According to a report released by UN science and technology committee, the earth in the 1990s was plagued by natural disasters such as earthquakes, floods and so on, resulting in a yearly loss of 40 billion on average, being three times as much as that of the 1980s. The report is based on the study of a group of specialists from different countries in recent 10 years. The report says that human activity, concentration of population in the city and the blind tapping of resources in develping countries are to be blamed for the degradation of ecological balance in that they have caused various calamities which in turn deteriorate the ecological environment. However, the report does not make any reference to the developed countries for the responsibility.