Cities can be sustainable because of their density, as Richard Florida notes: Ecologists have found that by concentrating their populations in smaller areas, cities and metros decrease human encroachment on natural habitats.
And while cities like Manila, Bangkok, and Mumbai are dense, their lack of public transportation and their governments' inability to regulate their car industries have made them extremely polluted.
Cities, especially those with global influence, are obvious targets for terrorists due to their high populations and their role as symbols of globalization that many terrorists despise.
Births, deaths and migration are the 'big three' of demography, jointly producing population stability or change
A population's composition may be described in terms of basic demographic features — age, sex, family and household status —and by features of the population's social and economic context — language, education, occupation, ethnicity, religion, income and wealth
The distribution of populations can be defined at multiple levels (local, regional, national, global) and with different types of boundaries (political, economic, geographic)
some communities have reservation against polio vaccination Role of education in public health awareness; do parents discriminate sons and daughter in matters relating to their health and education?
individual and family decisions behind migration, impact of immigration from one to another village or state, why is migration rate high with educated people, how has rural economy been affected by rural-urban migration?
the relation between birth rate and economic development, urbanization and industrialization, the differences in birth rate between rural and urban population, religion and birth control etc.
what is an ideal family size? Cost of rearing a child, family planning awareness and interest in birth control, need for education and aspiration for children