Characterizing sensitivity and uncertainty in a multiscale model of a complex coral reef system

Sensitivity and uncertainty are intrinsic properties of ecological models, and their characterization is an important step in the modelling process. We use a spatially explicit multi-scale model of a coral reef system to explore four aspects of model sensitivity and uncertainty: (i) sensitivity to initial conditions; (ii) sensitivity to parameter values; (iii) sensitivity to spatio-temporal resolution; and (iv) the effects of uncertainty about spatio-temporal variability of ecological processes on the shape of distributions of model predictions. We use reef community composition, visualized in multivariate space, as a response variable. This approach provides an easily interpretable representation of changes in reef community composition under different parameter conditions and spatio-temporal resolutions. It is also a useful means to visualize distributions of model outcomes under differing assumptions about the nature of variability in ecological processes in the real world. Our results indicate that reef state and recovery trajectories are particularly sensitive to parameters determining coral growth and mortality rates. Variability in model outcomes depends on assumptions about the way parameters vary in space and time, and is greater at local scales than at subregional and regional scales. We highlight the fact that predictions based on the kind of model presented here are likely to be more robust for subregions and regions than for particular reef localities.