Excessive deforestation, encroachment, human settlement, grazing, timber harvest and over-exploitation of natural resources have accelerated the deterioration of the local environment in Brahmaputra floodplains which in turn has threatened grassland birds.
This has been noted in a report “Identification of network of grassland corridors for Conservation of Threatened Birds of Brahmaputra Floodplains, India”.
Girish A Jathar Principle Investigator, Assistant Director, Climate Change & Himalaya Programme Bombay Natural History Society (BNHS) carried out the survey along with Akshaya Mohan Mane Project Scientist and Senior Ornithologist.
They were assisted by BNHS Scientist Team: Biswajit Chakdar, Nglukholala Khongsai, Himadri Mondal, Monsonjyoti Gogoi, and interns and volunteers Sanatomba Singh and Rakesh Muni.
Grasslands are the largest ecosystems and occupy 30-40 % of Earth’s land surface.
The threatened grassland birds found in the Brahmaputra floodplain are Bengal Florican (Houbaropsis bengalensis), Swamp Grass Babbler (Laticilla cinerascens), Swamp Francolin (Francolinus gularis) White-throated Bushchat (Saxicola insignis), Jerdon’s Babbler (Chrysomma altirostre), Slender-billed Babbler (Turdoides longirostris), Marsh Babbler (Pellorneum palustre), Black-breasted Parrotbill (Paradoxornis flavirostris), Bristled Grassbird (Chaetornis striata), Yellow-breasted Bunting (Emberiza aureola) and Finn’s Weaver (Ploceus megarhynchus).
The IUCN status notifies these birds as either vulnerable or endangered.
“In most of the non-protected areas, we found various anthropogenic activities and natural events which have changed the habitats leading to its degradation and transformation of the habitat. As the population has grown in the region, the land use has changed due to expansion of agriculture, settlement, developmental projects, and over-exploitation of natural resources in most of the big grasslands patches turning them into smaller and patchy fragments,” Jathar told India Today NE.
Over the last 45 years, the mosaic of grasslands, wetlands, and agriculture patches has been converted to either tea gardens or contiguous agriculture areas in most of the districts of Assam. Population growth has led to the expansion of urban and suburban areas in Kamrup, Dhubri, Majuli, and Tinsukia, the report stated.
During our surveys, we observed high anthropogenic activities in grassland areas of the Kamrup, Tinsukia, and Jorhat districts. In Dhubri where except for a couple of river islands, most of the grassland areas have been occupied by settlers and encroached on for agriculture. Although on river islands, the average grass percentage was quite high disturbances such as grass cutting, burning, grazing, waste generation, transportation, and sand extraction are equally high as compared to the other districts, Jathar said.
The study revealed that the land use of the island has changed significantly from fallow land to settlement, grassland, and water body; grassland to settlement, water body; and plantation to settlement and fallow land. As well as, Barman (2013) study found that the majority of the grassland and fallow lands were eroded by the Brahmaputra. The study also suggested that the total grassland declined by 22.62%, fallow land by 18.6%, areas of plantation by 2.19 %, and water bodies by 0.16 per cent . Scientists found that human settlement has increased by 1.47% from years 1998 to 2008 due to population pressure on Majuli island.
Our survey from non-protected areas of seven districts (23 sites) showed various man-made and natural threats to the grasslands namely, grazing, invasive species, grass-cutting, and burning activities, agriculture, uncontrolled tourism, waste disposal, transportation, fishing, sand extraction, settlement, feral dogs, developmental activities, floods, habitat succession, etc, the report stated.
During our survey and interaction with farmers and fishermen, we found that hunting, grazing, grass cutting, fire, agriculture, and floods are the major threats to the grasslands. In recent years, the land use of this area has been changed from grasslands to agriculture, Jathar said.
The Swamp Grass Babbler, Slender Billed Babbler, and Jerdon’s Babbler have been found mostly affected by anthropogenic activities in the study.
According to the study, Swamp Grass-babbler has been appearing to be much localized or present at very low densities along the Brahmaputra River. The survey found small populations surviving on river Islands of Brahmaputra floodplains. A total of 35 individuals were observed at four locations comprising grasslands and islands. All sites are non-protected areas and have immense anthropogenic pressure on their habitat.
During our survey, we observed Swamp Grass-babbler (20 individuals) in Saccharum procerum( a grass) dominated habitat with 70 % ground cover, and 150-300 cm average grass height. The habitat was a mixed mosaic of agricultural patches in and around the grassland. The agricultural invasion, grass usage, and habitat change by flood and siltation were observed threats to their habitat. The grass cutting was rampant on a couple of islands. The birds were observed foraging on insects on crops next to grassland habitat, the study reported.
“In 2018, we observed a pair of Slender Billed Babbler in Orang NP during its breeding season. However, in 2019 we could not find it at the same location. This could be possibly due to the degradation of habitat owing to grass burning at that time. In 2014, the birds were observed at the same locations in Orang NP,” Jathar said.
In our recent surveys, we found Jerdon’s Babbler in Agaratoli, Kohra ranges of Kaziranga National Park, Manas NP, and grasslands at Maguri Beel, Tinsukia. Scientists reported this species from Lika and nearby tall grassland patches of Dibru-Saikhowa NP in 2016. It has historical records from Orang NP since 2010 as well but no recent sightings from the area, the study said.
In a recent survey, Jerdon’s Babbler has been recorded in tall wet grasslands and reeds of Phragmites karka and Saccharum sp. with an average ground cover of 70-100 % and average grass height of 100-150 cm. The grassland habitats around Amarpur and Churki Chapori have been degraded due to agricultural expansion, overgrazing, fire, and seasonal floods in an area. Additionally, developmental projects such as big bridges have led to degradation and change in the habitat of Jerdon’s Babbler, the study revealed.
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