Emergy analysis of Chinese agriculture

Emergy analysis of Chinese agriculture

Agriculture, Ecosystems and Environment 115 (2006) 161–173 www.elsevier.com/locate/agee Emergy analysis of Chinese agriculture G.Q. Chen a,b,*, M.M. ...

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Agriculture, Ecosystems and Environment 115 (2006) 161–173 www.elsevier.com/locate/agee

Emergy analysis of Chinese agriculture G.Q. Chen a,b,*, M.M. Jiang a, B. Chen a, Z.F. Yang b, C. Lin c a

National Laboratory for Turbulence and Complex Systems, Department of Mechanics and Engineering Science, Peking University, Beijing 100871, China b National Laboratory for Environmental Simulation and Pollution Control, School of Environment, Beijing Normal University, Beijing 100875, China c Key Laboratory of Agricultural Bio-Environment Engineering Ministry of Agriculture, China Agriculture University, Beijing 100083, China Received 10 June 2005; received in revised form 10 January 2006; accepted 13 January 2006 Available online 17 February 2006

Abstract This study presents an ecological analysis of Chinese agriculture for the period from 1980 to 2000, on the basis of Odum’s well-known concept of emergy in ecological economy. Emergy analysis methods are explained, illustrated and used to diagram the agro-ecosystem, to evaluate environmental and economic inputs and harvested yield, and to assess the sustainability of the Chinese agriculture as a whole. Detailed structure of the input/output and system indicators are examined from a historical perspective for the contemporary Chinese agriculture in the latest two decades after China’s Reform and Open in the late 1980s. Temporal variation of indices such as increasing environmental load ratio (ELR), decreasing emergy self-support ratio (ESR) and decreasing emergy yield ratio (EYR) illustrate a weakening sustainability of the Chinese agro-ecosystem characteristic of profound transition from a self-supporting tradition to a modern industry based on non-renewable resource consumption. # 2006 Elsevier B.V. All rights reserved. Keywords: Emergy analysis; Chinese agriculture; Agro-ecosystem; Resource accounting; Sustainable development

1. Introduction For the world with a soaring population, there has been a great challenge to reconcile food production and natural conservation in the modern agriculture, which embodies a human-controlled agro-ecosystem dependent on both the environmental inputs, such as sunlight, wind, water and soil, and the purchased economic inputs, such as fertilizers, pesticides, fuels, electricity, mechanical equipment and some other industrial products. Systems ecological evaluation and assessment would be essential for a sound resource relocation for and sustainable development of the agriculture industry. To integrate the value of free environment investment, goods, services and information in a common unit, an ecological evaluation approach based on a novel concept * Corresponding author. Tel.: +86 10 62767167; fax: +86 10 62750416. E-mail address: [email protected] (G.Q. Chen). 0167-8809/$ – see front matter # 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.agee.2006.01.005

of emergy in terms of embodied energy was first presented in 1983 by Odum, out of a creative combination of energetics (Lotka, 1945) and systems ecology (Odum and Brown, 1975; Odum, 1994, 1988, 1996). Emergy (spelled with an ‘‘m’’) was used by Odum to evaluate the work previously done to make a product or service, which was described as the available energy (exergy) of one kind previously required to be used up directly and indirectly to make the product or service (Odum, 1988; Scienceman, 1987). It represents all the work given by the environment to sustain a certain system and produce a certain level of output. As a measure of energy used in the past, emergy (with unit emjoule) analysis is totally different from conventional energy (with unit joule) analysis which merely accounts for the remaining available energy at present, therefore proved a more feasible approach to evaluate the status and position of different energy carriers in universal energy hierarchy. Till now, various systems have been evaluated by emergy analysis on regional and


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national scales (e.g., Higgins, 2003; Ulgiati et al., 1994). Emergy analyses have been carried out for agroecosystems and agricultural industries, such as ethanol production (Bastianoni and Marchettini, 1996) and some crop production systems (Bastianoni et al., 2001; Lefroy and Rydberg, 2003). Emergy analyses have been emerging in China. As the pioneer in emergy study in China, Lan has led a series of researches on the sustainable development on national and regional scales (Lan et al., 2002). Lan and co-workers have assessed the resource and economic status of many provinces or autonomous regions and some cities. The Chinese agriculture has been preliminarily studied, on a national scale for three departments of crop production, stockbreeding and fishery and for two separate years of 1988 and 1998 by Lan. But the overall panorama of the Chinese agriculture in the recent decades remained to be revealed against striking historical background with drastic political and socioeconomic transitions. Based on emergy analysis, this study presents an overall ecological assessment of the overall Chinese agriculture, in the traditional sense of including four interactive subsectors of crop production, forestry, husbandry and fishery, for the period from 1980 to 2000, with the Taiwan province, Hong Kong and Macao Special Administrative Regions excluded. Emergy analysis methods are explained, illustrated and used to diagram the agro-ecosystem, estimate environmental and economic inputs and harvested yield, and to assess the sustainability of Chinese agriculture as a whole. Detailed structure of the inputs/yield and systematic indicators are examined from a historical perspective for the contemporary Chinese agriculture in the latest two decades after China’s Reform and Open in the late 1980s. Temporal variation of indices such as environmental load ratio (ELR), emergy self-support ratio (ESR) and emergy yield ratio (EYR) is explored to illustrate a weakening sustainability of the Chinese agro-ecosystem characteristic of profound transition from a self-supporting tradition to a modern industry based on non-renewable resource consumption.

