emergy analysis of chinese agriculture

Emergy analysis of Chinese agriculture

G.Q. Chen a,b,*, M.M. Jiang a, B. Chen a, Z.F. Yang b, C. Lin c

aNational Laboratory for Turbulence and Complex Systems, Department of Mechanics and Engineering Science,

Peking University, Beijing 100871, ChinabNational Laboratory for Environmental Simulation and Pollution Control, School of Environment,

Beijing Normal University, Beijing 100875, ChinacKey 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

www.elsevier.com/locate/agee

Agriculture, Ecosystems and Environment xxx (2006) xxx–xxx

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 evalua-

tion 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

AGEE-2750; No of Pages 13

G.Q. Chen et al. / Agriculture, Ecosystems and Environment xxx (2006) xxx–xxx2

national scales (e.g., Higgins, 2003; Ulgiati et al., 1994).

Emergy analyses have been carried out for agro-

ecosystems 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 sub-

sectors 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, illu-

strated 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.

2. Emergy analysis method for agriculture

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 J�1) as its unit. The larger the transformity, the more

solar energy is required for the production and maintenance

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 agro-

ecosystem. 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; non-

renewable 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:

Emergy yield ratio ðEYRÞ ¼ Y

NP þ RP(1)

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 NP þ RP

RR þ NR(2)

It is the ratio of the emergy inputs received from the

economy to the emergy investment from the free environ-

ment. The less the ratio, the less the economic costs. So the

process with lower ratio tends to compete, prosper in the

G.Q. Chen et al. / Agriculture, Ecosystems and Environment xxx (2006) xxx–xxx 3

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 NP þ NR

RR þ RP(3)

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.

Emergy self-support ratio ðESRÞ ¼ RR þ NR

Y(4)

It is the ratio of the emergy of all the environmental inputs to

the emergy of all products. This index indicates the envir-

onmental 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 eco-

nomic investment as emergy feedback from the main econ-

omy. A similar index is the renewable input ratio (RIR),

taken as (RR + NP)/Y, to represent the renewable contribu-

tion in the total inputs.

Environmental sustainability index ðESIÞ ¼ EYR

ELR(5)

It is the ratio of the emergy yield ratio EYR to the environ-

mental 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. Correspond-

ingly, 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 self-

supporting 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


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 self-

sufficient 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 degrada-

tion, 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 accord-

ing 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 farm-

ers with basic public housing, education and heath care.

With obvious disadvantages of communes based on the

collectivization, in the early 1980s, production responsi-

bility 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 cost-

effective 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


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, over-

stocking 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

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

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 con-

sequence 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

Non-renewable purchases mainly include electricity, fuels,

chemical fertilizers, pesticides, mechanical equipments,


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

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 non-

renewable 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 impor-

tance 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 environ-

ment 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 environ-

mental 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 one-

third 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

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 mil-

lion 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 non-

renewable feedback emergy. In the same year, the electricity


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 J�1, 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


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 manage-

ment 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 develop-

ment 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 infra-

structure 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 J�1 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 govern-

ment 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 Combus-

tion 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 mil-

lion ha, accounting for 26% of theworld’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


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

Table 1

System indices for Chinese agriculture in selected years

The C

1980

Flow

1 Free renewable resources (RR) (sej year�1) 8.47

2 Free non-renewable resources (NR) (sej year�1) 7.44

3 Non-renewable purchases (NP) (sej year�1) 7.26

4 Total available emergy (U = RR + NR + NP + RP) (sej year�1) 23.2

5 Free local resources (I = RR + NR) (sej year�1) 15.9

6 Total non-renewable inputs (NP + NR) (sej year�1) 14.7

7 Total yield (Y) (sej year�1) 16.6

Index

8 Emergy intensity (U/total land area) (sej m�2) 4.00

9 RR/U 0.37

10 NR/U 0.32

11 NP/U 0.31

12 (RR + NR)/U 0.69

13 (NP + NR)/U 0.63

14 Emergy yield ratio, EYR = Y/(NP + RP) 2.28

15 Emergy investment ratio, EIR = (NP + RP)/(RR + NR) 0.86

16 Environmental load ratio, ELR = (NP + NR)/(RR + RP) 1.74

17 Emergy self-support ratio, ESR = (RR + NR)/Y 0.96

18 Renewable input ratio, RIR = (RR + RP)/Y 0.51

19 Environmental sustainability index, ESI = EYR/ELR 1.32

than the normal forest. For example, the output of the

firewood forest was 10 t hm�2 while the normal forest was

only 0.75 t hm�2 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 high-

yield 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

hinese agro-ecosystem

(1023) 1985 (1023) 1990 (1023) 1995 (1023) 2000 (1023)

