Flight of the monarchs decreases in a changing climate
BY Sarah smith
The future of monarch butterflies is uncertain, says Nevis butterfly expert John Weber.
Technically considered not endangered but ”highly protected” under the Endangered Species Act, the butterflies have had boom and bust cycles locally.
“The population has been down the last several years,” he said. “But it did some rebounding this year.”
Weber has been doing an annual butterfly count in the region since 1995.
Nationally, scientists have been questioning whether global climate change is affecting monarch breeding and migrating habitats. Those scientists are wondering if the butterflies are flying further north from the corn and soybean belts as their habitat in Mexico becomes too warm.
“Monarch butterflies go through four stages during one life cycle, and through four generations in one year,” said the Duluth News Tribune recently.
“The four stages of the monarch butterfly life cycle are the egg, the larvae (caterpillar), the pupa (chrysalis), and the adult butterfly. The four generations are actually four different butterflies going through these four stages during one year until it is time to start over again with stage one and generation one.”
Weber said in 2013, after a particularly nasty winter, he counted only 87 monarchs in the spring. He and wife Marlene generally walk 200 miles throughout the region each summer to get an accurate count.
Generally, the first migratory stage occurs in February or March, when Monarchs come out of hibernation to find a mate.
Those butterflies migrate north and east to lay eggs, generally on milkweed plants, by March and April.
Weber said genetically modified organisms and “chemical warfare” have decimated the milkweed crop.
About 60 percent of local monarchs, from the corn/soybean belt, winter in Mexico, Weber said.
Over-wintering in the mountainous regions of central Mexico, has led to a 90 percent drop in the migratory rate of monarchs fluttering south over the last 10-15 years, Weber said he’s read.
In 1996 there were an estimated 1 billion monarchs wintering in Mexico. By 2013-14, that number had decreased radically to around 35 million, he said.
To stem the decline Mexico has strictly regulated logging on trees monarchs like to roost on, a type of fir tree, Weber said. That has been a hardship on the Mexican people, who have had to go without firewood and making wooden trinkets to sell. And it has stalled agricultural operations to feed the populace.
Weber said the government has given people financial incentives not to harvest fir trees in the winter habitat area. But illegal deforestation continues.
But bigger trees contain more thermal mass, Weber said. Daylight sun warms the trees, which then release warmth at night to keep butterflies warm.
The average lifespan of a monarch is around one month, unless they migrate, Weber said. Then they can live up to six to eight months “loafing around,” taking life easy.
Ice storms and other weather events in America can wipe out a population of monarchs, Weber believes.
The disappearance of the milkweed crop directly impacts monarchs. It’s the number one nectar source for lots of butterflies and bees.
“They are at the mercy of weather and the climate,” Weber said.
In 1996 he recorded the coldest temp in the region, 55 below. Because 2014 got off to a slow start, his current count is not finalized, he said. It took a while last spring for plants to emerge. But ironically, it was the Webers’ second best count season.
“Climate change is happening faster than scientists initially thought,” Weber said.
The early generation of monarchs lays eggs for the second generation, and so on, usually through the four generations every year.
The fourth generation of monarchs doesn’t fit the mold of its predecessors.
Born in September and October, this is the generation that migrates; thus, the longer lifespan.
Then the cycle starts over again.
Planting milkweed or not destroying it in your yard is a start toward preservation, Weber suggests.