Emergy analysis of cropping–grazing system in Inner Mongolia Autonomous Region, China

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Energy Policy 35 (2007) 3843–3855 www.elsevier.com/locate/enpol

Emergy analysis of cropping–grazing system in Inner Mongolia Autonomous Region, China L.X. Zhanga, Z.F. Yanga, G.Q. Chenb, a

National Laboratory for Environmental Simulation and Pollution Control, School of Environmental Sciences, Beijing Normal University, Beijing 100875, China b National Laboratory for Complex Systems and Turbulence, Department of Mechanics, Peking University, Beijing 100871, China Received 13 November 2006; accepted 29 January 2007 Available online 13 March 2007

Abstract An ecological energetic evaluation is presented in this paper as a complement to economic account for the cropping–grazing system in the Inner Mongolia Autonomous Region in China in the year 2000. Based on Odum’s well-known concept of emergy in terms of embodied solar energy as a unified measure for environmental resources, human or animal labors and industrial products, a systems diagram is developed for the crop and livestock productions with arms and sub-arms for free renewable natural resource input, purchased economic investment, yields of and interactive fluxes between the cropping and grazing sub-industries. In addition to conventional systems indices of the emergy yield ratio (EYR), emergy investment ratio (EIR), environmental load ratio (ELR) and environmental sustainability index (ESI) introduced for congregated systems ecological assessment with essential implication for sustainability, new indicators of soil emergy cost (SEC), self-support intensity (SSI) and self-support orientation (SSO) are defined to characterize the desertification and internal recycling associated with the special agricultural system. Extensive emergy accounting is made for the cropping-grazing system as a whole as well as for the cropping and grazing subsystems. The overall cropping–grazing system is shown with outstanding production competence compared with agricultural systems in some other provinces and the national average in China, though confronted with severe desertification associated with soil loss. The production of crops has higher emergy density and yield rate per unit area as well as higher rate of soil loss than grazing system. The soil emergy cost defined as the soil loss emergy divided by the yield emergy is estimated to be of the same value for both of the subsystems, but the grazing activity is with less extraction intensity, leaving rangeland to rest and rehabilitate. Suggestions with regard to the local sustainability and national ecological security in northern China are explored for land-use policy making. r 2007 Elsevier Ltd. All rights reserved. Keywords: Emergy; Cropping–grazing system; Land use

1. Introduction In many parts of northern China, especially in the cropping–grazing transition zone, the land has suffered a great deal from profound transformations between exploitation patterns during the past century (Wang, 2000). Cropland and rangeland coexist and transit between each other, but far more steppe has been cultivated for crop production than the farmland abandoned for grass Corresponding author. Tel.: +86 10 62767167; fax: +86 10 62754280.

E-mail addresses: [email protected], [email protected] (G.Q. Chen). 0301-4215/$ - see front matter r 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.enpol.2007.01.022

restoration since the foundation of the People’s Republic of China in 1949. The change of land-use pattern is considered an important cause of, as well as a result of, the land degradation observed in northern China. As direct and indirect consequences of land-use changes, conversion of natural grassland into cropland destroyed the sod that protects the soil and accelerated soil erosion by wind and water (Xu et al., 1993), In northern China, there are 3.9  105 km2 of sandy desertified land of different levels in year of 2000 (accounting for 15.23% of the monitoring area) and the annual expanding rate is 3595 km2, for which irrational cultivation and heavy grazing are considered to be responsible (Wang, 2000). Severe land degradation has

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been not only reducing the productivity and sustainability of agricultural systems, but also deteriorating both the local and off-site environments (Zhao et al., 2005). The sustainability of the crop and livestock production system is now in question in light of their land-use pattern and environmental impact, considering the frequent sanddust storms attacked the capital city of Beijing during the latest decade. An integrated approach to quantify the impact on environmental resources, economic investment and human or animal labor of the cropping–grazing system in this region with regard to local development and national ecological security is highly in need. The use of energy analysis to value transactions between human society and nature was initially based on the work of Lotka (1925) and gained prominence in the 1970s (Lefroy and Rydberg, 2003). As a great development of energy analysis methods, Odum’s ecological energetic analysis in ecological economics based on systems ecology contributes to a unified evaluation of environmental resources associated with an ecological economic system. The theoretical and conceptual basis for the emergy methodology is grounded in energetics and general systems ecology (Odum, 1971, 1988, 1996; Brown et al., 2000). One of the main strengths of emergy analysis is the possibility and capacity to evaluate resources and services in ecological economic systems on a common energy basis and to internalize the external costs normally considered free. Emergy is defined as the available energy of one kind previously used up directly and indirectly to make a service or product, usually quantified in solar energy equivalents and expressed as solar emJoules (sej). The ratio of emergy required to make a product or service to the present energy of the product or service is defined as the transformity and correspondingly the solar emJoules emergy of a product or service is calculated by multiplying units of energy by transformity. The units of transformity are solar emJoules J1, abbreviated as sej J1, solar kg1 (sej kg1) or even solar emJoules $1(sej $1). The theoretical background and detailed arithmetic for emergy analysis has been enunciated by Odum and his followers (Odum, 1996, 2000; Brown and Ulgiati, 1997; Odum et al., 2000). With emergy as a basic measure of real wealth on a long term and global scale, global public and ecological welfare could be maximized by maximizing empower, the rate of production and use of emergy, based on emergy evaluation, starting with a network diagram to identify energy and resources and pathways to be evaluated (Odum, 1996). By applying emergy concepts to an ecological economy as a system combined by nature and society, which energy and resource management maximizes economic vitality can be shown, thus society may improve industrial efficacy, innovate with less trial and error, and adapt to environmental and societal change more rapidly. Emergy analysis has been effectively used to evaluate the agricultural systems on national scale, e.g., in Italy (Ulgiati et al., 1994), Denmark (Haden, 2003) and China (Chen et al., 2006). It has also been adopted to assess agricultural

