The problem exists for several reasons.  One being where there are a lot of buildings and offices, there isn’t much room for trees.  Another problem is people are lazy and if there aren’t already trees grown naturally, they don’t want to take the time to plant trees, even if they live or stay in the area every day.  The problem doesn’t fix itself because while some trees can blow off seeds, causing a new tree to grow, it’s not enough to fix the problem, and there needs to be human contact within the issue so that people are planting trees and caring for them so they grow to be big and healthy.  If this problem is not fixed, parts of our city will not look nice, and over the course of time, the air will become very polluted.

Sources:

1.http://forestry.about.com/od/treephysiology/tp/tree_value.htm

2.http://www.mhmail.com/links/planting-trees.html