The number of Butterflies monarch who spend winter in the west of USA It has fallen to its second lower level in almost three decades, after pesticides, habitat loss and Climate change They have wreaked havoc in this beloved pollinizer.
Here are some outstanding points:
The survey began in 1997
Monarch butterflies, known for their distinctive orange and black wings, are found throughout North America. The East of the United States monarchs pass their winters in Mexico and are counted by the World Fund for Nature, which has not yet published data for this year. The monarchs west of the rocky mountains usually winter along the coast of California.
The Xerces Society for invertebrate conservation has been counting the west populations that pass winter along the coast of California, the north of Baja California and interior sites in California and Arizona for the last 28 years. The highest registered number was 1.2 million in 1997. The organization announced on Friday that it counted only 9,119 monarchs in 2024, a 96% decrease of the 233,394 it registered in 2023. The total was the second lowest since the survey began in 1997. The lowest record was 1,901 monarchs in 2020.
The survey noted that a place owned by the non -profit organism The Nature Conservancy in Santa Barbara, which last winter housed 33,200 monarchs, this year only welcomed 198 butterflies.
The heat could have affected the west monarchs hard
The monarchs throughout the continent face increasing threats, the main disappearance of the algodoncillo, the host plant for insect caterpillars. The plant has been disappearing due to a combination of drought, forest firesAgriculture and Urban Development, according to Monarch Joint Venture, a group that works to protect the monarchs. The pesticides have contaminated much of the remaining plants, according to the Xerces society.
It is not clear what caused such a pronounced fall in the western population in just one yearobserved Emma Pelton, biologist of endangered species. The population of monarchs is already small, he said, and the intense heat in the states of the west of the United States last year could have slowed reproduction.
The monarchs suffer when mercury reaches 37.7 Celsius (100 degrees Fahrenheit), and any temperature above 42.2º C (108º F) is lethal for insects, Pelton said. The west states experienced a heat wave in July that raised temperatures in some areas above 37.7º C (100º F). Palm Springs, for example, reached a record of 51.1º C (124º F) on July 5. Another heat wave hit northern California in October, and several cities broke heat records.
The future of west monarchs seems uncertain
Pelton said that it is too early to say what long -term impact could have dramatic losses in the general population of west monarchs. Insects have the potential for exponential growth, Pelton said. After the bottom of 1,901 butterflies in 2020, the population recovered at 247,246 insects the following year, an increase of almost 13,000%. The following year, the survey registered 335,479 monarchs.
“These are bad news”, Pelton said about the fall of the population in 2024. “But we have seen an incredible recovery. This does not mean that we will not have west monarchs. Hopefully it is a call for attention that a bad year can decrease its number significantly. ”
Federal officials work to protect them
He Federal Fishing and Wildlife Service He announced in December 2024 that he was working to place the monarchs in the list of threatened species, a measure that would prohibit anyone from killing, transporting them or making changes in the land that make it permanently unusable for the species, such as eradicating the entire Algodoncillo in the area. The list would also protect 1,779 hectares (4,395 acres) in seven coastal counties in California to which west monarchs come to spend the winter.
In March a period will conclude for the population to send comments on the proposal. The agency has until December to officially include the monarch in the list of threatened species, if officials decide to do so.
Earthjustice, an environmental law firm, asked the Environmental Protection Agency in December 2024 to force tests on the effects of pesticides on insects such as bees, moths and butterflies.