Land use change threaten bird habitat

Kathmandu, July 10: Nepal's unique biodiversity faces significant threats from climate change and land use change, impacting the distribution and habitats of various species of birds. A recent study conducted in Nepal by a team led by ornithologist Hem Bahadur Katuwal sheds light on the vulnerability of the Lesser Adjutant (Leptoptilos javanicus), commonly known as Bhudiphor Garud in Nepali, a large-sized waterbird species, to these environmental changes. 

The research reveals that climate and land use changes have a substantial influence on the distribution and nesting habitats of this globally vulnerable species.

Between 2012 and 2023, researchers collected distribution data from 24 districts and nesting site information from 18 districts in Nepal. The study documented 581 fledglings (young birds) from 346 nests in 109 territories during a nationwide breeding survey conducted in 2020, said ornithologist Katuwal, lead researcher.

The findings, based on an ensemble model, indicate that the Lesser Adjutant currently has a potential distribution of 15 per cent (21,637 km2) and a potential nesting habitat of 13 per cent (19,651 km2) within Nepal. Agricultural landscapes comprise the majority of the predicted distributional and nesting habitat, accounting for over 70 per cent of the suitable areas.

The study also predicts a potential range expansion for the Lesser Adjutant under SSP5–8.5 (Strategic Sustainability Plan for the conservation and management of a particular species) scenarios for the 2070s, projecting an increase of up to 15 per cent (21,573 km2) in distribution and up to 12 per cent (17,482 km2) in nesting habitat. This range expansion is expected to occur mainly within the current distribution and breeding range, particularly in Lumbini and Sudurpashchim provinces, extending to the northern portions of other provinces such as Siwalik and Mid-hill regions. 

However, the current Protected Areas and Important Bird and Biodiversity Areas in Nepal are deemed insufficient in providing optimal habitats for the species.

This species is primarily found in Southeast Asia, including countries such as India, Bangladesh, Myanmar, Thailand, Cambodia, Laos, Vietnam, Malaysia, Indonesia, and the Philippines. They inhabit wetland areas, including marshes, swamps, and riverbanks.

According to the research, despite the range expansion predicted by the model, the successful use of these novel habitats depends on the availability and protection of large-sized trees including Bombax ceiba, which are crucial for nesting.

Unfortunately, unplanned urbanisation and commercial activities have led to the decline of agricultural landscapes and the felling of large trees, exacerbating the challenges faced by the species, said Katuwal.

The Lesser Adjutant is listed as "Vulnerable" on the IUCN Red List of Threatened Species. Their population has been declining due to habitat loss and degradation, primarily caused by the conversion of wetlands for agriculture and urbanization. They are also vulnerable to hunting and disturbance. 

Conservation efforts are focused on protecting their habitats and raising awareness about their importance, he said.

According to Katuwal, the Lesser Adjutant plays a vital role in South and Southeast Asian ecosystems. Previous studies primarily focused on 

isolated locations and lacked comprehensive information on potential habitats and preferred nesting trees across Nepal. 

The current study highlights the need to consider emerging risks such as climate change and anthropogenic threats in conservation efforts for the species, he said.

Understanding the impacts of climate and land use change on large breeding waterbirds, like the Lesser Adjutant, is crucial for implementing effective conservation strategies in agricultural landscapes, Katuwal added.