SUMMERVILLE — The few milkweed plants are yellowed and wilting. And still no monarch butterfly eggs.
It’s as disturbing a circumstance as Natalie Tarpein has confronted in teaching her ninth-grade science class at Ashley Ridge High School. Growing the gorgeous orange monarchs in a net hanging from the back of her room is a class project and one of those “wow” moments for students.
Last year the class raised 20 caterpillars and released them as butterflies. This year there are simply no eggs on the plants in the school’s horticulture garden.
What’s happening at the school is a stark example of what’s being reported across the country. The number of migrating monarchs is way down so far.
The fear is that the declining species might be about to disappear.
Monarch butterflies are the spectacular “king” of insects. Each fall, flocks make a near-mythic migration from across North America to Mexico and Caribbean islands.
The awe-provoking aspect of the trip is that the butterflies migrating this year aren’t the ones who made it last year; they are descendants. Butterflies don’t live for more than a few months.
Lowcountry beaches are the heart of one of the eastern flyways, and at the peak of the migration, thousands of the butterflies at a time might be sipping nectar across a single barrier island.
On a good year. This year, “monarchs have been few and far between,” said naturalist Bill McCord, of James Island, who has tracked and tagged the insects for nearly 20 years.
Partly, it’s just been the weather. Monarchs migrate in waves on the back side of cold fronts. The recent cold snap is the first to start moving them south; their entire life cycle is keyed to weather changes, and a freakish year of variations apparently is taking its toll.
But there are bigger problems. Monarchs are losing their winter sanctuaries to agriculture. The butterfly lays eggs on milkweed and the caterpillars eat it. The plant is toxic, or poison, to most other creatures, including man. So is the butterfly that develops, and that protects it against predators.
But milkweed is a noxious plant, a weed. And a new generation of widely used crop and garden sprays is wiping it out.
Last year’s population of monarchs wintering in Mexico was the smallest since researchers began studying it in 1975, according to MonarchWatch.org, and the population has been trending steadily down over those two decades. With the steep drop-off in migrating numbers, this year isn’t looking any better.
McCord isn’t giving up yet, he said. In 2011, much like this year, he had seen and tagged few of the butterflies until they showed up en masse the first week of November. He ended up with his best year of tags, 3,500. Taggers in the Delaware Bay area last week said they were beginning to see more monarchs.
But the numbers reported aren’t good — not along the Delaware Bay, in the Appalachians or the Midwest, where the decline is considered precipitous.
“It’s unsettling,” McCord said.
As lessons go, the withering milkweed is a hard one for Tarpein’s science class.
“The weather’s changing,” said student Shawn Blue.
“It’s too late,” said student Kassandra Gonzalez.
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