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Slower Wind Speeds Spell Rapid Environmental Change

by
Scope Correspondent

Winds of change are coming, and they’re bringing poised to upend entire ecosystems. Over the last 30 years, average surface wind speeds over areas in Europe, Central Asia, Eastern Asia and North America have slowed by about 10 percent. The potential effects of “global stilling” could affect land, air and aquatic systems worldwide.

New research published in Ecology illuminates what, exactly, global stilling could mean for the hunters and hunted of the insect world. For predators, stilling winds make it easier to chow down, says Brandon Barton, the University of Wisconsin-Madison postdoc researcher who authored the study.

“If you’re trying to sit down and have dinner and the table was shaking all over the place, it would be kind of hard to cut your food and eat it,” he says. “But if your table is still, it’s much easier to eat your food.”

The Asian lady beetles in the experiment felt the same way. When placed on plants that were packed with tasty soybean aphids, lady beetle larvae ate fewer aphids and took five times as long to find food if the plant was moving. The results could show that slower winds make natural predators like the Asian lady beetle a better weapon in the fight against crop pests, says Barton.

“It is possible that slowing winds will increase the effectiveness of biological control and therefore fewer pesticides could be used,” he says. Though he cautions that “the only evidence is this one study” and it doesn’t address whether farmers would actually reduce pesticide use or not.

Decreased wind speeds could impact everything from pollination to precipitation patterns, Barton says. For example, a theoretical study of the effects of wind on seed dispersal published in Global Change Biology found that stilling could significantly limit the dispersal of plant seeds that require high wind speeds.

“We found nearly a 100-fold reduction in that upper limit of how fast those plant populations could move under the most dramatic stilling scenarios that we considered, more of about a 50 percent decline for the near term and slightly less dramatic stilling scenarios,” says Sally E. Thompson, lead author on the study and assistant professor of surface hydrology at the University of California, Berkeley. “…This was a really dramatic change. It suggested that for some plants—plants that really hang on to their seeds quite hard and don’t necessarily disperse them very far—that global stilling could almost be enough to really inhibit the ability of the plant populations to migrate at all.”

Despite these findings, global stilling remains controversial among scientists, Thompson says, in part because it’s tough to determine whether slower wind speeds are an anomaly or global trend.

“Our ability to measure what’s called the near surface wind speeds‚—so the speeds that are really quite close to the ground—is really dependent on having measuring stations in place,” she says. “That’s not happening in a nice sort of spatial way. It’s happening wherever there happens to be a weather station in the ground, so we just get these isolated points where we can see what the wind speed is doing.”

Where slowing speeds have been detected, it’s also difficult to isolate a cause. While some argue that the bulk of stilling can be chalked up to changes in land surface—more buildings, for example, mean slower surface winds—others link it to global warming.

“One of the drivers of global winds is equator-to-pole difference in temperature…,” says Thomas C. Peterson, principal scientist with the National Oceanic and Atmospheric Administration’s National Climatic Data Center. “…As the Arctic warms faster than the tropics, you decrease this pole-equator temperature gradient, which then the theory goes, that then decreases the wind speed in things like the jet stream.” Though Peterson adds that he hasn’t “read a thorough analysis that proves this is currently the case.”

The Asian lady beetle experiment is just one small example of how delicate ecosystems can change with stilling winds. We’ll need further research, in a wide variety of areas, to understand the full impact of slower wind speeds, Dr. Barton says. “I think maybe we’re only scratching the surface at the ways that changing wind will affect our future environment.”

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