Montane birds hit by forest logging, climate change, finds IISc study

Bengaluru: Researchers at the Indian Institute of Science (IISc) who studied bird communities in tropical mountains over 10 years have concluded that forest logging can lead to loss of large-bodied species and decrease biodiversity.

Examination of data from the Eaglenest Wildlife Sanctuary, Arunachal Pradesh, underlined the need to safeguard primary forests to mitigate the effects of climate change.

The team found that understorey (vegetation layer beneath the canopy) insectivores are negatively influenced by logging and show steep declines in numbers. Logged forests also have lower densities of foliage-dwelling insects, reducing the resource availability for the birds that reduces the abundance of large species.

The study, published in Global Ecology and Conservation, analysed how the composition of mid-elevation Eastern Himalayan understorey bird community changed in primary (undisturbed) forests as well as in logged forests.

Tropical montane forests are critical biodiversity centres and unique ecosystems that can start at about 150-200 m and reach up to 3,500 m high up on mountains. “In tropical mountains, each species has a particular niche where it is found. This restriction creates much more diversity in a small space,” Ritobroto Chanda, former project associate at the Centre for Ecological Sciences, IISc, and corresponding author of the study, said.

Umesh Srinivasan, Assistant Professor at CES and another author, noted that birds of tropical mountain ranges are extremely temperature-sensitive and are responding to global heating rapidly.

The team found that many bird species have started shifting to higher elevations due to rising temperatures. Logged forests have higher average temperatures and lower humidity than primary forests. Smaller birds seem to colonise logged forests better because they can tolerate higher temperatures, while the density of larger bird species appears to be increasing in primary forests, IISc said.

Eaglenest Wildlife Sanctuary is situated in the biodiversity hotspot of Eastern Himalayas and is home to over 500 bird species. The final analysis included 4,801 understorey insectivores from about 61 species.

Srinivasan urged logging managers to ensure that undisturbed forests across large elevational gradients are protected, to allow species to shift their ranges upwards in response to climate change, and maintain survival.