Lilacs are at their sweet, pungent peak across the Twin Cities and much of southern Minnesota right now, signifying the brief fullness of spring.

But the blossoms that have inspired poets and connected pioneers to both the Old World and the New are being seen in a new light, as tools to help measure climate change.

The National Phenology Network, coordinated by several federal agencies and universities, is trying to enlist lilac-lovers to report the dates their shrubs leaf out, bloom and fade. The aim, said chairman Mark D. Schwartz, a climatologist and geography professor at the University of Wisconsin-Milwaukee, is to gain insight into how a plant with a long history and a hemispheric range is adapting to a warming environment.

"If plants are changing, then insects, and mammals feeding on the insects, have to adapt in response," Schwartz said.

Lilacs are well-suited for study, having been brought to North America from Europe at least as far back as 1652. Today, they frequently mark prairie homesteads they've long outlasted. And as Schwartz and other climatologists see it, they're simply more common than weather stations.

Naturalist Jim Gilbert, an environmental studies instructor at Gustavus Adolphus College in St. Peter, said that in the 40 years he's been tracking the lilacs near his home in Waconia, their peak bloom date has moved up steadily from May 30 to about May 15. This year, that was Friday, when Gilbert noted they were indeed at peak from the Twin Cities to Mankato.

Using other lilac studies in the United States dating to the 1950s, Schwartz has determined that lilac bloom across North America now occurs about five days earlier than it used to.

It's moved slightly faster in Europe, slightly slower in China.

Bill McAuliffe • 612-673-7646