As part of its fight against an invasive insect, the city of Montreal will cut down 40,000 trees.

Emerald ash borers--bright green beetles, no more than 14 mm long--burrow beneath the tree bark of thousands of trees on the island of Montreal. The invasive insects likely hitched a ride from Asia aboard wood packing materials in the early 1990s. They eat ash trees from the inside out, killing them within 10 years, according to Natural Resources Canada.

The bugs have infested ash tree populations across Eastern Canada, stretching as far inland as Winnipeg. 

A brittle, dead ash tree could be lethal, according to Rodrigue Forget-Rochette, a forestry engineer. They're called "widowmakers," he said, because when they fall they could hit a person.

"If a tree falls alone in the forest, do we hear it? No. So it's the same thing there, so we need to let nature do its thing, but we don't need nature to get somebody hurt so that's why we react at that point," he said.

Workers have marked thousands of ash trees in parks throughout the city with a red ring. All such trees will be cut in the coming months, starting with those near where people walk and hang out.

To avoid disrupting the local bird nesting season, forestry engineers will only cut trees between November and March. For every tree they chop down, they'll plant another in its place.

The city will recycle the ash wood into furniture and used as signs.

With files from Emily Campbell