Emergy Analysis Of Agricultural Eco-Economic System In South Hilly Region

Hengdong is a typical hilly county in the south of China. It is helpful for us to understand the level of agricultural development and the existence questions in the south hilly counties in China, to analyze agricultural eco-economic system of Hengdong. In virtue of emergy analysis theory and the method founded by Odum, a famous American ecologist, all the things as follows were evaluated in this paper:the real condition of energy and material flows, the real value of energy and materials of input and output, the contribution of environmental sources to economic, the level of agricultural development and the existence questions in Hengdong agricultural eco-economic system in 1995,1999 and 2004. This study provides the instruction significance for the government to formulate the policy of agricultural development and the theory basis for the agricultural development of south hilly counties in China.The emergy analysis of resource basis of Hengdong agricultural eco-economic system has been performed, which includes renewable environmental resources emergy, nonrenewable environmental resources emergy, nonrenewable industrial subsidiary emergy and renewable organic subsidiary emergy, the results showed that the total emergy used for agricultural eco-economic system in Hengdong were estimated at 2.37X 1021 sej,2.64X 1021 sej and 3.07X 1021 sej, in 1995,1999 and 2004 respectively, with the upward trend. Natural resources are the basis for agriculture production of which real value and contribution to the economy were evaluated by using emergy theory. The renewable environmental resources emergy used for Hengdong agriculture, separately were 2.20 X 1020 sej,2.40 X 1020 sej and 2.43 X 1020 sej, in 1995,1999 and 2004, accounting for 9.27%,9.10%and 7.90% of the total input emergy in the year, with the decreasing trend. The nonrenewable environmental resources emergy in 1995,1999 and 2004, was the same for 1.89×1015 sej, but the proportion of that to the total input emergy were 4.97%,4.47% and 3.84% respectively, with gradually reducing. The nonrenewable industrial subsidiary emergy used in 1995,1999 and 2004 were estimated at 1.06X 1021 sej,1.16×1021 sej and 1.45 X 1021sej respectively, accounting for 44.67%,43.97% and 47.25% of the total input emergy, at first increase then reducing; the renewable organic subsidiary emergy use were separately estimated at 9.75×1020 sej,1.12×1021 sej and 1.26×1021 sej, accounting for 41.09%,42.46% and 41.01% of the total input emergy in 1995,1999 and 2004, with first declining after rising.From the analysis of yield emergy of system, it is clear that the total yield emergy of the agricultural system in Hengdong county, including crops yield emergy, livestock yield emergy, forestry yield emergy as well as fishing yield emergy were increasing from 1995 to 2004.In the 1995,1999 and 2004, the total yield were separately 1.93×1021 sej,2.63×1021 sej and 3.04X×1021 sej; the crops yield emergy were 6.63×1020 sej,7.45×1020 sej and 8.76×1020 sej respectively and the proportion of the crops yield emergy to the total yield emergy for the year were 34.38%,28.36% and 28.78% respectively, with first declining after rising.The livestock yield emergy calculated in 1995,1999 and 2004, were separately 1.15×1021 sej,1.72×1021 sej and 1.97×1021 sej, which were 59.81%,65.53% and 64.61% of the total yield emergy for the year, with first increasing after decreasing. In 1995,1999 and 2004, the forestry yield emergy were 6.18×1018 sej,8.41×1018 sej and 9.67×1018 sej respectively and the proportion of the forestry yield emergy to the total yield emergy for the year keeps constant at 0.32%. The fishing yield emergy separately estimated at 1.06×1020 sej, 1.52×1020 sej and 1.92×1020 sej in 1995,1999 and 2004, account for 5.49%,5.79% and 6.30% of the total yield emergy for the year, with the rise trend.By analyzing the emergy input and output of the system, the emergy-based evaluation index system of agricultural eco-economic system of Hengdong is founded. Based on the analysis of the several main emergy indices, we know that the Hengdong county agriculture is in the transition from traditional agriculture to modern agriculture, and the development level of which is higher than the average level in china, less than developed countries and regions. The agricultural development of Hengdong county is almost independence of environmental sources, while depends on purchased emergy which are gradually increasing. The net emergy yield ratio of Hengdong agricultural system which is decreasing gradually, is constantly lower; the environmental loading ratio which is still increasing, is relatively high, and the emergy per area and the emergy per person are growing steadly.According to these conclusions, five suggestions are put forward:firstly, enlarging basic energy sources of the agricultural eco-economic system in Hengdong and improving the ratio of utilization of natural resources; secondly, increasing the input of the science and technology and strongly exerting the supporting effect of science and technology, in the agricultural development; thirdly, increasing openness of system and enhancing the emergy feedback rate; fourthly, adjusting agricultural structure based local circumstances and establishing a rational agricultural structure; finally, regulating the subsidiary energy structure and reducing the environmental pressure.