Use of Geographical Information Systems in the search for additional populations, or sites suitable for re-establishment, of the endangered Northern Province endemic Euphorbia clivicola

Euphorbia clivicola R.A. Dyer, an endangered Northern Province endemic, is restricted to only two known populations, both of which are threatened with extinction. The area between and surrounding the known populations, totalling 8874 km(2), was therefore searched for sites where either unknown populations could exist, or which could represent a suitable habitat for the introduction of a new population. A raster-based Geographical Information Systems package, IDRISI for Windows, was utilized to manipulate two point vector files, representing rainfall and altitude of the searched area, digitized within the TOSCANELLI system. The lNTERPOL module produced two digital elevation models, from which the SURFACE module created slope and aspect images representative of the searched area. RECLASS and OVERLAY modules were finally utilized to identify 12 potential sites, covering only 1.4% of the total searched area. Ground-truthing is now needed to determine the presence or absence of further populations and to assess habitat suitability. This study emphasizes an additional application of GIS techniques to investigations with relevance to the biological sciences, specifically to problems of rare and threatened species. GIS represents a cost-effective alternative method for addressing these problems by focusing ground searching activities to only a small number of potential sites.