Ecosystems may be complex, but just how complex do we need our institutions to be to manage them effectively?

Background/Question/Methods:

Conservation management decisions are often implemented to reflect human scales, rather than the scale of the relevant ecological dynamics. Research frequently points out the loss in efficiency that results from this scale mismatch. However, the scale of management is influenced by social, economic and political constraints on management actors; by the higher implementation costs of spatially-variable management plans; and by the divergent objectives of the actors in different regions. The critical question is not whether conservation benefits would increase if management were planned at ecological scales, but whether such benefits are sufficient to justify the cost of alignment.

Fishery management often has strong spatial components, with harvest quotas, gear restrictions, and marine protected areas applying to specific locations. Such spatial management decisions are generally implemented at spatial scales that have a coarser resolution than the underlying population dynamics. We use a spatially-explicit bioeconomic metapopulation model of a line fishery within the Great Barrier Reef Marine Park to explore the relationship between scale mismatches and management efficiency, and to quantify the benefits that result from an increased alignment between management actions and key ecological scales. In this system, the management scales are defined by the boundaries of total allowable catch regions, while the important ecological scales are defined by complex biophysical connectivity between reef populations.

Results/Conclusions:

Given a particular scale of management (defined by the number of separate catch quotas), our approach identifies (1) the distribution of harvest efforts, and (2) the location of management boundaries, that maximise the profitability of the fished metapopulation. Assessing a range of management scales allows us to characterise the relationship between the size of the mismatch between ecological and management scales, and the magnitude of the resulting inefficiency. We further contrast the locations of the resulting boundaries with natural ecological boundaries created by the dispersal network that connects the reef populations. 

Decreasing the mismatch between management and ecological scales yields only diminishing efficiency returns, while incurring accelerating transaction costs. The result is that management efficiency is maximised by a management scale (or alternatively, a management resolution) that is much larger than the underlying ecological process: effectively, an optimal scale mismatch.