Bird species' decline causes concern

A recent Mongabay-India (MI) report highlights a two-decade-long bird monitoring study in Trans-Himalayan region of Spiti Valley in Himachal Pradesh, India, which finds that bird densities have declined most sharply in ungrazed steppe habitats, areas facing the least direct human disturbance. This points to broader stressors such as climate change operating beyond land-use change alone. The study underscores the importance of long-term, community-supported monitoring and maintaining landscape-level habitat diversity in high-altitude, multi-use regions like the Trans-Himalayas.

As the MI report states, the insights are documented in a study published in ‘Ecological Applications’ in which the researchers report that bird densities declined across habitats, but the only statistically significant decadal decline was in the ungrazed steppe, the habitat facing the least direct human disturbance. Ungrazed steppe refers to high-altitude grassland kept free from livestock grazing, where vegetation is allowed to grow largely undisturbed over long periods. Although often described as grasslands, the Spiti region is technically a cold desert, where vegetation occurs as rangelands, a mosaic of shrubs, alpine meadows, and sparse grasses. The study tracked changes in bird populations across Spiti’s diverse habitats, shaped by both local human activity and broader climate forces.

As the Abstract of the study points out, anthropogenic land use change due to farming and livestock grazing has altered biodiversity composition greatly in ecosystems around the world. This is especially true in grasslands and rangelands; however, these ecosystems in high-altitude regions remain understudied. Moreover, anthropogenic effects in these habitats in the long term remain poorly understood. The researchers studied bird densities and composition across four different habitats along a gradient of intensity of land use (crop fields, grazed meadows, grazed steppe, and ungrazed steppe), in the region. Ungrazed steppe harboured more habitat specialist species and high bird densities. Grazed habitats were generally unfavourable for birds, with lower densities and possibly lower species richness. Decadal changes in densities revealed declines in the least used ungrazed steppe habitat, highlighting a possible role of climate change. Holistic land management practices, including continuing traditional (organic) farming and maintaining ungrazed patches in grazed rangelands, could help maintain coexistence between biodiversity and people in these multiuse landscapes. Started in 2002, this continuing study is one of India’s longest running bird monitoring programs.

The results found that bird communities differed significantly across habitats, the MI report states. Crop fields supported the highest bird densities, but those communities were dominated by generalist and commensal species such as house sparrows and hill pigeons. Habitat specialists, birds closely tied to steppe vegetation and structure, were largely absent or present in very low numbers. The most concerning findings emerged when the researchers examined change over time as it points to deeper, systemic pressures beyond land-use change alone. Comparing the early period of the study (2002–2010) with the later years (2016–2023), bird densities declined across all habitats. However, the decline was statistically significant only in the ungrazed steppe. The study cannot directly separate climate effects from land-use change in disturbed habitats, but the authors hypothesize climate change could be contributing, especially because the ungrazed steppe remained stable in land use. Unlike land-use change, climate stress operates across entire landscapes. In Spiti, where elevations already approach the upper limits of habitable terrain, birds have little room to shift further upslope in response to warming.

The MI report says that similar studies in the Tibetan Plateau have shown that high-altitude birds are facing mounting pressures from climate change and land-use intensification. Spiti, while remote, is part of a wider pattern in the Trans-Himalaya, where the effects of warming are compounded by changing agricultural practices and infrastructure development.

Quoting another study from 2024 on Himalayan birds, the MI report points out that it highlights that “birds and much of the flora and fauna in tropical mountain ranges are extremely temperature-sensitive and are responding to global heating rapidly.” This supports the recent findings in Spiti, where birds are already facing significant declines in both disturbed and undisturbed habitats due to climate and land-use pressures. The findings challenge the assumption that protecting land from direct human use is sufficient to safeguard biodiversity and caution against framing conservation and livelihoods as opposing forces.