systems with other scales and management patterns with regard to their resource use, productivity, environmental impact, and overall sustainability (Rigby and Caceres, 2001; Lefroy and Rydberg, 2003; Martin et al., 2006; Cohen et al., 2006; Cavalett et al., 2006). Highly relevant to land degradation and desertification, the land use of agro-pastoral areas has been a focus in the fields of agricultural economics and agricultural ecology. Via mainstream monetary approach, extensive systems analyses on related land-use pattern (Mace, 1993), household decision making (Milner-Gulland et al., 1996; Okoruwa et al., 1996), nutrient cycling (Joshua, 2005) and sustainability of overall agriculture (Komatsu et al., 2005) have been conducted, aiming to reveal the ecological influences of climate change and of land degradation and the relationship between cropping and grazing subsystems as well. Recently, ecological economic evaluations based on the unified measure of emergy have been emerging with very promising outcomes to assess some typical agropastoral systems in north China, on small scales of family and county (e.g., Dong and Gao, 2005; Dong et al., 2005, 2006), with depth down to the coupling of the cropping and pastoral subsystems. Corresponding to the centralized administrative characteristics associated with the agriculture in China, larger-scale analysis is highly in need. This study presents an emergy assessment of the overall cropping–grazing system and its subsystems in Inner Mongolia Autonomous Region (abbreviated as IMAR) of China, to shed light for future effective land-use adjustment and appropriate management decisions therein. The objectives of this paper are: (1) to calculate the emergy flows and related indices and ratios of overall cropping– grazing system and its subsystems in IMAR, (2) to analyze the ecological sustainability of these systems compared with agricultural systems of other provinces and the national average, and to reveal the suitability of land-use styles as cropping and grazing to the local environment considering the ecological pressure and land degradation exerted by productions, and thereupon (3) to explore the implications for the local sustainability and the national ecological security in northern China. 2. Cropping–grazing system in the area of IMAR The IMAR, as shown in Fig. 1 with a total area of 118.3  104 km2, lies in northern China (971120 –1261040 E, 371240 –531230 N), mostly on the Inner Mongolian Plateau. The majority of the area belongs to the region of continental temperate monsoon climate except the very north-east part of continental cold temperate monsoon climate, both characterized by windy and dry winter and spring, and warm and comparatively rain-rich summer. The mean annual temperature is from 0 to 8 1C and mean annual precipitation is from 100 to 450 mm, all of which decrease gradually from east to west and from south to north. Inner Mongolia Grassland is a typical semi-arid grassland ecosystem of mid-latitude and sensitive to global

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Fig. 1. Map of Inner Mongolia Autonomous Region and its land-use pattern in 2000.

environmental change due to its peculiarity in ecogeography, and thus belongs to the core region of NECT (North East China Transect) in the IGBP study on the relation between global change and land use driven by human and climate (Ni and Zhang, 2000). In addition, the grassland ecosystem is also very essential to the ecological security pattern of China and this region is considered as an ecological backyard of Beijing and even the whole country. The accelerating grassland degradation in IMAR has been generally supposed to be primarily responsible for the increasing frequency and intensity of the dust storms in North China (Qian et al., 2006). Nomadic pastoralism predominated during most of the historical period since it is appropriate for the dry climate (Zheng et al., 2000), whereas the cultivation of steppe can be traced back to the Han Dynasty (206 BC–220 AD). The area of IMAR had experienced at least three times of largescale steppe cultivation associated with military, political or ecological alternations according to reliable historical records (Sun, 1996). During the Han Dynasty, the government implemented the policy of land settlement and enriching frontier and consequently large area of grassland and forestry was reclaimed for crops production in the middle of this region. Another fastigium of cultivation happened in the late Tang (618–907 AD) and Song (960–1279 AD) dynasties, when military reclamation mode and cultivation encouragement were adopted to reinforce frontier defense as well as enrich exchequer. The third large-scale reclamation there began in the middle period of the Qing Dynasty (1616–1911 AD), and reached its climax at the end of this dynasty when the cultivated area had already expanded to the eastern part of area and

about 70% of the grassland along the Great Wall had been cultivated. Each large scale of cultivation was followed by land degradation and subsequent cropland abandonment, and then nomadic pastoralism took over the degraded area gradually (Su et al., 2003). Pastoralism is a complex and sophisticated adaptation to the environment marked by extreme variability in temperature and precipitation, on time scales ranging from days to decades. In a word, the historical pattern of land-use transformation is thought to have occurred through a sequence of grassland cultivation, subsequent abandonment following over cultivation, overgrazing, or warfare and, finally, translocation of people to other grazing lands to repeat the process (Brogaard and Seaquist, 2005; Sheehy, 1992; Zhu et al., 1988). During these processes, the very important precondition is that there is enough land sparsely populated to have the repeating process possible, namely, there still have vacant land to buffer ecological disasters caused by land-use transformation, which is in contrast to the current situation with a high population density and large livestock number. The grassland in IMAR also suffered several waves of cultivation under the policy of Grain First in the times of Mao from 1949 to 1978 and meanwhile great efforts were made to combat desertification. More than 6.6  105 and 3.4  106 ha grassland had been cultivated for crops and non-staple foodstuffs production during the last two movements of cultivation in 1958 and 1973, resulting in destroy of one tenth of the high-quality grassland in IMAR (Zhang et al., 2001). The current pattern of land use varies in different regions of the IMAR: the northern part of IMAR takes animal husbandry as its main product and the other area out of desert and forest is mixed with cropland

