By: Nick Engelfried
A recently completed study by University of Toronto scientist James Thomson suggests global warming is interfering with the natural pollination of flowering plant species in at least some parts of the world. Thomson, who has spent nearly two decades studying pollination of the glacier lily in Colorado, says pollination levels are declining as the lilies begin to bloom earlier in the year in response to warmer spring temperatures.
Because the bumblebees mainly responsible for pollinating glacier lilies have not yet emerged from their winter hibernation, early-blooming lily blossoms are more likely to go un-pollinated. Lily flowers that aren’t pollinated cannot form seeds, and so are unable to reproduce.
Thomson’s study, published in the peer-reviewed science journal Transactions of the Royal Society B: Biological Sciences, necessarily focuses on a single plant species and its insect pollinators. However the implications for flowering plants everywhere are much broader, as many other species could turn out to respond to global warming in a similar manner to the glacier lily. The news is grim for food production in the US and other countries. Globally, one third of all fruits and vegetables grown for food rely on pollinators like bees to reproduce.
News about how global warming will affect insect pollinators also comes at a time when US honey bee populations are already suffering from a mysterious ailment known as colony collapse disorder. Declining honey bee populations mean US crops are increasingly dependent on native pollinator insects, like bumblebees. The idea that natural pollination cycles could be disrupted by global warming at the very time when they’re needed most presents a major challenge for the food business.
Before publishing his study Thomson collected data on the Colorado glacier lily for seventeen years, documenting a trend of decreased pollination over that time span. Because his study site was located far from major urban areas or likely sources of pesticides and pollution, Thomson believes a changing global climate is the main culprit in the decline. The flowers are pollinated mostly by queen bumblebees that have just emerged from hibernation in early spring. But while the lilies have responded to warmer temperatures by blooming earlier in the year, bumblebee hibernation cycles have failed to catch up.
If fruits and vegetables that provide people with food are similarly affected by changing temperatures, continued global warming will have major economic consequences. In 2008, a team of scientists from France and Germany estimated that each year insect pollinators provide the equivalent of US $217 billion in economic services worldwide.
Disruption of pollinator cycles would have serious consequences for food supplies in many countries, the severity of which would depend on how much global temperatures increase. Because human activities have already committed the planet to a certain amount of global warming, the only way to avoid major crop failures may be to rapidly cut back on fossil fuel consumption and minimize the amount of harm that is done.
Photo credit: Dendroica cerulea