Uncle Tony's computer: order-of-magnitude modelling as a screening tool in environmental analysis

Abstract

This paper describes a simple, quick, non data-intensive quantitative approach for sorting certain types of environmental issues into those that are unlikely to be problems; those likely to be problems; and those requiring further, more detailed investigation. It applies to situations where the impact results from an altered input to a system, for instance of a pollutant, or an altered output, for instance a harvest. It is based on a rough (order-of-magnitude) estimation of the degree to which a proposed action is likely to perturb the throughput of a given system. If the perturbation is an order of magnitude or smaller than the throughput, it is deemed unlikely to affect the ecology of that system in a material way. If larger than the throughput, it is very likely to have a substantial effect on the functioning of the system. If somewhere between the two limits, the problem requires further study. The method assumes a good, but not highly quantitative, knowledge of the system, and does not apply to cumulative effects.