Rhino fodder turns dry- Decline in moist grassland at Pobitora rings alarm bells
Guwahati, May 17: Rhinos at Pobitora Wildlife Sanctuary are slowly but surely losing their most preferred habitat — moist alluvial grasslands.
From 16.25 square km in 1977, the habitat, considered the best for rhinos, has shrunk to a mere 5.1 square km in 2009.
The implications for the sanctuary near here, which boasts the highest rhino density in the world, are scary with 84 rhinos at the park now jostling for space in the habitat, posing a challenge to the park managers.
Apart from making the rhinos more vulnerable to poachers and increase risk of straying, shortage of adequate habitat space could further compound the man-animal conflict.
A few years back, two persons were killed by rhinos at Chunchali on the outskirts of the city and probably the animals were from Pobitora.
Despite the problem of rhinos straying out, the park has, however, been relatively free from poaching in the past three years.
Satellite imageries in 2009 revealed that Pobitora is left with a mere 5.1 square km area of moist alluvial grasslands.
This was revealed in a study carried on “Assessment of habitat change and threats to the greater one-horned rhino (Rhinoceros unicornis) at Pobitora Wildlife Sanctuary” by Bibhab Talukdar and Pranjit Sarma of Aaranyak, a biodiversity conservation society.
The study, which used satellite imageries, disclosed that the area of moist alluvial grassland at Pobitora decreased by 11.15 square km during 1977 to 2009. It revealed that the area of moist alluvial grasslands was recorded at 16.25 square km in 1977, 10.67 square km in 1987, 5.57 square km in 1999 and 5.2 square km in 2004.
“Though rhinos prefer moist alluvial grassland most, in Pobitora, moist alluvial grassland is low and hence rhinos use dry grassland in an extensive manner,” Sarma, who heads the GIS (geographic information system) division of Aaranyak, said.
It was observed during field surveys that the moist alluvial grassland area declined at the sanctuary owing to the impact of subsequent floods and silt deposits in 1998 and 2004, followed by intense cattle grazing that increased from about 500 cattle in 1996 to more than 3,000 now.
The grassland growth at the park reduced substantially during 1998 and 2004, with excessive cattle grazing, a practice carried out by shepherds from the fringe villages, making matters worse.
“As such, the suitable rhino feeding sites have been declining. The deposition of silt has also reduced the size of wetlands and with it the area earlier covered with moist alluvial grassland” Sarma said.
”Not only that, the accumulation of water hyacinth and other aquatic plants has been found to reduce the area of moist alluvial grassland as observed in our field visits to the wildlife sanctuary since 1998,” Sarma added.
Over-grazing in the grassland areas and direct heat from the sun also reduces the moisture content of the soil. There has been a transformation of moist to dry grasslands at the wildlife sanctuary and thereafter from dry grassland to woodland.
Similarly, the net change in woodland area has seen an increase of 6.15 square km from 1977 to 2009 while dry grassland has decreased by 0.86 square km. Water bodies have increased by 1.01 square km and fallow land has increased by 4.85 square km during the period.
It has been found that woodland and fallow land has increased within the wildlife sanctuary over the years, which could have triggered food scarcity for rhinos during the dry winter months (November to March), forcing a significant number to stray out.
A forest department official said with a view to reduce pressure on limited grassland habitat, and given the increasing rhino population, translocation of 15-20 rhinos was the best way out. The move would further enhance rhino conservation, the official added.
Although the total notified area of Pobitora is 38.80 square km, the state government is yet to hand over an area of 11.07 square km to the park’s authority. As such, the forest department currently manages a total area of only 27.73 square km.