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Area (ha)

Percentage (%)

Cultivated land Forest land Grassland Water area Construction land Desert and desertified land

1.04  107 1.86  107 5.67  107 6.74  106 8.59  104 2.79  107

9.11 16.28 49.57 0.59 0.08 24.38

exploitation of the rangeland. Instead of improving the production capacity of rangeland, increasing the number of livestock is considered by local herdsman the basic way to gain more income. As cultivation of grassland with better conditions extends, the allocatable land for grazing activity decreases and livestock grazing is forced to be in the unfavorable rangeland, such as fragile semi-fixed dune areas. 3. Systems diagram and emergy analysis

and rangeland coexisting. The land for cropping and grazing accounts for 56.68%, and deserts and desertified land cover 24.38% of the total land of IMAR in 2000 (Table 1). Roughly 60% of the population relies on subsistence crops and livestock production. As a marginal rain-fed agriculture region, the most important crops for the economy of the area are corn, wheat and legume. Climate and soil conditions can satisfy plantation of some crops to some extent, i.e., grains can grow under such conditions, but cannot guarantee harvest every year, and therefore the production of grains incarnates characteristic of fluctuation (Zhang, 2004). Extensive ways of agricultural production have been adopted to evade the risk of crop failure. Since the very beginning of 1980s, the so-called Household Responsibility System (HRS) has been implemented in IMAR, which has not only stimulated the farmers to increase yield for themselves but also given the farmers much more rights to deal with their allocated land, albeit the land is state owned and supervised by the government principally. Usually the steppe is cultivated for 2 or 3 years and then abandoned when the fertility of soil decreases to a very low level. Subsequently, the abandoned arable land is under the action of wind and rainfall, resulting in serious desertification. Due to poverty and uncertainty of yield, farmers are unwilling to increase input and enhance management to the cultivated land except those basic croplands with better water and fertility conditions (Zhao et al., 2005). Compared with grain production, the livestock production is more dependent on natural resources, i.e., livestock is mainly fed by grazing on pasture with some subsidiary forage during night and winter. Three characteristics are very obvious associated with the grazing system in IMAR, that is, ceaseless increase of number of livestock, nearly no input to build and maintain the pasture, and exclusion by cultivation from better rangeland. As shown in released statistics, the number of livestock increased from 1.06  107 heads in 1949 to 7.3  107 heads in 2000 (IMSY, 2001). Furthermore, the implement of the HRS to rangeland is not so successful as to cropland due to the high cost of demarcation and the demand for integrity of grassland ecosystem by traditional herding activity. The ambiguity of rangeland division and unstable land-use policy prevented people from having enthusiasm to build and manage rangeland, resulting in short-term behavior of over-

Based on the energy circuit symbols by Odum (1996), an aggregated diagram for the IMAR cropping–grazing system is presented in Fig. 2 to illustrate the material and energy flows and the organization of major components that utilize those resources. As common with other agricultural systems (Lefroy and Rydberg, 2003; Bastianoni et al., 2001; Martin et al., 2006; Chen et al., 2006), the cropping–grazing system and its subsystems are driven by natural resources and economic investments, renewable or nonrenewable. Associated with this diagram, inputs to the cropping–grazing systems might be categorized into four types: 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 organic manure purchased from outside the boundary of the concerned system or subsystem. In IMAR, though the livestock mainly relies on grazing on rangeland, crop residues are very import supplementary forage. Correspondingly, the grazing sector, besides supplying meat for market, provides organic manure as well as livestock labor for cropping sector. It is important to note the exchange flows between the subsystems, i.e., from grazing to cropping (denoted as Igc), such as livestock labor and excretion manure, and from cropping to grazing (denoted as Icg), such as crop residues as forage. As internal interactions, these are not explicitly reflected in the whole cropping–grazing system analysis. Various systems indices have been proposed by Odum and his colleagues (Odum, 1996; Brown and Ulgiati, 1997; Ulgiati and Brown, 1998; Cohen et al., 2006) to assess various aspects of the system of interest, such as resources use intensity, process efficiency, economic–environment interactions and systems sustainability. For the present case, it is appropriate to introduce the following indices: Emergy yield ratio EYR 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 EIR ¼

NP þ RP . RR þ NR

(2)

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Fig. 2. Diagram of aggregated energy and material flows for the cropping–grazing systems in IMAR.

It is the ratio of the emergy inputs received from the economy to the emergy investments from the free environment. The less the ratio, the less the economic costs. So the process with lower ratio tends to compete, prosper in the market. Generally, the higher the ratio, the higher the economic development level of a system: Environmental load ratio ELR ¼

NP þ NR . RR þ RP

(3)

It is the ratio of total emergy of the non-renewable inputs, external and local, to the total emergy of the renewable inputs. It is an indicator of the pressure of agricultural systems on the environment and may be considered a measure of ecosystem stress due to agriculture production (Ulgiati and Brown, 1998). The lower this ratio, the lower the stress to the environment: Environmental sustainability ESI ¼

EYR . ELR

(4)

The environmental sustainability index (ESI) is a ratio of the EYR to the environmental load ratio (ELR), indicating whether the yield of the system is favorable compared to the stresses imposed upon the environment. The larger the ESI, the higher the sustainability of a system. In addition to the familiar indices described above, we choose to present some new indices with special interest for

the concerned system as follows: Soil Emergy Cost SEC ¼

NR . Y

(5)

This index provides a soil cost-benefit ratio for agriculture, comparing agricultural yields against emergy loss associated with eroded soil, i.e. how much soil loss per unit emergy yield. Because erosion is embodied as a provider of agricultural yields, the value for the index must be less than unity; Selfsupport ratio SSR ¼

