But a handful of recent studies have rocked the small and disputatious world of monarch science, suggesting, in the words of University of Georgia ecologist Andy Davis, “that everything we thought we knew about the monarch population is wrong” and that the butterfly does not need our help. In fact, scientists say that home rearing and commercial breeding of monarchs — and the release of them at weddings, funerals, and other events — is one of biggest threats the butterfly now faces.
Two studies, in particular, have challenged the conventional wisdom about the monarchs. Publishing in Current Biology in September, researchers who sequenced the DNA of the butterfly’s primary host plant, common milkweed (Asclepias syriaca ), and analyzed existing monarch DNA concluded that neither the monarchs nor the milkweed had suffered a catastrophic decline in the past 75 years. Their findings contradicted the widely held belief that the butterfly is imperiled due to the eradication of milkweeds by the spread of agriculture using the herbicide glyphosate and genetically modified crops, especially in the Midwest.
In a 2022 article in Global Change Biology , a statistical analysis of the North American Butterfly Association’s (NABA) massive database also found that the butterfly has suffered no sharp decline across its summer breeding range, as had been the prevailing view, and that the population there has actually increased by some 30 percent during the past 25 years. “There clearly are long-term declines in winter colony sizes,” says Davis, a coauthor of the study, but “they do not appear to be affecting the collective breeding population of [Eastern] monarchs.”
Article from my favorite mag…essentially discovered an overwintering population in the swamps of South Carolina.
FWIW, have planted a few areas of common milkweed, mostly because it is an easy to grow pollinator attractor. Have spotted on monarch caterpillar over the years on a plant. Think I have spotted several monarchs but there is another butterfly that looks very similar so hard to tell at times.
This is a bit of an exaggeration as the majority of scientists in the field do not believe Monarchs are endangered. Well at least the majority that I know of.
Monarch butterflies are found on every continent not named Antarctica. In none are numbers showing consistent decline.
Monarchs are only known to migrate in North America and Australia. Florida for example has long been known to have a large non-migratory population. Most Monarchs do not migrate.
There has been a decline a milkweed in several Midwestern states due to agricultural practices and use of herbicides. This has caused Monarch overwintering populations to shift eastward.
Monarchs are being used by some environmental groups as a “poster child” for endangered species because of their popularity. However, these groups present (IMO) a biased view of the data and are disliked (in my experience) by the scientific community.
Two Monarch features may be at risk. The first is that a subset of Monarchs in the western US migrate to sites in California. These represent a separate population and there is some evidence that their numbers are declining. The second is that climate change may be reducing the need for migration. Hence what may be disappearing is the migration behavior of Monarchs, rather than the species itself.
Milkweed naturally grows in a dispersed fashion while most gardeners and butterfly enthusiasts will grow them in large clumps. The problem with the latter is that it encourages parasitism. We have milkweed cropping up spontaneously in several locations in the yard and have in the past grown them in clumps. With the latter there would be so many larvae that the plant would be eaten to the ground. Not so much with the former, so I can understand the parasitism issue. Have found the chrysalis in all sorts of weird locations.
Scientists have. As a result, the International Union for Conservation of Nature has largely reversed their position while still saving some face. One should try to post the most current news.
After much deliberation, the Standards and Petitions Committee announced on September 27, 2023, that the IUCN would change their listing of the migratory monarch butterfly from endangered to vulnerable on December 11, 2023. …The status change of the migratory monarch on the IUCN’s Red List is due to a shift in the data used to evaluate the species, not due to a change in the current population. While concerns remain about the sustainability of the monarch migration, conservation efforts will persist. IUCN Changes Migratory Monarch Status from… • Monarch Joint Venture
Populations have been declining by some measures at the overwintering locations (in Mexico and California). During the same period, populations have been steady at the breeding grounds (the Midwestern and Eastern United States). Whether the species is endangered depends on the location (overwinter or breeding) emphasized.
What most entomologists will say is that if the Monarch population in the United States has remained mostly unchanged, there is no justification for claiming it is endangered in the U.S… It doesn’t fit the traditional definition. The most one can say is that there is declining trend for Monarchs that migrate to Mexico. It is possible that the migratory behavior is endangered, but no evidence that the species is endangered.