Plants’ earlier bloom times hurting some creatures
By Brigid Schulte,
Cristol Fleming has gone out hunting for the first wildflower blooms of spring for close to four decades. She knows where every tiny bluish clump of rare phacelia can be found, where every fragile yellow trout lily grows.
And in the definitive guide she co-authored on finding Washington area wildflowers, she writes that mid- to late April is the best time to see the forests and riverbanks carpeted with a riot of these delicate blooms.
So it was with some consternation that the local field botanist found two of her favorite early flowers — sprigs of white and purple “harbinger of spring” no higher than an inch and graceful white twinleaf — in full bloom in the chill of late March.
Fleming was expecting to see some “spring beauty,” one of the earliest bloomers of the area, and perhaps a few of the weedier species. But she found, among others, “Dutchman’s breeches,” the funny little white flower that looks like long underwear hanging upside down, and cut-leaved toothwort.
“I was surprised to see that,” she said. “That’s something I would have expected two weeks later.”
Bloom hunters like Fleming, who for 40 years have been tramping through the woods, roaming along riverbanks and scrambling over rocky outcrops to document the first blooms of spring in the Washington area, worry that what they have been seeing is nothing less than the slow, inexorable shift of global warming.
They even have a name for it: season creep. And it’s happening all over the world.
For 1,000 years, the Koreans have recorded the first cherry blossoms of spring, so central is that flower to their cultural identity. For 300 years, Europeans have meticulously tracked when grapevines bloom to time planting and harvest. On both continents, botanists are finding earlier and earlier blooming.
In Washington, chronicling blooms began as sort of a rite of spring for botanists and amateur flower lovers eager to see the first signs of life after a long, barren winter. Initially, they wrote down their findings for more than 600 species in an enormous log book at the Smithsonian Institution’s National Herbarium year after year.
But over time, they began to notice the native blooms coming earlier and earlier. In a 2005 analysis of 100 of the most popular flowers they hunted, Smithsonian botanists found that 90 species bloomed two to 44 days earlier than they had 20 years ago; only 10 species, on average, bloomed later. Even the famous cherry blossoms along the Tidal Basin, they found, were blooming six to nine days earlier than they had in the 1970s.
“There is always variation from year-to-year in nature. And I don’t want to sound alarmist that spring is coming earlier and earlier,” said Fleming, who is in her 70s. “But, boy, every year, we do feel it.”
Botanists poring over the Asian and European blooming records, the Smithsonian log, and the accounts of American observers such as Henry David Thoreau and explorers Meriwether Lewis and William Clark, are finding the same phenomenon.
“When you gather together all the scientific studies that have documented this, we can see that about 80 percent of the species are changing earlier in the spring,” said Jake Weltzin, an ecologist with the U.S. Geological Survey.
Weltzin was in town this week trying to drum up support for the new National Phenology Network that he runs. Its aim is to do for the entire United States what bloom hunters like Fleming have done for the Washington area: track the patterns of season creep and explain why that matters to humans.
It’s already begun to matter for the plant and animal world. Some species in the complex chain of interdependence have been unable to keep up.
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.”