The impact of land-use, climate change and habitat characteristics on the distribution of the endemic Cacosternum capense in the Cape Floristic Region

Abstract

Changes in land-use within the Western Cape, South Africa, have substantially reduced the natural habitat of the endemic frog Cacosternum capense (Cape Caco), yet the combined effects of land-use and climate change remain poorly understood. This study integrates fine-scale habitat suitability assessments with species distribution models to investigate habitat preferences, distribution patterns and potential threats to C. capense, with the aim of informing conservation strategies. Field data on microhabitat characteristics identified key factors influencing species presence and abundance. Species distribution models were implemented using MaxEnt and projected across historical (1970–2000), present-day (2021–2040) and future (2041–2060) periods. Jackknife analysis assessed the relative importance of environmental variables, while four climate models based on shared socio-economic pathways were used to forecast future habitat suitability. Cacosternum capense preferred habitats with low to moderate vegetation cover and medium to high sedge and grass cover, occurring in shallow waters with sandy soils. In contrast, large ponds, deep water and dense vegetation negatively affected abundance. Low-intensity agriculture had limited effects, whereas high-intensity farming significantly reduced habitat suitability. Habitat degradation and fragmentation have resulted in a 76.2% loss of the species' historical range, with only 6.6% of remaining suitable habitat within protected areas. Future projections indicate further declines, with suitable habitat expected to shrink to 0.1%–6.3% of its original extent. Urgent conservation measures are needed.