Nighttime lights captured by satellite imagery were found to be useful to locate and quantify human activities including centers of population, economic activity, and electricity usage, and are an especially valuable technique... [ view full abstract ]
Nighttime lights captured by satellite imagery were found to be useful to locate and quantify human activities including centers of population, economic activity, and electricity usage, and are an especially valuable technique for regions with poor socio-economic statistics. Intuitively, these data sources would be of great value to material stock accounting since a high correlation between sources of light and anthropogenic activities is expected. Despite this potential, to this date only a few studies explored this direction and have done so in very limited spatial scopes and restricted material types, possibly due to hardships in obtaining reliable models to convert the statistical relationship between emitted lights to material stocks.
In this study we overcome these methodological challenges to present the first global estimate of the construction materials stocked in buildings and their locations at the resolution of metropolitan areas. Our preliminary results show that in 2011, the around 250 billion square meters of global building floor space contained as much as 500 billion tonnes of concrete, 40 billion tonnes of sand & mortar, 22 billion tonnes of steel, 0.5 billion tonnes of aluminum, and 0.5 billion tonnes of ceramics, which are in similar orders of scale to previous studies of stocks at national levels.
Material stocks are, unsurprisingly, concentrated in urban areas and unevenly geographically distributed in the global north, as well as in the rapidly developing countries of China and India. The high spatial resolutions that become available with this method enable us to uncover previously unknown characteristics of the building-up of material stocks such as the spatial distribution of embedded CO2 that were part of the production and construction of the built environment. It also enables to differentiate country typologies in regards to the distribution of material stocks throughout their land mass. For example, India’s distribution is more even and similar to Europe, as compared with countries such as China and Russia which have uneven distributions between large regions of their geographies more similar to the United States, and unlike countries such as Brazil and Saudi Arabia, which have very high material stock levels concentrated in very small parts of their territory. This enables us to discuss the material and energetic requirements as well as the environmental and economic trends and socio-economic metabolic implications of these new results.