I gc þ I cg . RPgrazing þ RPcropping

(6)

With RPgrazing and RPcropping denoting the total renewable purchased resources of these two subsystems, this ratio represents the magnitude of the internally cycling renewable resources compared with the sum of the renewable resources as purchased externally. Selfsupport orientation SSO ¼

I gc  I cg . I gc þ I cg

(7)

This index indicates the orientation of the self-support as internal interaction. It is worth noticing that: for an extreme case of crop production with no support from grazing system, the index values at 1; for another extreme case of livestock production with no support from cropping industry, the index values at 1; for a somewhat

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moderate case of mutual support with equal emergy flux to each other, the index values at 0; for cases with emergy flux from grazing to cropping greater than that from cropping to grazing, the value is positive, otherwise negative. The index is bounded by 1 and 1. A variety of data resources are used to build a comparatively reliable database. Some types of data are specific and available on statistics books or experimental reports, while others not promptly accessible, such as soil erosion data for the whole region, and therefore appropriate methods have to be used to get an estimation. In this study, most of data, especially the economic inputs of goods and services and the yields, are taken primarily from the official statistics of IMAR and China (IMSY, 2001; CRSY, 2001). Land-use data with a scale of 1:250,000 of 2000 is provided by the Institute of Remote Sensing Application, Chinese Academy of Sciences (IRSA/CAS), as shown in Fig. 1 and Table 1. Renewable flow data are compiled from existing and derived data (Ma, 1999). In addition, the first authors had surveyed several regions of

IMAR such as Horqin, Mu Us, Xilingol and Alxa for data collection for his doctoral dissertation (Zhang, 2004) from 1999 to 2004 and synchronously accumulated some parameters essential for emergy calculation. As 1 year is taken as the time scale for the present analysis of the cropping–grazing system in the year of 2000, all buildings and tools used in the production systems are converted to annual flows based on their expected useful life adjusted by local investigation. 4. Results and discussion 4.1. The overall cropping–grazing system Enumerated in Table 2 are the local renewable resources, local non-renewable resources, and investments from economic system for the cropping–grazing system as a whole in the IMAR of 2000. The whole cropping–grazing system is estimated to be supported by a total emergy of 1220.76E+20 sej in 2000. The operation of the agricultural

Table 2 Emergy evaluation table for overall cropping–grazing system in IMAR Number

Item

Emergy (E20 sej yr1)

Emergy (E13 sej ha1 yr1)

Annual flow

Transformity

Renewable resources from free environment (RR) 1 Sunlight (J) 2 Wind, kinetic energy (J) 3 Evapotranspiration, chemical energy (J) 4 Runoff, geopotencial energy (J) 5 Earth cycle (J) Total RR

2.97E+21 5.55E+18 1.37E+18 1.13E+17 6.77E+17

1 2.45E+03 3.06E+04 1.76E+04 5.80E+04

29.75 136.05 419.02 19.89 392.76 438.91

4.43 20.27 62.44 2.96 58.53 65.41

Nonrenewable resources from free environment (NR) 6 Soil loss (J) Total NR

2.71286E+17

1.92E+05

520.87 520.87

77.62 77.62

Nonrenewable purchases (NP) 7 Electricity (J) 8 Diesel (J) 9 Nitrogen fertilizer, N (g) 10 Phosphorus fertilizer, P (g) 11 Potash fertilizer, K (g) 12 Compound fertilizer (g) 13 Pesticides (g) 14 Plastic mulch (g) 15 Equipment depreciation ($) 16 Buildings ($) Total NP

1.09E+15 1.54E+16 4.28E+11 1.44E+11 3.10E+10 1.44E+11 8.91E+09 6.32E+10 5.21E+07 3.63E+08

2.69E+05 1.06E+05 2.41E+10 2.20E+10 1.74E+09 2.80E+09 1.48E+10 3.20E+09 1.21E+13 1.21E+13

2.94 16.32 103.15 31.68 0.54 4.03 1.32 2.02 6.30 43.93 212.23

0.44 2.43 15.37 4.72 0.08 0.60 0.20 0.30 0.94 6.55 31.63

1.14E+16 1.05E+16

7.86E+04 3.80E+05

9.00 39.75 48.74 1220.76

1.34 5.92 7.26 181.92

Renewable subsidiary resources from economy (RP) 17 Seed (J) 18 Human labor (J) Total RP Total input 19 Crop production 20 Livestock production Total yield (J)

3.73E+17 2.17E+16 3.95E+17

Transformity references for respective row number: 1. Odum et al., 2000; 2. Odum et al., 2000; 3. Odum et al., 2000; 4. Odum et al., 2000; 5. Odum, 2000; 6. Cohen et al., 2006; 7. Odum et al., 2000; 8. Odum et al., 2000; 9. Brandt-Williams, 2002; 10. Brandt-Williams, 2002; 11. Brandt-Williams, 2002; 12. Lan et al., 2002; 13. Brandt-Williams, 2002; 14. Brown and Bardi, 2001; 15. Jiang and Chen, 2006; 16. Jiang and Chen, 2006; 17.Cohen et al., 2006; 18. Lan et al., 2002.

