Guest Essay by Kip Hansen — 17 October 2024 — 1700 words/7 minutes
The marvelous mysterious Monarch Butterfly is at it again: baffling lepidopterists — a branch of entomology concerning the scientific study of moths and the two superfamilies of butterflies — with questions they can’t answer.
The observational evidence is this:
It is clear that [Monarch] winter colonies in Mexico are declining, yet some recent studies suggest that summer breeding populations are relatively stable and similar to historical abundances.
Here they are speaking of the Eastern United States Monarch population — the Monarch population that migrates from as far north as Canada every fall south to the mountains of central Mexico. If your are not already familiar with the mysterious nature of this phenomenon, read my primer on the Monarch Migration or any of my earlier Monarch essays here.
There exists a modern scientific controversy about the monarchs and their migration – such a big hullabaloo that I have named it The Monarch Wars. The basis of the Monarch Wars is:
1) Some governmental agencies, scientists and activist groups want to declare the Monarch Butterfly, or one of its two Northern Hemisphere populations, as an Endangered Species. In 2022, the U.S. Fish and Wildlife Service “determined that listing the monarch under the Endangered Species Act is warranted but precluded at this time by higher priority listing actions.” The IUCN unilaterally declared the Monarch Endangered and in 2022 added it to the IUCN Red List as Endangered. However, IUCN then delisted monarchs in 2023, declaring them only “Vulnerable”.
2) Other scientists, groups and interests oppose the listing of this nearly ubiquitous species as endangered – showing evidence that it is not suffering population declines or fragmented populations.
3) There is a third view that proposes that the Monarch Migration itself, as a phenomenon, should be declared Endangered.
The evidence is unfortunately clear — for all sides in the controversy.
How is this possible?
The latest study is:
Dramatic Recent Declines in the Size of Monarch Butterfly (Danaus plexippus) Roosts During Fall Migration [ full pre-print .pdf ]
by Andrew K. Davis, Jordan R. Croy and William E. Snyder out of the University of Georgia in Athens, GA, USA.
Their Abstract starts with this line:
“The conservation status of monarch butterflies in North America is a topic of intense scrutiny and debate.”
For several years I have been calling this The Monarch Wars.
Let’s look at the evidence once more:
“It is clear that winter colonies in Mexico are declining”
Clearly winter colonies in Mexico are declining – in the first 20 years of the record, there were some boom years and some low years, less than 5 hectares, but the entire two decades show much larger roosting populations. The most recent decade has had very low roosting numbers.
And Summer Populations?
The above image, from Crossley et al. (2022) published in Global Change Biology clearly shows that the summer population of Danaus plexippus, the Monarch Butterfly, seen as the vertical orange line, has not shown radical declines over the last two decades, but, if anything, shows a slight increase of about 0.7% per year. Not a big increase, but certainly not a sharp, dangerous or worrying decline.
[Note: The Mexico overwintering population graph covers three more years than the summer Population study. Those three years were boom years for the overwintering population.]
The most recent study, Davis et al. (2024) is about the sizes of Monarch roosts that they form during their migration south, when they stop for the night. Davis et al. say:
“Observations of far fewer overwintering monarch butterflies, alongside apparent rebounds during the summer breeding season, have led to heated debate whether monarchs are truly endangered. We used ~2600 citizen scientist observations of monarch “roosts” – mass aggregations of fall-migrating monarchs – to assess whether they are struggling to reach Mexico.”
And this is an important and interesting question. Are there plenty of monarchs in the summer which then fail to reach the overwintering grounds in Mexico, and if so, for what reasons?
Their plain language summary:
“Positive effects of a warming and greening flyway were overwhelmed by unexplained declines in roost size of up to 80%, increasing all along the path of their arduous southern migration.”
They find that “a warming and greening flyway” — and feel free to label this CO2-enhanced atmosphere and maybe climate change — had positive effects on the annual migration. Yet there remained “unexplained declines in [in during-migration] roost size of up to 80%”, declines which increased along the southern route.
To this author’s dismay, they conclude:
“This suggests that to save monarchs, we should focus on avoiding well-meaning efforts such as planting non-native milkweeds that foster parasites, sicken monarchs, and disrupt migration.”
I do not think that that conclusion is warranted or supported based on the evidence of the study. It is a valid hypothesis – a possible explanation – but certainly not strongly supported. Like all hypotheses, it is a guess, based on some data.
