Threats to Monarchs
Monarch Habitat
The reduction in natural stands of milkweed is the primary cause
of the decline in populations of Monarch butterflies. Milkweed commonly grows in large open fields, in and around farmland. The increase in housing & commercial developments clear milkweed
habitats overnight.
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Simply, reduce the food supply - reduce the number of Monarch caterpillars able to reach adulthood.
Source: Bing
Source: Bing
Herbicides & Pesticides
Herbicides used by farmers permanently eliminate milkweed and noxious weeds commonly seen around perimeter fences. Reduction of milkweed plants not only reduce food for caterpillars but eliminate the potential for female Monarchs to lay eggs.
Pesticides are not selective. Pesticides kill pollinators in their attempt to eliminate locust, grasshoppers and other destructive crop insects. Milkweed has little value to farmers to ever want to develop a herbicide to spare a plant that has potential cardiac effects on livestock.
Climate Change
Climate change has an impact on both the Monarch butterfly and its food supply. Temperature increases can change the growth cycle of milkweed. It can extend the growing season and therefore potentially delay migration. Climate change is associated with amplified warm and cold weather events. Severe weather events in overwintering mountainous regions of Mexico have wiped out tens of thousands of Monarchs in past winters.
Unseasonable warming in overwintering regions can trigger a premature migration resulting in Monarchs arriving back in the southeast U.S. before nectar and milkweed is available and where late winter storms can threaten generations of Monarchs returning north.
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