What makes a city vibrant? Traditional metrics like population density or land-use mix give partial answers at best — they tell you how many people are somewhere, but not what they’re actually doing.
In this perspective paper, together with Edward Chung Yim Yiu, Diogo Pacheco, and Federico Botta, we borrow a framework from ecology. Biodiversity is measured through species richness (how many different species) and abundance (how many individuals of each). We argue urban vibrancy works the same way: what matters is the diversity of human activities in a place — not just how busy it is, but how varied the things people are doing are. We propose a taxonomy of 12 urban activity categories (working, eating, exercising, socialising, celebrating, and so on) and a roadmap for measuring them using mobile, geospatial, and imaging data.
The ecological analogy also runs the other way: just as ecosystems can suffer from overcrowding, cities can tip into congestion and conflict when activities exceed the local carrying capacity. Touristification is a good example.
Yiu, E.C.Y., Pacheco, D., Di Clemente, R., & Botta, F. (2026). Urban vibrancy: An analogy of biodiversity, retail diversity, and activity-based urban diversity measures. PNAS Nexus, 5(5), pgag130. https://doi.org/10.1093/pnasnexus/pgag130
The paper is out now in PNAS Nexus. Read it here.