A dimensionally consistent aggregation framework for biophysical metrics

We develop a formal representation of the economy-ecosystem interaction problem by distinguishing between stock-flow, and fund-flux spaces (Georgescu-Roegen, 1971). We then define dimensionless quantities in both the cardinal stock-flow space and the ordinal fund-flux space. This leads to analytic definitions of natural capital and natural income in the fund-flux space. We show that a stock-fund representation of the economy-ecosystem interaction problem helps investigate aggregation properties of biophysical metrics. In particular, we show how a metric that is dimensionally consistent in the stock-flow space can have dimensional problems in the fund-flux space. Ecological footprint is used as an illustrative example. Finally, we argue that dimensionally consistent metrics are keys to further the development of biophysical assessments as a tool for practical environmental policy.