8.46 8.47 8.50 9.81

7.44 7.44 7.44 7.44

9.43 12.7 16.8 19.2

25.3 28.6 32.8 36.5

15.9 15.9 15.9 17.2

16.9 20.2 24.2 26.7

21.4 26.9 36.0 40.0

� 1011 4.37 � 1011 4.94 � 1011 5.63 � 1011 5.35 � 1011

0.33 0.29 0.26 0.27

0.29 0.26 0.23 0.20

0.37 0.45 0.51 0.53

0.63 0.56 0.49 0.47

0.67 0.70 0.74 0.73

2.27 2.11 2.14 2.08

0.59 0.80 1.06 1.11

2.00 2.38 2.85 2.72

0.74 0.59 0.44 0.43

0.40 0.32 0.24 0.25

1.14 0.89 0.75 0.77


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 varia-

tions 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 m�2 in 1980 and

maximum of 5.35 � 1011 sej m�2 in 1995. Compared with

corresponding data of 9.31�1011 sej m�2 in 1993 for the

United States (Odum, 1996) and 8.98 � 1011 sej m�2 in

1994 for Italy (Ulgiati et al., 1994), the Chinese agro-

ecosystem 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 consump-

tion 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.

Table 2

Index comparison

Item Emergy index Ch

1 (NP + RP)/U 0.5

2 (RR + NR)/U 0.4

3 RR/U 0.2

4 Emergy yield ratio (EYR) 2.0

5 Emergy investment ratio (EIR) 1.1

6 Environmental load ratio (ELR) 2.7

7 Environmental sustainability index (ESI) 0.7

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

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 agro-

ecosystem 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-industrializa-

tion, 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 Liechten-

stein, Austria, Switzerland and Italy (Willer and Yussefi,

2004), have established policies to facilitate the transforma-

tion from petroleum-based agriculture to organic agricul-

ture. 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

ina (2000) Italy (1989) Switzerland (1996)

3 0.94 \

7 0.17 0.20

7 0.16 0.18

8 1.12 1.26

1 8.52 4.10

2 10.43 4.50

7 0.11 0.28


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 renew-

able 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 envir-

onment. 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 agricul-

ture 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 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 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. T
he 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 one-

half of that for the modern agriculture in typical

developed countries such as the United States and Italy.

2. T
hough 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. T
he 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. T
he 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 under-

industrialization of the Chinese agriculture.

5. T
he environmental load ratio, in terms of the non-
renewable 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. T
he environmental sustainability index for the Chinese
agriculture has been dramatically reduced, along the


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).

References

AEM, 1983. Agro-Technical Economic Manual. Agriculture Press, Beijing

(in Chinese).

Bastianoni, S., Marchettini, N., 1996. Ethanol production from biomass:

analysis of process efficiency and sustainability. Biomass Bioenergy 11,

411–418.

Bastianoni, S., Marchettini, N., Panzieri, M., Tiezzi, E., 2001. Sustainability

assessment of a farm in the Chianti Area (Italy). J. Cleaner Prod. 9, 365–

373.

Brown, M.T., Herenden, R.A., 1996. Embodied energy analysis and emergy

analysis: a comparative view. Ecol. Econ. 19, 219–235.

Brown, M.T., Ulgiati, S., 1997. Emergy-based indices and ratios to evaluate

sustainability: monitoring economies and technology toward environ-

mentally sound innovation. Ecol. Eng. 9, 51–69.

Brown, M.T., Buranakarn, V., 2003. Emergy indices and ratios for sustain-

able material cycles and recycle options. Resour. Conserv. Recycl. 38,

1–22.

