Hi everyone - I know it's been a while since my last post, but today's entry should make up for that. Hold on to your butts - today I'm sharing what I said, word-for-word, to the USFWS, on the issue of the monarch listing in the U.S. For those who have been living under a rock, the service has recently proposed to list monarchs as "Threatened" under the Endangered Species Act, after a years-long "assessment" period of the monarchs' population status. And also for those living under a rock, I believe this assessment is wrong.
For those members of my Thoughtful Monarch Facebook group reading this, you'll likely recall that I had said that I wouldn't bother with this, since I didn't think these comments would have much impact. However, because of my own extensive experience with studying the monarchs, and including my personal involvement with the IUCN's listing debacle two years ago, I have been "strongly encouraged" to contribute an objective comment to the listing anyway, if for no other reason than to have it as a matter of public record. And more importantly, if there is no response from the service, then that would be on record too.
So, I spent the last few days reviewing all of the documents involved in this assessment, which are all posted online at the USFWS website - link here. For the nerdy people out there, you really should browse through all of these documents, including the reviewer comments of the proposal, as they are quite illuminating. Apparently, I'm not the only scientist with a negative take on this proposal. The fact that this decision went forward anyway, despite the negative issues raised by multiple reviewers, is quite telling.
After all of this, I put together the following commentary, which I have just now uploaded to the comments section of the assessment. Note that this comment is lengthy, because it contains actual science and evidence, as opposed to the vast majority of comments already entered on the assessment (50,000 comments!). So again, hold onto your butts...
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Comment on USFWS Proposal to list monarch butterflies as Threatened
Andy Davis, PhD
University of Georgia
Rationale for this comment
I was strongly encouraged to submit this comment so that it would be entered into the public record, and so that it could be retrieved in the future, and more importantly, so that any official response, or lack thereof, would also be a matter of public record.
As a scientist, I have been studying the monarch butterfly for 25+ years, including its famous long-distance migration in North America. In the last two decades I have also been personally involved in multiple collaborations and projects that have assessed the population size of monarchs, using various approaches and datasets. This includes analyses of migration count data (Garland and Davis 2002, Meitner et al. 2004, Walton et al. 2005, Gibbs et al. 2006, Badgett and Davis 2015), and counts of breeding monarchs (Crossley et al. 2022). I also organized a special collection of peer-reviewed studies that examined long-term trends in monarch abundance from a variety of sources (Davis and Dyer 2015). Throughout this time, I have always maintained that to truly understand the population status of this wide-ranging species, we must endeavor to use all available scientific data, and from multiple time periods of its annual cycle. This was the case back in 2012, when I pointed out how long-term declines of Mexican overwintering colonies, as outlined in Brower et al. (Brower et al. 2012), did not match up with counts of migrants at a northern monitoring stations (Davis 2012). Similarly, my own analyses of long-term trends in springtime colonization success also did not show evidence of overall decline (Howard and Davis 2015), which again highlights the fact that the population cannot be judged by snapshots of one time period. More recently, I collaborated with expert statisticians and entomologists to examine long-term trends in breeding-season abundance of monarchs throughout their entire range, and we again found little evidence of overall decline (Crossley et al. 2022). This body of work has consistently shown the same evidence, that the monarchs in North America, and especially within the United States, are not in trouble.
As a final point of relevance here, I was also personally involved in the recent debacle by the International Union for the Conservation of Nature (IUCN), who had deemed North American monarchs to be “Endangered” based solely on the trends found at the wintering colonies (Walker et al. 2022). I personally challenged that decision, which led to a formal review by an impartial committee, which found enough merit in the challenge to downgrade their listing to “Threatened.” This did not go far enough, in my opinion, though my involvement in that case is what matters here. From all of this experience and body of work in the last 13 years, I would argue that my comments here, on the USFWS listing of monarchs in the U.S., deserve to be heard.
Comments on the proposal to list monarchs in the U.S. as “Threatened”
I have thoroughly reviewed all of the documents provided online by the USFWS regarding the monarch listing, including the original petition from 2014, the proposal to list monarchs as threatened, and importantly, the reviewer comments on the proposal. I find that there are substantial problems with the proposal, so that if the listing were to be finalized based on this document, it would be a tragic miscarriage for science. Below, I elaborate on these problems.
Problematic Issues
1. Reliance on overwintering colony data alone
As outlined above, I have always contended that the complex life cycle of this migratory species requires an evaluation of all available data throughout its annual cycle, because of the tremendous resiliency of the species, and because events at one stage do not necessarily extend to others. This was not done in the USFWS proposal, as the entirety of the analyses was focused only on the long-term trends of the size of the winter colonies. While these data do look alarming if viewed alone, they do not tell the whole story, especially considering that counts of breeding monarchs have remained steady (Crossley et al. 2022), as have counts of fall-migrating monarchs at northern monitoring sites (Ethier 2020, Culbertson et al. 2022), the exception being one of the two monitoring sites at Long Point, Ontario, where a slight decline was seen at one (Crewe and McCracken 2015).
