There are no quick fixes to deal with the problems of the invasive plant called parrot’s feather on Somenos Creek and Somenos Lake.
Speaking to North Cowichan’s council on Feb. 6, Dave Priekshot, a consultant for the Somenos Marsh Wildlife Society and Madrone Environmental Services, said the problem with parrot’s feather in the creek and lake is one of the worst he has ever seen.
He said a management plan is needed to deal with the issue.
“There’s a need to get a handle on what is achievable,” he said.
“But to completely remove the parrot’s feather (from the creek and mouth of the lake) is unlikely. The issue is linked to several other factors, but we need to begin a process that will lead to some reasonable solutions.”
Parrot’s feather is a popular aquatic garden species and intentional planting has spread it into natural water bodies.
The species is known to out-compete and replace native aquatic vegetation with its dense stands, and has impacted a number of freshwater bodies in B.C.
Once established, parrot’s feather is a difficult invasive plant to manage.
Several homeowners adjacent to Somenos Lake sent a letter to the municipality in September outlining the problem.
The homeowners said they believe that the lake is effectively being blocked at its outlet by dense mats of parrot’s feather that have been allowed to grow unimpeded since first identified in Somenos Creek in 2015.
They said that, besides interfering with water flow and the salmon and trout in the waterways, parrot’s feather is creating stagnant water, which creates hazards such as a breeding ground for mosquitoes near a large urban area.
On a related issue, North Cowichan established a task force last year to deal with the proliferation of toxic blue-green algae in Quamichan Lake after four dogs died due to ingesting the algae in 2016.
Priekshot presented several options that could be considered to deal with the parrot’s feather problem.
They include introducing predators and parasites that eat parrot’s feather into the water system, but he said adding more species to the system could lead to new and unanticipated problems.
Priekshot said efforts to reduce the amount of phosphates, which parrot’s feather thrive on, entering the system could have an impact, but it’s a longer-term solution that would be slower to manifest.
He said using herbicides like triclopyr, glyphosate or diquat would provide fast results at a low cost.
“But it’s illegal to use herbicides in aquatic environments so a lengthy permission process would be required,” he said.
“There’s also the public perception around using chemicals, the effects on other vegetation and animals, and repeated application of the chemicals would be required.”
Priekshot said another option would be to physically pull, vacuum or dredge the parrot’s feather out which would see the total removal of the plant in a relatively short time.
“But it’s expensive and it would have to be done every four to five years,” he said.
“As well, the further spread of parrot’s feather through fragmentation using this management method is possible.”
Priekshot said shading the parrot’s feather is a low-cost solution, but it would take a long time and will not lead to 100 per cent removal of the plants.
He said the next steps will be to engage with the public and Cowichan Tribes, as well as provincial agencies, to determine which management option would be best for the water system.
“We also intend to begin some experimental work on shading this summer,” Priekshot said.
“I don’t think that dealing with this problem is impossible. It will take a bit of work and time, but I believe we’ll get there.”
Asked by North Cowichan’s CAO Ted Swabey what the cost implications of the different management options were, Priekshot said his best guess is that they could cost from tens of thousands of dollars for a chemical solution and up to millions of dollars for major dredging.
“It seems daunting, if not overwhelming, for local governments,” Swabey said.
“We can’t afford to spend millions of dollars on this every few years. This is a serious problem and we’d need help to deal with it.”