CHENNAI: The ecologically sensitive Pallikaranai marsh is reeling under a new threat. Reduced to a mere 695 hectares due to ‘development activities’ as well as blatant encroachments over the years, it is now being overrun by Typha, a rapidly-growing and invasive native grass species that is forcing away migratory birds.
Deficient rainfall and other natural causes have led to the ‘invasion’ that threatens to change the very character of the precious wetland and could lead to an ecological disaster if not properly managed, fear conservationists on the eve of World Wetlands Day (February 2).
Ranjit Daniels of city-based biodiversity research organisation Care Earth says the Pallikaranai marsh, where the grass keeps changing the proportion of water to land, is a classic example of how wetlands change influenced by rainfall and vegetation succession. The grass has now covered the mudflats, forcing waders such as sandpipers and black-winged stilts to look for new habitats.
Birds cannot be confined to a demarcated boundary and shift their habitat according to the availability of resources, said Daniels. This is particularly true in the case of visitors to wetlands from the northern hemisphere as well as local migrants. The dynamics of wetlands, where the reduction in the water-spread area forces birds to look for alternative sites, should be foremost on the minds of the authorities when they take up conservation measures, he said. The focus should be on protecting wetland complexes rather than concentrate on individual wetlands.
Other experts said the authorities should also factor in climate change which plays an important role in changing habitats. The natural drivers of such changes, said former head of the TN forest force and principal chief conservator of forests C K Sreedharan, include changes in solar activity and large volcanic eruptions. “We now live in an era in which both human and nature-induced factors cause climate change which affects the quality of life now and in the future. Plant, animals, and humans will be definitely subjected to the consequences of climate change for thousands of years with a little remedy,” he said.
The near-dry wetlands are also due to a poor northeast monsoon in Tamil Nadu during 2018, accounting for a rainfall deficit of as much as 54%. It is being attributed, among other factors, to the absorption of heat by oceans, affecting the precipitation over land. The effect is showing.
The arrival of migratory birds for nesting and breeding to the various wetlands in the state is almost nil. Birds are fortunately endowed with the inherent capacity to change their regulatory migratory haunts and move to other conducive areas to survive. But, they may have to forego a breeding season resulting in future populations going into decline, warned Sreedharan.