What's happening is so noticeable that scientists can track it from space. Satellites measuring when land turns green found that spring "green up" is arriving eight hours earlier every year on average since 1982 north of the Mason-Dixon line. (Related: "Warming Sign? Another Early Spring for Rocky Mountains" [April 9, 2007].)
The federal government and some university scientists are so alarmed by the changes that last fall they created a National Phenology Network at the U.S. Geological Survey to monitor these changes.
The idea, said biologist and network director Jake Weltzin, is "to better understand the changes, and more important—what do they mean? How does it affect humankind?"
Animals at Risk
There are winners, losers, and lots of unknowns when global warming messes with natural timing.
People may appreciate smaller heating bills from shorter winters, a longer growing season, and maybe even better tasting wines from some early grape harvests. But biologists also foresee big problems.
While some plants and animals use the amount of sunlight to figure out when it is spring, others base it on heat building in their tissues, much like a roasting turkey with a pop-up thermometer. Around the world, those internal thermometers are going to "pop" earlier than they once did.
The changes could push some species to extinction. That's because certain plants and animals are dependent on each other for food and shelter. If the plants bloom or bear fruit before animals return or surface from hibernation, the critters could starve. And plants that bud too early can be devastated by a late freeze.
The young of tree swallows—which in upstate New York are laying eggs nine days earlier than in the 1960s—often starve in those last gasp cold snaps because insects stop flying in the cold, ornithologists said.
University of Maryland biology professor David Inouye noticed an unusually early February robin in his neighborhood this year and noted, "sometimes the early bird is the one that's killed by the winter storm."
The checkerspot butterfly disappeared from Stanford's Jasper Ridge preserve because shifts in rainfall patterns changed the timing of plants on which it develops. When the plant dries out too early, the caterpillars die, said Notre Dame biology professor Jessica Hellmann.
"It's an early warning sign in that it's an additional onslaught that a lot of our threatened species can't handle," Hellmann said.
It's not easy on some people either. A controlled federal field study shows that warmer temperatures and increased atmospheric carbon dioxide cause earlier, longer, and stronger allergy seasons.
"For wind-pollinated plants, it's probably the strongest signal we have yet of climate change," said University of Massachusetts professor of aerobiology Christine Rogers. "It's a huge health impact. Seventeen percent of the American population is allergic to pollen."
This past winter's weather could send a mixed message. Globally, it was the coolest December through February since 2001 and a year of heavy snowfall. (See a photo gallery of some of the unusual winter weather.)
Despite that, it was still warmer than average for the 20th century.
Unlike sea ice in the Arctic, which recently has shown record ice losses, the way climate change is tinkering with the natural timing of day-to-day life is concrete and local. People can experience it with all five senses.
You can see the trees and bushes blooming earlier. A photo of Lowell Cemetery, in Lowell, Massachusetts, taken May 30, 1868, shows bare limbs. But the same scene photographed May 30, 2005, by Boston University biology professor Richard Primack shows them in full spring greenery.
You can smell the lilacs and honeysuckle. In the U.S. West, they are coming out two to four days earlier each decade over more than half a century, according to a 2001 study.
You can hear it in the birds. Scientists in Gothic, Colorado, have watched the first robin of spring arrive earlier each year in that mountain ghost town, marching forward from April 9 in 1981 to March 14 last year. This year, heavy snows may keep the birds away until April.
You can feel it in your nose from increased allergies. Spring airborne pollen is being released about 20 hours earlier every year, according to a Swiss study that looked at common allergies since 1979.
You can even taste it in the honey. Bees, which sample many plants, are producing their peak amount of honey weeks earlier. The nectar is coming from different plants now, which means noticeably different honey—at least in Highland, Maryland, where Wayne Esaias has been monitoring honey production since 1992. Instead of the rich, red, earthy tulip poplar honey that used to be prevalent, bees are producing lighter, fruitier black locust honey. Esaias, a NASA oceanographer as well as beekeeper, says global warming is a factor.
In D.C., seven of the past 20 Cherry Blossom Festivals have started after peak bloom. This year will be close, the National Park Service predicts.
Last year, Knoxville's dogwood blooms came and went before the city's dogwood festival started. Boston's Arnold Arboretum permanently rescheduled Lilac Sunday to a May date eight days earlier than it once was.
Even western wildfires have a timing connection to global warming and are coming earlier. An early spring generally means the plants that fuel fires are drier, producing nastier fire seasons, said University of Arizona geology professor Steve Yool.
It's such a good correlation that Weltzin, the phenology network director, is talking about using real-time lilac data to predict upcoming fire seasons. Lilacs, which are found in most parts of the country, offer some of the broadest climate overview data going back to the 1950s.
This year, though, it's the early red maple that's creating buzz, as well as sniffles.
A New Jersey conservationist posted an urgent message on a biology listserv on February 1 about the early blooming. A 2001 study found that since 1970, that tree is blossoming on average at least 19 days earlier in Washington, D.C.
Such changes have "implications for the animals that are dependent on this plant," Weltzin said, as he stood beneath a blooming red maple in late February.
By the time the animals arrive, "the flowers may already be done for the year." The animals may have to find a new food source.
"It's all a part of life," Weltzin said. "Timing is everything."
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