Monarch butterflies are said to be a thermometer of climate change in North America. Each year, between November and March, monarch butterflies migrate thousands of miles from the United States and Canada, and over-winter in Mexico. There, they densely cover the trees in the Monarch Butterfly Biosphere Reserve and are a major tourist attraction. But that may be changing, along with our climate.
According to Mexico’s annual report on monarch populations, which was just released, the number of hectares occupied by the butterflies in the 2012-2013 season dropped by fifty-nine percent compared to the year before. The area occupied, and its density, is used as an indication of the size of the population. At barely 1.19 hectares (2.94 acres) occupied, this year’s was the smallest monarch population in almost two decades.
The report says that the probable causes for the decline in butterflies during the migration and hibernation are the reduction in milkweed availability in feeding and reproduction sites throughout the United States and Canada, and extreme weather events affecting the reproductive generations in the United States during spring and summer 2012.
Butterflies are not just lovely harbingers of Spring; they are important to our food supply. Along with hummingbirds and bees (which are facing their own population declines, probably due to disease and pesticide use), butterflies are part of a large group of species known as “pollinators.” Their role of pollinating flowering plants, including trees, is critical to humans because an estimated third of our food supply, as well as some of our fibers and medicines, depends on them.
One of the things that we can do to help is to populate our gardens with native plants that attract and feed these pollinators. Here’s an article from Natural Life Magazine that will provide you with assistance as you plan this year’s pollinator-friendly garden. And also check out this informative article about goldenrod; this much-maligned plant is not a weed or an allergen, and it is often the last flower visited by nectar-sipping butterflies before they migrate.