Opinion: Lessons in conservation from Pallikaranai marsh, writes Jayshree Vencatesan

Located in south Chennai, this semi-natural marsh with a unique hydrology that combines freshwater and brackish water systems, Pallikaranai marsh stands testimony to the efficacy of science based advocacy for conservation of natural resources.  

The area around Pallikaranai marsh was historically the natural water holding zone for the city of Chennai. This watershed extends around 231 sq. km, in which the remnant Pallikaranai marsh is centrally located.  

In addition to the marsh, there are about 34 man- made water-bodies within the watershed, as also the Nanmangalam Reserved Forest.   

If the year 1965 is considered as a reference point, the last 50 years have led to a 90 percent habitat loss of the Pallikaranai marsh, and the 683 ha that is currently under protection by the Tamil Nadu Forest Department represents only 10 percent of the original expanse.  

Within this loss of wetland area, three broad patterns can be discerned; the first, where large tracts of the marsh, especially those along the residential areas and  erstwhile villages of Thoraipakkam, Pallikaranai and Perungudi have been reclaimed into terrestrial habitats and converted into residential colonies. The second loss is characterised by habitat fragmentation wherein roads, infrastructure, municipal landfills, sewage treatment facilities etc. have fragmented the marsh into smaller portions and grossly impacted the natural drainage pattern. The third is a direct consequence of the first two, as also the unscientific manner of addressing flood control, wherein large tracts of the marsh have been invaded by invasive species of plants notably Prosopis juliflora and water hyacinth.

Historically, the marsh received copious volumes of freshwater due to seasonal surface run-off. The run-off was cleaner and well-oxidised as the surface over which it flowed was more open, covered with grass and low vegetation and less polluted with organic and inorganic wastes. Current patterns of surface runoff are very different and continue to change. Important changes are in the course of the flow; much of the run-off water has been diverted through narrow channels and closed storm-water drains, offering less scope for free oxidation as the water flows. There is also considerable mixing of organic waste in the water as the channels are generally used to dispose wastes during the dry months. 

The bitter truth is that Chennai has not been effective in factoring in wetland protection and conservation as a critical component in urban planning.  Worse still,  de-silting of water-bodies is proclaimed as the panacea for wetland degradation. It is therefore no surprise that availability of water in Chennai is 1,08l/capita/day compared to the other big cities like Delhi with 2,70l/capita/ day or Mumbai 2,60l/capita/ day. In fact, Chennai has the lowest availability of water among the largest cities in India and is categorised as a ‘water stressed region’. That a city which has historically averaged 1,248 mm as its annual rainfall could be designated a water stressed region clearly calls for something rather rudimentary – better management of wetlands.  — The writer is Managing Trustee, Care Earth