They are correct when they say “This suggests that climate change might generally be benefiting monarch migration by creating milder flight conditions and enhancing nectar availability along the flyway (but see 24).”
Ah, yes, there is a but. You can read the but here. It is a complex calculation of “energy expenditure” that might be found true of migrating monarch butterflies under warmer temperatures, not of real butterflies actually migrating, of course.
The reasoning of Davis et al. goes like this:
“That is, while roost sizes were declining throughout the flyway, these declines grew increasingly severe further along the migration route. This latitudinal gradient in roost size declines would be consistent with increasing mortality during migration and/or monarchs increasingly abandoning migration as they move south. This apparent disruption of migration might be the missing puzzle piece that explains relatively stable summer populations in the Midwest and declining overwintering populations in Mexico.”
Alas, Davis et al., despite being a very well done investigation, offers no definitive or actionable findings. “Then what is driving the clear, dramatic declines in roost size seen in these data? We can only speculate,…”.
And speculate they do. While none of the speculations are new, they include:
1) Prevalence of the monarch parasite Ophryocystis elektroscirrha (“OE”) which has increased over the last decade, some say “ten-fold”.
2) The widespread planting of non-native milkweeds such as Asclepias curassavica and Calotropis gigantea by homeowners and even land managers. Some feel that this leads to more parasitisation. There have been some studies that suggested that monarch caterpillars feeding on these species might suffer stunting or weakening. Or that the longer growing season for these species might lure the monarchs to remain north later into the Fall.
3) The raising and releasing thousands of captive-reared monarchs each year. Some studies have implied that captive bred monarchs are weaker or have reduced navigational ability. There are worries that interbreeding of captive and wild monarchs will harm the species as a whole.
4) Finally, year-round resident populations of monarchs appear to be increasingly common and growing along the western and southern edges of the species range. Vague worries about interbreeding of non-migrating monarchs and migrating monarchs and thus genetic dilution are included. This is the “monarchs increasingly abandoning migration as they move south” hypothesis. Another possibility is that more-and-more monarchs migrate to the South, find it perfectly suitable, and settle down there for the winters.
All, as in every single one, of the monarch butterflies found in northern regions, where winters are freezing and below, are the offspring of monarchs that have migrated north from overwintering somewhere warmer in the south. Thus, stable or even growing summer populations in the north seems inconsistent with very small numbers of monarchs overwintering in Mexico. Yet it is the case.
West Coast Monarchs
A similar, but more profound, situation was found with the West Coast monarch population in the winters of 2020-2021 and into the next year, 2021-2022:
You see, that recovery is simply biologically impossible. Thus a mangled version of the Sherlock Holmes quote can be applied: “When you have eliminated the impossible, whatever remains, however improbable, must be the truth”. For that recovery, which is a physical fact, we must eliminate the impossible and doing that requires that the monarchs were overwintering somewhere – just not where they were expected and thus uncounted.
This is one of the speculative explanations for the mystery of the Eastern Population as well – the monarchs may be overwintering in Mexico after all, just not at the usual or known locations where they are expected, thus failing to be counted.
Bottom Lines:
1) We simply don’t know how or why this situation is occurring: far fewer Monarchs overwintering in Mexico yet stable or even growing population in the summer in the north.
2) There are four or five good speculative answers, but none of them stand out or have stronger evidence. It is more probable that the situation is a combination of one or more of the suggested explanations; or the dreaded something else.
3) One thing is fairly certain now: the slight warming seen in continental North America over the last 20 years, of maybe 1.5 degrees F, commonly called climate change, is not the cause but rather more likely a mitigating factor benefiting the monarchs.
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Author’s Comment:
In my part of the United States, I saw very few monarchs this last summer.
I am fascinated by the evidence about monarchs and the growing realization that so much of it driven by a “Save the Monarchs” bias. As in almost all fields of science, the desires of researchers lead directly to their findings. Those looking for disasters will find them, as has been the case with the monarchs. But those researchers are stymied by other evidence – stable summer populations.
In science, the evidence should lead to a proper framing of the situation, which, if it is deemed undesirable, then the evidence should suggest solutions that will correct or mitigate the discovered causes of the undesired situation.
