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Emergy Analysis of Chinese Agriculture
Transcript of 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
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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
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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 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
G.Q. Chen et al. / Agriculture, Ecosystems and Environment xxx (2006) xxx–xxx4
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
G.Q. Chen et al. / Agriculture, Ecosystems and Environment xxx (2006) xxx–xxx 5
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,
G.Q. Chen et al. / Agriculture, Ecosystems and Environment xxx (2006) xxx–xxx6
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
G.Q. Chen et al. / Agriculture, Ecosystems and Environment xxx (2006) xxx–xxx 7
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
G.Q. Chen et al. / Agriculture, Ecosystems and Environment xxx (2006) xxx–xxx8
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
G.Q. Chen et al. / Agriculture, Ecosystems and Environment xxx (2006) xxx–xxx 9
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
G.Q. Chen et al. / Agriculture, Ecosystems and Environment xxx (2006) xxx–xxx10
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
G.Q. Chen et al. / Agriculture, Ecosystems and Environment xxx (2006) xxx–xxx 11
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 inputper 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 resourcesdeclines 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 emergydivided 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 economicinvestment 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 Chineseagriculture has been dramatically reduced, along the
G.Q. Chen et al. / Agriculture, Ecosystems and Environment xxx (2006) xxx–xxx12
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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