizens of Ann Arbor and citizens of other cities to become aware of the environmental state of the park. And then, a lot of them become more attached towards stewardship of these natural areas across time. And as time goes on, it's been found that citizen science actually helps increase environmental awareness, it helps cities secure better funding for management actions, and it allows for more environmental activism across cities and more advocacy for the protection of parks and natural areas that people love. So overall, citizen science is an incredibly useful tool, both academically and in terms of increasing participation in the natural scientists and making sure that there's more natural stewards and inspiring a future generation of environmentalists and naturalists to sort of become better environmental advocates.
David Fair: Well, thank you so much for taking time today and sharing the information and findings! I appreciate it!
Ludovico Behrendt: Of course!
David Fair: That is Ludovico Behrendt. He is an environmental data analyst with the Ann Arbor Natural Area Preservation Division discussing the findings of a nearly 30-year butterfly monitoring program. For more information, stop by our website at WEMU.org. Issues of the Environment is produced in partnership with the Office of the Washtenaw County Resources Commissioner, and you hear it every Wednesday. I'm David Fair, and this is your community NPR station, 89.1 WEMU-FM Ypsilanti.
Non-commercial, fact based reporting is made possible by your financial support. Make your donation to WEMU today to keep your community NPR station thriving.
Like 89.1 WEMU on Facebook and follow us on X (Twitter)
Contact WEMU News at 734.487.3363 or email us at studio@wemu.org