Jumping the gun with solutions to problems for which the causes are only suspected lead us on a merry chase and often make the original problem even worse.
For monarchs, I still favor planting native milkweeds in your gardens (private and public), discouraging mowing of highways verges and the edges and space between corn fields, and, of course, admission that we still don’t understand what is going on with the monarchs which should lead to more and better research.
Thanks for reading.
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How well is their wintering location protected?
Is there good or any information about this species in pre colonial times? I should think this is important.
Joseph ==> The Mexican overwintering sites are protected by law — for that that may be worth. The sites are remote and there exists a strong local resident watch-care group consisting of authorized Monarch guides and researchers. But, in the end, no real protection. Illegal logging in the general area is a know risk, though no one ever actually cuts trees where monarchs roost — the illegal logging is a disturbance factor though.
The actual location of the overwintering sites in Mexico was totally UNKNOWN before 1975 — no one knew where the Monarchs went. The location was kept secret for many more years after the discovery.
So, no, no idea about early populations or roost sizes — butterfly counts were not a thing before about 1985.
The reason I asked about pre colonial conditions- is because of a debate here in Wokeachusetts. The state DFW (div. of fish and wildlife)- was promoting huge clearcuts on state forest land. I asked why. They said that there is a shortage or early succession forests and thus, a shortage of wildlife that likes that ecosystem. When most farming was abandoned here 100-130 years ago, those abandoned acreages for some decades were ideal for early succession wildlife species- like grouse, the New England cottontail rabbit, and many bird species. Often there were many old orchards too that were still productive- for the wildlife. Now, most of the forests are in the mid life range- not young stands. Sure, it’s good to have a diversity of age classes. But, in pre colonial times, those desired species were very rare- so arguing a desperate need for huge clearcuts- which of course alienate enviro groups, was a bad idea- all for species rare 300 years ago. I wanted to promote forestry work that LOOKS GOOD, that is nice thinings that left the forests looking BETTER- like parks. A half century ago, most logging here was high grading (cut the best and left the rest). I spent decades saying we need to have nicer logging- that actually is better economically, over the long term- get rid of high grading and huge clearcuts that just alienate forestry haters. I didn’t win the argument at that time- but now the enviros/greens here want to end all forestry- not just huge clearcuts, which of course emit a lot of CO2, not that I think that’s a problem. So both the state people and the enviros argue incorrectly- and I crazily got caught in the middle of these disputes.
So, regarding the Monarchs, it would be useful to have a better understanding of their population in pre colonial times- to get a sense of whether or not the species is actually endangered in any way. I wonder how much logging- good or bad- in their winter ground area effects them. Nature is complicated. Too often groups argue with slanted views but they all claim to have science on their side.
Joseph ==> Thanks for the interesting perspective. Unfortunately, we don’t have time machines, and that means that almost all North American time series (in almost all subjects of interest to science) are far too short to be of much use — even the longest being only 100-200 years in length — and that means also not necessarily accurate enough for science.
On early succession forests, I believe there are too few acres/square miles of succession forests in the Northeastern US. Most of the farmland in Mass, CT, Eastern NY, VT, NH, Maine are rocky and not hugely productive. Some good for hay and pasturage, but not massive grain fields. [Truck farming can be done anywhere the season is suitable though.]
All up along NY’s Mohawk River abandoned pasture and hay fields are left to transition back to forest….in the Central Hudson Valley of NY, any small plot of land left uncut becomes young mixed forest in 10-20 years.
Changing land use is far more important for species’ habitat than the piddling changes assigned to the cause “climate change”. When land use changes, there are species winners and losers.
The opening up of the land through forest fire, clear cutting, agriculture or beaver ponds transitioning to meadows is a good thing.
Dark, crowded conifer forests of like-age junk trees are ugly and mostly useless…..
The ‘roosting somewhere else’ hypothesis seems reasonable.
I believe Kevin Trenberth has a new paper out, showing the missing Monarchs are hiding in the ocean.
Pat ==> Well, oceanic monarchs is a stretch, but they gotta be somewhere.
Funny you say that- UFOologists now say the UFOs are hiding in the ocean. Seriously.
