Ensuring Persistence of Marine Reserves: Catastrophes Require Adopting an Insurance Factor

When viewed across long temporal and large spatial scales, severe disturbances in marine ecosystems are not uncommon. Events such as hurricanes, oil spills, disease outbreaks, hypoxic events, harmful algal blooms, and coral bleaching can cause massive mortality and dramatic habitat effects on local or even regional scales. Although designers of marine reserves might assume low risk from such events over the short term, catastrophes are quite probable over the long term and must be considered for successful implementation of reserves. A simple way to increase performance of a reserve network is to incorporate into the reserve design a mechanism for calculating how much additional area would be required to buffer the reserve against effects of catastrophes. In this paper, we develop a method to determine this "insurance factor": a multiplier to calculate the additional reserve area necessary to ensure that functional goals of reserves will be met within a given "catastrophe regime." We document and analyze the characteristics of two relatively well-studied types of disturbances: oil spills and hurricanes. We examine historical data to characterize catastrophe regimes within which reserves must function and use these regimes to illustrate the application of the insurance factor. This tool can be applied to any reserve design for which goals are defined by a quantifiable measure, such as a fraction of shoreline, that is necessary to accomplish a particular function. In the absence of such quantitative measures, the concept of additional area as insurance against catastrophes may still be useful.