Unless steps are taken to prepare cities, new growth will result in unplanned expansions of “existing slum settlements—poorly located, unserviced ghettoes, often on the urban periphery,” says Sierra.

Sierra说，如果城市不能做好准备，新的增长将导致“位置恶劣、缺少服务并往往位于城市周边地区的现有贫民区”的恶性扩张。