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Table 3 Emergy and related indices for cropping–grazing system compared with those of other provinces and the national average of China Item

IMAR (2000)

Hainan Province (1994)

Jiangsu Province (2001)

China’s average (2000)

Emergy intensity (sej m2) Fration used, locally renewable Fration of use purchased Emergy yield ratio (EYR) Emergy investment ration (EIR) Environmental load ratio (ELR) Environmental sustainability (ESI) Soil emergy cost (SEC)

1.82E+11 0.36 0.21 4.68 0.27 1.50 3.11 0.43

— 0.29 0.70 1.27 2.33 2.44 0.52 0.01

6.57E+11 0.21 0.78 4.17 3.52 3.75 1.11 0.003

5.35E+11 0.27 0.53 2.08 1.11 2.72 0.77 0.19

production heavily relies on local free environmental resources, with 78.62% of the total input from local environment, of which the largest emergy inflow is soil erosion (77.62E+13 sej ha1 yr1) accounting for 42.67% of total input and 54.27% of free environmental resources, respectively. Among the renewable emergy sources, the rainfall is the largest. To avoid double accounting (Odum et al., 2000; Cohen et al., 2006), only the rainfall flow (rainfall chemical potential+geopotential) is included in the accounting of RR although all the emergy input items are estimated. In addition to soil loss and rainfall, nitrogen fertilizers with emergy of 15.37E+13 sej ha1 yr1 is the third largest input in the emergy budget. High soil erosion rate and chemical fertilizers input ratio reflect the fragile characteristics of agricultural production in IMAR with unfavorable climate and unstable land surface and heavy cost paid by the environment for the cropping agriculture in arid and semi-arid regions as IMAR in China. The emergy inputs of electricity, diesel and mechanical equipment, of 0.44E+13, 2.43E+13 and 0.94E+ 13 sej ha1 yr1, respectively, are much less than the former three items, indicting that the agriculture in IMAR still remains characteristic of non-mechanized farming. For the non-mechanized agriculture, the emergy amount of labor input (5.92E+13 sej ha1 yr1) is not very high, due to the extensive farming pattern adopted by local farmers to avoid risk. In the traditional sense, Chinese agriculture includes four interactive subsystems of farming, forestry, husbandry and fishery. In areas of arid and semi-arid as IMAR, the productions of forestry and fishery play very minor roles and thus can be neglected. It makes sense to compare the cropping–grazing system with agricultural systems of other provinces and the national average, as illustrated in Table 3. The emergy intensity of 1.82E+11 sej m2 yr1 associated with the overall cropping–grazing system is relatively low compared with 6.75E+11 sej m2 yr1 associated with Jiangsu province (Liu and Li, 2005) and 5.35E+ 11 sej m2 yr1 for the national average (Chen et al., 2006). In addition, the agriculture in IMAR with a fraction of purchased investment of 0.21 depends much more on free environment resources than those in Hainan Province (Zhang et al., 1999) with 0.7, Jiangsu Province with 0.78

and the national average with 0.53, respectively. Moreover, the fraction of locally renewable free resources in IMAR is 0.36, higher than 0.29 in Hainan, 0.21 in Jiangsu and 0.27 in the national average. The emergy yield ratio (EYR) is used to evaluate the potential contribution of agriculture to economy and how efficiently the system uses available local resources. The value of EYR is 4.68, more than two times of 2.08 for the national average. To some extent, the highest EYR for cropping–grazing system in IMAR implicates its highest competitiveness among the four. The emergy investment ratio, EIR, is only 0.27, much lower than those of the other three systems. A lower EIR associates with a system depending more on the environment. For all the four systems under comparison, the cropping–grazing system in IMAR has the least value of ELR while that in Jiangsu had the largest value, indicating the different stress exerted on environment. We are thus prompted to draw a conclusion that the agricultural production system seems to be with a good sustainability, as further indicated by the ESI value of 3.11 for the cropping–grazing system in IMAR against 0.52, 1.11 and 0.77 for Hainan, Jiangsu and the national average, respectively. However, the value of SEC is up to 0.43, i.e., 0.43 sej emergy of soil loss is involved when unit sej of product is yielded, much higher than those for the other three ones, 0.01 for Hainan, 0.003 for Jiangsu and 0.19 for national average. The cropping-grazing system as a whole is then assessed of outstanding production competence at high cost of soil loss. 4.2. The cropping and grazing subsystems Emergy accounts for cropping subsystem and grazing subsystem are summarized in Tables 4 and 5. For both systems, rainfall is the largest of the renewable emergy sources and taken as total renewable contribution (RR) to avoid double accounting. In addition to rainfall input, the largest emergy inflows of cropping system are associated with soil erosion, nitrogen fertilizer and organic manure from animal excrement. Those four account for 78.96% of total emergy budget. In contrast, grazing system have the largest of renewable emergy inputs per hectare (59.89E+13 sej ha1 yr1) from free environment followed by soil loss (51.21E+13 sej ha1 yr1) and these two items

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Table 4 Emergy evaluation table for cropping subsystem in IMAR Number

Item

Emergy (E20 sej yr1)

Emergy (E13 sej ha1 yr1)

Annual flow

Transformity

Renewable resources from free environment (RR) 1 Sunlight (J) 2 Wind, kinetic energy (J) 3 Evapotranspiration, chemical energy (J) 4 Runoff, geopotencial energy (J) 5 Earth cycle (J) Total RR

4.26E+20 8.62E+17 2.78E+17 5.85E+16 1.05E+17

1 2.45E+03 3.06E+04 1.76E+04 5.80E+04

4.26 21.12 85.11 10.30 60.97 95.42

4.09 20.27 81.71 9.89 58.53 91.60

Nonrenewable resources from free environment (NR) 6 Soil loss (J) Total NR

1.21E+17

1.92E+05

231.92 231.92

222.64 222.64

Nonrenewable 7 8 9 10 11 12 13 14 15 Total NP

1.09E+15 1.54E+16 4.28E+11 6.29E+10 2.57E+10 1.44E+11 8.91E+09 6.32E+10 4.17E+07

2.69E+05 1.06E+05 2.41E+10 2.20E+10 1.74E+09 2.80E+09 1.48E+10 3.20E+09 1.21E+13

2.94 16.32 103.15 13.83 0.45 4.03 1.32 2.02 5.04 149.10

2.82 15.67 99.02 13.28 0.43 3.87 1.27 1.94 4.84 143.14

1.14E+16 6.04E+16 2.99E+16 8.14E+15

7.86E+04 9.25E+04 1.46E+05 3.80E+05

9.00 55.84 43.71 30.93 139.48 615.91

8.64 53.61 41.96 29.70 133.90 591.29

purchases (NP) Electricity (J) Diesel (J) Nitrogen fertilizer, N (g) Phosphorus fertilizer, P (g) Potash fertilizer, K(g) Compound fertilizer, (g) Pesticides (g) Plastic mulch (g) Equipment depreciation ($)