of the resource, product or service of interest, and the higher their position in the energy hierarchy of the universe (Odum, 1988, 1996). With the same output, the system with a lower transformity is ecologically more efficient. During the past three decades, Odum and his collaborators have calculated transformities for various products and services. There are detailed references for emergy algebra and evaluation (Odum, 1996; Brown and Herenden, 1996; Brown and Ulgiati, 1997; Brown and Buranakarn, 2003). In emergy analysis, we generally translate each form of energy in a system into its solar energy equivalent, or solar emergy, by way of a conversion factor (transformity) that reflects the energy’s qualitative value. Through multiplying the inputs and outputs by their respective transformities, the emergy amount of each resource, service and corresponding product can be calculated. Based on the same unit, these amounts can be analyzed easily through a series of emergy related ratios and indices, which are used for better evaluation of the concerned system. These indices indicate various performance characteristics of the system in terms of efficiency and sustainability (Campbell, 1997). An ecological system of interest is diagrammed with the use of energy system symbols (Odum, 1994, 1996, 2000; Ulgiati and Brown, 2001; Lefroy and Rydberg, 2003). Shown in Fig. 1 is typical diagram associated with an agroecosystem. In this diagram, inputs to the agro-ecosystem might be categorized into four types (Bastianoni et al., 2001; Lefroy and Rydberg, 2003): free renewable local resources (RR), such as sunlight, rain and wind; free non-renewable local resources (NR), soil erosion, for instance; nonrenewable purchased inputs (NP), such as purchased fossil fuels and chemical fertilizers; and renewable purchased inputs (RP), such as water resources purchased from outside the concerned boundary of the concerned system. For the overall agro-ecosystem for the agriculture sector of a country, 1 year is reasonably taken as the time cycle for the system analysis, as most of the agriculture productions are harvested annually. Associated with an agro-ecosystem, some basic indices of ecological interest (Odum and Odum, 1983; Ulgiati et al., 1995; Odum, 1996; Brown and Ulgiati, 1997; Ulgiati and Brown, 1998) are as follows:

2. Emergy analysis method for agriculture Emergy yield ratio ðEYRÞ ¼ Each kind of available energy has its emergy with different units expressed, for example, solar emjoule, coal emjoule, electrical emjoule. But because the biosphere is usually considered driven by solar energy and most kinds of available energy are derived from solar energy directly or indirectly, solar insolation emergy is used as a common measure in most application. Correspondingly, solar emergy per unit energy, that is, solar transformity, is used to measure the quality of energy and its position in the universal energy transformation hierarchy with solar emjoules per joule (sej J1) as its unit. The larger the transformity, the more solar energy is required for the production and maintenance



This index is taken as the emergy output divided by the emergy input as feedback from the outside economy. The higher the value of this index, the greater the return obtained per unit of emergy invested. Emergy investment ratio ðEIRÞ ¼



It is the ratio of the emergy inputs received from the economy to the emergy investment from the free environment. The less the ratio, the less the economic costs. So the process with lower ratio tends to compete, prosper in the

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Fig. 1. Typical diagram associated with agro-ecosystem.

market. The higher the ratio, the higher the economic development level of a system. Environmental load ratio ðELRÞ ¼



Providing additional information to EYR, the environmental loading ratio expresses the use of environmental services by a system, indicating a load on the environment. It is the ratio of the total emergy of the non-renewable inputs to the emergy of the total renewable inputs. The lower the ratio, the lower the stress to the environment. RR þ NR Emergy self-support ratio ðESRÞ ¼ Y


It is the ratio of the emergy of all the environmental inputs to the emergy of all products. This index indicates the environmental contribution to a productive system. The system with higher ratio depends more on free environment and has more potential to raise productivity in case of more economic investment as emergy feedback from the main economy. A similar index is the renewable input ratio (RIR), taken as (RR + NP)/Y, to represent the renewable contribution in the total inputs. Environmental sustainability index ðESIÞ ¼



It is the ratio of the emergy yield ratio EYR to the environmental load ratio ELR, indicating if a process provides a suitable contribution to the user with a low environmental pressure, associated with the definition of the sustainability

made by Odum as opposite to the idea of a steady level, lasting for ever. The ESI takes both ecological and economic compatibility into account. As pointed out by Ulgiati and Brown (1998), a higher ESI is not just provided by a lower requirement of feedback, but by a larger renewable input in comparison with the feedback itself. The larger the ESI, the higher the sustainability of a system.

3. Agriculture in China As a developing country with a huge population, now up to 1.3 billion, China depends greatly on the development of agriculture, which provides food and fiber for its population and plays a fundamental role in the national economy. The Chinese agricultural sector comprises four departments, i.e., crop production, forestry, stockbreeding and fishery, which are under intensive interactions. For example, most of forage needed by livestock comes from the grass and crop production subsystems directly or indirectly. Correspondingly, the stockbreeding sector, besides producing meat for market, is an important component of the crop production subsystem since it provides the latter with indispensable feedback inputs of organic manure and livestock labor. The intensive cultivation tradition also results in a selfsupporting and recycling mechanism. The local environment invests the system with free resources including sunlight, precipitation, earth heat and fertile soil. The sustainability of the agro-ecosystem needs other purchased inputs, mainly involving electricity, petroleum and machineries, from the


