In the case
of the Aspen sunflower (Helianthella quinquenervis), for instance, global
warming has led to smaller snow packs in the mountains, which means earlier
snow melts -- an important cue for wildflower blooms.
Paradoxically, as the Aspen sunflowers are triggered to bloom earlier each
year, it becomes more likely that they will be damaged by exposure to late spring
frost. Inouye's research shows that from 1992 to 1998, such frosts on average killed
about a third of the Aspen sunflower buds in
his plots. Between 1999 and 2006, however, the typical percentage doubled, with
nearly three-quarters of all buds being killed by frost in an average year.
Inouye says he has seen whole fields of this particular flower (shown in the
photograph) decimated by frost. "Given the rate of global warming, we'll see
some wildflower extinctions," he says. "There is little doubt about that."