Renewable subsidiary resources from economy (RP) 16 Seed (J) 17 Organic manure from animal excrements (J) 18 Livestock labor (J) 19 Human labor (J) Total RP Total input 20 21 22 23 24 25 26 27 28 29 30 31 Total Yield (J)

Rice (J) Wheat (J) Corn (J) Millet (J) Soybean (J) Tubers (J) Sunflower Seeds (J) Rape-seeds (J) Beetroots (J) Vegetables (J) Fruits (J) Crop Residues (J)

1.04E+16 2.42E+16 8.81E+16 1.08E+16 1.65E+16 2.60E+16 1.73E+16 8.04E+15 3.94E+15 7.60E+15 4.21E+15 2.13E+17 4.30E+17

Transformity references for respective row number: 1. Odum et al., 2000; 2. Odum et al., 2000; 3. Odum et al., 2000; 4. Odum et al., 2000; 5. Odum, 2000; 6. Cohen et al., 2006; 7. Odum et al., 2000; 8. Odum et al., 2000; 9. Brandt-Williams, 2002; 10. Brandt-Williams, 2002; 11. Brandt-Williams, 2002; 12. Lan et al., 2002; 13. Brandt-Williams, 2002; 14. Brown and Bardi, 2001; 15.Jiang and Chen, 2006; 16. Cohen et al., 2006; 17.Cohen et al., 2006; 18. Lan et al., 2002; 19. Lan et al., 2002.

accounted for 81.90%, indicating strong dependence on local natural resources. It should be pointed out that both systems have high emergy input of soil loss. In cultivation system, the soil loss ranks the largest among inputs and has an annual flow of 222.64E+13 sej ha1, more than four times that in the grazing system. Human labor, forage from crop residues, mechanical equipment and sheds for animals are the main feedback inputs for livestock production, of which buildings and forage from crop residues account for the majority, with 7.75E+13 and 15.03E+13 sej ha1 yr1, respectively. For

cropping system, the purchased chemical fertilizers, including nitrogen fertilizer, phosphorus fertilizer, potash fertilizer and compound fertilizer, contribute almost 20% of the total emergy budget while machinery and fuels only account for 3.47%. Correspondingly, human labor and livestock labor contribute as the main driving forces, of 29.70E+13 and 41.96E+13 sej ha1 yr1 respectively. High chemical fertilizers input and low technical level reflect the land-use manners of short-term exploitation for instant benefit without sustainable strategy and planning adopted by local farmers.

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Table 5 Emergy evaluation table for grazing subsystem in IMAR Annual flow

Transformity

Emergy (E20 sej yr1)

Renewable resources from free environment (RR) 1 Sunlight (J) 2 Wind, kinetic energy (J) 3 Evapotranspiration, chemical energy (J) 4 Runoff, geopotencial energy (J) 5 Earth cycle (J) Total RR

2.32E+21 4.69E+18 1.09E+18 3.18E+16 5.72E+17

1 2.45E+03 3.06E+04 1.76E+04 5.80E+04

23.17 114.93 333.91 5.61 331.79 339.52

4.09 20.27 58.90 0.99 58.53 59.89

Nonrenewable resources from free environment (NR) 6 Soil loss (J) Total NR

1.51E+17

1.92E+05

290.31 290.31

51.21 51.21

Nonrenewable purchases (NP) 7 Equipment depreciation ($) 8 Buildings ($) Total NP

1.04E+07 3.63E+08

1.21E+13 1.21E+13

1.26 43.93 45.19

0.22 7.75 7.97

5.72E+16 2.32E+15

1.49E+05 3.80E+05

85.23 8.81 94.04 769.06

15.03 1.55 16.59 135.67

Number

Item

Renewable subsidiary resources from economy (RP) 9 Forage from crop residues (J) 10 Human labor (J) Total RP Total input 11 12 13 14 15 16 17 18 Total yield (J)

Beef (J) Mutton (J) Milks (J) Wool (J) Skins (J) Newly increased livestock (J) Animal excrements for cropping (J) Livestock labor for cropping (J)

Emergy (E13 sej ha1 yr1)

1.14E+15 2.70E+15 2.43E+15 3.62E+15 1.98E+15 9.82E+15 6.04E+16 2.99E+16 1.12E+17

Transformity references for respective row number: 1. Odum et al., 2000; 2. Odum et al., 2000; 3. Odum et al., 2000; 4. Odum et al., 2000; 5. Odum, 2000; 6. Cohen et al., 2006; 7. Jiang and Chen, 2006; 8. Jiang and Chen, 2006; 9. Ulgiati and Brown, 2001; 10. Lan et al., 2002.