Campbell, D.E., 1997. Emergy analysis of human carrying capacity and

regional sustainability: an example using the state of Maine. Environ.

Monit. Assess. 51, 531–569.

Chen, Y.J., Wu, K., Lu, B., Yuan, Z., Xu, Y.X., 2005. The change situation,

change causes and protective measures of the cultivated land resources

in the different regions of China. Chin. Agric. Sci. Bull. 21 (8), 373–376

(in Chinese).

CASY, 1980–2001. China Agriculture Statistical Yearbook. China Statis-

tical Publishing House, Beijing (in Chinese).

CEY, 1980–2001. China Electricity Yearbook. China Statistical Publishing

House, Beijing (in Chinese).

CESY, 1980–2001. China Energy Statistical Yearbook. China Statistical

Publishing House, Beijing (in Chinese).

CFY, 1980–2001. China Forestry Yearbook. China Forestry Press, Beijing.

CMA, 1999. China Ministry of Agriculture. Review on History of Land

Managerial Responsibility System of Contracting, Management and

Administration on Rural Cooperative Economy, vol. 11., pp. 19–21 (in

Chinese).

CSY, 1980–2001. China Statistical Yearbook. China Statistical Publishing

House, Beijing (in Chinese).

Dennis, T.Y., 1997. China’s land arrangements and rural labor mobility.

Chin. Econ. Rev. 8 (2), 101–115.

Fan, S., 1990. Regional Productivity Growth in China’s Agriculture. West-

view Press, p. 15.

Guo, S. (Ed.), 1995. Rural Economics in China: Research on Reforms.

Xinhua Press, Beijing (in Chinese).

Higgins, J.B., 2003. Emergy analysis of the Oak openings region. Ecol. Eng.

21 (1), 75–109.

Huo, M.Y., Zhang, Z.S., 2001. Natural Resources of China. Higher Educa-

tion Publishing House, Beijing (in Chinese).

Jig, W., Nan, Z.G., 1994. Facing problems and protecting measures of land

environment in China. Res. Soil Water Conserv. 1 (5), 101–104 (in

Chinese).

Jiang, M.M., Chen, G.Q., 2004. Emergy Accounting for Chinese Agricul-

ture. Systems Ecology Report, No. 2004-1001. National Laboratory for

Turbulence and Complex Systems, Peking University.

Jiang, S., 1997. Sustainable utilizations of grassland resources in China.

Acta Agresia Sin. 5 (2), 73–79 (in Chinese).

Lan, S.F., Qin, P., Lu, H.F. (Eds.), 2002. Emergy Analysis of Eco-economic

System. Chemical Industry Press, Beijing (in Chinese).

Larson, B.B., Clifford, B. (Eds.), 1997. World Bank Report, At China’s

Table: Food Security Options. World Bank, Washington, DC.

Lefroy, E., Rydberg, T., 2003. Emergy evaluation of three cropping systems

in southwestern Australia. Ecol. Model. 161, 195–211.

Liu, Q., Li, L., 2005. Forestry of China, 2005, Strategy for the Sustainable

Development and Ecological Protection of Forestry, vol. 18. , p. 44 (in

Chinese).

Lotka, A.J., 1945. The law of evolution as a maximum principle. Hum. Biol.

17, 167.

Odum, H.T., Brown, M.T., 1975. Carrying Capacity for Man and Nature in

South Florida. Final Report to the National Park Service. US Dept.

Interior and State of Florida, Division of State Planning.

Odum, H.T., 1994. Ecological and General Systems: An Introduction to

Systems Ecology. University Press of Colorado.

Odum, H.T., Odum, E.C., 1983. Energy analysis overview of nations.

Working Paper WP-83-82. International Institute for Applied Systems

Analysis, Laxenburg, Austria, p. 421.

Odum, H.T., 1988. Self organization, transformity, and information. Science

242, 1132–1139.

Odum, H.T., 1996. Environmental Accounting: Emergy and Environmental

Decision Making. Wiley, New York.

Odum, H.T., 2000. Emergy evaluation of an OTEC electrical power system.

Energy 25, 389–393.

