Pashan Lake,where a large number of migratory birds are seen in February-March,is now covered not by birds but Pistia (stratiotes),a water weed that spreads rapidly,evoking a hue and cry from local environmentalists. The virtual Pistia invasion started recently and the lake was covered around a week or so back,they said. They are seeking the urgent removal of the weed,which they say not only uses up dissolved oxygen in water,but also prevents oxygen from the air to mix with the water as it reduces the interface.
PMC officials,who had ignored the weed so far,first said it was water hyacinth but later agreed it was Pistia. They said they will soon start removing it.
Jayant Kulkarni,a city based environmental researcher and a regular visitor to the lake,says,The growth of Pistia this year has been unforeseen. A couple of months ago we saw it starting to spread from the shore and now it has captured almost all the area. It is really necessary that civic authorities look into this issue urgently. Pistia also favours mosquito breeding.
The man-made Pashan lake is home to numerous local and migratory birds including many waders and ducks like Northern Shoveler,Northern Pintail,Garganey and Common Pochard.
Dharmaraj Patil,an ecology researcher,says,The uncontrolled growth of this weed is an indicator of rising pollution. This weed also blocks light vital to submerged plants,in turn killing them. The subsequent bio-degradation further reduces dissolved oxygen. This can make potentially dangerous changes in the delicate wetland ecosystem.
Patil adds,The migration of birds is also based on their yearly learning along with hereditary instincts. One a generation learns about inhabitable conditions,birds will stop coming to the place.
Kulkarni says,Getting rid of the weed is a costly affair. It has to be deweeded physically before it starts flowering and producing seeds.
Shashikant Pardeshi,a resident of the area for 30 years,says,I have not seen the growth of this sort of weed anytime in my life. We have stopped going near the lake.
When contacted,Bhanudas Mane,deputy commissioner,PMC garden department,said it was water hyacinth but later agreed it was Pistia. We will soon remove it. We have asked fishermen in the area to give us boats.