Sustainable development has been the key concept, both in economic policies and in environmental management. On the basis of an systems ecology perspective, this study suggests the sustainable development of Korea's natural environment and economic activity using the EMERGY evaluation. The total EMERGY use(7,730 E20sej/yr) in Korea is 81 percent from imported sources, fuels and goods and services. The ratio of outside investment to attracting natural resources is already large, like other industrialized countries. Continued availability of purchased inputs at a favorable balance of EMERGY trade, currently about 2.85 to 1 net EMERGY, is the basis for present economic activity and must decrease as the net EMERGY of purchased inputs including fossil fuels goes down. EMERGY yield ratio and environmental loading ratio were 1.23 and 20.30, respectively. The population level is already in excess of carrying capacity. Its carrying capacity for steady state on its renewable sources is only 2.2 million people, compared to 45.9 million in 1997. EMERGY sustainability index is therefore less than one, which is indicative of highly developed consumer oriented economies. Until now the development of a country has been achieved by the economic growth, but it can be sustained in the long run by the use of renewable resource systems, the efficiency of energy usage, and the transformation of the social-economic structure based on an ecological-recycling concept.

Sustainable development has been the key concept, both in economic policies and in environmental management since 1970s. In the view of systems ecology, sustainable resource use strategies are considered to be essential in achieving sustainable development. During the last three decades, the discipline of systems ecology has applied ecological energetic analysis to the evaluation of the contribution of natural environments to economic systems. EMERGY analysis of main energy flows driving the economy of humans and life support systems of a city was made including environmental energies, fuel, and inputs, all expressed as solar emjoules. Total EMERGY use of Pusan was 3.89 E22 sej/yr, about 90 percent of it was purchased sources from outside during eleven years from 1985 to 1995. EMERGY flows from the environment were less than 10 percent. EMERGY yield ratio and environmental loading ratio were 1.10 and 10.45, respectively. EMERGY sustainability index is therefore less than one, which is indicative of highly developed consumer oriented economies. Development of a city has been achieved in the short run by the economic growth, but it can be sustained in the long run by the use of renewable resource systems.

Pusan has experienced some different paths of urbanization and industrialization compared to other cities, and has faced the problem of over-saturation in environmental capacity. Pusan needs to find out sustainable development strategies based on Agenda 21 by UNCED in 1992 to secure urban renewal. Therefore, Pusan`s sustainable development strategies focus on the 1)research on environmental capacity and reasonable population accommodation 2)supply of basic environmental facilities for the human settlement 3)protection and efficient management of environmental pollution 4)saving and control of energy and other resources 5)independent and stable execution of plan based on biological relation 6)harmony between nature and urban spatial organization. In addition, these policies can be suggested along with the conclusions; First, establishment of green plan-middle and long term environmental goals included in the urban planning to reduce environmental deterioration and pollution. Second, computation of sustainability index-the index is necessary to sustainable urban development, which is related with green GNP of the national level. Third, capacity estimation of nature and social environment-estimation of environmental capacity to the civilized area is required become an ecopolis, and is required to focus on the western area of Pusan which has high degree of potentiality.