The cropping subsystem is highly benefited from the grazing subsystem by making use of animal excrements as organic manure. The use intensity of organic manure is 53.61E+13 sej ha1 yr1, but less than that of nitrogen fertilizers. The use of organic manure is considered a sustainable strategy for agriculture, which can alleviate pollution and soil degradation caused by excessive chemical fertilizer use. According to local investigation, only about 20% of the animal excrement was collected and used because local farmers take it very trouble to collect dispersed manure compared with buying chemical fertilizers at the cost they could accept. As to grazing subsystem, the crop residues from cultivation system is a very important supplementary forage sources, especially during the winter and early spring. The emergy assigned to the yield from cropping system is 591.29E+13 sej ha1 yr1. The total yield of cropping system is 4.30E+17 J, including 2.13E+17 J of crop residues and about 5.72E+16 J of crop residues, is supplied to grazing system as forage (Icg), only accounting for 26.8% of total crop residues production, with most of other crop residues consumed mainly for rural cooking and heating. The grazing system uses a total emergy of 135.67E+13 sej ha1 yr1. In addition to the livestock

products of 2.17E+16 J, the grazing system also provide manure of animal excrements of 6.04E+16 J and livestock labor of 2.99E+16 J for cropping system, constituting the internal flow of Igc. The summary of emergy-based indices calculated for subsystems of cropping–grazing system is presented in Table 6. Notably, the ratio of emergy intensity, defined as total emergy input or yield per unit area, for the cropping subsystem to that for the pastoral is very near to the ratio of soil emergy cost of the cropping to that of the pastoral. That is, for both of the subsystems, the total emergy input is proportional to the soil loss. The values of EYR for the cropping subsystem and livestock subsystem are 2.13 and 5.52, respectively, indicating that the grazing subsystem depends more on available local resources. The EIR is 0.88 for crop production in IMAR, demonstrating that the production is still under traditional status except increased use of chemical fertilizers and pesticides. In addition, the value of 1.62 for ELR of cropping system, higher than 0.77 of grazing system, remains much less than 2.72 for the national average. Correspondingly, the environmental sustainable index (ESI) for the grazing system is greater than that for cropping system.

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Table 6 Index comparison between cropping and grazing subsystems in IMAR Item

Expression

Cropping system

Grazing system

Ratio between two systems

Total emergy used, U (sej ha1 yr1) Product yield (J ha1) Emergy intensity (sej m2) % Renewable Soil loss density (sej m2) Emergy yield ratio (EYR) Emergy investment ration (EIR) Environmental load ratio (ELR) Environmental sustainability (ESI) Soil emergy cost (SEC) Soil emergy cost (SEC) Self-support intensity (SSI)

RR+NR+RP+NP Y U/area (RR+RP)/U NR/area U/(NP+RP) (NP+RP)/(RR+NR) (NP+NR)/(RR+RP) EYR/ELR NR/U NR/U

591.29E+13 4.13E+10 5.91E+11 0.38 2.23E+11 2.13 0.88 1.62 1.32 0.38 0.38

135.67 E+13 3.83E+08 1.36E+11 0.56 5.12E+10 5.52 0.69 0.77 7.14 0.38 0.40 0.79

4.36 107.89 4.36 0.68 4.35 0.39 1.28 2.10 0.18 1.00

Self-support orientation (SSO)

I gc þI cg RPgrazing þRPcropping I gc I cg I gc þI cg

Compared with the grazing system, cropping system in IMAR has higher yield ratio, higher ELR, lower percentage of renewable resources use and lower ESI value. Considering a sustainable agriculture associated with ‘‘the ability to maintain production over long time frames despite major ecological and socio-economic perturbations and stress’’ (Conway, 1985; Altieri, 1987), in the long run, processes with a high percent of renewable emergy are likely to be more sustainable than those with a high proportion of non-renewable emergy. Although the yield rate of cropping is much higher than grazing on land, nearly 108 times in energy unit and more than four times in emergy unit, the cultivating activity resulted in greater surface deflation by turn soil under action of wind and water especially in IMAR with sandy soils and heavy wind force in the winter and spring. Because of higher yield rate per unit land, the local residents have tried to reclaim this marginal land for crops, i.e. turning grassland to cropland under the strategy of subsistence agriculture. Due to possible crop failures caused by marginal natural suitability for plantation involving unstable climatic conditions and sandy soil vulnerable to erosion, extensive cultivation habit has been adopted, characterized by simple management and low economic inputs in the past years. In recent years, local farmers have tended to increase chemical fertilizer use to ensure crop production as showed in emergy analysis of 2000, due to the fact that cultivation of grassland is prohibited by governments though not stopped absolutely, i.e. reclamation of grassland is no longer an easy thing anymore. Furthermore, in the past especially in times of Mao, under the policy of Grain First, the function of this region was pitched on production function to meet local self-support target, without considering its ecological importance to the local and the whole nation. With the increasing environmental deterioration in northern China, the orientation of this region began to be changed, to care more about its ecological significance. The prohibition of cultivation of grassland and de-farming for this region reflect the policy adjustments of central and local governments, but much more works need to be done. Firstly, clear

0.08

orientation of this region should be put forward by central government, which means no necessity for self-sufficient production and import of economic compensation for ecological services. Secondly, parts of cultivation should be abandoned, i.e. returning marginal cultivated land to grassland restoration, to sacrifice economic benefits of short term and local to gain sustainability of long term and the whole according to the emergy analysis above. In addition, measures like stubble remaining and no-tillage, which not only can reduce soil erosion but also can reserve crop residues in land as manure, should be encouraged. And at last, a land-use program for this region is essential and necessary with regarding to local comparative predominance, development strategy and ecological construction. The soil emergy cost (SEC) is estimated to be of the same value of 0.38 for the both subsystems, illustrating that not mater cultivation or grazing is adopted in this land, the soil cost per unit yield is the same at current climate conditions, land-use pattern and technical level. This index provides us with much information on land-use policy adjustment and desertification control, for instance, (1) before we take actions of de-farming, prohibiting grazing, and enclosing recovery, the cutting down of ecological pressure is prerequisite, i.e. reducing emergy extraction from land. Therefore non-agricultural employment of local labors, e.g., ecological migration and going to city as rural worker prevailing in China at present, is advisable; (2) measures have to be taken to cut down the value of SEC if we want to increase yield without deteriorating soil quality further, i.e. to increase the capability of capturing and concentrating renewable resources to produce higher quality output at certain cost. As mentioned above, the factors associated with soil cost are climatic condition, land-use pattern and technology level. It is impossible and uneconomical to change climatic condition for agricultural production whereas transformation of land use manner and renovation of technology are feasible and required. Field test demonstrated the effect of land-use adjustment and intensive farming in a region of Houshan in IMAR. The result

