Commuters travel on motorbikes on a street in Lahore. The city’s air quality deteriorated over the past decade when most of its trees were felled to make way for more residents — and their vehicles, powered by cheap, dirty fuel.

Commuters travel on motorbikes on a street in Lahore. The city’s air quality deteriorated over the past decade when most of its trees were felled to make way for more residents — and their vehicles, powered by cheap, dirty fuel.