Invasive milfoil will thrive in Okanagan lakes impacted by climate change - InfoNews

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Invasive milfoil will thrive in Okanagan lakes impacted by climate change

February 24, 2020 - 7:00 AM

With increasing global temperatures and the expectation that the Okanagan will face more droughts and floods, one nasty invader will thrive in an environment created by climate change.

Eurasian milfoil has made a home for itself in Okanagan lakes since the 1970s. Every year, the Okanagan Basin Water Board spends between $800,000 to $850,000 to remove the plant using large water rototillers that pull the plants from the lake bottoms.

There will be more milfoil as floods bring nutrients to the lakes and droughts allow the plant to grow under the direct sunlight, said water board operations manager James Littley.

Milfoil creates a number of problems for Okanagan residents, including creating a hazard for swimmers and boats, and it impacts water quality, he said.

“Once it begins to decompose at the bottom of the lake, it robs the lake of oxygen which increases algae blooms and toxic algae blooms in some cases. There have been cases in the States where fish have died in thick milfoil beds because there’s such a lack of oxygen that fish swim into it and suffocate,” he said.

An Okanagan climate change report was recently presented to regional districts around the Okanagan Valley. Amongst the report’s main conclusions is a prediction of longer warm seasons and shorter cold seasons.

READ MORE: Climate change projections report has a little good news for the Okanagan

Longer growing seasons and more days over 30 C means warmer lake temperatures. If lake temperatures reach more than 10 C for longer periods, milfoil populations will increase. Since rototilling has to be done while water temperatures are cooler, this also means the rototilling season will be cut short, Littley said.

Milfoil was likely released in North America from a fish tank, as it was commonly used in aquariums, “and it would have just spread on people’s boats and trailers.”

It exists in every Okanagan lake.

There’s no way to eradicate it, he said, but rototilling keeps it in check. The machines pull out the plants at their roots and after a few years, there is almost a 100 per cent reduction of the invasive plant in the rototilled areas.

If left unchecked, foreshores like Kelowna’s, from Tolko Mill to Mission Creek, would be covered in milfoil.

READ MORE: Milfoil is invading more Okanagan beaches as rototilling bans spread

Littley said he couldn’t predict what the cost to remove milfoil will be in the next 10 or so years, or how much milfoil the water board will have to deal with in the future.

“Milfoil is one example, but you think about what will grow in hotter temperatures and just for an example zebra and quagga mussels can reproduce once a year in Canada. In Lake Mead in Nevada they can reproduce six times a year because they don’t have that freezing cycle.”

“Algae and other types of pollutants won’t grow in subfreezing temperatures, so the warmer the climate gets and the warmer the water gets, the more water quality concerns we are going to have,” he said.

The Okanagan Basin Water Board is permitted to remove milfoil from 50 kilometres of shoreline each year, but the exact amount that is actually rototilled ranges depending on the season, Littley said.


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