For ecologists, the disappearance of sparrows is a sign of the shrinking bio-diversity in the city.
Apart from blaming the expanding concrete jungle, some experts say the planting of exotic trees such as the Gulmohar and the Copperpod, which are not native to India, are driving away birds, insects and animals such squirrels and monkeys.
Anand Pendharkar (38)
An ecologist, and founder trustee of Sprouts, a wildlife conservation group, Pendharkar explains the impact of the depletion of indigenous trees in the city, in an interview to the Hindustan Times.
What is the difference between an indigenous and an exotic tree?
Indigenous trees such as the Banyan and the Peepal have been in the city for thousands of years. They thrive in the conditions of the local environment and are a source of food and shelter for the birds, animals and insects that inhabit the area.
The exotic varieties such as the Gulmohar and Copperpod have been brought to the city from another environment, and cause lots of problems in the local ecosystem. They can’t regenerate on their own, they don’t survive easily, and for the local fauna, they’re as useful as a plastic tree.
How exactly does an exotic tree damage the ecosystem?
Birds, insects and animals in an area have eating habits formed over thousands of years.
They won’t eat the fruit of a tree that is alien to them, the bees won’t suck nectar from its flowers, and no creature will make a nest in them as the kind of material they need is often not available in the exotic trees.
In other words, they get neither food nor shelter from them. So, when you plant an exotic tree in place of an indigenous one, you’re taking away their home from them and driving them away from that area.
Some say birds like crows, pigeons and kites do nest in trees like the Gulmohar and the Rain Tree. Isn’t that a good thing?
Crows and pigeons are the equivalents of pests among birds. They’re scavengers and have very high adaptability. They can live almost anywhere.
Also, if these birds are the only ones nesting in the exotic trees, where will the rest go? The biological diversity of any neighbourhood will turn extremely depleted if all of them start having exotic trees.
How do you know the decrease in the city’s bird population is not just because of development?
If that were true, you would find a low population density among these birds in all areas — which we haven’t seen.
I’ve seen sunbirds, orioles, tailorbirds and rare birds like the monarch flycatcher come to my building society in Andheri, after we planted a few indigenous trees in the area.
I don’t live near the national park, so these birds have
come here intentionally. You’ll see the same thing in the IIT Powai campus, and in the Bhavan’s College campus. But go to Shivaji Park and tell me if you can spot any birds or butterflies.
Many people have expressed concerns about the steady decline in the city’s sparrow population. Is this also somehow related to the loss of indigenous trees?
Definitely. Sparrows need a certain kind of wood to make their nests. The wood in Gulmohar trees is too soft for them. They need the kind of wood that is available in trees like the Indian Coral Tree, Teak or Bhend.
Without them, they have no place to live, and will migrate away from the area. Another reason for the decrease in their numbers is the loss of wetlands and grasslands, which were a source of food for them.