Despite the presence of a record number of people working to count the insects, this year’s population census for monarch butterflies wintering in California has fallen to a 5-year low, according to a new report from the Xerces Society for Invertebrate Conservation.
Altogether, this year’s count — of just 200,000 monarch butterflies — represents just a fifth of the average of just two decades ago (1.2 million), despite the fact that the numbering of people working to count the insects has increased since then.
The takeaway of this all is that the study published last year found that the western population of monarch butterflies faced a 63% chance of extinction in just the next 20 years, and an 84% chance within 50 years, which likely has something to it. (“Western” refers to populations west of the Rocky Mountains.)
The US Fish and Wildlife Service is currently mulling the addition of monarch butterflies to the federal list of endangered and threatened species, reportedly.
“It’s certainly concerning,” noted Sarina Jepsen, the endangered species program director for the Xerces Society.
Reuters provides more:
“Western monarchs are born on milkweed plants in such states as Arizona, Idaho, Utah, and Washington before embarking on a seasonal migration to California. The annual count in California, done at the end of autumn by dozens of volunteers and scientists, last saw a severe low in 2012, with 144,812 butterflies across 136 sites, she said.
“In another troubling trend, the 200,000 butterflies found in the 2017 survey stemmed from monitoring of 262 sites, which were even more sites than were tracked the previous year when 300,000 monarchs were counted, Jepsen said.
“Factors that may have compounded monarchs’ plight in California in recent months include unseasonably warm temperatures, wildfires, smoke from wildfires and mudslides, all of which may have played roles in reports of monarchs migrating and breeding later than usual, she said.”
The situation with regard to the western monarch butterfly is mirrored by that of the monarch butterflies found in the eastern and central regions of the US (which overwinter in Mexico) — where populations that used to number in the tens of millions have been on a steep decline over the last few decades.
The factors implicated to date in the decline of both populations, include: deforestation, increasing pesticide use, temperature changes, and general habitat loss (human expansion).