The number of monarch butterflies that showed up at their winter resting grounds decreased about 53 percent this year, Mexican officials said Friday.
Some activists called the decline "heartbreaking," but the Mexico head of the World Wildlife Fund said the reduction "is not alarming."
WWF Mexico director Jorge Rickards said the previous year's large numbers were "atypical" and the monarchs had returned to their average population levels of recent years.
The government commission for natural protected areas said the butterflies' population was "stable," even though they covered only 2.8 hectares (6.9 acres) this year. That was down from 6.05 hectares (14.95 acres) the previous year. Because the monarchs cluster so densely in pine and fir trees, it is easier to count them by area rather than by individuals.
Monarch butterflies are seen at El Rosario sanctuary for monarch butterflies in the western state of Michoacan, near Ocampo, Mexico. /VCG
"The last season, 2018-19, was very good, with 6.05 hectares of forest cover, but it was certainly atypical, thanks to the fact that the first generation of butterflies in the spring of 2018 encountered favourable weather conditions to reproduce," he said.
In contrast, butterflies in the spring of 2019 encountered colder weather in Texas than the previous year, and thus were less able to reproduce.
Monarch butterflies are seen on the ground at El Rosario sanctuary for monarch butterflies in the western state of Michoacan, near Ocampo, Mexico. /VCG
In contrast to Rickards' view, Tierra Curry, a senior scientist at the Center for Biological Diversity, wrote that "scientists were expecting the count to be down slightly, but this level of decrease is heartbreaking."
"More protections are clearly needed for this migratory wonder and its habitat," Curry wrote.
Environmentalist and author Homero Aridjis said that "the decline of over 53 percent of populations in the butterfly reserve is worrisome, above all because of the effects of climate change on the migration route and on the wintering grounds in Mexico."
Aridjis said crime and deforestation in Mexico is also a cause for alarm. One butterfly activist and a part-time guide in the reserve were murdered earlier this year.
(Cover image via VCG)
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