A Geographical-Ecological Model for Landscape Conservation in Western Samoa

Abstract

The Theory of Landscape Ecology holds that the biological and material interactions among ecosystems are highly (often mainly) influenced by their relationships in geographical space. A conservation corollary states that measuring, modelling, and preserving these spatial relationships provides a useful, approximating approach to conserving the interactions among the ecosystems (ecotopes) of landscapes, potentially resulting in the maintenance of an ecologically stable or metastable landscape. The latter can be defined as a landscape where the patterns and processes of component ecosystem interaction are changing relatively slowly and where entropy gradients are shallow. In an ecologically stable or meta-stable landscape, component ecosystems will persist without simplification or collapse, and the ordinary processes of material and biological interaction among ecosystems will not change rapidly. Networks of nature reserves, corridors, and buffers were designed for the maintenance of ecologically meta-stable landscapes on the islands of Savai'i and 'Upolu in Western Samoa. The approach involved generating a new map of the vegetation of Western Samoa and the incorporation of these and other data in a geographic information system in order to facilitate cartographic modelling. Intermediate products included maps of the landtypes, the normative vegetation, and the normative ecosystems of Western Samoa. Ecosystem priorities for conservation were selected on the basis of new indices of rarity and threat. The networks were developed using a rule-based decision model for relatively rare ecosystem types and using a graphical solution for more common types. The rules required the inclusion of all occurrences of the rarest ecosystems and inclusion of all occurrences for moderately rare ecosystems with the exclusion of primary agricultural land in customary tenure. The graphical solution for common ecosystem types emphasized the development of high quality corridors. Finally, buffers were defined around the network cores. The networks were verified, and the process used to generate them was generalized as the Regional Ecosystem Analysis and Landscape Conservation (REAL Conservation) methodology.