Pillet, G., Maradan, D., Zingg, N., Brandt-Williams, S., 2001. Externalities:

theory and assessment. In: Brown, M.T. (Ed.), Emergy Synthesis:

Theory and Applications of the Emergy Methodology. Proceedings

of the First Biennial Emergy Analysis Research Conference, Gaines-

ville, FL, USA, pp. 39–51.

Scienceman, D.M., 1987. Energy and emergy. In: Pillet, G., Murota, T.

(Eds.), Environmental Economics. Roland Leimgruber, Geneva, pp.

257–276.

State Environmental Protection Administration of China (SEPAC), 2003.

http://www.yzsfs.com/policy_law/zc/zc1.htm (10/20/2004; in Chinese).

The China Agenda for the 21st Century, 1994. The Whitebook of the

Population, Environment and Development. Chinese Environmental

Press, Beijing (in Chinese).

Tilley, D.R., Swank, W.T., 2003. Emergy-based environmental systems

assessment of a multi-purpose temperate mixed-forest watershed of the

southern Appalachian Mountains, USA. J. Environ. Manage. 69, 213–

227.

Ulgiati, S., Odum, H.T., Bastianoni, S., 1993. Emergy analysis of italian

agricultural system. The role of energy quality and environmental

inputs. In: Bonati, L., Cosentino, U., Lasagni, M., Moro, G., Pitea,

D., Schiraldi, A. (Eds.), Trends in Ecological Physical Chemistry.

Elsevier Science Publishers, Amsterdam, pp. 187–215.

Ulgiati, S., Odum, H.T., Bastianoni, S., 1994. Emergy analysis, environ-

mental loading and sustainability: an emergy analysis of Italy. Ecol.

Modell. 73, 215–268.

Ulgiati, S., Brown, M.T., Bastianoni, S., Marchettini, N., 1995. Emergy

based indices and ratios to evaluate the sustainable use of resources.

Ecol. Eng. 5, 519–531.

Ulgiati, S., Brown, M.T., 1997. Emergy based indices and ratios to evaluate

sustainability: monitoring economies and technology toward environ-

mentally sound innovation. Ecol. Eng. 9, 51–69.

Ulgiati, S., Brown, M.T., 1998. Monitoring patterns of sustainability in

natural and man-made ecosystems. Ecol. Model. 108, 23–36.

Ulgiati, S., Brown, M.T., 2001. Emergy accounting of human-domin-

ated, large scale ecosystems. In: Jorgensen, S.E. (Ed.), Thermody-

namics and Ecological Modelling. Lewis Publications, Boca Raton,

Florida.

Walsh, Karen, M., 2001. Nitrogen oxides and nitrous oxide fluxes in an

upland agro-ecosystem of the North China Plain: field measurements,

biogeochemical simulation, and climatic sensitivity (China). Disserta-

http://www.yzsfs.com/policy_law/zc/zc1.htm


tion Abstracts International, Section B, vol. 63-01, p. 0134 (advisers:

Schimel, D.S., Ojima, D.S.).

Wang, K., Han, J.G., Zhou, H., 2002. The current situation and developing

strategy of Chinese grassland industry. Acta Ecol. Sin. 10 (4), 293–297

(in Chinese).

Wang, Z., 2000. Study on causes, harms and preventing ways of soil and

water loss in China. World Res. Adv. Sci. Technol. 22 (3), 78–83 (in

Chinese).

Willer, H., Yussefi, M. (Eds.), 2004. SOEL-Survey, The World of Organic

Agriculture: Statistics and Emerging Trends, http://www.soel.de/oeko-

landbau/weltweit.html (11/12/2004).

Xu, H.L., Wan, X.N., Wang, Z.Y., Zhang, M.Q., 2001. Water: Resource

Exploitation and Protection. Geologic Press, Beijing, p. 279 (in Chi-

nese).

Zhang, W.L., Tian, Z.X., Zhang, N., Li, X.Q., 1996. Nitrate pollution of

groundwater in northern China. Agric. Ecosyst. Environ. 59, 223–231.

http://www.soel.de/oekolandbau/weltweit.html

http://www.soel.de/oekolandbau/weltweit.html

emergy analysis of chinese agriculture

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