|Recent years have seen a growing interest in sustainable development and the shift towards a more resource efficient economy. The concept of “social metabolism” views a socioeconomic system as a system of material throughput. Societies organize materials and energy flows from nature (and by way of trade with other societies) for its reproduction and maintenance. A large part of these flows gets accumulated as part of the built environment (also called “material stocks”) to deliver critical services to society such as transport, health, education, housing, etc. The more stocks, the more flows are required to maintain the stocks. This dynamic feedback loop is called the “material-stock-flow-service” nexus. For a shift towards a more resource efficient economy, accounting for material stocks, its composition, and long-term dynamics of in-use materials is fundamental.
This research presents a methodology based on a spatial approach using Geographic Information Systems (GIS) for quantifying and analyzing stocks and services associated with buildings. A bottom-up approach was adopted for identifying in-use stocks in two study areas, (a) Grenada, a small island developing state in the Caribbean, and (b) the City of Kitchener, which is a rapidly growing urban area in Ontario, Canada. This research was conducted from both city and island perspectives to assess the socio-economic metabolism of buildings and their relationship with services in two different geographic contexts. Estimated primary construction materials include cement, aggregates, steel, and timber. In a North American context, masonry brick was a widely occurring building material in Kitchener, and therefore was also accounted.
This study found that 125 tonnes per capita of material stocks were accumulated in Kitchener in 2016, equivalent to 29,000 kilo tonnes. A total of 132 tonnes per capita was estimated in Grenada in 2014, equivalent to 14,012 kilo tonnes of material stock. In terms of services, the residential class was the highest occurring in both Grenada and Kitchener accounting for 93 tonnes per capita and 89 tonnes per capita, respectively. Tourism and commercial service classes were the next highest in Grenada accounting for 12% and 5% of total in-use stocks. In Kitchener, educational services were second at 7.3% of total in-use stocks and commercial services were third at 7.1%. When exploring scenarios of future stocks in Grenada based on indicators such as population, and tourism visitors, if visitors continue to increase during a 20-year period, tourism stocks will likely rise by almost 50%. This will significantly impact Grenada’s economy, since an increase in tourism stocks can lead to a shift in GDP, potentially leading to a large reliance on tourism as a primary source of income. More frequent extreme weather events related to climate change also threatens the supply of critical services to society. For example, located in Grand Anse (0.28 km2 enumeration district) are 18% of the total tourism material stocks equivalent to 308,494 tonnes. If another disaster event such as Hurricane Ivan were to occur, these large agglomerated stock areas could devastate Grenada and put the economy in decline until re-construction can occur. Mapping the spatial distribution of material stocks can help communities to mitigate and plan for the effects of climate change, especially since most of Grenada’s built infrastructure is located along coastal areas. This study demonstrates how to link material stock accounting with the services that they provide, thus enhancing understanding of the socio-economic metabolism of cities and small island nations, which is important for planning and sustainable development.