Measurement Scales and Ecosystem Management

Summary

Ecosystem management involves managing relatively large areas with a regional perspective within a quasi-experimental framework. Monitoring the effects of management decisions in the context of quantified management and monitoring objectives is necessary to evaluate the extent to which those objectives are being met. The temporal and spatial scales at which environmental perturbations influence components of the natural system need to be defined in conjunction with the dispersion of those components in the landscape. These data then provide a model of the dynamic mosaic of landscape components that should be mimicked by management directed at maintaining or restoring ecosystem function and processes. Understanding the functional hierarchy of the components is critical to determining the variables in which to monitor response. Within this hierarchy, the responses of larger scale variables to perturbation should be slower than those at smaller scales that operate with faster dynamics. Incorporating the spatial and temporal dynamics of species and communities of concern within the model of environmental perturbations should help identify both the scales at which perturbation or management operates and the smaller scale at which monitoring will detect changes before slowly responding variables are significantly altered. As a result, monitoring should focus both on variables that are dynamically slower and more rapid than the scale at which management is applied. Variables that respond slowly to perturbation should be monitored at high precision over large spatial areas to detect change over short time frames. Monitoring carefully selected indicators of these slow variables is critical because they may provide the most powerful management tools. More rapidly responding variables that are functionally linked to the species of concern should be identified and monitored at lower effort. These variables are expected to have lower impact on the management target, but provide an early warning of change in the system. Finally, explicit evaluation of spatial scale effects within sampling designs for experimental tests of management techniques, or comparative evaluation of management units using spatial analysis, should elucidate the scales at which future monitoring will identify significant changes in the variables examined.