This is just my thought. If someone has or bought 3 acres of unused land in the accessible area, in the half of the land he can grow a small forest and later turn it into a private picnic destination with walkways for jogging, small water bodies, etc. With time, the remaining half would cover many times then value of the forested land. One can build apartment complexes, restaurants and other businesses, or sell the residential land for the same. Plus points are, you would give clean air to the environment, and as the traffic increase, the economy in the region would also thrive with small local businesses.
To grow forest, on some places we just need to leave the land as it is, and some other regions, investment in irrigation and cultivation of nature friendly fast growing trees and plants must be needed.
Edit: I'm visualizing India here. Other places with less unused land might adapt to technology to curb the pollution.