  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. 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. 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.
