Clothier, BE; Green, , SR; Deurer, M
The soil-plant-atmosphere ecosystems which cloak the lands of our earth are the planet's critical zones, and they provide valuable ecosystem services (NRC, 2004). Through these systems there are massive fluxes and storages of mass and energy, and these provide both valuable productive and ecosystem goods and services.The annual value of 17 terrestrial ecosystem services, all involving the soil-plant-atmosphere system, Costanza et al. (1997) estimated to be US$5.74 trillion. When oceanic services were added in, the global value of the earth-surface's natural capital and ecosystem services amounted to US$33 trillion per year. Gross global productivity only sums to $18 trillion yr(-1). Thus, understanding and managing the soil-plant-atmosphere system is critical, not only for our economic futures, but also for the health of our environment, and the wealth of our social systems (van der Velde et al. 2007).New Zealand's former Parliamentary Commissioner for the Environment commented in 2004 that "... New Zealanders are highly dependent on our natural capital - our waters, soils and biodiversity - for sustaining wealth-generating capabilities [yet] our farming systems are financially and environmentally brittle [and] fundamental redesign of farming systems is required" (PCE, 2004).Quantitative modelling is a valuable means by which we can organise our knowledge so that it can be applied to manage better our productive ecosystems, and so that it can be used for developing policies, implementing actions, and monitoring outcomes to protect our natural capital and ecosystem services. There is a strong end-user pull for scientists to develop better models and sophisticated decision-support tools to realise these outcomes (Green et al., 2006). Huge prospects.Unfortunately, as Joseph Fourier (1768-1830) lamented, "... nature is indifferent to the difficulties it causes [modellers]", for the fluxes and fate of mass and energy in the soil-plant-atmosphere system are governed by a myriad of linked and non-linear processes. Not only is the 'biophysics' of the soil-plant-atmosphere system complex, but there is the end-user need for simple models to provide results at larger spatial scales and greater temporal orders than our detailed knowledge of the local mechanisms easily allows (Corwin, et al., 2006). Big problems.Fortunately, the computing power we currently have at our disposal, as evidenced by Moore's Law, now more simply enables us to solve complex, non-linear, inter-dependent equations. But, there are pitfalls.In this address, we discuss how models can be used to describe fate and transport processes in the soil-plant-atmosphere systems. We draw from a range of examples to highlight prospects, problems and pitfalls. These include: the fluxes of water in the rootzones of grapevines and fruit trees and the need for sustainable irrigation; the transport of copper-chromium-arsenic (CCA) from treated-timber posts in vineyards and the need to protect soils and regional groundwater systems; valuing the natural capital of soil and its ecosystem services to quantify terroir in viticulture, as well as the catchment-scale, non-point source pollution of rivers as a result of nitrogen leakage from a mosaic of diverse farming enterprises.We show how detailed modelling can be used to reveal patterns and thresholds that permit the upscaling of knowledge in time and space via the application of simpler means, such as stochastic analyses, mass-balance schemes, ecological econometrics, and transfer functions. These larger-scale results are then more easily useable by end-users and policy agencies. Through our discussions of these we seek to refute Philip's (1991) jeremiad that ". by 2066 we shall be deep into the electronic Dark Ages, [where modelling, the] shadow-boxing surrogate for science, [has led to] a battery of expert systems, some of them designed on the self-fulfilling premise that the user is an imbecile".