An Assessment of Habitat Diversity and Transformation on La Réunion Island (Mascarene Islands, Indian Ocean) as a Basis for Identifying Broad-scale Conservation Priorities

Abstract

Most natural habitat in the Mascarene Islands (Mauritius, La Réunion and Rodrigues) has been transformed. Although urbanisation, agriculture and alien plant invasions have transformed large areas in La Réunion, the island has by far the greatest area of intact habitats in the Mascarenes, but remaining natural areas are under threat. We propose a protocol for defining a system of habitat types and for using these to provide a preliminary assessment of conservation priorities for La Réunion. The protocol draws on existing data and expert knowledge to map habitat types, assesses the extent of habitat transformation, and quantifies heterogeneity between habitat types based on climate, topography and geology. The pattern of habitat transformation was uneven among the nineteen habitat types identified. While three habitats have lost > 95% of their original area, four still retain> 80% of their original extent. Habitat types could be grouped into the following categories: (i) transformed habitats with low levels of plant endemism, (ii) habitats confined to homogenous geology with high levels of plantendemism, and (iii) species-rich heterogeneous habitats on diverse geological types. Priority habitats were also identified using municipalities as a basis for implementation. Urgent action is required for several habitat types where a large part of the original extent has been transformed. Three municipalities which contain more than 10 habitat types should receive conservation priority. The analysis provides the basis for setting conservation priorities in La Réunion at the regional and local scale. Implications of the results are discussed with reference to requirements for finer-scale conservation planning.