Rabindra Sarovar: A Sustainable Hotspot

Situated in the South of Kolkata, popular for its calm environment and fresh air supplying attribute, Rabindra Sarovar acts as an urban greenspace. It is surrounded by groves of old trees and has tree-covered islands. Due to regular use for recreational sports and purposes, the water surface in the artificial wetland is free of any emergent vegetation. Of the countless water bodies surrounding the city, Rabindra Sarovar, the lake of national importance and the second-largest waterbody in Kolkata, is bordered on the north by Southern Avenue, by the Rus road on the west, Dhakuria on the east, and the Kolkata Suburban Railways in the Southside. Around 73 acres constitute the water body and 119 acres constitute the residual area having a variety of floral species which are century old. 

It is true bliss with its spacious pedestrian walks and diverse flora and fauna, serving as an important accessory lung to the metropolitan city and, providing a natural carbon-dioxide sink, apart from its heritage and aesthetic value. Considered a large ecological reserve of great importance and recreational value, the lake ecosystem plays an important role in the urban environment and benefits society, serving as a suitable habitat for many amphibians, fish, reptiles, waterfowl, and migratory birds. Given its importance, the lake was declared a "national lake" in 1997 during the National Lake Conservation Program of the Ministry of Environment, Forests, and Climate Change.

FLORAL DIVERSITY

From marshy jungles, Lake Rabindra Sarovar was moved to its current state under the supervision of the Calcutta Horticultural Society. During the excavation of the lake, some remaining intact earth blocks in the middle of the lake were lifted and planted with flowering trees and shrubs. These blocks are now islands and have become attractive features of the lake. According to the flora studies of Rabindra Sarovar, it was found that there are about 366 species of terrestrial vascular plants and about 7,000 trees surrounding the lake. Some parts of the lake featured floating plants such as water lilies and other vascular plants. Some medicinal plants, such as Aegle marmelos, Aloe vera, Azadirachta indica, etc., are also recorded on the lake's website. The diversity of species in a small area is an indicator of the good environmental condition in the city. The abundance of flowers and undisturbed habitat is very necessary for species diversity. The density of the tree canopy is very important for the ecological security of the city and the development of the lake area as the lungs of South Kolkata.

FAUNAL DIVERSITY

The lake is a paradise for poultry farmers and attracts countless species of migratory birds and native birds. However, the administration’s efforts to improve long-abandoned lakes, islands and coastlines have deprived birds of nearly a century of solitude, which accumulates in large numbers along the lake and breeds in the area. At least 107 species of resident and migratory birds have been found in the lake of Rabindra-Sarovar. It is not known why birds were chosen to visit this skyscraper-lined lake, but the lake and its islands are home to many types of migratory birds each winter. The list of migratory birds (according to various reports in Rabindra Sarovar) includes – the Cotton Pygmy Goose (found exclusively in India, Pakistan, and Bangladesh), large-billed leaf warbler (found in central China and parts of the Himalayas), Tickell’s leaf warbler (parts of Asia), black-headed cuckoo shrike (India and parts of Southeast Asia), Asian sub-tail, and various flycatchers. The lake is home to many birds, such as the Painted Storks, the Trans-Himalayan migrants that have been spotted at Sarovar are Taiga Flycatcher and Blyth’s reed warbler, etc. In addition to migratory birds, there are a plethora of common birds found in the lake.

Urbanization of the ecosystem is best done by birds who act as excellent bio-indicators. Besides, birds are also identified as indicators of the quality of aquatic and terrestrial habitats. Bird diversity puts a major impact on the environmental change on biodiversity resources. In addition to the diversity of birds, Rabindra Sarovar is home to a fantastic diversity of invertebrates - mainly insects. Insects belonging to the orders Hemiptera (worms), Coleoptera (beetles), Lepidoptera (butterflies), and Lepidoptera (ants) have been documented in many studies. The lake is also rich in vertebrate animal diversity, including various fish, amphibians, reptiles, mammals, etc.

CLIMATE

Kolkata has a tropical climate. The average annual temperature is 26.8°C (80°F) whereas monthly the temperatures range from 19°C to 0°C (67°F to 86°F). Temperatures often exceed 40 ° C (104 ° F) in summer due to hot and humid weather in May and June. Winter leads to seasonal lows in temperature for two and a half months dipping to 12°C-14°C during December and January.

