Abstract

The design of nature reserves is becoming, more and more, a crucial task for ensuring the conservation of endangered wildlife. In order to guarantee the preservation of species and a general ecological functioning, the designed reserves must typically verify a series of spatial requirements. Among the required characteristics, practitioners and researchers have pointed out two crucial aspects: (i) connectivity, so as to avoid spatial fragmentation, and (ii) the design of buffer zones surrounding (or protecting) so-called core areas.In this paper, we introduce the Generalized Reserve Set Covering Problem with Connectivity and Buffer Requirements. This problem extends the classical Reserve Set Covering Problem and allows to address these two requirements simultaneously. A solution framework based on Integer Linear Programming and branch-and-cut is developed. The framework is enhanced by valid inequalities, a construction and a primal heuristic and local branching. The problem and the framework are presented in a modular way to allow practitioners to select the constraints fitting to their needs and to analyze the effect of e.g., only enforcing connectivity or buffer zones.An extensive computational study on grid-graph instances and real-life instances based on data from three states of the U.S. and one region of Australia is carried out to assess the suitability of the proposed model to deal with the challenges faced by decision-makers in natural reserve design. In the study, we also analyze the effects on the structure of solutions when only enforcing connectivity or buffer zones or just solving a generalized version of the classical Reserve Set Covering Problem. The results show, on the one hand, the flexibility of the proposed models to provide solutions according to the decision-makers’ requirements, and on the other hand, the effectiveness of the devised algorithm for providing good solutions in reasonable computing times.

Highlights

  • Introduction and MotivationDemographic expansion, natural resource exploitation, and the consequences of climate change, are among the processes that had resulted in a dramatic loss of biodiversity in the last decades

  • The Generalized Reserve Set Covering Problem (GRSC)-CB allows to design a reserve comprised by one or more connected components; each of them consisting of a core surrounded by a buffer zone

  • The first observation that can be made from the obtained result is that solving GRSC-CB with a single connected component is computationally much more challenging than solving GRSC-CB in which the number of components is relaxed to a greater value

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Summary

Introduction and Motivation

Demographic expansion, natural resource exploitation, and the consequences of climate change, are among the processes that had resulted in a dramatic loss of biodiversity in the last decades. The main contribution of our work consists of providing, for the first time, a modeling and algorithmic framework for the optimal design of wildlife reserves by simultaneously integrating three criteria: connectivity requirements, construction of buffer zones and minimum quotas of ecological suitability. This is done by introducing the Generalized Reserve Set Covering Problem with Connectivity and Buffer Requirements (GRSC-CB).

Modeling the GRSC Problem
Modeling the Buffer Zone
The Complete Model
A Branch-and-Cut Framework for the GRSC-CB
Valid Inequalities
Constraint-Separation
Construction Heuristic and Primal Heuristic
Result
Local Branching-based Heuristic
Computational Results
Benchmark Instances
Computational Setting
Results on Grid-Graph Instances
Case Study
Conclusions
Full Text
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