Monarch butterfly populations wintering in Mexico have declined 53% since last season, according to recent surveys. Biologists use the acreage of forest they occupy to estimate population changes. The latest survey found the area of forest occupied by monarchs had fallen from 15 acres in the 2018-2019 season to 7 acres this year, where 11 colonies congregated. WWF says lower temperatures in southern Texas led to a slow growth of eggs and larvae during the spring, decreasing later generations in the multi-generational migration.
“The current monarch butterfly population decline is not an alarming one, but we must remain vigilant and not allow it to become a trend in the coming years,” said Jorge Rickards, managing director, of WWF-Mexico, which led the survey in collaboration with Mexican government and nonprofit partners.
Read more from WWF here.