Monarch Butterfly Count Nears 30-Year Low

01An American non-profit group says the number of monarch butterflies spending the winter in the western United States has dropped to its second lowest mark in nearly 30 years.

02The Xerces Society for Invertebrate Conservation, based in Oregon, said the causes for this include the use of chemicals to kill insects, known as pesticides.

03The group also blames reductions in habitat and climate change.

04Monarch butterflies are known for their clear orange and black markings.

05They live across North America.

06Monarchs in the eastern United States spend the winter in Mexico.

07The World Wildlife Fund, a non-profit based in Switzerland, counts them there, but has not yet released data for this year.

08Monarchs west of the Rocky Mountains usually spend the winter along the California coast.

09The Xerces Society for Invertebrate Conservation has been counting western overwinter populations in California and Arizona for the last 28 years.

10The highest number recorded was 1.2 million in 1997.

11The organization announced Friday that it counted just 9,119 monarchs in 2024, a decrease of 96% from 233,394 in 2023.

12The total was the second lowest since the survey began in 1997.

13The record low count was 1,901 monarchs in 2020.

14The survey noted that a place in Santa Barbara that saw 33,200 monarchs last winter had only 198 butterflies this year.

15Monarchs across North America face increasing threats.

16One is the supply of a plant, milkweed, which they feed on as caterpillars.

17Monarch Joint Venture is a non-profit group based in Minnesota that aims to protect monarchs.

18The group said milkweed has been disappearing because of dry weather, wildfires, agriculture, and urban development.

19The Xerces Society said pesticides might be on the remaining plants.

20Emma Pelton is a biologist with the Xerces Society.

21She said it is unclear what caused such a sharp decrease in the western population in just one year.

22The monarch population is already small, she said, and heat above 37.7 degrees Celsius in the western states last year might have slowed breeding.

23Monarchs suffer when the temperature gets up to 37.7 degrees Celsius, and any temperatures above 42.2 degrees Celsius will kill the insects, Pelton said.

24The western states saw a heat wave in July with temperatures in some areas well past 37.7 degrees.

25Palm Springs, for example, reportedly reached a record 51.1 degrees Celsius on July 5th.

26Another heat wave hit northern California in early October, with several cities breaking heat records.

27Pelton said that it is too early to tell what long-term effect the sharp drop might have on the overall western monarch population.

28Insects can reproduce very quickly, Pelton said.

29After a low point of 1,901 butterflies in 2020, the population recovered to 247,246 insects the following year, an increase of nearly 13,000%.

30The year after that, the survey recorded 335,479 monarchs.

31This is bad news, Pelton said, of the 2024 population drop, but we have seen incredible recovery.

32This doesn't mean we're not going to have western monarchs.

33The U.S.

34Fish and Wildlife Service announced in December 2024 that it wanted to list monarchs as threatened.

35Such a move would ban people from killing or transporting them.

36The proposed change would also ban property owners from making changes to their property that would make it unusable to the butterflies.

37For example, removing all milkweed from a property would be banned by law.

38Earthjustice is an environmental non-profit legal group based in San Francisco.

39It asked the Environmental Protection Agency in December 2024 to require testing of pesticides' effects on insects such as bees, moths, and butterflies.

40I'm Jill Robbins.

41I'm Jill Robbins.

42I'm Jill Robbins.

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44I'm Jill Robbins.

45I'm Jill Robbins.