NANAIMO, B.C. - Huge flocks of Canada geese can be unwanted pests in any location, but several Vancouver Island cities say the geese have moved past messy and aggressive and are harming the environment.

Nanaimo environmental protection officer Kevin Brydges says Canada geese were brought to the island for hunting in the 1970s and 1980s and have adapted so well that they no longer migrate in winter.

Researchers at Vancouver Island University say as many as 1,800 birds overwinter in Nanaimo, leaving droppings and eating through grasses vital to the health of river estuaries.

Confirmation of the size of the Nanaimo flock will help the city decide on a management strategy, which Brydges says may include population control similar to a cull carried out in the nearby City of Parksville last year.

Tim Clermont, with Guardians of Mid-Island Estuaries, says before the Parksville cull, the geese had eaten almost 80 per cent of estuary grasses and destroyed shelter for migrating salmon.

“They affect tourism when people come here to enjoy our beaches. And when you have lots of geese, sometimes they've had to close beaches,” Clermont says.