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main economy, especially for modernized agriculture management. This paper investigates the resource status of the Chinese agro-ecosystem from 1980 to 2000 based on the data from the Chinese official national statistics (CSY, 1980–2001; CASY, 1980–2001; CEY, 1980–2001; CESY, 1980–2001; CFY, 1980–2001), the total input and output are analyzed with detailed emergy-based accounting, and the data for the typical year of 2000 are listed in Appendix. The pattern of Chinese agriculture changes greatly along with the history. Compared with the petroleum-intensive agriculture in developed countries, the agriculture in China has its characteristics in terms of labor-intensive cultivation and relying heavily on free environmental resources. In fact, Chinese agriculture represents one of the most intensively managed and biogeochemically important ecosystems in the world (Walsh and Karen, 2001). In history, Chinese agriculture had ever followed a mode of highly selfsufficient family operation. Farmers cultivated according to the needs of their own family and sold only a few items for cash. This low-energy agriculture had been sustained by feedback inputs from organic manure, labor of humans and livestock. By this mode, the loss of natural resources consumed can be complemented in a short period through many natural ways such as fallowing, exertion of organic manure, and remaining crop residues in land. Effective for thousands of years, this traditional mode proved sustainable for the times with limited population and abundant natural resources. With the great change in Chinese society including decreasing arable land, soaring population and profound conversion of political situation, the traditional mode of extensive cultivation was no longer appropriate for the rapid development in agriculture productivity. As a serious problem facing China, the arable land base is steadily diminished by soil degradation, residential and industrial encroachment and infrastructure construction (Chen et al., 2005). Since 1957, the area of cultivated land in China has decreased by 16,720,000 ha, which amounts to 2.7 times of the cultivated land area of Sichuan, the province with a maximum population in the country (CSY, 2001). As the land became increasingly degraded and less productive, farmers had to overuse the land, and more intensive agriculture and overgrazing followed caused greater degradation, to form a vicious circulation. At the same time, the population of China leapt from 0.96 billion in 1978 to 1.26 billion in 2000, when China’s cultivated land per head was down to only about 800 m2, well below the world average by a factor of 25% (CSY, 2001). This is a striking conflict between the huge population and limited arable land. The other stimulation came from policy adjustment. With the ending of the Land Reform and the accomplishment of the Mutual Aid Teams during 1949–1955, the large-scale production was impeded for the socialization of all means of production including lands, animals and other production tools, which were equally distributed to farmers. The time of collectivization (1957–1979) was immediately subsequent to the last period and served as the main organization form of

Chinese agriculture with three levels, that is, production team, brigade and commune. Labor forces worked according to contract of finishing jobs in certain quantity and quality during a specified period, and every people was constrained to a certain group belonging to a production team. Under this system, peasant or the production team were not entitled to make decisions about the crop farming and investments on the agricultural production, which greatly retarded the enthusiasm of labors and led to the lower labor productivity although collectivization provided farmers with basic public housing, education and heath care. With obvious disadvantages of communes based on the collectivization, in the early 1980s, production responsibility systems based on households spontaneously emerged and over time were performed in the countryside by the state. Till 1987, 180 million farmer families had accomplished transformation to this system, which accounted for 98% of total families in rural area (Guo, 1995). Once lands were allowed to be farmed by individual households rather than collectively, farmers were propelled to increase yield for themselves, which therefore brought a striking development in agricultural productivity. Merely in the 5 years from 1980 to 1984, grain production has risen by 32%. The production of crops experienced a, respectively, stagnant period during 1985–1989, which was closely correlated with the upper limit of the land capacity. But another important reason lies in the fact that many peasants were engaged in more profitable sideline production once they completed the remaining state grain quotas. Some lands were also idled because farming on them was not costeffective with too much expense on chemical fertilizers and pesticides (Fan, 1990). At the same time, the emergence of the rural industries that are supported by the local government attracted most of surplus laborers released from the farmland. For the stability of land policy, the full due of land contract was usually more than 15 years in 1984 (CASY, 1985). Till 1993, the Central Conference on rural policy prescribed extending the due to another 30 years and entitled farmers with free transferred right of management during the contract period. This policy laid solid foundation for the large-scale crop farming and management. In the same year, with the ‘‘grain coupon’’ being abolished, the marketing of the grain was also decontrolled by the Chinese government, which further promotes the form of free market. In some places, barren lands, such as hill, valley, slope and beach are auctioned with more than 50 years management time. Also, the heavy burden of the peasants was reduced with extraction of less than 5% of the net income of peasants as reserving fees (CMA, 1999). All actions taken above stimulated labor enthusiasm and released the pressure of the demand for scarce arable land. The crop production made corresponding development with the adjustment of policies. The transition to intensive farming is a natural choice of the current societal situation, which is closely related to great subsidiary energy inputs, especially the enhancive use

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of pesticides, mineral fertilizers and machineries. For instance, fertilizer utilization in China has quadrupled since 1978 (CSY, 2001), and the amount of the fertilizer use increased continuously for decades. A large quantity of petroleum-energy inputs from economy raised the yield of crop production in short time and solved the conflict between a large population and limiting arable land to some extent, but it also brought some problems (Larson and Clifford, 1997). Though agricultural policies have put emphasis on environment protection since 1978, phenomena of environmental damage were ubiquitous all around the nation. In some places, denudation, overstocking and monocropping was frequent, unsuitable ploughing of marginal lands is widespread for cultivation, and fallowing is abandoned in place of estrepement (Dennis, 1997). All these phenomena accelerate the depreciation of environment such as soil erosion, water scarcity and desertification. A systematic emergy accounting has been carried out (Jiang and Chen, 2004) for an ecological analysis of the Chinese agriculture.

4. Input evaluation results As the sum of all input flows from both the environment and economy, the total emergy input is presented in Fig. 2, illustrating a steady increase from 2.32  1024 sej in 1980 to 3.65  1024 sej in 2000. This apparent rise is positively correlated with the increase in the system yields these years. In Chinese agriculture, the amounts of the renewable input flows (RR, including the flow of rain, geothermal heat and water for irrigation) and non-renewable feedback resources (NP + NR) are 8.47  1023 sej and 1.47  1024 sej in 1980, and 9.81  1023 sej and 2.67  1024 sej in 2000, respectively. Fig. 2 shows the increasing trends of the both resources. Apparently, non-renewable resources contribute more and


