Look up in many cities today and the skyline is changing colour. Rooftops once covered in gravel and air-conditioning units are becoming gardens, meadows and even small farms — a quiet green revolution overhead.
The benefits stack up fast. Green roofs cool buildings (cutting air-conditioning demand), absorb stormwater, filter air, and give pollinators a foothold in concrete deserts. Some cities now require them on new large buildings.
From policy to produce
Rooftop farms in particular are booming, growing herbs and greens metres from the restaurants that serve them. What they lose in scale they gain in freshness — harvest-to-plate in under an hour.
Challenges remain: weight limits, waterproofing and maintenance costs. But as one urban ecologist put it, "the cheapest land in a city is the land nobody was using — the roof."