A city like Bangalore has almost an impossible amount of scooters on roads. Almost every house has at least one, and most homes have easily 1 for every two people staying in the home. And its not like US where there are laws on building homes. People take a 1200 sqft plot and build 4 floors, with 4 families, so at least 6 two wheelers for a small plot of land. This is even possible because auto rickshaws and buses have gotten expensive. Public transport of any kind is expensive, unpredictable and not worth when you look at the overall comfort and economics of having our own scooter.
At the other hand trees are being cut at an alarming rate. The area where I stay, around 15 years back, had a drive where students from an agricultural campus plotted a tree per home. In the time since a countable few trees remain. People cut trees for various reasons, some which are down right stupid. Reasons go like- A big tree will attract birds who will in turn crap on our cars/scooters, or that chirping birds disturb their morning sleep to impossibility of cutting the tree if grows too high.
The garbage landfill are full. So the government often doesn't collect garbage on time. Sometimes even a whole month passes before the garbage is collected. So you have massive piles of trash(Medical and all other toxic waste included) piling right at the corner of the lane. This causes mosquitoes to breed, and then diseases like dengue spread. The most obvious solution people around the place work to is burn the trash, causing all this toxic fumes to now mix in the air and reach almost everyone's lungs in the area.
On top of this comes industrial pollution. Rivers and lakes are being polluted, encroached and destroyed almost everywhere. Bangalore's lakes have almost disappeared. Many remaining are now cesspools. There was a lake which caught fire recently.
India needs something on the lines of Clean air act, and clean water act urgently. Feasibility of implementation remains a problem though.