more to the total input, which is negative for the long-term development of the system. Heavy reliance on non-renewable resources may cause continuous depletion of environment and increasing unbalance between input and output. Once without enough input invested from outside, an inescapable consequence will be the collapse of the whole system. 4.1. Renewable input The operation of the Chinese agro-ecosystem depends on continuous investment from free environment involving sunlight, water from rain and irrigation, wind, geothermal power and nutrition of soil. Due to the relative stability of the nature, the emergy value of this part increases not much, which is 8.47  1023 sej in 1980 and 9.81  1023 sej in 2000. The minor augmentation mainly attributes to the increase in the land area, which is the sum of all the areas involving cultivated lands, tea gardens, orchards, forests, grasslands, cultivated inland waters and cultivated seashore lands. Although cultivated land area of crop production subsystem is declined obviously, land area of other subsystems, such as forestry and fishery, increased these years. The total land area in the present calculation thus is offset. Of all free renewable input flows (sunlight, rain, wind and geothermal heat), the emergy of geothermal heat comes from the earth storage with a much greater turnover time than 1 year (Tilley and Swank, 2003), so we take it into account with an emergy amount of 4.18  1023 sej on the average. As suggested by Odum (1996), to avoid possible double-accounting for the renewable inputs, for example, sunlight, wind and rain, deriving from solar energy directly or indirectly, only the largest contribution, the rain in the present case, is taken into account although all the emergy input items are estimated. Water scarcity is one of the most limiting factors in Chinese agriculture, particularly in northern corn- and wheat-growing regions (Larson and Clifford, 1997). Irrigated farming has been so prevailing in China, that water used for irrigation accounts for 70.4% of total water consumption in 2000, for instance (Xu et al., 2001). As an important input, the emergy amount of irrigating water is 7.01  1022 sej in 2000, only a little less than the chemical potential emergy of the rain (1.31  1022 sej) for the same year. The heavy consumption of irrigating water was set down to delivery waste and inefficient on-farm water use. It is estimated that only 30% of the water diverted into irrigation canals is actually delivered to crop root zones (Xu et al., 2001). Apparently, some measures, such as lining the canals, constructing hose systems, and setting appropriate water price, should be taken to improve the efficiency of irrigation systems. 4.2. Non-renewable input

Fig. 2. Emergy of total input, total renewable and non-renewable input.

Non-renewable purchases mainly include electricity, fuels, chemical fertilizers, pesticides, mechanical equipments,


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greenhouses, plastic mulch, stables and industrial forage. With an increasing trend shown as Fig. 2, the invested emergy of this part increases greatly from 7.26  1023 sej in 1980 to 1.92  1024 sej in 2000. Of all non-renewable purchases, chemical fertilizer makes up the largest fraction in terms of emergy. Take the year 2000 for instance, with an amount of 1.11  1024 sej, all forms of chemical fertilizers account for 41.6% of the total nonrenewable resources (2.67  1024 sej). The wide use of fertilizer, whose amount increased at a striking rate in recent decades and accounted for 30.53% of the total input by 2000, is a primary impulse for the steady rise in the gain yield. Nitrogen (N), phosphate (P2O5) and potash (K2O) have been the three basic kinds of fertilizers widely applied in China with an emergy amount of 87.67  1022 sej, 12.30  1022 sej and 8.91  1022 sej in 2000, respectively. Although the importance of proper nutrient balance has been well known and generalized ratio of 100:50:25 for weight of the pure content of nitrogen:phosphate:potash has been recommended for many years, unbalanced supply and application of nutrients has been remained ubiquitous in China (Larson and Clifford, 1997). Also, an obvious imbalance of fertilizer exertion has been prevailing in Chinese crop production for a long time. The consumption of the nitrogen fertilizer is shown apparently too much compared with the under-application of phosphate and potash, which diminished the efficiency of nutrition uptake, and led to lower crop production than it would have been with balanced fertilizer application. As a serious problem facing the Chinese agriculture, the excessive fertilizer application and poor nutrient use efficiency have resulted in high nitrogen losses to the surrounding environment with disastrous consequences to atmospheric and groundwater quality, public health, and in the end, agriculture itself (Zhang et al., 1996), which should be paid more attention and taken urgent actions to deal with by Chinese government. The emergy-based accounting shows that the topsoil loss emergy is as high as 7.44  1023 sej annually on the average in China, which is only a little less than the consumption of fertilizer. That means nearly 48.9% of the free environmental investment and 27.9% of the non-renewable emergy input comes from soil erosion in 2000, which has been a heavy price paid by environment in the development of Chinese agriculture. Data (CSY, 2000, 2001) shows that, lands undergone soil erosion have accounted for almost onethird of the Chinese total arable land in recent years. Chinese government has done much to alleviate the soil erosion and environmental degeneration (Liu and Li, 2005). For instance, forestation taken as an effective treatment and a basic long-term national strategy is performed widely these years for the recovery of healthy ecological environment. Excessive pesticide use, which has increased in amount from 1.67  1023 sej in 1980 to 5.25  1023 sej in 2000 (Fig. 3), is another cause leading to agricultural pollution. Pesticide residues in environment contaminate not only soil and water resources, but also atmosphere, threatening the

Fig. 3. Variation of total fertilizer, pesticide and mechanical equipment use.

