"I was a graduate student studying hummingbirds and bumble bees, and I wanted to know what flower nectar resources are available for them, so I started counting flowers," Inouye said.
Others initially took part, but Inouye stuck with it. Eventually he set his own students to the task. By counting blooms in each of 30 plots every other day, up to five months per year, for four decades, the group amassed a data set of more than 2 million flowers they have counted. For this study, University of Arizona doctoral student Paul CaraDonna, University of Maryland postdoctoral research associate Amy Iler and Inouye looked at data on the 60 most common species.
Bloom times are changing fast, the researchers found. The date the first spring flower appears has advanced more than 6 days per decade over the course of the study. The spring peak, when masses of wildflowers burst into bloom, has moved up 5 days per decade. And the last flower of fall occurred about 3 days later every decade.
"The flowering season is about one month longer than it used to be" Iler said, "which is a big change for a mountain ecosystem with a short growing season."
Of all the species that have changed their flowering schedules in some way, only 17% shifted their entire bloom cycle earlier. The rest showed more complicated changes.
"What we show is that first flowering isn't always the best predictor of all the changes we find," CaraDonna said. "It's important to take a closer look in order to understand all the ways that climate change affects these wildflower communities."
The changes are likely to have a strong impact for better or worse on pollinating insects and migratory birds. For example, Inouye said, hummingbirds that summer in
|Contact: Heather Dewar|
University of Maryland