Climate change putting bees and plants out of synchronization


Research published in the journal Ecology Letters on Wednesday delves into nine years of bee observations collected by the Rocky Mountain Biological Laboratory, based in Crested Butte, Colorado, to understand the ecological variables driving each stage of the honey-makers’ life cycle.

“Elevation played a large role in when bees start foraging, as well as the bees’ functional traits, such as whether bees nested below or above ground, and the life stage in which they overwintered,” Michael Stemkovski, an ecologist at Utah State University, explained in a statement. “We found all of these factors predicted bee emergence, but the most important factor was snowmelt timing.”

Stemkovski is one of 11 researchers from across the U.S. and Canada who contributed to the study of 23,742 individual bees, representing 67 species captured in colored pan traps at 18 sites throughout the Elk Mountains of western Colorado. Elevation among the sites ranged from 2,456 to 3,438 meters above sea level.

“We find bee emergence timing is advancing with snowmelt timing, but bee phenology — timing of emergence, peak abundance and senescence—is less sensitive than flower phenology,” North Carolina State University applied ecology professor Rebecca Irwin said in a statement. “Given global concerns about pollinator declines, the research provides important insight into the potential for reduced synchrony between flowers and their pollinators under climate change.”

Like flowers, bees appear to be most influenced by snowmelt, using it as a cue to emerge from their winter state. While snow once fell in November and melted in May, in recent years the snow has begun melting sooner and falling later.

Based on 39 years of flower observations from the Rocky Mountain Biological Laboratory, researchers estimate that first flowering occurred about .8 days earlier for every day the snowmelt comes early.

Bees, however, are emerging from overwintering at a slightly slower rate. For every early day of snowmelt, bees emerge only about .49 days early.

The timing of bees in peak foraging also shifted by around 0.49 days, and senescence by some 0.28 days earlier for every advanced day of snowmelt.

“Thus, bee phenophases are potentially less sensitive than flowering phenophases to shifts in snowmelt timing, with bee emergence advancing at 55% the rate of first flowering, and bee peak advancing at 67% and 93% the rate of the two flower peaks,” researchers explain in the paper.

Given enough time, the pollinators and the pollen-producers may sync back into a common rhythm, but researchers worry that given the rapid onset of climate change, many bee species won’t have time to adapt.

If the cycles of bees and flowers fall too out of whack, researchers say an important symbiotic relationship will be lost, one from which both actors had benefited.

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