Sustainability and the global biogeochemical cycles : integrated modelling of coupled economic and environmental systems : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Ecological Economics at Massey University, Manawatu, New Zealand
The global biogeochemical cycles (GBCs), which include cycles of C, N, P, S, Cl, I, and H2O, are extremely important biosphere functions, critical to the maintenance of conditions necessary for all life. Importantly, perturbation of these GBCs has the potential to affect the structure and functioning of the Earth system as a whole. While biogeochemistry research to date has largely focused on ‘natural’ processes, human economic activities are increasingly recognised as integral components of the GBCs. This thesis draws on both static and dynamic-system modelling approaches to describe the coupled economic and GBC systems, and to develop tools to assist in learning about these systems, with the aim of progressing towards sustainability. First, by drawing on the theoretical frameworks of Input-Output Analysis and Material Flow Analysis, an extensive and coherent static system model of the global C, N, P and S cycles is presented. Data within that static model are then used to calculate a set of sustainability indicators, based on a new and novel concept of ‘ecotime’. Essentially, these indicators describe the level at which the global economy, through its transformation of useful resources (i.e. raw materials) into residuals (i.e. wastes, pollutants, emission), appropriates biogeochemical processes. Changes in these and other indicators, under possible future scenarios, are also able to be investigated by a new dynamic model known as ‘Ecocycle’. Ecocycle constitutes one of very few attempts to develop an integrated model of the Earth system, explicitly capturing relationships between the GBCs and human activities. A notable feature of Ecocycle is that it represents the general equilibrium-seeking behaviour of an economy within a System Dynamics modelling approach, rather than through an optimisation approach as typically employed. A further significant methodological contribution of the thesis is the development of a technique for translating IO-based accounts between alternative process-by-commodity, commodity-by-commodity, and process-by-process frameworks. This method is required for both the static and dynamic components of the thesis.