Global societal material stocks such as infrastructures and settlements (here: Tempe, Arizona) are approximately as heavy as all organisms on the planet. Photo: © Helmut Haberl, 2010

Material stocks in buildings, infrastructures and machinery, in combination with biophysical resource flows (materials and energy), deliver crucial services to society; for example, shelter, water supply, mobility, healthcare, education, and so on. How much energy and materials are required for delivery of any specific service strongly depends on the patterns of material stocks (the so-called 'stock-flow-service nexus'). For example, spatial patterns of settlements and infrastructures co-determine transport demand for services such as social inclusion, commuting, education or healthcare.

Material stocks are of crucial importance for sustainability due to their eminent social, economic and ecological implications: Most resource uses and emissions stem from building, maintaining and using stocks. Almost 60% of all material resources extracted worldwide are used to build up and maintain material stocks in buildings, infrastructures and machinery.

Material stocks do not only deliver key services, they also strongly influence how these services are provided. For example, whether one moves from A to B by foot, on a bicycle, by car or by train will depend
not only on the distance from A to B, but also on the available transport infrastructures connecting these points of interest. Material stocks hence create long-term lock-ins of resource use patterns (land, energy, etc.) whose “efficiency” of service provision may be quite variable. Moreover, specific patterns of material stocks also encourage or discourage certain practices of dwelling, being mobile or nourishing
oneself - which also may be associated with drastically different resource requirements (the so-called 'stock-flow-practice' nexus).

Transformations towards sustainability presuppose that provisioning systems that link resource use with social wellbeing outcomes are altered so that a good life for all can be provided for within planetary
boundaries. This implies fundamental changes of stock-flow-practice as well as stock-flow-service nexus phenomena.

In this broad context, MATSTOCKS launched an array of research activities to better understand these nexus phenomena. This included empirical work to quantify material stocks globally at the national
level for the period 1900-2016 with a resolution of 10-20 material (aggregates, concrete, steel, glass, timber, etc.) and 10-20 functional (roads, buildings, vehicles, etc.) categories. This was achieved by
developing the dynamic material flow model MISO 2.0 capable of quantifying material stocks based on material flow accounts, as well as calculating scenarios of their possible future trajectories.

Other methods & models were developed to calculate material stocks with a 'stock-based' approach; i.e., by assessing the material intensity of structures. These were used to map built structures based on data from remote sensing and earth observation for several countries (e.g., Germany, Austria, the UK, the conterminous US) and globally. This resulted in publication of maps of material stocks in buildings and infrastructure with substantial spatial (10-100m) and thematic (10-20 material categories, c 5-10 types of built structures) detail.

Additional modelling methods were developed to assess current and project future material stocks in power plants, thereby among others evaluating the additional resource demand of replacing coal, oil, gas and nuclear power plants by low-carbon alternatives (e.g., wind or solar power).

In close connection with these empirical and model-based assessments of material stocks, MATSTOCKS also embarked on conceptual and theoretical work, among others on energy and material services, the role of material stocks in provisioning systems, as well as options to intervene into the development of resource-hungry structures. Examples are investigations into the possible role of superblocks in cities, which can contribute to improving the quality of life in dense settlements while reducing their resource requirements and emissions, or the political regulation of urban sprawl; i.e., particularly resource-inefficient settlement patterns.

Funding: European Commission, ERC