health of consumers. Some toxicity extends to species other than the target population and persists in the environment for a long time. Statistics (Jig and Nan, 1994) showed that the area nearly amounting to 2 million ha out of the 13 million ha in China has been polluted till 1994, and consequent annual loss of crop yield was as high as 2 billion kg. In 2000, pesticide input accounts for 27.29% of the total purchased non-renewable resources. Compared with other purchased feedback flows such as fertilizers and pesticides, the consumption of which are 1.11  1024 sej and 5.25  1023 sej, respectively, in 2000, the investment from mechanical equipment is much less than that from the former two (Fig. 3). This partly attributes to the longer average life expectancy of machines. In the present paper, the depreciation rate is treated as 10% annually (according to data from AEM, 1983), with which the mechanical equipment use is only 4.80  1022 sej in 1980 and 1.57  1023 sej in 2000, accounting for 6.62% and 8.15% of the total purchased non-renewable energy, respectively. This ratio is apparently very low and reveals that the Chinese agriculture still remains characteristic of non-mechanized farming. The inadequate mechanization in agriculture was to some extent due to the complicated geographic condition in China. Statistic shows that about 66% of China’s land area is mountainous, especially in most of the western, southern and southwest regions (Fan, 1990). This mountainous terrain is a great limit to the application of large agricultural machines. Only the lands in the eastern regions are appropriate for crop production with large mechanical equipments on a large scale. The inputs of fuels and electricity increased steadily but slowly in the recent 21 years. Of the three main oils of diesel, gasoline and lubrication used in Chinese agriculture, the emergy amount of diesel use makes up the largest fraction due to the wide application of the mechanical equipments with diesel engines. For instance, in 2000, the emergy amount of diesel is 4.45  1022 sej, which is nearly 80% of the total oil used in agriculture and 2% of the total nonrenewable feedback emergy. In the same year, the electricity

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Fig. 4. Yield variation.

use in agriculture (only for production) is 3.88  1022 sej, with 91% for crop production, 3% for stockbreeding, 2% for forestry and 3% for fishery (CEY, 2001). The emergy amount of the other purchased industrial products, mainly including greenhouses, plastic mulch, stables and industrial forage, takes only a little portion and is not going to be discussed in detail. For example, in 2000, the total emergy of these products is 3.16  1022 sej, is only 1.6% of the total purchased investment.

5. Yield evaluation results Of the four subsystems for stockbreeding, crop, forestry and fishery productions, the variation of the yield emergy is shown in Fig. 4 for the period from 1980 to 2000. 5.1. Stockbreeding production The stockbreeding production has increased at the highest rate among the four subsystems, and its yield has increased more than three times, as presented in Fig. 5.

Fig. 5. Emergy of stockbreeding products.


Stockbreeding products mainly comprise meat, milk, wool, eggs, honey and silkworm cocoon, of which meat production is the primary important and takes up the main part of the total yield. Fig. 5 indicates the developing trends of the major products. The increase of stockbreeding production, which mainly comprises yields of meat, milk and eggs, reflects a structural change happened in Chinese food consumption. For example, as an increasingly important food in an average Chinese diet, the emergy amount of meat has increased four times since 1980 (CASY, 1980–2001). In 2000, the stockbreeding subsystem contributes the most to total system yield with an amount of 2.13  1024 sej emergy, which is 54% of the total output of 4.00  1024 sej. High yield of the stockbreeding subsystem is attributed to the large output of pork and high transformities of stockbreeding production. Compared with crops and vegetables, animals take up higher energy hierarchy in nature with more solar energy consumed. So when be expressed in emergy unit, stockbreeding production takes more share in total yield. For instance, with transformity as high as 2.00  106 sej J1, pork embodies 1.33  1024 sej emergy and contributes 62% to total stockbreeding yield. Data indicate that of four main meats produced in 2000, pork, beef, poultry and mutton, pork as the largest part takes up 81% of total meat production, and the proportion of other three are 9% (poultry), 7% (beef) and 3% (mutton), respectively. This reflects the important role of pork in Chinese food consumption. In stockbreeding systems of China, animals convert energy and protein from plants with low efficiency. So the rapid increase in meat production is inevitably correlated with the consumption of a great deal of forage. Besides forage comes from crop residues and coarse grains, stockbreeding depends greatly on herbaceous and woody forage plants in the rangeland. With the development of stockbreeding, the degradation of the rangeland brought by overgrazing has become very serious considering the degenerated rangeland areas summing up to 9.0  107 ha. Consequent desertification areas increased at the rate of 2.5  105 ha annually, resulting in decline on the rangeland resources yield, especially in agro-pastoral transitional zones (CASY, 1998; Jiang, 1997). For example, between 1949 and 1979, there was 3.5  106 ha rangeland reclaimed by the state farm system in Xinjiang and 2.1  106 ha in Inner Mongolia (Jiang, 1997; Wang et al., 2002). To alleviating the increasing pressure imposed on the natural pasture, the Chinese government started to convert the reclaimed land, which resulted in desertification, to pasture in 1980 while rotational grazing by fence (Kulun) was also tried in some places. From 1983 to 2000, the improved rangeland area of China rises from 1.26  106 ha to 4.28  106 ha. In addition, the nationwide rangeland production contract responsibility akin to the agriculture production was generalized which stimulate the incentives of the herdsmen to protect, construct and utilize the


