OBWB message – to municipal governments

Here is the message the Okanagan Basin Water Board wants local government to take to the Provincial Government in September

Invasive Milfoil Control and the Rocky Mountain Ridged Mussel in the Okanagan

The Okanagan Basin Water Board (OBWB) has been controlling invasive Eurasian water milfoil in the Okanagan since the 1970s. The program was developed by the B.C. Ministry of Environment after more than 17 years of scientific testing of control methods. Two methods – rototilling and harvesting – were selected as the most effective at reducing weed density and keeping public areas clear for beach users.

Rototilling removes milfoil roots from the lake bottom during the winter while the plant is dormant and reduces stem density by up to 90% in a single treatment. This prevents the plant from growing during the summer, and promotes healthier water quality and better habitat for native plant and animal species.

Harvesting is used during the summer to cut the top portion of the milfoil plants and remove the cut sections from the water. Harvesting has no long-term effect on milfoil growth and is a purely aesthetic treatment for public-use areas where rototilling is unfeasible or not permitted. Harvesting is not a substitute for rototilling.

Today, milfoil operators have on-board computers, loaded with up-to-date maps of all environmental
work-windows and restrictions. Treatment areas are pre-approved through provincial and federal
permitting processes, and all operations are GPS tracked and reported to the province annually. OBWB’s operations are monitored by a Qualified Environmental Professional who has the authority to halt operations over any environmental concerns.

In 2018, the province introduced new regulations, intended to protect the native Rocky Mountain
Ridged Mussel (RMRM). These regulations established a 100-meter buffer zone, prohibiting milfoil
control anywhere an individual RMRM, or an RMRM shell fragment is found. This approach is based
on Section 38 of the Species At Risk Act which says that “…cost effective measures to prevent the
reduction or loss of the species should not be postponed for a lack of full scientific certainty.”
However, scientific studies form other regions have shown that uncontrolled milfoil growth leads to
decreased water quality and direct harm to a number of native species of plants and animals,
including other species of freshwater mussels.

In 2019, OBWB wrote a detailed letter to the Species at Risk Program of Fisheries and Oceans Canada recommending that RMRM not be up-listed to ‘endangered’ under the Species at Risk Act. The letter cited significant scientific and economic evidence to support ongoing milfoil rototilling in the Okanagan to protect water quality, other native species of both plants and animals, and the economy.

In August 2019, the Minister of Fisheries and Oceans Canada acknowledged that local communities raised “a number of important concerns… with respect to the possible unintended impacts on the ability to effectively control the Eurasian Watermilfoil in the same habitat as these mussels.” RMRM remains listed as a ‘species of special concern.’

Currently, provincial regulations mean that each new RMRM individual found in a rototilling area will
cause the restrictions on milfoil rototilling to expand, leading to an increase in this invasive lake
weed. OBWB believes a more balanced, evidence-based approach is needed, taking into account social and economic factors as well as the need to maintain adequate protection for the mussels and other native species.

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