Exactly. It seems very possible that Monarchs are simply roosting in more places, because warmer temperatures require less ideal roosting spots. So the people haunting the known “ideal” roosting spots are simply not seeing the other ones.
c1ue ==> The Davis study finds that monarchs are not roosting to keep warm or even to protect them from adverse weather — Davis et al. found larger roosts in warmer places and better weather — contrary to the long-held beliefs.
But yes, looking for monarchs where they were last decade may result in missing where they are this decade.
Kip — are there any micro GPS transponders small enough to tag a Monarch?
Pat ==> Not that I know of. There is a GPS in a chip — found in many cell phones, tablets and laptops — but the chip probably weighs as much as a monarch itself.
What about an African Monarch?
Laden or unladen?
Monarch butterflies feed on flower nectar. Monarch butterfly larvae feed on milkweed. If there are sufficient numbers before migration, but not afterwards, they have probably not found sufficient food to survive. Warming should produce more flowers. But herbicides are widely used, which may affect the number of flowering plants along the migration route. They do migrate through my area every year, in Oregon. I’ve seen streets brown with them, and tire tracks through them in our mountains. Agriculture controls huge areas between here and Mexico. That probably accounts for declining numbers that successfully migrate. It certainly has nothing to do with Co2…
jshotsky ==> Some good guesses. In Oregon, you have the Western Monarch population, which migrates not to Mexico, but to the coast of California south of Monterey all the way to San Luis Obispo.
The David et al study found that the flyway (migration path) is greening (more vegetation thus more flowers and feeding opportunities). Considering area (square miles) herbicides are applied to a small percentage of the land — agricultural (and some road verges). The reduction of milkweed in agricultural fields due to RoundUp use was considered a possibility for general population decline, but that decline does not appear to be real, just a worry.
Monarchs migrate in the fall as fields are long past being planted but rather are being harvested.
Certainly there are loses during the migration – like your “crushed on the highway” scenario (I have seen similar scenes).
Read the Davis et al. paper and see what they have to say.
“but to the coast of California south of Monterey all the way to San Luis Obispo”
At this point, that might as well be Mexico.
I’ve noticed more milkweed around here in Colorado than ever before. It’s rare that I see a monarch butterfly, however.
Scissor ==> What’s your elevation? High Colorado?
Read my comment. A professor that studies Monarchs calls cities Green Deserts. Lots of green lawns but little in the way of flowers. He said Monarchs can starve before they can fly past large cities.
They won’t starve in my back yard. 🙂
Ben ==> We don’t seem to find that in the Fall migration on the East Coast. Monarchs are funneled down the peninsula that is New Jersey, passing Cape May in such profusion that they have an annual celebration of them and people flock there to see them passing by. The monarchs fly right through and past one of the largest megalopolises in the United States, the NJ/NY/Ct megalopolis, and then down through the Rest of the Boston-to-Washington corridor.
This year in central New Jersey I’ve not seen many Monarchs, could be related to it being the driest summer/fall I can remember, only had to mow lawn twice!
‘
Would they please carry away some crazy Lib judges?
Flowers everywhere I live.
(In recent years small blue flowers and some white flowers have been spreading along sides of busy roads.)
The observer expectation bias in operation. In science you find what you expect because your expectations bias your search..
And you see only what you want to see.
ferd ==> Yep Yep Yep.
The only way that summer populations remain intact is that winter populations also remain intact. Thus the monarchs are simply wintering in unknown locations.
ferd ==> Yes, that’s my best guess as well: They gotta be somewhere.
(As I used to tell my kids: “Everything is somewhere!”)
Kip:
As I haven’t been closely following the plight of the butterflies, the following comment is totally off the cuff and rather unscientific. However…
There has been a drastic decline in all species of butterflies during the most recent summer in Nova Scotia, Canada. With very few exceptions, the only butterfly noticed was a small white butterfly, which showed up throughout southern Nova Scotia.
No monarchs were noted and only the occasional appearance (less than half dozen) of other butterflies, other than the white species, was observed.
For whatever reason(s), we are definitely having a problem in our area.
Do you have windmills around ?
Dale ==> I take it you are speaking from personal observation? (not official butterfly counts or some such?) As I explain to family members — all counts of things are location sensitive. Number of apples on the dining room table is not the same as the number of apples in the refrig crisping drawer and neither are the same as the total number of apples in the house. Temperatures measured by thermometers measure the ambient air temperature in a spot the size of your little fingernail.