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rangeland resources in a rational way. With the efforts made by the government, the degeneration of pasture is temporarily alleviated, albeit the fragile ecological balance is difficult to maintain in the long term, especially in the northern agro-pastoral areas where the poor crop management and productivity, lack of water resources and overgrazing are widespread. This is undoubtedly an arduous task ahead the country in a long run. Fortunately, increasing number of people have begun to know that, for the sustainability of the ecological environment, the development of the stockbreeding must be in harmony with the capacity of the d and grass subsystem. 5.2. Crop production The major products are grain, such as rice, wheat, soybeans, corn and tubers, oil plants, such as rapeseed, peanut and sunflower seed, sugar plants, mainly sugarcane and beet roots, and some other products for living, such as cotton, vegetable and fruits. Total output of the crop production subsystem increases slower compared with the stockbreeding subsystem, and the amount is 9.30  1023 sej in 1980 and 1.25  1024 sej in 2000 (CASY, 2001). As discussed afore, political infrastructure and organization of the agricultural production in the rural areas have changed frequently since the foundation of the People’s Republic of China in 1949. Rapid transformation of the rural policies exerted main influence on the crop yields. The structure of the crop production, which reflects the priorities and measures taken by the government, has been adjusted since 1980. The rice, wheat and soybeans, which are called ‘‘fine grains’’, together with the corn and tubers, which are called ‘‘coarse grains’’, constitute the grain. As the fundamental resources supporting the large population of China, grains production is primarily important for the economic development. The emergy yield of main grain crops represents that all these grain crops yielded with increasing trends these years, wherein for the year of 2000 the maximum emergy is for the rice, amounting to 1.41  1023 sej, the second for the tuber, 1.35  1023 sej and the third for the wheat, 1.22  1023 sej. Compared with the raw data of grain output, obvious changes appear in order due to the differences in their transformities, among which the highest of 2.60  105 sej J1 is for the tubers. The crop residue is an important yield of crop production, which amounts to 5.64  1023 sej and is 45% of total crop production in 2000. As one of important biomass resources, most crop residues are consumed in China, though reserving them in land is more profitable for sustainable land use. Some of them are processed into fodders or other products, others are consumed as fuel in rural areas. It is estimated that there are still about 35 million families (140 million people) all around the country depends on hay (rice straw) as the main fuel for cooking and heating and one family consumes annually 7000–10,000 kg of hay. Excess consumption of

biomass resources will break down the balance of the local ecological environment. For example, the combustion of crop residues not only releases a great deal of CO2 to the environment but also brings many other environment problems such as soil exhaustion, air pollution and consequent global warming. These years, Chinese government has enacted a series of rules and policies to prohibit the burning of crop residues and encourages their synthetic utilization, especially reserving crop residues in land as manure. For example, a file named as Administration Statutes Concerning Prohibiting of Crop Residue Combustion and Encouraging Synthetic Application was issued in 2003 (SEPAC, 2003). With strict enforcement, these measures are expected to be effective in preventing environmental deterioration in Chinese rural area in the near future. 5.3. Forestry production The forest resources are scarce in China, especially in the Yellow River Basin wherein percentage coverage of forest is extremely low, leading to serious soil and water loss associated with dramatically declining fertility of the cultivated land (Wang, 2000). Thereby, forestry is directly related to the agriculture as the basic guarantee. In the present paper, only important forest products including logs, seeds, bamboos and firewood are taken into account. Some staple products such as saplings are not considered in calculation because most of them remain in the forestry subsystem. During these 21 years, forestry production declined from 1.49  1023 sej to 1.38  1023 sej. An important reason lies in the fact that irrational felling of the nationwide forests has been gradually prohibited for strict laws and regulations in recent years, so most of forestry increment remained in the system without consumption. Forests had ever been seriously destroyed by deforestation and other unsuitable use in China. These years, the Chinese government has taken effective actions to protect and recover its forest resources. The development of Chinese agriculture also has involved the rapid replacement of endemic woodland, shrubbery and forest vegetation with synthetic annual grassland of crops pastures since 2000 years ago. After over 30 years of forestation efforts, China’s present forestry area has accounted for 16.55% of the total Chinese area, and its artificial forest preservation area has reached 46.69 million ha, accounting for 26% of the world’s total artificial forest area, and thus ranking first in the world. These measures prevent soil degradation to some extent and contribute much to the improvement of ecological environment. Of all forestry products, firewood, consisting primarily of low-quality brush and branches, accounts for a striking proportion, which is as high as 82% with emergy value of 1.13  1023 sej in 2000 (CASY, 2001). As a kind of significant biomass fuel, firewood is used exclusively by rural households and accounts for a large share of total energy consumption in rural area (Huo and Zhang, 2001). It

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is indicated that in the rural areas the total firewood served as fuel amounting to 1.23  1023 sej on the average during the past two decades, which means firewood amounting to 420– 560 million m3 is consumed annually, decimating every year 23 million ha of forests (Huo and Zhang, 2001). Most of them are free thus not included in economic analysis. The utilization of biomass energy alleviates the pressure of the fossil fuel supply. However, excess demand for biomass emergy will break down the balance of the local ecological environment. For example, the people living in the rural areas prefer to fell too much firewood without any cost than purchase fossil fuel and electricity, which subsequently results in soil and water loss and degradation of the soil fertility in the near future. Firewood forest has been constructed gradually since 1981 so as to provide stable and increasing firewood sources and restrict the excess fell from the normal forests (CFY, 1980–2001). The firewood forest increased in the 1980s and decreased in the 1990s, for the energy utilization mode of the rural areas became multiple and simple burning of firewood by firewood oven were not so popular as before. Till 2000, the total area of the firewood forest in China has increased to 5.4  106 ha (CFY, 2001). As the small-size coal kilns are prohibited in China, the peasants cannot get the local coal resources as fuel. Also, the use of LPG is too complicated for the rural areas, regarding the installment of the devices and the safe supply of the LPG. Firewood seems to be an appropriate choice for the peasants with relatively lower income. In view of the ecological environment, the firewood produced by the firewood forest generates little pollution; the CO2 emitted when burned being in balance with the CO2 absorbed by the forest, and is renewable with higher output


than the normal forest. For example, the output of the firewood forest was 10 t hm2 while the normal forest was only 0.75 t hm2 on average in Anhui province (Huo and Zhang, 2001). 5.4. Fishery production Although the output emergy of the fishery subsystem did not contribute much to the total yield of the agro-ecosystem, it developed at a very rapid rate during the period from 1980 to 2000 and data indicate that the fishery production has increased more than nine times since 1980. In 2000, the fishery production accounts for about 12% of the total yield of the agro-ecosystem with an emergy amount of 4.76  1023 sej. Fishes are undoubtedly the primary products in various fishery yields with an emergy amount of 3.29  1022 sej in 1980 and 2.45  1023 sej in 2000 (CASY, 1980–2001). Besides that, shrimps, crabs, and shells are relatively highyield products in the Chinese fishery. The rise of the fishery yield is closely related with the adjustment and establishment of appropriate policies. From 1980s, the government started to protect the marine fishery resources, constricting the inshore production and developing marine fish farming. The artificially cultured fishery products steadily increased in 1980s and soared after 1996 while the naturally grown fishery products increased slowly. From 1999, the Agricultural Ministry proposed the ‘‘Zero Growth Plan’’, resulting in the gradually decreased marine fishing production. The structure of the freshwater fishery products manifests that the artificially cultured mode has become the predominant way for freshwater fishery in China. Both

