In addition, he says, the widespread planting of genetically modified crops has allowed farmers to more effectively kill milkweed, the plant that monarchs need as caterpillars.
In March, conservation groups reported the smallest overwintering population of monarchs since their colonies were discovered in Mexico by scientists in 1975.
Taylor said he has so far persuaded about 7,000 gardeners to establish “waystations” for the monarchs. But with the loss of almost 200 million acres of monarch habitat over the past 20 years, he would like to see 7 million gardeners come to their rescue.
Mace Vaughan, pollinator program director for the
, a conservation group based in Portland, Ore., agrees. “To me that’s the core of pollinator conservation. If we tie enough [gardens] together, we can have a significant benefit.”
Providing nectar plants for monarchs, of course, will help other butterfly species. Other pollinators — notably honeybees and bumblebees — are facing problems of their own. Here, too, the gardener can make a difference by installing plants rich in nectar and pollen and by using pesticides carefully, if at all.
Sharon Metcalf lives in a cul-de-sac of townhouses in Bethesda, backing up to a grassy hillside and public woodland. She decided she would come to the aid of the monarch after watching the Imax film, “Flight of the Butterflies,” at the Smithsonian’s National Museum of Natural History.
She planted a bank of swamp milkweed across the hillside and then converted her little patch of lawn, adding nectar-rich perennials to some existing shrubs and planting additional milkweed among them.
She says the adult butterfly can detect milkweed plants from as far as a mile away. The butterfly lays eggs on the leaves, which hatch into hungry worms. Chemicals in the leaf make the caterpillars and adults distasteful to birds, and the striking markings of the caterpillar and the butterfly signal the fact.
“I was noticing fewer hummingbirds. I was getting turtles at some point, but they seemed to be disappearing. I was noticing in the lights at night fewer and fewer insects,” she said. “I realized if I wanted to create a healthier ecosystem, a good visible place to start is with monarchs, particularly because of their decline.”