Local weather events, odd seasonal shifts can have huge effects on butterfly populations — and population dynamics are “chaotic” (as in Chaos Theory).
I can confirm the observation in so far, as in earlier times, 80ies and 90ies, after a longer car trip at late evening or night trip, I had to clean the wind shild because of a lot of dead insects and night flying butterflies. That isn’t necessary anymore.
Krishna ==> Some of that is due to better aerodynamic flow over your car hood designed specifically to push bugs up and over instead into your windshield. Some of that is due to simple mathematics: total number of bugs above roadway divided by the number of car windshields traveling the road. (the last would reduce bug spats by 2/3s by itself). Some of it is where you travel now – urban or single-lane highway through agricultural areas. The WaPo had a piece about this (part of which I disagree with).
Once I traveld 400km forth and back over weekends for a longer time. The wind shilds of the cars I used to drive didn’t change a lot in respect of aerodynamics. The most aerodynamic car I drove was an Opel GT and it was th most affected car by night insects.
40 years ago when we sailed Mexico in winter I headed south until I could sit outside at night naked and be warm.
At the time that led us to Bahia Navidad. Now according to the IPCC we should be wintering along with the monarchs in Nome Alaska.
Humor – a difficult concept.
Thank you for keeping up with the monarch butterfly story. Last year we saw what I thought was more than usual but here on the Colorado Front Range they just aren’t very common and what I saw was unremarkable. However, this year I saw ONE. The unusual thing about that was that I saw it on my patch of showy milkweed. That patch has been there for at least 30 years, and this is the first year I recorded a single individual. I was able to photograph it and make a point to note it was there but don’t know what to think. I looked for eggs and caterpillar but found none. I did notice that it had subdued color which I found out isn’t that unusual. Nothing very scientific but certainly has me puzzled just a bit.
Steve ==> I suggest that you join in a little Citizen Science and record sightings at https://journeynorth.org/monarchs.
I’d love to see your photograph if you still have it….You can attach it to a comment here using the little image icon in the lower right hand corner of the Comment form.
Just throwing in my anecdotal two cents. I live in SE Virginia (Tidewater area). I plant milkweed for monarchs and parsley for black swallowtails, and this seems to have been a normal year for monarchs for me at least. I generally see one or two monarchs pretty regularly (not sure if the same one or two or different), and have seen several recently (not sure how late they’re supposed to leave this area), although I have never seen a swarm in this area.
What’s puzzling is I seem to have notice a dramatic decline in the black swallowtails. I used to plant 12 or more parsley plants so we could have some, knowing the BSTs would also eat the parsley. In the past I’ve had the parsley eaten down to bare branches by the caterpillars. The last couple years I’ve only seen a few caterpillars and a couple BST butterflies.
End of anecdotal report….
Phil ==> Black swallowtails, like all butterflies, tend to to be bit here today, gone tomorrow, or here every year for a decade and then absent the next. Population dynamics answers most of the questions but you are doing the right thing.
You can plant all the right things to attract and feed various butterfly species, but you can’t make them come….
Thanks for the response. At least we had more parsley for ourselves this year. 🙂
When the kids were little, I had an old aquarium tank with a screened top that I used to put the black swallowtail and monarch chrysalises in so the kids could watch them emerge and then put them on their fingers and let them go. ahh, memories…not little any more.
Phil ==> While some butterfly activists discourage such activity,I believe it is helpful overall. Many chrysalises are parasitized by wasps etc when out in open nature, protecting them in a screened enclosure until emergence is a positive thing. The trick is to make sure you watch closely and release them into the wild very soon, once the wings are dried and fully expanded to prevent the butterfly from damaging itself trying to fly through the glass.
Hey, but maybe grandkids? local school kids?
No grandkids yet, but momma is hoping real hard.
Gee, I thought “if you build it, they will come”.
Here is the photo. I have a video, but I don’t think I can attach it. This was taken on August 7, 2024.
Steve ==> Thanks! I’ve saved your photo for my next monarch essay….with credit, of course.
Well, that’s cool! Notice the subdued color?
Steve ==> Yes, lighter than usual — but monarchs, like many species, have a fairly wide range of coloration — but certainly less usual.
The greens want stasis – nothing changes.
Impossible, of course.
Then there are the politicians who run on a platform of “We need change. Trust me.”
