The decline in breeding areas of monarch butterflies in the United States is the main cause of their recent decline in eastern North America, according to research from the University of Guelph.
The study demonstrates that industrial farming has contributed to the decline of milkweed, the sole plant by which monarch larvae feed and on which butterflies lay their eggs, in a proportion of 21% between 1995 and 2013.
According to the researchers, the lower abundance of milkweed can cause a multitude of problems in monarchs, affecting larval growth until eggs are laid.
“Reducing the negative effects of the milkweed’s disappearance in the breeding areas of the monarch should be the number one priority for the conservation of the species and to slow or stop the decline of the species in the eastern part of the country, North America. Planting milkweed in the south and center of the United States would have an important immediate effect, “said Tyler Flockhart and Ryan Norris, two of the researchers.
The two researchers are the first to arrive at such conclusions. The most widely accepted assumption is that climate change and deforestation in Mexico in the monarch migration areas was the greatest threat to the species.
This hypothesis has led to several presidential decrees in Mexico to protect the butterfly migration area and prevent illegal deforestation.
Despite their results, the researchers consider that these Mexican government decisions were the right ones. “Protecting butterfly migration areas has undoubtedly helped protect monarchs. However, our results now show that a new danger threatens them, “says Tyler Flockhart.
The study was published in the Journal of Animal Ecology .
Did you know?
The entire monarch population of eastern North America migrates each winter to about 12 wintering areas in central Mexico, where they remain relatively inactive. When colonies migrate north again in March and early April, females stop in the United States where they lay eggs on milkweed plants. It is then the descendants of this new generation of monarch who continue the migration to the north.
Erin VanDyke lives on her family farm and has more than 35 years of hands-on experience with the use of livestock guard dogs for predator control. On their farm, Jan and her family use corgis as herding dogs and have raised Shetland sheep, Fainting goats, Morgan and Trakehner horses, and historic breeds of chickens and turkeys. Erin is also an active beekeeper.