Cell model on a 29 x 29 grid. Plants: logistic growth limited by water, temperature and pollution. Pollinators: logistic growth on plant habitat, predation by birds, dispersal throttled by roads and blocked by buildings. Birds: need nearby trees and insects, hurt by traffic noise. Heat island: building and road heat minus tree, grass and water cooling, blurred over neighbours (Oke 1982). Biodiversity = evenness of the three groups times their mean abundance (a simple composite, not a field index).