Centennial evolution of Hong Kong 1910–2050: a building material metabolism perspective

Building materials and their centennial metabolic patterns offer a perspective from which to understand a city’s past, present, and future, but existing studies mostly focus on short-term metabolism. By investigating Hong Kong’s building material stock and flow (or building material metabolism, BMM), this study aims to understand the centennial evolution of a city with a rich history, international status, advanced economy, and close connection with the world. We quantify BMM using the stock-driven approach, derive flows based on stock changes, and interpret its patterns based on temporal and correlation (with socioeconomic factors) analyses, respectively. We find that, by the mid-2030s, total building material stock may saturate at around 417.93 Mt with a rough inflow–outflow balance of 13.29 Mt/year, but stock per capita has plateaued at about 53.67 t/capita since the mid-2010s. The long-term changes in both building material stock and flow comply with an S-curve, shaped mainly by industrialization and subsequent deindustrialization but also fluctuating due to key socioeconomic events. Based on a stock productivity comparison, we also find that Hong Kong has achieved and sustained an advanced economy via a lower BMM requirement than other typical developed economies, indicating a more material-efficient development pathway. These findings not only provide insights into the centennial BMM trajectory and its interaction with socioeconomic factors, but also offer historical experience and sustainable development implications for developing economies, especially those in mainland China and throughout Asia.