Maryland Coastal Bays

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Monarch Butterfly Decline - May 7, 2017

 Monarch Butterfly Decline 

The monarch butterfly is one of the most recognizable and beloved North American butterflies, not just for its beautiful coloration, but for its spectacular migration to Mexico and California each fall. Over the past two decades, monarch butterfly populations have dwindled by about 80 percent. That statistic is more than just alarming; it is downright frightening. This iconic insect, with orange and black wings covered with little white dots, has always been a mainstay for schools to use to study migration, life cycles, and more. It is almost inconceivable that these amazing insects may soon be a thing of the past.

The Xerces Society for Invertebrate Conservation, an international non-profit dedicated to protecting invertebrates and the habitats they depend on, says that the monarch population has declined for numerous reasons. Logging and land development of the monarchs’ winter habitat in Mexico and southern California has had a major impact on reducing their numbers. The monarchs can migrate from as far north as Canada and over-winter in just a few acres of trees in the mountains of Mexico or on the California Coast, depending on whether they migrated from east or west of the Rocky Mountains. When the monarchs do arrive at their over-wintering locations, they cluster together tightly in trees and hibernate before mating and traveling back north. If these important winter habitats are lost due to logging or development, then the butterflies can be displaced, creating a snowball effect on the local ecosystem that depends on the migration of these butterflies.

Climate change is another major problem for these relatively small and lightweight insects. Global climate change means more severe weather, like droughts, heat waves, and cold snaps, which put severe stress on the monarchs. Climate change could also lead to a change in temperature ranges and other environmental conditions which could potentially alter the monarchs’ winter and summer habitats to unsuitable areas. 

Monarchs rely on a large population to help ensure the species’ continued survival. Bird and mammalian predators can eat nearly half of the over-wintering populations in Mexico and California, and large storm events can wipe out millions of these butterflies at a time. In 2002, a winter storm alone killed nearly 500 million monarchs, roughly fourteen times the size of the current North American population.

According to the Xerces Society, the widespread planting of genetically engineered crops in the U.S. Midwest, a summer breeding hotspot for the monarch, is one of the biggest contributors to the population decline. Genetically engineered crops, while beneficial in many ways, are also designed to be herbicide-resistant. This has led to a dramatic surge in the widespread use of certain herbicides on genetically engendered crops. The monarch caterpillar is renowned for only eating milkweed; the caterpillar adopts the poisonous nature of the plant it consumes the milkweed and begins its transformation into its butterfly stage. Glyphosate-based herbicides have no effect on the genetically engineered crops but kill surrounding weeds, including milkweed. According to some estimates, nearly 165 million acres of monarch habitat have already been lost in the Midwest alone, nearly a third of the butterflies’ summer breeding area.

In the past, milkweed was seen as a nuisance plant and, because it is not overly attractive, was not heavily planted in gardens. The weeding out of milkweed plants from home gardens and farms, and the removal of native milkweed habitat for infrastructure like roads and buildings, caused this important plant species to dwindle in population. There are several ways in which you can help restore monarch populations! Planting the monarchs’ host plant milkweed (of which there are 115 species in North America and the Caribbean) in your garden is a wonderful start. In the eastern U.S. the most commonly used larval food source is the broadly distributed common milkweed (Asclepias syriaca). Another way to assist monarch butterflies is to plant native, fall flowering plants so that when the final generation of butterflies is preparing to migrate, they have many sources of nectar. They store this nectar not just for their migration, but also to use while hibernating. The milkweed habitat decline is one of the most pressing threats facing monarchs today and although these steps will not solve all the dangers they are facing, every little bit counts!

To help in the recovery of milkweed habitat for monarchs, the Maryland Coastal Bays Program is distributing free common milkweed plants. If you are interested in creating a monarch habitat, contact Katherine at (410) 213-2297 ext. 109, kphillips@mdcoastalbays.org or stop by our office at 8219 Stephen Decatur Highway Berlin, MD. Office hours are Monday through Friday, 9:00 AM to 5:00 PM. Quantities are limited.

Rice is the Chesapeake Conservation Corps Volunteer with the Maryland Coastal Bays Program and Jackson is the former Education Coordinator.



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