iSeeChange: Where Have All the Wasps Gone?

Jul 9, 2013

View from behind Maria Hodkin's home. Under the dirt lies the Stewart Ditch, a previously-exposed water source now flowing through an enclosed pipe.
Credit Travis Bubenik, KVNF

For this week’s iSeeChange report, we explore concerns about ditch lining in the area, and whether these manmade environmental changes (much like the ditches themselves) may alter their surroundings.

Last week on the Almanac, Stewart Mesa resident noticed fewer numbers of wasps around her house. She says usually by this time of the summer, her front porch is practically overrun with wasps. But this year they seem to have disappeared. 

"There are very few wasps flying around, and hardly any nests that I can find," says Hodkins. "Usually they're under all our eaves, in the outbuildings and swarming around all the time." 

Hodkins wonders whether that has to do with the ditch that used to flow right behind her property. That open water source fed deer, birds, and her willow trees, but it’s since been covered and now flows through a closed underground pipe. Projects like these, ditch lining as they’re called, are funded by the Bureau of Reclamation, and aim to reduce salt and selenium in water sources throughout the Colorado River Basin.

Sarah Sauter, Director of the Conservation Center in Paonia, says high levels of selenium in water can cause reproductive problems or deformities in fish and aquatic birds, while salt deposits can inhibit plant growth. Ditch-lining projects aim to protect against those threats. 

The state’s been controlling salt levels in the river since 1974, but the Stewart Mesa ditch project showed up in Hodkin’s backyard just last November. So could that vanished water source be keeping wasps away? Hodkins says her experience tells her it might.

"Every time I water the garden or fill the bird bath, the wasps start flying around it," she says. "So I know that that's a factor that they're attracted to." Hodkins admits having fewer wasps around is a relief, but she's worried that since wasps are pollinators, their absence might have farther-reaching effects.

She says her neighbors have noticed the absence of wasps as well. Marilyn Stone owns a house just down the road from Hodkins, also on the Stewart Ditch, and she’s noticed some changes to the Woodhouse Toads that usually pop up around her property this time of year. Namely, they’re smaller.

"Usually when we see them they're probably about an inch long," says Stone. "These are much smaller this year, even though it's later in the year, so something must have delayed them. They're about the size of my fingernail and my little finger, they're really tiny." 

Stone says those young, small toads are usually out much earlier in the summer. Both her and her husband Mike Drake say they’re not sure that ditch lining has anything to do with the later sight of toads. In fact, Drake says since covering up the ditch got rid of what was essentially a canyon in their backyard, they can now make better use of that land. Drake says when he's finished renovating his property where the ditch was, the habitat will actually be better than before.

There are, of course, many other factors that could be affecting wasp populations besides the ditch being gone. Frank Peairs, who studies insects at Colorado State University, said lower wasp numbers this year could be a food chain disruption caused by the drought: wasps feed on smaller insects, ones that rely on plants for food, but dry weather can kill that plant life. So fewer small bugs, fewer wasps.

Wasps may be just some of the wildlife affected by taking away these open water sources. But according to Sarah Sauter, ditch-lining projects have to account for that.  

"When the ditches are being lined, the ditch company is required to mitigate for that habitat loss," says Sauter.

Whatever effect ditch lining may have on wasps, toads or other wildlife, Sauter says its pros outweigh its cons.

"It is going for a much greater good to improve wildlife and fish habitat in the main stem of the river."