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showed that compared with traditional model, the new agriculture increased solar use efficiency by 8.3%, energy conversion efficiency by 19.4%, N output by 26.15%, N conversion efficiency by 57.1%, P output by 12.1%, P conversion efficiency by 45.0%, water use efficiency by 17.7% and economic benefits by 16.1% (Fan et al., 2004). The self-support intensity (SSI) and self-support orientation (SSO) designed in this article are to reflect material and energy exchange between the cropping and grazing subsystems. The value of 0.79 for SSI indicates that the exchange flux between these two systems accounts for 79% of total renewable purchased resources. The value of 0.08 for SSO shows a relatively balanced interaction is reached between these two subsystems. Besides over-cultivation, the grassland in IMAR also faces serious overgrazing problems. As mentioned above, grassland of high-soil quality had been cultivated for crops and grazing activities have to be forced to grassland of bad conditions, such as semi-fixed sand dune area with low resistance to disturbance. Moreover, there are undoubtedly too much animals grazing on grassland. The carrying capacity of livestock in IMAR was once estimated as 4.0  107 sheep unit (Bao, 2002), while the actual livestock on grassland was 6.80E  107 sheep unit in 2000 (IMSY, 2001). It is essential to increase production efficiency once taking measures of defaming and cutting down of animal quantity. Apart from external supports involving technique, financing aid and even experts, it is alternative to taking advantage of each subsystem to increase production efficient and absorb renewable resources from outside to enhance self-supporting capability. The IMAR are bounded by several provinces mainly engaged in cultivation, such as Liaoning, Heilongjiang, Jilin, Hebei and Shanxi, which can provide with large amount of crop residues for forages. All needed is to establish corresponding market unavailable currently to import emergy for grazing system. As to cropping system, planting grass on marginal farming land returned to natural recovery is advocated by many experts (Dong et al., 2005), which can definitely enhance coupled interaction, increase livestock production and decrease soil loss. Of all non-renewable purchases, the chemical fertilizers make up the largest fraction in terms of emergy. The excessive fertilizer application and large amount of soil loss have resulted in high nitrogen losses to the surrounding environment with disastrous consequence to atmospheric and groundwater quality and soil structure change with serious consequence to soil production capacity (Wang et al., 2002; Guo et al., 2003). Compared with other areas in China, the IMAR has great advantage in the forthcoming regulation of farming production pattern by increasing use percentage of organic manure from animal excrement.

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on the overall system and subsystems of IMAR in northern China to identify their production efficiency and environmental sustainability associated with serious land degradation, considering local development and national ecological security. In addition to conventional systems indices of EYR, EIR, ELR and ESI introduced for a congregated systems ecological assessment with essential implication to the sustainability, new indicators of soil emergy cost (SEC), self-support intensity (SSI) and self-support orientation (SSO) are defined to characterize the internal recycling associated with the special agricultural system. Extensive emergy account has been made for the concerned systems and subsystems, and concrete conclusions are drawn as follows: (1) The whole cropping–grazing system is estimated to be supported by a total emergy of 1220.76E+20 sej yr1 in 2000. The operation of the agricultural production heavily relies on local free environmental resources, with 78.62% of the total input from local environment, of which the largest emergy inflow is soil erosion (77.62E+13 sej ha1 yr1) accounting for 42.67% of total input and 54.27% of free environmental resources, respectively. (2) The overall cropping–grazing system is shown with outstanding production competence compared with agricultural systems in other provinces and the national average in China, as indicated by ESI value of 3.11 for the cropping–grazing system in IMAR against 0.52, 1.11 and 0.77 for Hainan, Jiangsu and the national average, respectively, though confronted with severe desertification associated with soil loss, with the value of SEC up to 0.43, much higher than that of three other ones, i.e., 0.01 for Hainan, 0.003 for Jiangsu and 0.19 for national average. (3) The production of crops has higher emergy density and yield rate per unit area as well as higher rate of soil loss than grazing system. Though the yield rate of cropping is nearly 108 times in energy unit and more than four times that of grazing, the cultivation system have an annual soil loss of 222.64E+13 sej ha1, 4.35 times that in the grazing system. (4) The SEC is estimated to be of the same value of 0.38 for the both subsystems, showing that not mater cultivation activity or grazing activity is adopted on this land, the soil cost per unit yield is the same at current climate conditions, land-use pattern and technical level. (5) The value of 0.79 for SSI and 0.08 for SSO for IMAR 2000 shows very strong but near balanced mutual support between the cropping and pastoral subsystems.

Acknowledgment 5. Conclusions Ecological energetic evaluations based upon Odum’s concept of emergy as embodied solar energy are conducted

This work has been supported by the National Key Program for Basic Research (973 Program, Grant nos. 2006CB403304 and 2005CB724204).

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Appendix A. Supplementary Materials Supplementary data associated with this article can be found in the online version at doi:10.1016/j.enpol. 2007.01.022.

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