Pollution has always been a major concern in Kolkata and suspended particulate matter (SPM) levels are increasing higher than in other major cities in India, resulting in regular smog and haze. Whereas on the other hand the average temperature of the wetlands examined is 31.83 ?c which ranges from 30.70 ?c (Habildar tank) to 33.18 ?c (Hedua Park). And the highest temperature has been recorded in the pond under NRS hospital due to its high ambient density, while the minimum temperature has been recorded in Rabindra Sarovar (27.74 ?c). 

BACKGROUND

The city suffers from unbalanced growth, a rapidly growing population, constant pressure from migrant workers from rural areas, district towns, neighboring states, and industrial pollution. The lake at the southern end of the bustling and seriously polluted city is an oasis with wide paths; Giants, ancient trees, scenic views, and tranquility. In May 1958 the Calcutta Improvement Trust (CIT) named the lake (previously called Dhakuria Lake) Rabindra Sarovar after the legendary Bengal poet and scholar, Nobel Prize Winner Rabindranath Tagore for its unique ecosystem and environment, extensive green cover, and local flora and fauna. Gradually it has become an important cultural and recreation center of equal interest to pedestrians, joggers, sports, health and environmental enthusiasts, bird watchers, ecologists, botanists, wildlife photographers, local citizens, and tourists. 

Later, the lake's status as a national lake was upgraded due to its ecological importance. However, the lack of education and awareness is a result of the poor management of the lake and severe human pressures are causing lakes to show signs of rapid degradation in terms of vulnerable aquatic ecosystems and local environments.

FACTORS RESPONSIBLE FOR THE LAKE POLLUTION

The lake has unlimited growth of several local species, including Aponogeton, Azolla, Eleocharis, Hydrilla, Hygroryza, Ipomoea, Lemna, Nelumbo, Nymphaea, Potamogeton, Salvia, Utricularia, and various semi-aquatic and aquatic species of grass. Unlimited growth of aquatic vegetation turning into thick mats of floating vegetation has become a common problem, as well as falling water levels on various sides and corners of the lake. However, the authorities responsible for the lake do not show enough initiative to regularly clean up and remove the vegetation when required. Among hundreds of large mats accumulated in major parts of the lake, especially the coastline, which has trapped large amounts of floating waste and gradually deteriorated specifically the quality of the lake's water. Only during the monsoon, did it turn out that the level of contamination of the water parameters like the high load of pathogenic bacteria in the water, the low biological and biochemical demand for oxygen, the increase in alkalinity and turbidity helped show a certain reduction due to the extra amount of water in the lake due to heavy annual rainfall. But for most of the year, the lake's water quality continues to deteriorate due to extremely high local human pressures.

Due to the deteriorating water quality, swimming and rowing activities in lake water have been severely restricted causing skin allergies and reported fibers in the skin. The high disease-causing load in the water is attributed to the direct mixing of animal and human remains in the water, which increases eutrophication and works as highly loaded organic solids in water. In addition, the practice of idol submersion by indiscriminately throwing different idols and flowers as a part of Hindu celebrations and rituals directly into the lake water has become another major problem. This factor contributes to serious water pollution through the seepage of oil-based paints of synthetic lead from idols submerged in the water bodies, dumping of flowers, fruits, and various synthetic materials associated with idol production causes water rot, causing long-term environmental damage to aquatic ecosystems.

EFFORTS MADE

Kolkata Municipal Corporation (KMC) is working to protect the environment of the lake and its surrounding areas under the strict supervision of the State Pollution Control Commission. Recently, a curb was implemented for negligent disposal of household waste in and by the lake. However, recovery is hampered by a lack of available funds, as well as the poor nature of the area due to little or no maintenance. Restoring the lake ecosystem will be quite costly, according to KMC officials, due to problems with ongoing algae blooms, waterweed infection, and dumping of waste along the lakeshore. The drainage system will require substantial renovation and care should be taken to ensure better aesthetics as well as rapid erosion of the lake.

Awareness of the ecology and delicate biodiversity of this unique ecosystem in a bustling city like Kolkata is slowly gaining momentum. Civic groups and clubs are campaigning to restore and maintain the lake's ecosystem. The level of awareness of keeping the lake water and nearby facilities free from contamination and disturbances has certainly increased. The lake has over the last five or six decades been a point of positive social interaction and appreciation of the aesthetics and beauty of nature, and we must realize that all good things have a price. Security/surveillance of the entire area has been significantly improved through measures like the installation of large steel gates on entrances/exits with private security personnel stationed regularly for surveillance and patrol. However, measures are still needed for the continued sustainability and protection of this man-made ecosystem.