Table 1 System indices for Chinese agriculture in selected years The Chinese agro-ecosystem

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

Flow Free renewable resources (RR) (sej year1) Free non-renewable resources (NR) (sej year1) Non-renewable purchases (NP) (sej year1) Total available emergy (U = RR + NR + NP + RP) (sej year1) Free local resources (I = RR + NR) (sej year1) Total non-renewable inputs (NP + NR) (sej year1) Total yield (Y) (sej year1) Index Emergy intensity (U/total land area) (sej m2) RR/U NR/U NP/U (RR + NR)/U (NP + NR)/U Emergy yield ratio, EYR = Y/(NP + RP) Emergy investment ratio, EIR = (NP + RP)/(RR + NR) Environmental load ratio, ELR = (NP + NR)/(RR + RP) Emergy self-support ratio, ESR = (RR + NR)/Y Renewable input ratio, RIR = (RR + RP)/Y Environmental sustainability index, ESI = EYR/ELR

1980 (1023)

1985 (1023)

1990 (1023)

1995 (1023)

2000 (1023)

8.47 7.44 7.26 23.2 15.9 14.7 16.6

8.46 7.44 9.43 25.3 15.9 16.9 21.4

8.47 7.44 12.7 28.6 15.9 20.2 26.9

8.50 7.44 16.8 32.8 15.9 24.2 36.0

9.81 7.44 19.2 36.5 17.2 26.7 40.0

4.00  10 11 0.37 0.32 0.31 0.69 0.63 2.28 0.86 1.74 0.96 0.51 1.32

4.37  1011 0.33 0.29 0.37 0.63 0.67 2.27 0.59 2.00 0.74 0.40 1.14

4.94  1011 0.29 0.26 0.45 0.56 0.70 2.11 0.80 2.38 0.59 0.32 0.89

5.63  1011 0.26 0.23 0.51 0.49 0.74 2.14 1.06 2.85 0.44 0.24 0.75

5.35  10 11 0.27 0.20 0.53 0.47 0.73 2.08 1.11 2.72 0.43 0.25 0.77


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increases in the yield of marine and limnetic fishes depend on the expansion of the breeding areas, which rose slightly between 1980 and 2000, indicating the traditional fishing mode is transferred into breeding mode that is encouraged and supported by the government.

6. System indices and discussion Listed in Table 1 as an aggregation of emergy estimation for the Chinese agriculture 1980–2000 at an interval of 5 years are the total emergy input, yield and indices. With some of the indices, such as RR/U, NR/U and NP/U (with total investment U = RR + NR + NP + RP), and their variations discussed in previous sections, special emphasis would be placed on the basic indices introduced in Section 2. Listed in item 8 in Table 1 is the emergy intensity, taken as the total input emergy divided by the land area, varying with the minimum of 4.00  1011 sej m2 in 1980 and maximum of 5.35  1011 sej m2 in 1995. Compared with corresponding data of 9.311011 sej m2 in 1993 for the United States (Odum, 1996) and 8.98  1011 sej m2 in 1994 for Italy (Ulgiati et al., 1994), the Chinese agroecosystem consumes less emergy per unit area with relatively low economic development level. Of the total input emergy, the proportion of the free environment investment declines noticeably from 69% in 1980 to 47% in 2000 as shown in Table 1. Correspondingly, the proportion as feedback from the main economy, indicated by the index (NP + RP)/U, rises from 31% to 53%, due to the increasing subsidiary emergy invested into the agro-ecosystem to sustain its operation. The consumption of the non-renewable resources cannot be compensated in the short run, so there are potential dangers of source exhaustion and environmental destruction. The variation of the indices is an obvious indicator for the transformation of Chinese agriculture. However, compared with the developed countries, Switzerland and Italia for instance, Chinese agriculture still remains underdeveloped as illustrated by some selected indices shown in Table 2 for the reason that the agriculture in China depends more on free environment resources than that in Italia and Switzerland, for which the index, (RR + NR)/U, indicating the proportion of free environmental input, are 17% and 20%, respectively, in the distinctively studied years of 1989 and 1996.

