A climate change-related phenomenon dubbed "global-stilling" could influence the predator-prey balance.
The Asian lady beetle, which is a natural predator of the soybean aphid, is challenged by winds that sway and bend the greenery hosting the prey. If this wind is stilled, that challenge would be significantly reduced, allowing the predators to munch away, the University of Wisconsin-Madison reported.
"There are all sorts of other things that are changing in the environment that affect animals and plants and their interactions," Brandon Barton, a UW-Madison postdoctoral researcher, said. "My students and I were standing out in a cornfield one day as big gusts of wind came by, and the corn stalks were bending almost double. From the perspective of an animal living in the corn, we thought, 'That's got to have a big effect.'"
Wind speeds in the U.S. Midwest are expected to decline by 15 percent over the 21st century. The Earth's poles are believed to be warming faster than the equator, which is interfering with temperature differentiations that drive winds. Humans have also been putting up wind barriers such as buildings and more natural structures.
"In North America, we've been replanting trees that were lost in the 1800s, after settlers showed up and just leveled places like New England," Barton said.
To make the findings Barton planted plots of soybeans in alfalfa fields, protecting some patches from the wind and leaving others exposed. He found two-thirds more lady beetles in the plots that were sheltered from the wind and twice as many soybean aphids in those that were not.
Wind did not appear to have an effect on the presence of the aphids, which can strongly anchor themselves to the plants as they feed.
"The aphids appear on the plants whether it's windy or not, and we showed that in lab experiments," Barton said. "But when you add the predators, with the wind block, the beetles eat something like twice as many aphids."
In a lab experiment the researchers simulated the wind with fans and machines that tugged the plants to shake and bend them.
"How do you do your duty as a predator if your entire world is moving around?" Barton said. "If the plant is moving, it takes four times as long for the predator to start eating, and it eats less than half as many aphids in an hour."
The findings suggest slower natural wind speeds could reduce the need for pesticides to wipe out crop-harming aphids.
The research was funded by the National Science Foundation and was published in the Sept. issue of the journal Ecology.
