Even repainting roofs from black to white can make a major difference for minimal cost.

Planting trees is great in many ways (quality of life and air quality in addition to heat mitigation) but is pricier. It can also take several years to "bear fruit" (even for non fruit-bearing trees ;-) because generally you plant saplings, which can take decades to grow to a size where they provide significant shade. NYC hust completed an initiative to plant a million new trees, and it's barely made a dent in the amount of treeless sidewalks, let alone unshaded space in the city.

It would have been nice if the article had made more concrete recommendations, tho, I agree.

Also special pavement materials and decrease urban footprint https://www.epa.gov/heat-islands/heat-island-cooling-strateg...

Replacing parking lots seems like the most obvious win all around to me.

Combine the two: rooftop gardens. Chicago has been pretty successful encouraging the development of green roofs with grants and the like: https://www.cityofchicago.org/city/en/depts/dcd/supp_info/su...

But roofs aren't really important at pedestrian level, I've seen many recent buildings having fixed external blinds, leaving an air gap between glass/concrete which should help draw up the hot air.

Energy efficiency is also important as tall buildings can use significantly more energy than they receive in sunlight.

Sod roofs