The emergy yield ratio is used to evaluate the potential contribution of the agro-ecosystem to economy. To avoid losing out from the point of view of the main economy, the output of a system should be at least equal to the investment, that is, the emergy input from economy, when the emergy yield ratio is equal to one. The higher the ratio, the higher the system yields per input emergy. The value of EYR for the Chinese agro-ecosystem, which decreases from 2.28 in 1980 to 2.08 in 2000, is always higher than 1.12 in 1989 for Italia and 1.26 in 1996 for Switzerland, as shown in Table 2. To some extent, the highest EYR for the Chinese agroecosystem implicates its highest competitiveness among the three. The emergy investment ratio EIR increases from 0.86 in 1980 to 1.11 in 2000 for Chinese agro-ecosystem. A lower EIR associates with a system depending more on the environment. Although Chinese agriculture has experienced a noticeable transformation from traditional to modern pattern to some extent, compared with the agriculture in Italia and Switzerland with the EIR as high as 8.52 and 4.10, respectively, Chinese agriculture is still under-industrialization, with a lower EIR of 1.11 in 2000. However, although Chinese agriculture greatly relies on organic emergy and free environmental resources, it is not an organic agriculture (generally considered sustainable agriculture) in general. As a trend advocated worldwide, organic agriculture is being increasingly associated with the reduced use of petroleum energy embodied in pesticides and chemical fertilizers under strict management. Many countries, including Liechtenstein, Austria, Switzerland and Italy (Willer and Yussefi, 2004), have established policies to facilitate the transformation from petroleum-based agriculture to organic agriculture. As the country with the largest land area under organic management, Liechtenstein has used 26.4% of its land area for organic agriculture up to 2003. But in China, the proportion is only 0.06% (Willer and Yussefi, 2004). The reduction of the feedback emergy input is indicated by the decrease of the EIR amount, which means that the economic development must be in tune with the investment of subsidiary energy, such as fertilizers and pesticides, for the sustainability of the agro-ecosystem. Another important ratio is the environmental load ratio, expressed as (NP + NR)/(RR + RP), which increases from 1.74 in 1980 to 2.72 in 2000, indicates the stress level to some particular environment brought by a system. The more

Table 2 Index comparison Item

Emergy index

China (2000)

Italy (1989)

Switzerland (1996)

1 2 3 4 5 6 7

(NP + RP)/U (RR + NR)/U RR/U Emergy yield ratio (EYR) Emergy investment ratio (EIR) Environmental load ratio (ELR) Environmental sustainability index (ESI)

0.53 0.47 0.27 2.08 1.11 2.72 0.77

0.94 0.17 0.16 1.12 8.52 10.43 0.11

\ 0.20 0.18 1.26 4.10 4.50 0.28

Source: Ulgiati et al. (1993) and Pillet et al. (2001).

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the consumption of non-renewable resources, the heavier the load on the environment. Excessive loading on environment by human might result in severe degradation in ecological function of a system (Ulgiati and Brown, 1997). Since the Chinese agro-ecosystem has a relatively low technological level, the ELR of China is much lower than that in some developed countries as presented in Table 2. With the highest ELR value, Italian agriculture system is shown most intensively consuming the non-renewable environmental resources and exerting the greatest load on environment, associated with the large industrial energy input on limited land resource. On the contrary, the lowest amount of the ELR for the Chinese agro-ecosystem means that there is plenty room for further development from the mainstream point of view of modern industrialized agriculture. Emergy self-support ratio and renewable input ratio are expressed as (RR + NR)/Y and (RR + RP)/Y, indicating the respective contributions from the environment and renewable resources to the yield. Both indices decline from 1980 to 2000 as illustrated in Fig. 6, which represents that the environmental sustainability is declining for the Chinese agriculture. The general trend of the environmental sustainability index ESI declines in the two decades with the maximum 1.32 in 1980 and the minimum 0.67 in 1997, which indicates the agriculture sustainability decreases in China after the Reform and Open in the late 1980s. After the year 1997, the slight rebound presented in the figure illustrates an increasing sustainability, which is closely correlated with the enforcement of a series of policies urging the sustainability of Chinese agriculture and ecological environment. For example, the China Agenda for the 21st century issued in 1994, which stated that the sustainable agriculture is the premise of and guarantee for the sustainable development of the Chinese economy (The China Agenda for the 21st Century, 1994). Fig. 6 also shows that, for the agriculture sector, the value of ESI for China is much larger

Fig. 6. Variation of ESR, RIR and ESI indices.


than corresponding values of 0.11 for Italy in 1989 and 0.28 for Switzerland in 1996. It is an apparent illustration for the sustainability and competitiveness of the Chinese agriculture with relatively more renewable input and less feedback investment.

7. Conclusions As an alternative to conventional market-based analysis, this study presents a non-monetary, ecological analysis of Chinese agriculture for the period from 1980 to 2000, on the basis of Odum’s well-known concept of emergy in ecological economy. Emergy analysis methods are explained, illustrated and used to diagram the agroecosystem, to evaluate environmental and economic inputs and harvested yield, and to assess the sustainability of the Chinese agriculture as a whole. Detailed structure and temporal variation of the input/output and system indicators are examined from a historical perspective for the contemporary Chinese agriculture in the latest two decades after China’s Reform and Open in the late 1980s. Concrete conclusions are drawn as follows: 1. The input intensity, in terms of the average emergy input per unit land area, for the Chinese agriculture has been considerably increased, but only amount to about onehalf of that for the modern agriculture in typical developed countries such as the United States and Italy. 2. Though its fraction of the free environmental resources declines remarkably, the agriculture in China depends much more on free environmental resources than that in such developed countries as Italy and Switzerland. 3. The emergy yield ratio, in terms of the yield emergy divided by the economic investment emergy, for the agriculture in China is, though slightly decreased, about two times that for the agriculture in such developed countries like Italy and Switzerland. This reflects the great competitiveness of the Chinese agriculture. 4. The emergy investment ratio, in terms of the economic investment emergy divided by the free environmental emergy, for the agriculture in China is, though increased, several times less that for the agriculture in such developed countries like Italy and Switzerland. This is due to the self-sustaining and recycling tradition with intensive cultivation and organic manure and underindustrialization of the Chinese agriculture. 5. The environmental load ratio, in terms of the nonrenewable input emergy divided by the renewable input emergy, for the agriculture in China is, though noticeably increased, much less than that for the agriculture in such developed countries like Italy and Switzerland. The Chinese agriculture depends much more on renewable resources. 6. The environmental sustainability index for the Chinese agriculture has been dramatically reduced, along the


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profound transition from a self-supporting tradition to the modernized style with intensive economic investment.

Acknowledgement This study has been supported by the National Key Basic Research Program (Grant No. 2005CB724204).

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