Seems greens endorsing politicians is a best a conflict of interest.
What a fascinating article! Great job, Kip!!
Thanks, Dave.
So to summarize:
a: professional grifters have found yet another ‘current thing’ that cannot be definitively assessed or explained: so:
b. Said thing is morphed into a narrative that allows for the generation of fear-porn pushed by government, loathsome academia and media and thereafter:
c: ‘scientists’ and eco-warriors can bandwagon together to steal money (government assisted theft) to:
D. ‘stop the bad thing from happening’. Whilst:
E. Countless ‘studies’ are funded through grift to ensure the effort is never going away
then,
rinse, lather, repeat for the next current thing
“rinse, lather, repeat for the next current thing”
Did you mean, “Spin, blather, rebleat”? 😎
In 2022 I contacted a professor at Texas A&M that studies Monarchs. I had some questions as to whether more densely packed housing and higher 6 ft privacy fences compared to 4 ft chain link fences were a problem for butterflies. He said that butterflies fly high enough that this was not a problem.
He then went on to explain what was a problem. Lack of food and water for butterflies in large cities. Few people grow flower beds and wild flowers and plants have been replaced by lawns so there is limited food for migrating Monarchs. Monarchs also become fatigued and/or are starve before they can travel through miles of concrete and asphalt.
He calls cities Green Deserts.
Ben ==> That might be Craig Coates or Craig Wilson at Texas A&M — remember which?
In large cities, urban centers, you simply do not have the habitat for most butterflies. Butterflies go to and stay in areas that provide the things they need: space, shelter, food, water.
A larger area like NY’s Central Park can suffice.
However, in suburbia, the endless housing tracks of a city like Los Angeles, where I grew up, do provide all the necessary things, even for monarchs and swallowtails. Many homes have flower gardens or shrubbery that provides nectar.
In my area of the Northeastern U.S., the near endless mixed hardwoods forest offers very little habitat for monarchs which can be found only in the valleys and meadows. Road building has improved habitat for butterflies, by the required broad treeless verges that substitute for meadows.
Likewise, fallow cropland does the same.
Dr. Craig Wilson. Sorry for my delay in replying. I was busy yesterday. I went back and reread Dr. Wilson’s email to me. I misquoted him regarding green deserts. His exact words were, “Encouraging civilians to plant natives and reduce lawns that are ‘green deserts’ is a great idea but needs a whole lot of re-education.”
Rarely do I see a large butterfly – Dry lands of Central Washington
Here are photos of what I do see:
https://northwestbutterflies.blogspot.com/2019/09/late-season-butterflies.html
Home page: Northwest Butterflies
The site is by a migrant from Kittitas County, Caitlin LaBar, now living in SW Washington State.
John ==> Thanks for the local report. The Drylands of Central Washington are not a great place for butterflies. There are some, even swallowtails. The site you link has some nice photos.
Don’t see a lot of butterflies on Whidbey Island either.
Is anyone looking for dead Monarchs along the migratory path?
Bob ==> The Monarchs are so fragile that they don’t last long in the natural environment. Occasionally there will been enough bodies on a highway or something especially where monarchs alighted to sip morning dew and then been run over…but mostly the scavengers of the natural world clean them up pretty fast. I very seldom find a dead butterfly on any of my serious ambles through the countryside, if i do, it is a memorable treat.
Kip… I am sure you didn’t mean it in that ‘sicko’ vein. “a memorable treat) lol
sturmudgeon ==> I am actually excited and thrilled by unusual finds — live or dead. To find an intact dead butterfly is very rare in my experience, so happy to find one and wonder why and how.
Is that sicko? Don’t know, maybe….
If there are too many to justify “endangered”, split into subspecies until there aren’t. No study needed.
Mike ==> They are already trying that — into Western Monarchs and Eastern Monarchs. Alternatively, a third category, Migrating Monarchs…or the U.S. Monarch Migration Phenomenon.
Part of the problem is Endangered in the US means the US FWS (and other Federal agencies) are then obligated to protect and preserve “critical habitat” regardless of cost. Where is the critical habitat of a ubiquitous species? In summer, they are nearly everywhere…..
Mebbe the sneaky critters found new hiding places in Mexico after episodes of over-population.
(Herring fish switch rivers when numbers headed for their birth estuary are high, salmon switch rivers when conditions are poor for a few weeks (they use water temperature as a measure of depth of water in path upstream to spawning areas.)
