A vertical forest is therefore not simply a greener high-rise. It is a building that depends on the successful coordination of natural and engineered systems. The structure must carry the load.

Smoother surfaces usually mean less resistance—but not always. A recent Tohoku University study found that microscopic distributed roughness reduced measured drag on a streamlined wind-tunnel model under specific transitional-flow conditions, offering engineers a fascinating reminder that even reliable design rules can have carefully engineered exceptions.