A truly objective approach to assessing the monarch population status would be to include each of these long-term datasets from multiple regions and timepoints, and then evaluate the big-picture. In doing so, it would become clear to any objective observer that the declines at winter colonies, while problematic, do not signify impending doom for the entire population, since the population appears to be able to compensate each summer, and, across an immense breeding range. In fact, multiple studies have specifically sought to determine if the smaller winter colony sizes have any bearing on the subsequent summer population size, and the answer was no in each case (Inamine et al. 2016, Saunders et al. 2018, Crewe et al. 2019). This is because of 1) the tremendous reproductive capacity of monarchs, and 2) of the heavy influence of environmental conditions during any given spring.
Given that there is no overall decline in the summer months, but the appearance of declines at the winter colonies, a reasonable conclusion would be that the true problem is not that the entire breeding population is declining, but that the monarchs are increasingly failing to reach their winter destinations each fall. In fact, this very finding was revealed in a recent analyses of migration roost observations (Davis et al. 2024); the size of migration roosts has indeed diminished over time especially at the most southern regions, indicating failure to even reach Mexico. Thus, if the monarchs are increasingly failing to reach the winter colonies, then how can these colony sizes truly reflect the “size of the entire population,” especially in recent years? Once again, another reason not to rely solely on the winter colony data.
Another problematic issue with the sole reliance of winter colony data, especially at the Mexican colonies, is that these data cannot tell us exactly how many monarchs there are at the colonies, since we do not know how dense are the clusters, or even how many trees are covered with monarchs in each colony. This very issue was pointed out by outside reviewers of the IUCN listing document, which also relied exclusively on the winter colony size estimates. Consider, that while the outside perimeter of the colonies may have declined over time, it may be that the monarchs are more densely (or loosely) clustered now. We simply do not know enough about their clustering to be able to reliably estimate the true numbers of monarchs at the Mexican colonies. I note that these or other problems with the winter colony estimates were pointed out by reviewers of the USFWS proposal, and yet nothing was done about that and the entire proposal was still based on these winter data alone.
I note that a weak rationale was given for the reliance on the winter colony data, which was by referencing a single study that appeared to provide support for this myopic approach (Pleasants et al. 2023). According to that one study, no other data should be examined other than the winter colony data! It should be pointed out that that study hinged on a logical fallacy, whereby the authors assumed at the start that the winter colony size data represented the gold standard of population assessment, and so the authors tried to find other datasets that matched those trends. The study did NOT prove in any way that the winter colony data are superior, or, that they should be used solely to determine population trends. In fact, the same study provided other unpublished data from the long-term citizen science program, the Monarch Larva Monitoring Project, which showed how the abundance of larval monarchs has remained steady or even increased over time throughout the monarch breeding range (Pleasants et al. 2023). The authors did not have an explanation for that, but a reasonable conclusion would be that the summertime reproduction success is stable, which again, is consistent with counts of breeding adult monarchs (Crossley et al. 2022).
Again, I note that this reliance on only the winter colony data had been pointed out as a problem during the review of this proposal, but yet the service did not heed that warning.
Given all of these problems with the USFWS approach to assess the monarch population, I am not confident that the service has conducted this assessment with objectivity. Moreover, failing to respond to objective reviewer comments (as was the case here) is concerning. In fact, this is cause for rejection of scientific manuscripts submitted to journals. Overall, the purposeful refusal to broaden the scope of the assessment smacks of personal biases or agendas, which have no business in science, or especially in regulatory decisions like this.
2. Reviewer concerns not addressed
Here, I will highlight multiple cases where there were problems identified in the proposal by outside reviewers, based on the reviews provided online. The refusal to address these reviews also implies that the service was only interested in one outcome of this assessment. Note that there were multiple cases where one or more reviewers echoed many of my own objections above. I especially wish to highlight the concerns raised by one, Dr. Paul Goldstein, who had appeared to conduct an incredibly detailed and thorough review of this proposal. Highlighting these will ensure those comments are not overlooked in the minutia of the assessment documents.
Regardless of how one feels about the applicability of using the winter colony datasets alone, Dr. Goldstein had raised multiple concerns about the specific modeling approach and conclusions based on those winter colony time series, especially the trends, or lack thereof, in these data within the last decade. Indeed, in recent years the winter colony sizes have appeared to have stabilized, although at a lower size. Dr. Goldstein rightly pointed out that this stabilization implies no current, or ongoing threat of extinction, and also highlighted the recent statistical analyses by Meehan and Crossley (2023), which concurred with this idea. Dr. Goldstein pointed out that this is a crucial point when making decisions regarding current endangerment risk of a species, and one which the IUCN also relies heavily on.
