Threatened sangai deer’s habitat likely to shrink due to climate change

The suitable habitat of the threatened sangai or brow-antlered deer (Rucervus eldii eldii) found only in Manipur’s Keibul Lamjao National Park (KLNP) in northeast India is likely to narrow down and become limited by 2050-2070 due to climate change, according to new research.

The study published in the journal Environmental Monitoring and Assessment has revealed that the suitable distribution areas for the sangai deer will be narrower and will be restricted to the central core zone of the protected area (KLNP).

Unlike other national parks in India, KLNP is a 40 square km patch comprising mainly of floating biomass (locally called phumdi) and water body, in the southern rim of the saucer-shaped Loktak Lake, a Ramsar wetland of international importance and the largest freshwater lake in northeast India. As per the 2016 census, the park is home to 260 sangai.

The study modelled and analysed the habitat suitability potential for the current scenario and projected the future scenarios of potential habitat suitability of the sangai in KLNP based on climatic conditions and topography of the region.

Carried out by Vicky Anand and others from the Department of Civil Engineering, National Institute of Technology Manipur, Imphal under the guidance of Bakimchandra Oinam, the study used two climate change scenarios or representative concentration pathway (RCP) scenarios (RCP 2.6 and RCP 8.5) to create geographical distribution maps spinning to 2050 and 2070 and compared them to the current potential distribution map. The driving factors for the impacts are rainfall in the monsoon (wettest) months and isothermality.

“The study result indicates that the high suitability zones within the KLNP will decrease in terms of area (i.e. the spatial extent) and the high suitability zone will be limited to the central core zone of KLNP.  Secondly, the high suitability zone will shift from the western periphery of KLNP towards the central region,” Bakimchandra Oinam told Mongabay-India.

Sangai or the Indian Eld’s deer is one of the three subspecies of Eld’s deer found in South and South-East Asia. It has adapted itself to a unique habitat of the floating meadows or phumdi at KLNP, a marked difference from the other two, according to background information provided by the Wildlife Institute of India (WII). The sangai is identified under the Ministry of Environment, Forest and Climate Change funded Endangered Species Recovery Programme that is executed by the WII.

Sangai is listed as ‘Endangered’ in the IUCN Red List of Threatened Species and Schedule I of the Indian Wild Life (Protection) Act, 1972. Sangai is also included in Appendix 1 of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). The deer was thought to have gone extinct in 1951 until a remnant population was rediscovered in 1953 at the south-eastern fringe of Manipur’s Loktak lake in a survey conducted under the auspices of the IUCN.

Role of climate change in sangai’s survival

The WII had called for having a second home for the sangai as the present population at KLNP is a single, isolated population, and highlighted that the proposed reintroduction to a second site needs to be expedited. Their report identified encroachments into the lake, changes in the lake’s hydrology, impacts of the Ithai barrage, excessive proliferation and thinning of the meadows, susceptibility of the deer to inbreeding depression as some of the major challenges to the conservation of sangai. Poaching and death from disease are other factors affecting the sangai population and an appropriate protection strategy and disease-monitoring plan need to be developed and implemented to reduce mortality, the report said. Five sites were identified of which Pumlen Pat was considered as the most appropriate, but there were protests from locals.

The present study pointed out that isothermality and rainfall in the wettest months (monsoon season) are the two most important or significant climatic variables which influence the habitat of the sangai. Isothermality quantifies how long the day-to-night temperatures oscillate relative to the summer-to-winter (annual) oscillations.

The findings are linked to concerns raised by Anand and co-authors in a 2020 paper that highlighted a likely increase in both precipitation and temperature in the Manipur river basin which encompasses Loktak Lake and KLNP. The study found a high risk of floods in the lower regions near Loktak Lake and landslides in the northern part of the basin but said there is “no major concern” about water scarcity in the coming decades in the Manipur river basin.

Vicky Anand adds that precipitation is expected to increase more during monsoon and post-monsoon season as compared to pre-monsoon and dry season which may lead to stagnation of water in the low-lying wetland areas near Loktak Lake and further increase the risk of flooding in the future; the deer would be hemmed in by heavy rains and flood to specific hardgrounds in the park.

The KLNP has three hillocks and the 100-200 metre wide area called Thangbral-yangbi (locally) stretching from west to east is the only hard ground in the entire park; the rest of the area is covered by swampy phumdis. These features provide suitable feeding, bedding, and breeding ground for the sangai. But flooding in the monsoon season increases the water level of Loktak Lake which adversely affects the swampy phumdis. The three hillocks and the Thangbral-yangbi are the only hardgrounds in the entire park on which the deer can take rest and shelter especially during the heavy rains and floods, which makes the suitability zone very confined especially during monsoon, according to the authors.

The modelling results revealed that the area that has most suited to sheltering the sangai is decreasing, whereas the area not conducive to the sangai is increasing, especially in the northeastern zone of KLNP adjacent to the main water body of Loktak Lake which is of major concern. The second major observation is a shift in the high suitability potential zone from the western, northwestern and southwestern periphery of the KLNP to the central core zone of KLNP which is very limited but is the prime habitat of the deer.

“It was observed that the high suitability potential zone from western periphery of the KLNP to the central zone is getting shifted in the year 2050 but still the high potential patches are in minor contact with the western periphery, but in 2070 under both the RCPs it was seen that the high potential zone is completely limited to the central core zone of KLNP making the high suitability zone very limited and is of serious concern,” the study said.

Bakimchandra Oinam warned if such a situation persists then the natural habitat of sangai at KLNP (which is the only natural home of the deer) will be degraded beyond its recovery range.

“Three steps need to be taken to get back the natural habitat of sangai,” Oinam added. They are intensive ex-situ conservation, search for a suitable area which has similar physiographic (landforms) and climatic conditions like KLNP or the suitable climate parameters range predicted by the model as per current scenario; and demarcation of proper boundary along the eco-sensitive zone of KLNP to minimise anthropogenic pressures.

Chongpi Tuboi, Project Scientist Wildlife Institute of India who was not associated with the study told Mongabay India that the study rightly points out that the suitable habitat for sangai in the northern and southernmost boundaries of KLNP is limited. “These areas are primarily comprised of thin layers of phumdis and open water bodies,” Tuboi said. The authors claim that the central zone of the Park, including the hillocks, is most suitable for the sangai, is consistent with the availability of thick phumdis and low anthropogenic disturbances in this region, she said. The central zone is the prime habitat, and a significant proportion of the sangai population inhabits the area.

“This study gives an excellent glimpse of the shrinking habitat of the rare and endangered sangai of Manipur. The future predictions with the expected climate change scenario affirm the study by the Wildlife Institute of India that alternate actions such as relocation for the conservation of sangai are imperative. Such studies that can scientifically suggest appropriate habitats and predict future trends can guide decision-makers to manage this endangered population,” Tuboi said.

Banner image: A male sangai. Photo by Raul654 via Wikimedia Commons.