The correct answer to this open question is the following.
Although there are no options attached we can answer the following.
Hundreds of acres of forest were cleared each week to make room for new residents. Without controls on development, housing tracts pushed deep into the rural fringe.
And this is exactly what happens when there is no zone planning to stop urbanization to enter the rural areas or the country. Cities start to expand and become larger and larger than they constantly "devours" rural zones that originally were used for agriculture. Housing developers cut down trees, affecting the environment and the wildlife that used to live there. Fewer trees mean more air pollution and less oxygen.
We have many examples: the city of Los Angeles, Atlanta, Portland, New York-New Jersey, or Toronto in Canada.