Dr. Goldstein repeatedly pointed out that the proposal appeared to mischaracterize the species as one that is fragile and in trouble, when in fact, it is globally-distributed, which highlights its adaptability. And, Dr. Goldstein repeatedly referenced the extreme resiliency of the species, meaning it can bounce back from low numbers. He argued that these are not traits of a fragile species.
It should be noted that based on Dr. Goldstein’s review of the proposal, he had serious reservations about its accuracy. When asked, ‘Overall, does our updated assessment effectively capture the current status of the monarch?’ he replied ‘No.’ When asked ‘Do the updates adequately capture new information relevant to the species needs?’ he replied, ‘No.’ When asked ‘Do the updates adequately capture new information relevant to the species current and future stressors?’ he replied ‘No.’
To me, these objective, and negative, reviewer comments are telling, meaning that they cast serious doubt on the validity of this assessment. As far as I can tell, his comments were ignored.
Ramifications of going forward with listing
Regardless of the problems identified above in the entire listing proposal document, there would be some important (negative) ramifications if this listing were to go forward. One of the other comments by Dr. Goldstein deserves further mention and discussion here. He rightly pointed out that if monarchs are awarded special protection, this could backfire especially in the agricultural sector. Farmers and landowners would be incentivized to make efforts to rid their lands of milkweed, so as not to risk harming monarchs and facing federal regulations. Because of this risk, Dr. Goldstein wrote, “I am not convinced that a listing is the appropriate tool for protecting this species or its individual populations.”
One of my own concerns over this issue comes from a purely scientific perspective. If this listing decision were to go forward, despite the overwhelming evidence of population stability and resiliency, it would perpetuate an ongoing (false) narrative about this species. We would be left with a situation where the entire world believes in something that is not scientifically factual. If this is the case, then why should scientists (like me) continue to conduct science that will be ignored? We would be living in a world where the public perception of a subject is what is most important, not the facts and evidence.
The listing decision would also perpetuate and exacerbate an ongoing problem with monarchs, whereby well-meaning members of the public attempt to “rescue” any monarch caterpillars in their yards, and rear them in captivity. This comes from a misplaced desire to “save the monarchs from extinction,” which is a narrative that is being driven by listing decisions like this. These public rearing efforts have been shown to be problematic for the ability of monarchs to complete their long-distance migration (Steffy 2015, Tenger-Trolander et al. 2019, Davis et al. 2020, Tenger-Trolander and Kronforst 2020). With hundreds of thousands of these captive monarchs being released each year, the result will be a gradual watering down of the population fitness, and reductions in migration success, which is exactly what we are seeing even now (Davis et al. 2024).
Conclusion
In this comment I have outlined multiple cases where the USFWS proposal to list monarchs as federally Threatened in the United States was based on inaccuracies, lack of objectivity, and refusal to listen to objective reviewers. None of these conditions have a place in science, and certainly, we should not use situations like this when making regulatory decisions about the status of a species. Moreover, there would be some serious consequences (and harm to monarchs!) if this listing were to move forward, even despite the problems.
As a scientist who has studied monarchs for 25+ years, my goal here is not only to ensure that the public narrative around this species matches the data (which should be the goal for all scientists), but also, to ensure the future health of the monarchs’ unique long-distance migration, which would be in further peril if this listing were to go forth.
Literature Cited
Badgett, G., and A. K. Davis. 2015. Population trends of monarchs at a northern monitoring site: analyses of 19 years of fall migration counts at Peninsula Point, MI. Annals of the Entomological Society of America 108: 700-706.
Brower, L. P., O. R. Taylor, E. H. Williams, D. A. Slayback, R. R. Zubieta, and M. I. Ramirez. 2012. Decline of monarch butterflies overwintering in Mexico: is the migratory phenomenon at risk? Insect Conservation and Diversity 5: 95-100.
Crewe, T. L., and J. D. McCracken. 2015. Long-term trends in the number of monarch butterflies counted on fall migration at Long Point, Ontario, Canada (1995-2014). Annals of the Entomological Society of America 108: 707-717.
Crewe, T. L., G. W. Mitchell, and M. Larrivee. 2019. Size of the Canadian breeding population of monarch butterflies is driven by factors acting during spring migration and recolonization. Frontiers in Ecology and Evolution 7: 12.
Crossley, M. S., T. D. Meehan, M. D. Moran, J. Glassberg, W. E. Snyder, and A. K. Davis. 2022. Opposing global change drivers counterbalance trends in breeding North American monarch butterflies. Global Change Biology 28: 4726-4735.
