I have proposed the technomass as an indicator to understand the metabolic behaviour of urban ecosystems. Technomass accounts for all the matter that has been transformed by human labour per unit of surface and time, thus tracing a direct link to economics. The underlying idea is to develop a coupled understanding of economic and ecological processes in urban environments, using the framework of metabolism. From this departure point, technomass can significantly help ecologist to summarise the complex spatial structure of urban environments and planners to understand the ecological and economic consequences of particular urban forms. From the metabolic point of view, technomass can help in overcoming the current linear approach to materials, to see that metabolic chains they change along complex processes, from matter to money, and to matter again to be accumulated and consumed.

From the ecological point of view, the principle is quite simple: all ecosystems have a material behaviour, concerning matter accumulation. In many ecosystems like forest, marine, agriculture and the like, such accumulated matter is called biomass, a fundamental indicator to understand the ecosystem’s behaviour. Its productivity is driven by ecological processes and drivers, which can be however altered by anthropogenic intervention.  Surprisingly, urban ecosystems do not have any indicator to account for the material productivity. Of course in urban ecosystems, the material productivity, i.e. the rate and volume of technomass accumulation, is driven by socio-economic processes and drivers. For this reason, technomass gives attention to built structures. At the end of the day, and without resting any relevance to green components, urban environments are built, composed and develop over the basis of technomass, the anthropogenic socially produced matter present in ALL urban ecosystems.

The technomass indicator allows to essential things. First, to avoid Nature/Society dichotomies (Moore 2015), by providing a holistic indicator which is complex, embedded and entangled with ecological and socio-economic processes. The second it reduces the complexity of the built environment and thus can provide a compelling picture of several dimensions of human development, like urbanisation, heat generation, biodiversity, among many others, in a spatially explicit manner.