Grassland Bird Species Decline With Colonial-Era Landscape Change in a Tropical Montane Ecosystem

The impacts of colonial-era ecosystem changes on tropical biodiversity are poorly understood. We analyzed a 170-year dataset on land cover and bird observations in an Old World tropical montane landscape in the Western Ghats, India, to determine if and how historical landscape changes have impacted 85 bird species. A comparison of historical land cover and classified satellite imagery (1848-2018) revealed approximately an 80% decrease in grassland area and a concomitant increase in tea and timber plantations stemming from colonial-era policies and associated legacies of large-scale planting of cash crops and exotic woody species. We found that relative species abundances of about 90% of grassland birds have significantly declined while around 53% of forest bird species remained stable or even increased in relative abundance over the same period. Over 74% of generalist bird species have become more common over the same period, possibly due to reduced habitat specialization. Our findings show that colonial-era policies, continued postindependence, of tree planting across open natural ecosystems have resulted in severe loss of grassland habitats and a concomitant decline in the relative abundance of grassland bird species.