Climate change is occurring for many various causes. Firstly, natural disasters are the one of the most serious problems facing humans today. The United Nations Environment Programme (UNDP) reports that 75% of the world 's population lived in areas affected by natural disasters from 1980 to 2000 (UNDP 2004). Furthermore, floods, drought and more extreme hurricanes can lead to displaced millions of people. For example, there were terrible floods in the Yangtze Basin, China, in 1998 and 2002. In addition, sea level rise is also an important reason that will directly impact the disappearing land, agriculture production, large areas of migration and the city could be flooded.
Many large cities are located close to the coast, so these cities will probably be most affected by sea level rise. McGranahan et al. (2006 p.51) report that large urban settlements tend to choose low-lying coastal zones as their new habitats, and nearly 65% of huge cities which have over 5 million people are located in these zones. Other problems are some supplies of water resources and
References: list UNFPA: State of the world population, 2007: Unleashing the potential of urban growth, Chapter 5, viewed 16 July 2013 Hunt, A. & Watkiss, P. 2011, ‘Climate change impacts and adaptation in cities: a review of the literature‘, Climatic Change, vol. 104, pp. 13-49. UNDP 2012, ‘Building Greener Cities’, Asia Pacific Human Development Resource, pp. 121-143.