By Lucy Gibson
South of Velachery, a residential area of Chennai, there used to be thousands of acres of marshland called Kazhuveli. The marshland was a sanctuary for resident birds, such as the median egret, and migratory birds, such as the brown shrike that flew from its far off breeding grounds in Siberia.
However, over the past few decades, rapid development and encroachment have caused this marshland to disappear. All that remains of the Kazhuveli marshland is its southern portions. This makes up the Pallikaranai wetland.
Pallikaranai wetland is the only surviving wetland ecosystem of the city of Chennai.
It is also a site of strategic importance for biodiversity. Towards the end of their long migration, migratory birds have but few options for touchdown, before the miles of ocean beyond Tamil Nadu, except Pallikaranai wetland. Migratory birds, including greater flamingos, have been arriving at Pallikaranai in increasing numbers. In 2016, the rare and endangered Calidris tenuirostris(great knots) were spotted in the marsh – their last sighting had been in 1950-60.
On average, solely considering avian life, Pallikaranai marsh hosts over 40,000 birds in the migratory season, and over 5,000 resident birds through the year. It also serves as a breeding ground for resident birds like the threatened black-headed ibis, and the near-threatened spot-billed pelican.
Birds are just one element of Pallikaranai’s biodiversity. Plants, freshwater fish, mammals, reptiles that often go unnoticed, are also vulnerable to changes in wetlands and the interconnected water channels that feed them.
However, in amongst this wealth of biodiversity, is a darker and deeper problem.
An Anna University study in February 2019 noted that the marshland emitted a staggering 8.4 giga-tonnes of methane annually. Methane is a far more potent greenhouse gas than carbon dioxide, trapping up to 100 times more heat in the atmosphere than carbon dioxide in a 5-year period. While a healthy marshland can act as a much needed carbon sink, the extremely high levels of emissions today are upsetting the ecological balance of the ecosystem, as well as emitting large quantities of greenhouse gas up into the atmosphere. The study highlighted the 50-year old Perungudi dumpyard as the culprit.
In the 1970s, Perungudi dumpyard covered 19 acres, and was based in Sevaram village in Perungudi. But this filled up quickly. By the mid-1980s, the area was completely full, and the Chennai Corporation shifted the dumpyard to its present location in Pallikaranai. As a result, the marsh which originally covered 12,000 acres, had, by 2002 shrunk to 1,470 acres. Conversely, the dumpyard at Pallikaranai, which covered 140 acres in 2002, has expanded to 340 acres in 2007. This expansion is continuous even today.
The Chennai Corporation dumps 2,000 tonnes of waste into the marsh daily. As Perungudi dumpyard extends out into the wetland, the water has become increasingly contaminated by toxins found in the rubbish. This has resulted in leaching of heavy metals in the marsh, including chromium, lead, iron, manganese, cobalt, nickel, copper, zinc and cadmium. Water quality analysis indicated the presence of mercury, lead, and cadmium in quantities four times over permissible levels.
Thankfully, the MOEFCC under the National Action Plan for Conservation of Migratory Birds in Central Asian Flyway, the Pallikaranai marshland was prioritised. The State government declared it would commence the eco-restoration of Pallikaranai during 2018-2023. But there has been no suggestion of moving the Perungudi dumpyard, nor has Pallikaranai been added to the Ramsar site list which would gain it international predominance
With limited progress the toxins are leaching in. Since wetlands are common property it is essential that this trend be quelled to prevent the further destruction of Pallikaranai’s ecosystem.
There is scope for recovery, but only if the degradation is stemmed now.