A 5,000-hectare habitat of teeming fauna and flora has shrunk to a tenth of its size, and has turned a threat to the region and to its residents' health.

If you ever find yourself on the Velachery-Tambaram Road, a few kilometres south of Chennai city, you will be treated to an attractive view of a serene wetland – the Pallikaranai marsh. A few feet down the road, an unpleasant odour hits the nostrils sharply, indicating that there is more to the marsh than just a picturesque view. Before you can guess the source of the odour, you are in for a rude shock. Mounds of garbage, rotting and burning all over the marsh, greet your eyes.

Apart from being a home to hundreds of plants and animals, the Pallikaranai also houses one of Chennai's largest official dump sites. Over 250 acres of the marsh is choked by half of the city's garbage. The Chennai Corporation dumps 1,500 tonnes of waste into the Pallakaranai daily. But, garbage dumping is not the only problem that the wetland faces.

Once spread over 5,000 hectares, the marsh has been reduced to less than 500 hectares over the past 50 years. Rampant and unplanned urban development has gone hand in hand with reclaiming wetlands for commercial and industrial purposes, and the Pallikaranai is among the victims of the process. A myriad constructions and infrastructure projects have encroached upon the area.

These range from the National Institute of Ocean Technology, the Centre of Wind Energy Technology, and Chennai's Mass Rapid Transport System to mushrooming IT parks, restaurants, shopping malls, skyscrapers, hospitals and flyovers. With an increasing emphasis on infrastructure and development in the southern part of the city, the area around Pallikaranai has seen ad hoc proliferation of residential complexes and congested neighbourhoods over recent years.

The marsh is also polluted with millions of litres of untreated sewage, illegally discharged by the Chennai Sewerage Board, every year. This, along with unscientific dumping and burning of garbage, has contaminated the surface and ground water in South Chennai.

The SIPCOT Area Community Environmental Monitors group analyzed an ambient air sample collected downwind of the garbage dump in Pallikaranai and found that it contained at least 27 chemicals, 15 of which greatly exceed health-based standards set by the United States Environmental Protection Agency. Many of these chemicals target the central nervous system as well as the respiratory and cardio-vascular systems, besides the liver, kidneys, and blood, causing skin and eyerelated medical problems.

Three of the 27 chemicals are also known to cause cancer in humans and were found in quantities as high as 34,000 times above safe levels. Water and air pollution at the Pallikaranai has raised serious health concerns for residents in the area.

Wetlands are crucial in preventing coastal erosion and mitigating the effects of floods and cyclones. They also act as natural and long-term reservoirs of fresh water and play a significant role in ground water recharge as well as soil and water conservation. Additionally, they serve as breeding grounds for diverse, fragile organisms. Possessing aesthetic and heritage value, they also provide avenues for recreation and tourism, and thus livelihoods for the locals.

The United Nations Environmental Programme estimates that wetlands cover six per cent of the earth's land surface. Of these, India's share amounts to over 600,000 hectares. One-third of the country's wetlands have been wiped out entirely, altered or severely degraded, with little regard for their value and functions. A survey by the Wildlife Institute of India reveals that 70 to 80 per cent of freshwater marshes in India have been destroyed over the past five decades and continue to disappear at an alarming rate of two to three per cent every year. Loss of wetlands has led to an increase in flooding, reduction of water quality and a rapid decline in species and habitats.

The Pallikaranai provides an illustration. It is connected to 31 different water bodies, all of which release surplus water into the marsh during the monsoons. Therefore, the mash and its related tanks are part of a system that is crucial for mitigating flood waters. The water bodies in this system are inter-dependent; thus deterioration of the wetland cannot but result in the death of related water bodies.. The Pallikaranai's alteration has resulted in increased flooding in Velachery, a residential area in the vicinity of the wetland that struggles with poor drainage and inadequate culverts and canals during the monsoons.

In an attempt to preserve what remains of Pallikaranai, the Tamil Nadu Government declared a major portion of the marshland a reserve forest and handed it to the Forest Department under the Forest Act. Little effort, however, has been made towards its conservation. Garbage and sewage continues to be dumped into the marsh and new construction projects encroach upon its water bodies every day. The powers that be have taken no initiative to halt the callous destruction of this precious marshland.

Unless immediate action is taken by the State and local authorities, Chennai faces the risk of losing one of its last remaining ecosystems.