My understanding is that populations always fluctuate, weather on the migration route being a major cause.
I suggest that overall humans caused large populations by tilling ground thus helping weeds grow, new weed control methods returned populations toward historical levels.
BTW, what about the populations in the western flyway?
Keith ==> The Western Monarch population is reported here.
Seems obvious to me: IT’S THE CHEMTRAILS!!!
Kip; Thanks for an excellent, interesting article. I was intrigued by the butterfly pics as we have one of them – vanessa atalanta – here in the UK, known as the Red Admiral. Another – vanessa annabella – looks identical to our vanessa cardui, the Painted Lady. How did the Red Admiral come to be found on both continents….transported with plants, perhaps?
The discussion in comments about abandoned farmland, succession forests, etc brought to mind an excellent book: “Wilding” by Isabella Tree. It describes how she and her husband went about re-wilding their family farm and estate in southern England. The results were extraordinary in terms of returning species, improved biodiversity and so on. It is a very heartening story and a good antidote to the endless doom and gloom. The Knepp estate is now a very popular destination for birders and general wildlife enthusiasts.
I expect you know the book but I thought it would be of interest to readers here.
There is a follow-up: “The Guide to Re-wilding” which is what it says. Even though most of it is aimed at farmers, landowners and govt agencies, it is still a fascinating read. It also includes sections addressing small areas and gardens with much useful info and advice for those who want to encourage nature in their surroundings.
Mike ==> Re-wilding is an interesting concept – if one has the land, time and money. Some governments are interested in it …. but I don’t know of any large scale projects.
Too competitive with solar farms means difficult to impossible to accomplish.
This whole discussion brings to mind the old movie “Fly Away Home”. Somehow someone needs to track the migration to see if there are really new overwintering locations.
Yooper ==> They have been trying to track the migration for decades. But butterflies are much smaller than geese.
Not knowing anything about the field of lepidopterology, my first thought was maybe the data are incomplete or poor quality, thus making any conclusions or hypotheses suspect. I think accurately counting moving butterflies over such vast areas would be very difficult .
bean ==> and you got that right! That’s a big part of the problem.
“Blasting, billowing, bursting forth with the power of 10 billion butterfly sneezes…”
While Monarchs are beautiful creatures and it is enjoyable to see a field of them flying around (I summer in the Adirondacks), I would prefer they exist to not exist. However, I cannot support the notion that all, or even any, species must be “protected” to avoid their extinction, whether humankind is the primary cause of that or not.
Nature evolves. Species come and go and “nature” moves on. For humankind to have an ethos that “nature” must stay the way it is now because we like it that way is hubris and nonsense.
Despite what some “scientists” might say, it is highly unlikely, short of global nuclear war, that mankind — at least in current times and for any foreseeable future — could somehow cause a “mass extinction” is nonsense beyond comprehension. Even short of “mass extinction,” it is highly unlikely that humankind could cause species extinction that would be detrimental to our stability as a species. Could we destroy specific experiences of beauty; e.g., seeing Monarchs? Sure, we’ve done that on local scales before (e.g., New Zealand). But on a global scale, due to humankind impact on climate (to the extent there is any)? Seriously, get a grip.
I’m not for saving species when the cost to society is more than trivial…and it should be voluntary, anyway. Using government force to require us to spend our wealth on saving species is an improper use of force, despite what some might like to force others to do or not do.
Meisha ==> I think that you share that opinion with most people capable of critical thinking….
Along the Eastern migration route that works out to 1.15 citizen scientists per linear mile.
The Western migration route should work out to a near equal distance.
If we divvy the citizen scientists into a total 6,000 miles that works out into 2.3 citizen scientists per linear mile.
Why linear miles?
Because that is the distance, not the area.
Both Western and Eastern monarch migration routes cover immense amounts of square miles.
That paltry 2600 citizen scientists barely scratch the surface of studying monarchs, especially if their studying monarchs involves mostly driving, then binoculars.
Here in Virginia I’ve seen a few monarchs this year, not a lot. We’re mostly rural here, but suburbia has started encroaching.
I only have native milkweeds on my property.
I do have a couple of butterfly bushes, but they’re mostly visited by swallowtails and cool bee imitating hovering moths.