After rising surprisingly last year, Monarch butterfly numbers appear to be down once again this year, a trend that has seen declining numbers of the colorful creature over the past decade, says a Texas A&M University expert.
Craig Wilson, a senior research associate in the Center for Mathematics and Science Education (CMSE) and longtime butterfly enthusiast, says early figures show fewer Monarch numbers for 2016-17. Last year, about 100 million Monarchs were estimated – almost double the amount from the previous year — in their breeding grounds in Mexico, but this year it appears another decline is likely.
“Their breeding grounds were hit by late winter storms that blew down trees and damaged their habitat severely, enough to kill many millions of them,” he explains.
“That means fewer made it to the breeding grounds last year and so fewer made it to Mexico in the fall of 2016.”
Monarchs have had a rough time of it in recent years.
Wilson says their numbers are less than one-tenth of what they were in 1996, when it was estimated that 1 billion Monarchs would be present. A low point occurred in 2013-14 when only 34 million Monarchs were estimated.
Wilson says that Monarchs overwinter and breed in Mexico and then have three more generations as they travel north to Canada.
“Texas is a crucial place for them – they have to pass through the state on their way north in the spring and lay eggs,” he points out.
It is critical that Monarchs have access to milkweed, the only type of plant that Monarch caterpillars will digest as the multiple generational migration heads north.
But declining milkweed habitat linked to the increase of herbicide-resistant crops, very dry conditions over much of Texas and numerous wildfires have hampered their 2,000-mile journey to Canada in recent years. A study from the U.S. Fish and Wildlife Service says that about 900 million Monarchs have vanished since 1990.
Wilson says more milkweed is needed for the Monarch’s long-term survival.
“There are still plenty of reasons to be concerned, mainly because the number of milkweed plants – the one plant that is vital to their existence – has been decreasing in the past decade,” he notes. “There are new programs to establish milkweed planting, and the public is urged to become involved and to plant milkweed. The Monarch’s miraculous migration depends on it.
“The mayors of numerous Texas, cities like College Station and Bryan, have committed to the Mayors’ Monarch pledge to plant Monarch friendly habitats within city limits with milkweeds to feed the nascent caterpillars. They are supporting efforts to help Monarchs along with citizen scientists.”
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