Winter Monarch count down 22% from last year


The annual number of migratory monarchs wintering in Mexico is once again dismal for the iconic orange and black butterflies. This year’s tally showed a 22% drop from 2022, leaving the butterfly highly vulnerable to extinction.

The count found only 2.21 hectares of occupied forest in the monarch’s traditional wintering range. The total number of monarchs is 64% below the minimum threshold that scientists believe is necessary for migratory pollinators not to be threatened with extinction in North America. Monarchs east of the Rocky Mountains have declined by about 90% since the mid-1990s.

“Despite heroic efforts to save monarchs by planting milkweed, we could still lose these extraordinary butterflies if we don’t take bolder action,” said Tierra Curry, senior scientist at the Center for Biological Diversity. “Monarchs were once incredibly common. Now they are the face of the extinction crisis as US populations plummet amid habitat loss and climate collapse.

Monarchs are currently on the waiting list of candidates for Endangered Species Act protection. The US Fish and Wildlife Service has a 2024 deadline to make a final listing decision.

Eastern population dangerously low since 2008

In late summer, eastern monarchs migrate from the northern United States and southern Canada to the high elevation fir forests of central Mexico. Scientists estimate population size by measuring the area of ​​trees turned orange by the butterflies grouping together. The annual count is carried out by the Mexican National Commission for Natural Protected Areas and the World Wildlife Fund Mexico. The eastern population has been dangerously low since 2008.

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Scientists led by the Center for Biological Diversity and the Center for Food Safety petitioned the Fish and Wildlife Service to protect the butterfly under the Endangered Species Act in 2014.

“We asked for monarch butterflies to be protected nine years ago, but they still face an onslaught of pesticides and habitat loss,” said George Kimbrell, legal director for the Center for Food Safety. “This year’s tally shows once again that they continue to be in dire need of protection under the Endangered Species Act. The Fish and Wildlife Service has already agreed to make a final decision; now they just have to do the good, the one that conservation, science and the law demand: protect the monarchs.

Monarchs are threatened by pesticides, climate change, the loss of the American prairies and illegal logging where they migrate for the winter. They are also threatened during their migrations by roadkill and habitat fragmentation.

Monarchs have lost an estimated 165 million acres of breeding habitat in the United States to spraying and herbicide development in recent decades. The caterpillars only eat milkweed, but the plant has been devastated by increased herbicide spraying in conjunction with corn and soybean crops that have been genetically modified to tolerate direct spraying. Butterflies are also threatened by neonicotinoid insecticides, fungicides and other chemicals toxic to young caterpillars.

Most monarch butterflies west of the Rocky Mountains overwinter on the central California coast. Their numbers rebounded this year to more than 330,000 butterflies in Thanksgiving counts. But deadly storms led to a 58% decline, with just 117,000 butterflies surviving through January. Overall, the West’s population has declined by more than 95% since the 1980s.

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In Canada, monarchs should be listed as endangered under the Species at Risk Act. In Mexico, they are considered a species of special concern.

Thanks to the Center for Biological Diversity for providing this news.