Designing a reserve system with heterogeneous sites: Extending the SLOSS debate from an economic perspective

In reserve design, determining the number, size, and management inputs of reserves under a limited conservation area budget is crucial for effective biodiversity conservation. This is embedded in the classic “single large or several small” (SLOSS) debate; yet, the literature rarely considers management effectiveness and economic costs. We therefore develop a theoretical model to choose the number as well as size and management inputs of each protected area to maximize net benefits, defined as benefits from system-level species richness minus management and opportunity costs. Unlike previous studies, we relax the assumption that all reserve sites should be equally sized. Our objective is to analyze how (i) across-habitat heterogeneity (dissimilarity in species composition between reserves) and (ii) effectiveness of management inputs in generating conservation outcomes affect optimal reserve design. Our analysis reveals that higher across-habitat heterogeneity often favors establishing multiple smaller protected areas (several smalls); however, incorporating management effectiveness can instead support choosing several larger reserves (several larges), even under high heterogeneity. These findings extend the literature on the SLOSS debate and underscore the importance of incorporating management effectiveness into the design of protected areas.