[lev99]

How will pollution be solved by de-urbanization?

Urban citizens have better access to low carbon transportation (Walking, Biking, Mass Transit).

Urban citizens are easier to reach in many last mile problems. Power lines can be shared by more users. Less network cable needs to be laid per user. Fewer miles of water pipes are required.

Apartments common in urban areas are more fuel efficient for heating/cooling than stand alone houses commonly seen in suburbs and rural areas.

[erikpukinskis]

If you think of pollution not as an issue with the total quantity, but instead spikes of concentrated, it makes sense.