Abstract
Here we report that prioritizing sites in order of rarity-weighted richness (RWR) is a simple, reliable way to identify sites that represent all species in the fewest number of sites (minimum set problem) or to identify sites that represent the largest number of species within a given number of sites (maximum coverage problem). We compared the number of species represented in sites prioritized by RWR to numbers of species represented in sites prioritized by the Zonation software package for 11 datasets in which the size of individual planning units (sites) ranged from <1 ha to 2,500 km2. On average, RWR solutions were more efficient than Zonation solutions. Integer programming remains the only guaranteed way find an optimal solution, and heuristic algorithms remain superior for conservation prioritizations that consider compactness and multiple near-optimal solutions in addition to species representation. But because RWR can be implemented easily and quickly in R or a spreadsheet, it is an attractive alternative to integer programming or heuristic algorithms in some conservation prioritization contexts.
Highlights
The minimum set problem [1] is to identify a set of sites within a planning area that represent all conservation targets in the fewest number of sites
It is closely related to the maximum coverage problem, which is to represent the largest number of species in a given number of sites
Both problems emphasize efficiency; the minimum set problem is appropriate for comprehensive long-term plans whereas maximum coverage is appropriate for short-term plans when resources are insufficient to meet all targets
Summary
The minimum set problem [1] is to identify a set of sites (individual planning units) within a planning area that represent all conservation targets (typically species) in the fewest number of sites. It is closely related to the maximum coverage problem, which is to represent the largest number of species in a given number of sites. Both problems emphasize efficiency; the minimum set problem is appropriate for comprehensive long-term plans whereas maximum coverage is appropriate for short-term plans when resources are insufficient to meet all targets. A set of sites that satisfies or nearly satisfies a minimum set or maximum coverage problem is referred to as a “solution.” For over 30 years, conservation biologist have known that selecting sites in order of species richness provides poor solutions [2,3,4]. PLOS ONE | DOI:10.1371/journal.pone.0119905 March 17, 2015
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