Culbertson, K. A., M. S. Garland, R. K. Walton, L. Zemaitis, and V. M. Pocius. 2022. Long-term monitoring indicates shifting fall migration timing in monarch butterflies (Danaus plexippus). Global Change Biology 28: 727-738.
Davis, A. K. 2012. Are migratory monarchs really declining in eastern North America? Examining evidence from two fall census programs. Insect Conservation and Diversity 5: 101-105.
Davis, A. K., and L. Dyer. 2015. Long-term trends in eastern North American monarch butterflies: a collection of studies focusing on spring, summer, and fall dynamics. Annals of the Entomological Society of America 108: 661-663.
Davis, A. K., F. M. Smith, and A. M. Ballew. 2020. A poor substitute for the real thing: captive-reared monarch butterflies are weaker, paler and have less elongated wings than wild migrants. Biology Letters 16: 5.
Davis, A. K., J. R. Croy, and W. E. Snyder. 2024. Dramatic recent declines in the size of monarch butterfly (Danaus plexippus) roosts during fall migration. Proceedings of the National Academy of Sciences of the United States of America 121.
Ethier, D. 2020. Population trends of Monarch butterflies (Danaus plexippus) migrating from the core of Canada’s eastern breeding population. Annals of the Entomological Society of America.
Garland, M. S., and A. K. Davis. 2002. An examination of monarch butterfly (Danaus plexippus) autumn migration in coastal Virginia. American Midland Naturalist 147: 170-174.
Gibbs, D., R. Walton, L. Brower, and A. K. Davis. 2006. Monarch butterfly (Lepidoptera, Nymphalidae) migration monitoring at Chincoteague, VA and Cape May, NJ: a comparison of long-term trends. Journal of the Kansas Entomological Society 79: 156-164.
Howard, E., and A. K. Davis. 2015. Investigating long-term changes in the spring migration of monarch butterflies (Lepidoptera: Nymphalidae) using 18 years of data from Journey North, a citizen science program. Annals of the Entomological Society of America 108: 664-669.
Inamine, H., S. P. Ellner, J. P. Springer, and A. A. Agrawal. 2016. Linking the continental migratory cycle of the monarch butterfly to understand its population decline. Oikos 125: 1081-1091.
Meehan, T. D., and M. S. Crossley. 2023. Change in monarch winter abundance over the past decade: a red list perspective. Insect Conservation and Diversity Online - https://doi.org/10.1111/icad.12646.
Meitner, C. J., L. P. Brower, and A. K. Davis. 2004. Migration patterns and environmental effects on stopover of monarch butterflies (Lepidoptera, Nymphalidae) at Peninsula Point, Michigan. Environmental Entomology 33: 249-256.
Pleasants, J., W. E. Thogmartin, K. S. Oberhauser, O. R. Taylor, and C. Stenoien. 2023. A comparison of summer, fall and winter estimates of monarch population size before and after milkweed eradication from crop fields in North America. Insect Conservation and Diversity.
Saunders, S. P., L. Ries, K. S. Oberhauser, W. E. Thogmartin, and E. F. Zipkin. 2018. Local and cross-seasonal associations of climate and land use with abundance of monarch butterflies Danaus plexippus. Ecography 41: 278-290.
Steffy, G. 2015. Trends observed in fall migrant monarch butterflies (Lepidoptera: Nymphalidae) east of the Appalachian Mountains at an inland stopover in southern Pennsylvania over an eighteen year period. Annals of the Entomological Society of America 108: 718-728.
Tenger-Trolander, A., and M. R. Kronforst. 2020. Migration behaviour of commercial monarchs reared outdoors and wild-derived monarchs reared indoors. Proceedings of the Royal Society B-Biological Sciences 287: 8.
Tenger-Trolander, A., W. Lu, M. Noyes, and M. R. Kronforst. 2019. Contemporary loss of migration in monarch butterflies. Proceedings of the National Academy of Sciences of the United States of America 116: 14671-14676.
Walker, A., K. S. Oberhauser, E. M. Pelton, J. M. Pleasants, and W. E. Thogmartin. 2022. Danaus plexippus ssp. plexippus (errata version published in 2022). The IUCN Red List of Threatened Species 2022: e.T194052138A219151401. <https://dx.doi.org/10.2305/IUCN.UK.2022-1.RLTS.T194052138A219151401.en>.
Walton, R. K., L. P. Brower, and A. K. Davis. 2005. Long-term monitoring and fall migration patterns of the monarch butterfly (Nymphalidae: Danainae) in Cape May, NJ. Annals of the Entomological Society of America 98: 682-689.
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