Scientists have been buzzing for years about the dwindling number of bees and linking that to less pollination, but a new Canadian study suggests the decline could also be blamed on climate change.
James Thomson, a scientist with the University of Toronto, has spent 17 years studying the wild lily from his log cabin in a remote plot of land in Colorado's Rocky Mountains. He's discovered that the flowers have been blooming earlier.
"Everyone tends to jump to the conclusion that if my lilies are having a decline in their pollination rate, it must be that the bee populations are dying off, but … I'm not at all sure that that's happening," said Prof. Thomson.
"The plants are now blooming earlier than they used to and I don't think the bees are very active in the early spring," he explained.
He has called the discovery a "climate-driven" mismatch between when flowers bloom and when bees emerge from hibernation.
Prof. Thomson said he studied the flowers on a piece of "pristine" land that is free from pesticides, agriculture and human disturbances, but still subject to climate change.
Three times each year, Prof. Thomson would walk through the meadow full of glacier lilies, and would compare the fruiting rate - when the flower begins to produce seeds and fruit - between a control group of lilies and lilies he pollinated himself by hand.
Over the years, Prof. Thomson said he discovered an increasing difference between the two groups.
"Early in the year, when bumblebee queens are still hibernating, the fruiting rates are especially low," Prof. Thomson said.
"The bees tend to be doing less and less pollination."
For several years, researchers have worried about the fate of bee populations, and warned about the consequences of declining pollinators, saying the world's plants rely on pollinators for fertilization and reproduction.
Prof. Thomson said his findings show the consequences for flowers in his study could range from mild to severe, because if the flowers fail to set fruit or make fewer seeds, the plant will have a reduced reproductive output and this could lead to the extinction of the plant.
While his study doesn't show a decline in bumblebees, Prof. Thomson acknowledged some places in North America and Europe do have dwindling populations.
"In North America, there have been drastic declines in one subgenus of short-tongued bees," Prof. Thomson said.
He also added his study has nothing to do with the decline of the honeybee population, because the location where he was researching does not have those bees.
But Prof. Thomson said while others have speculated on climate's effect on pollination, he is the first to produce "long-term evidence of a downward trend."
"I'm closer to a smoking gun than anybody else," Prof. Thomson said.
Thomson's study was published in the Philosophical Transactions of the Royal Society B: Biological Sciences on Monday.