Though there are multiple reasons the population is growing so rapidly, there are a countless amount of events and tragedies holding the population back. There is a lot of deforestation and desertification going on in Asia. They are exploiting the land for a profit, for example in Burma they exploit timber, oil and mineral resources to support their government. There are also poor farmers all over using improper irrigation and fertilization practices causing a lot of the soil to be toxic. Another huge issue in Asia is water, due to the massive population it costs a ridiculous amount to treat the water so most water is polluted by untreated sewage, salt water, and industrial discharges.
In closing, Asian cities have been tended to grow more quickly than Western cities. Although, there are many attributes this such as population dynamics, economic markets and or/socio-political conditions, poor planning and disregarding environmental hazards like flood plains have held them back and only one, in my opinion, is the main reason for extreme growth. I