Securing lowland forests is critical for bird conservation in the Western Ghats biodiversity hotspot

Abstract

In the human-dominated tropics, agroforestry and forest remnants are important for biodiversity conservation outside protected areas. However, the capacity of habitats outside protected areas to sustain taxonomically, functionally and phylogenetically diverse communities comprising habitat specialists and species of conservation concern is unclear. This is particularly relevant in India’s Western Ghats biodiversity hotspot, where protected areas have limited spatial coverage and underrepresent lowland forests. Here, we assessed bird diversity, composition and occurrence (using joint species distribution models) by surveying 184 transects of variable lengths in a 15,000 km ² landscape spanning high-elevation protected areas and low-elevation habitats (mean 863 m, range 12–1,111 m), including reserved forests (which have a lower level of protection), degraded private forests and agroforestry plantations (cashew, rubber and mango). Forests in general, and reserved forests in particular, had higher taxonomic, functional and phylogenetic diversity, with higher occurrence probabilities of frugivorous bird species associated with evergreen forest and of conservation concern (nationally declining population trends) than agroforests. However, the ranking of land-use types varied across different diversity metrics; e.g. rubber plantations had greater functional and phylogenetic diversity but lower occurrence probabilities than cashew and mango plantations. We highlight the importance of examining multiple dimensions of biodiversity in assessments across land-use types, and of the value of protecting and restoring threatened lowland forests for bird conservation in the Western Ghats.