-Adapted from Smithsonian Insider
From Plant Press, Vol. 19, No. 3, July 2016.
Unless you’ve been living under a rock for the last few years, you’ve doubtless caught at least a passing reference to the plight of the beleaguered bee. Bees of all types pollinate an estimated 75 percent of our fruit, nut and vegetable crops, and they’ve been suffering population declines in recent years from a variety of suspected sources. These die-offs are a major concern to farmers and hobby beekeepers, as well as anyone who likes to eat.
Bees like food too, but a new study led by the U.S. Department of Agriculture’s Agricultural Research Service has found that recent increases in carbon dioxide emissions over the last several decades have made a key autumnal food source less nutritious than in the past. This adds one more potential factor to the cocktail of stressors making bees vulnerable to attack by pests, pathogens and pesticides.
USDA Agricultural Research Service plant physiologist Lewis Ziska, together with colleagues from Purdue University, Williams College and the Smithsonian, compared the protein content of pollen from historic specimens of Canada goldenrod (Solidago canadensis) from the U.S. National Herbarium collection at the Smithsonian’s National Museum of Natural History with pollen from field trials simulating varying levels of atmospheric carbon dioxide. They found that as CO2 levels increased, the protein content of the pollen decreased. The study was published in the journal Proceedings of the Royal Society B (283: 20160414; 2016).
Goldenrod, which blooms from July through October across most of North America, is one of the most widely available sources of pollen for late-year foraging. Though nectar is the bees’ main food source during the warmer months, bees need the fats, vitamins and minerals from pollen protein to make it through the winter. Because they only store small amounts of it, fluctuations in the amount or quality of the pollen itself can directly affect bee health.