Climate change may be preventing bees from carrying out the vital job of pollination by upsetting their life cycles, a study has shown.

Flowering times of mountain lilies in the US appear to be out of synch with their bumble bee pollinators, evidence suggests.

As a result, fewer of the plants are being pollinated and bearing fruit.

The findings point to a phenomenon that may only be local, or could be globally widespread.

Reports of declining populations of bees and other flower-visiting creatures have raised concerns about pollination levels.

There are major implications for farming and food supplies: A third of the world’s fruits and vegetables would not exist without the help of bees and other pollinators.

The new research provides early evidence that climate change may be playing a role in driving down pollination.

“Bee numbers may have declined at our research site, but we suspect that a climate-driven mismatch between the times when flowers open and when bees emerge from hibernation is a more important factor,” said biologist James Thomson, from the University of Toronto in Canada.

Prof. Thomson conducted a 17-year pollination study of the glacier lily, Erythronium grandiflorum, in the Rocky Mountains of Colorado – one of the longest investigations of its kind ever conducted.

He found a progressive decline in pollination over the years which was most pronounced early in the flowering season.

Three times a year Prof. Thomson compared the fruiting rate of flowers that were left to be pollinated naturally, or given extra doses of pollen by hand.

“Early in the year, when bumble bee queens are still hibernating, the fruiting rates are especially low,” he said.

“This is sobering because it suggests that pollination is vulnerable even in a relatively pristine environment that is free of pesticides and human disturbance but still subject to climate change.”