In Europe, the leaves of the English oak are coming out earlier, Weltzin explained, which means the winter moth caterpillar that feeds on them are also coming out earlier. But the pied flycatcher birds that eat those caterpillars are still migrating north at that time, so when they do arrive, the caterpillars have already turned into moths and are gone. That has decimated the bird population in recent years.
Likewise in San Francisco, some populations of the Edith’s Checkerspot butterfly are simply gone. With the gradual warming of Earth and ocean temperatures that have also shifted rainfall patterns, the leaves of the plantago plant come out earlier. The leaves, which the checkerspot caterpillar depends on for food, are already dried and withered by the time the larvae emerge.
And these failures to adapt, or adapt in time, are what worry Cris Fleming.
A search for spring
On a blustery April evening this week, Fleming, bundled up in a blue fleece jacket and warm hat and gloves, joined about a dozen other bloom hunters at the Carderock Recreation Area in Maryland along the Potomac River. For three decades, Fleming taught plant identification for the U.S. Department of Agriculture and led blossom hunting trips for the Smithsonian and the Audubon Naturalist Society. For her, the search for early spring blooms started out as an almost metaphysical pursuit.
“This is something you can count on year after year — the return of spring, the thrill of seeing that life returns, beauty goes on,” she said, poking at the dead brown leaves on the ground with a stick to better see the minuscule white blooms of early saxifrage. “In a world where there’s so much you can’t count on, it’s nice to have something that you can.”
She made her way down a steep, muddy set of stairs leading to the Potomac. The banks were awash in swaths of Virginia bluebells. She trod among delicate yellow buttercups, pungent wild spring onion leaves and the innocent white petals of bloodroot, whose red sap is toxic to people.
She ducked under two trees that have fallen in recent windstorms and came to a rocky slope.
She scanned the rock face for signs of the butterfly-shaped leaves of the twinleaf, Jeffersonia diphylla, named for Thomas Jefferson, that she found in such abundance in late March. She spotted one or two. The rest had already disappeared for the season.
That’s why plants like harbinger of spring and twinleaf are called ephemerals, Fleming explained: The blooms last barely a week. “Neither of them will be here in the next few days,” she sighed.
What if, she worries, these plant life cycles are speeding up, but their insect pollinators’ life cycles are not? And what if the warming Earth changes the habitat?
“Unlike animals, plants can’t just get up and move,” she said. “If they end up in a climate that’s too warm, well, they’ll just die.”
On April 15, Fleming will go on another of her early spring bloom walks along Turkey Run. “But I may already be too late.”