Posted on 09 January 2013 by Richard McGuire
The restoration of wetlands habitat north of Osoyoos will not exacerbate the mosquito problem, say officials with Ducks Unlimited, the organization doing the work.
They were responding to concerns expressed by Osoyoos Mayor Stu Wells, who worries that the area north of Osoyoos Lake with its oxbow lakes could become a breeding ground for mosquitoes carrying the West Nile Virus.
“That is the most notorious mosquito-breeding area in the whole regional district,” said Wells, who notes that water doesn’t flow through the oxbow lakes.
“They are not linked up,” he said. “There’s no flow of water through them. They are exactly what I said they are. They are dugouts.”
The project comes at a time when the province has cut back nearly $300,000 in mosquito abatement funding to the Regional District of Okanagan-Similkameen (RDOS) aimed at controlling West Nile Virus, the mayor says.
Brad Arner, Manager of Conservation Programs with Ducks Unlimited in Kamloops, however, suggests the habitat restoration work his organization is doing will instead reduce mosquito problems.
Ducks Unlimited has dredged oxbow lakes that have filled up with sediment over the years, restoring them to their original courses. They are also planting riparian vegetation that provides habitat to birds, mammals and aquatic species.
“Certainly mosquitoes are always a concern when people hear about wetlands,” said Arner. “Our response back is always that healthy wetlands don’t produce nearly as many mosquitoes as stagnant standing small bodies of water.”
Healthy wetlands, he notes, contain numerous invertebrates that feed on mosquitoes.
While acknowledging the area will still produce some mosquitoes, Arner says the situation is much worse when there are small standing pools of water on land or in barrels.
His colleague, Bruce Harrison, who is overseeing the project for Ducks Unlimited agrees.
“That property may have had some mosquito issues in the past because it was flooded grass, and flooded grass tends to really support mosquitoes well,” said Harrison, BC Head of Conservation Science and Planning for Ducks Unlimited. “When you get these more permanent water bodies, not only does it support a natural predator community that feeds on the mosquitoes, but it also isn’t their ideal breeding ground. They like shallower water than that.”
The official responsible for mosquito abatement in RDOS also confirms that mosquitoes don’t tend to breed in deeper water.
“It depends on the depth of the water,” says Doug French, RDOS Public Works Manager. “If it’s over 18 inches, it’s really not too bad, and if Ducks Unlimited are going to that depth or deeper, then it might not be too bad, but typically the unattended oxbows are bad for mosquitoes and we do treat them.”
French says, however, that the RDOS cannot go onto land to treat for mosquitoes unless the landowner gives permission.
Ducks Unlimited and the Nature Conservancy of Canada, which own different portions of the land in the project, don’t allow RDOS to control mosquitoes on their property except in cases where West Nile Virus is found and provincial legislation requires it.
French says the RDOS was approved by the province for $293,000 in funding in 2011 to control West Nile Virus, however only $276,000 was actually spent.
This is on top of annual spending of $150,000 by the RDOS for nuisance mosquito abatement in general.
The province did not provide the funding in 2012, French says, because West Nile was no longer considered to be a threat. In 2009, West Nile Virus was found in the southern Okanagan near Osoyoos. That year the virus was only found in the tarsalis mosquito, in which the virus was able to incubate because of the warmer weather that year, according to a 2010 study published in Emerging Infectious Diseases by the Atlanta-based Centers for Disease Control and Prevention.
The study notes that mountainous landscape is less conducive to West Nile Virus, but the Okanagan Valley is one of the few non-mountainous areas in southern B.C. Valleys act as paths of least resistance and as a conduit for migrating birds. The South Okanagan also has areas of irrigation clustered with human habitation near rivers and lakes.
Unlike most of B.C., the South Okanagan also has a climate favourable to amplification and transmission of West Nile, the study says.
Harrison of Ducks Unlimited says the project is on 160 acres of land purchased in 2002 and 2004 separately by Ducks Unlimited and the Nature Conservancy of Canada.
The excavation work of opening up the historic oxbows is essentially finished except for some distribution of soil. Some of the planting work will continue in the spring, Harrison adds.
The riparian shrubs will provide cover, nesting and food for birds and amphibians, including endangered species, he says. Additionally, the amphibians need open water, which was reduced over the years as the oxbows filled in, due to creation of a manmade water channel and agriculture on the land.