Colonial-era landscape modifications, in which natural grasslands were cleared and replaced by exotic timber and tea plantations, are to blame for the devastating declines in grassland bird populations in India’s Nilgiri Hills. According to a new study, “Grassland Bird Species Decline With Colonial-Era Landscape Change in a Tropical Montane Ecosystem,” published in the Global Change Biology journal, researchers studied more than 170 years’ worth of land cover maps and bird observation surveys.
“What’s unique about this work,” said Vijay Ramesh, lead author and postdoctoral fellow at the Cornell Lab of Ornithology, “is that we contrasted historical datasets from two centuries ago with present-day data collected from the field. We show that maps, hunting records, and museum specimens can be leveraged to estimate baseline environmental conditions against which data from modern ecological surveys and satellite imagery can be compared.”
The research team – led by scientists from Columbia University, the K. Lisa Yang Center for Conservation Bioacoustics at the Cornell Lab of Ornithology, Indian Institute of Science Education and Research Tirupati, and 10 other institutions – found that 90% of grassland birds have declined relative to abundance since the 1850s. Eight out of the nine grassland bird species studied by the research team showed significant population declines, whilst birds such as the Nilgiri Pipit and the Malabar Lark showed the steepest declines over time.
“British settlers viewed grasslands as wastelands, and this notion has resulted in the large-scale plantations of tea, and exotic timber species (such as acacia, eucalyptus, and pine) that we see today in this highly biodiverse region,” said Ramesh. Somewhat surprisingly, however, the authors found that 53% of the forest birds they studied had not declined as dramatically over the past two centuries. “Some forest birds in the Nilgiri hills seem to be using timber plantations even though these monocultures do not offer the complex habitat structure that native forests can provide,” said Ramesh.
But the authors stress that this result is specific to the historical context in India and does not provide evidence that plantations are suitable replacements for all forest birds. Unlike forest birds that moved into timber plantations, grassland birds had little alternative habitat in the region: “We are losing grasslands at a rapid rate today, which has resulted in cascading effects on fauna that depend on these unique habitats. While forest conservation certainly requires continued attention, we hope that our work urges policymakers also to prioritise grassland protection and restoration equally. The key message we want readers to take away is that open natural ecosystems such as grasslands are undervalued hotspots of biological diversity,” Ramesh said. The results are now available to the public, and Ramesh hopes that conservation practitioners and Indian forest departments can assess which areas have undergone conversion from grassland to plantations and where restoration should be focused.
For more information: V. Ramesh, P. Hariharan, P. R. Gupte, A. V. Mohan, V. A. Akshay, A. Rajan, C. Das, I. Lockwood, V. V. Robin, M. W. Tingley, R. DeFries (2025). Grassland Bird Species Decline With Colonial-Era Landscape Change in a Tropical Montane Ecosystem. Global Change Biology 31:e70358. https://doi.org/10.1111/gcb.70358
