Ecology 89, 353–362 (2008)

Credit: DAVID INOUYE

Early snowmelt in the Rocky Mountains of the US is killing off the region's wildflowers, and scientists say the culprit is climate change. In recent decades, snow has begun to melt earlier in the season, warming the ground and leading to the premature arrival of leaf and flower buds. But the timing of spring frost events has remained fixed, and without the protective blanket of snow, delicate plant parts are left exposed.

David Inouye of the University of Maryland studied the onset of growth and subsequent frost damage to buds in three frost-sensitive species of perennial wildflower that bloom after the winter snowpack melts: subalpine larkspur, Aspen sunflower and Aspen fleabane. He found that an average of 36.1 percent of Aspen sunflower buds were frosted between 1992 and 1998, but that this shot to 73.9 percent in the 1999–2006 period. In only one year since 1998 did all plants escape frost damage.

If, owing to freezing temperatures, plants do not bud or early flowers are killed, the plant population can decline over time, warns the author. This could affect the entire ecosystem, from plant-specific seed-eating fruit flies to large mammals such as deer and elk that munch on wildflower blossoms.