Ontario's decision to repeal Toronto's green roof bylaw is drawing concern from the city's mayor as well as opposition MPPs, who say the tool helps to increase efficiency, cool urban areas and prevent flooding.

Toronto was the first in North America to have a green roof bylaw. Adopted in 2009, the bylaw made it mandatory for green roofs to be built on new commercial, institutional and residential developments with a minimum gross floor area of 2,000 square metres.

The bylaw led to more than 1,200 green roofs across Toronto, according to the city, but the province is now making the roofs voluntary.

Mayor Olivia Chow is "disappointed" by the decision, said her press secretary, Braman Thillainathan.

"For more than 15 years, Toronto’s green roof bylaw has helped divert stormwater and reduc

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