03/22/2023
New Reports Reveal Monarch Population Decline and Habitat Degradation
World Wildlife Fund-Mexico and its partners today released two new reports on 3/21/2023, related to the population and winter habitat of the Eastern migratory monarch butterfly.
Together, they highlight a difficult year for the species, with one showing a continued population decline and the second revealing increased forest degradation where most monarchs cluster in colonies during the winter.
According to the annual survey, Forest Area Occupied by Monarch Butterflies Colonies in Mexico During the 2022-2023 Hibernation Season, the presence of monarchs in their wintering grounds in Mexico decreased by 22% when compared to last winter, down from 7.02 acres to 5.46 acres this winter. The annual WWF-Mexico-led survey measures the area of forest in which monarch butterflies hibernate each winter, providing a scientifically robust indicator of their population status.
The second report, Forest Degradation at the Core Zone of the Monarch Butterfly Biosphere Reserve (2021-2022), found that 145 acres of forest have been degraded, a significant increase when compared to the 46.53 acres lost in the previous period (2020-2021). According to the analysis, sanitation cutting – the removal or pruning of trees to prevent spreading disease or insects -- was the main cause of forest degradation accounting for 71 acres, followed by forest fires (37.36 acres), and illegal logging (33.13 acres).
WWF-Mexico’s General Director Jorge Rickards said that the population decrease reflects the instability that the migratory phenomenon faces. “The reduction of breeding habitat in the United States due to the use of herbicides and land use changes, forest degradation in the wintering sites in Mexico, and extreme weather conditions in all terrestrial ecosystems of the continent."
The Eastern population of the migratory monarch butterfly has seriously declined over the last 25 years. In the winter of 1995-96, monarchs covered nearly 45 acres of forests. Since then, while numbers have fluctuated up and down, there continues to be a downward trend.
Rickards called on Canada, Mexico, and the United States to continue coordinated efforts to preserve the monarch’s migratory flyway in the US and Canada, as well as in the monarch’s hibernation sites in Mexico. “It is not just about conserving a species, it’s also about conserving a unique migratory phenomenon in nature. Monarchs contribute to healthy and diverse terrestrial ecosystems across North America as they carry pollen from one plant to another. With 80% of agricultural food production depending on pollinators like Monarchs, when people help the species, we are also helping ourselves.”
Every year Eastern monarch butterflies travel up to 2,800 miles from Canada and the US to their overwintering sites in the forests of Michoacán and the State of Mexico, where the Monarch Butterfly Biosphere Reserve (MBBR) is located. Monarchs require a large and healthy forest mass to protect them from winds, rain, and low temperatures that are common at night in these forests.
In addition to providing monarchs the right microclimate conditions for hibernation, the MBBR’s forests are one of the main freshwater contributors to the Cutzamala Hydrological System that provides water to more than 5 million people in Mexico City and its metropolitan area. Furthermore, these forest ecosystems are an important reservoir of biodiversity as they are home to 132 species of birds, 56 species of mammals, 432 species of vascular plants and 211 species of fungi.
Please plant Milkweed (Asclepias) for the Monarchs!
