Ecological Functions and Their Values in Chinese Cropland Ecosystem

CHINA POPULATION, RESOURCES AND ENVIRONMENT Volume 17, Issue 4, July 2007 Online English edition of the Chinese language journal Cite this article as: Chn Popu Res Envi, 2007, 17(4): 55–60.

SHORT COMMUNICATION

Ecological Functions and Their Values in Chinese Cropland Ecosystem Sun Xinzhang 1,* , Zhou Hailin1, Xie Gaodi2 1. Administrative Center for China’s 21 Agenda, Beijing 100038, China; 2. Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing 100101, China

Abstract: Cropland ecosystem not only provides people with grains, vegetables, fibers, etc., but also plays an important role in air regulation, soil and water conservation, environmental decontamination, etc. Furthermore, cropland ecosystem has negative effects on our environment, such as soil and water pollution, because of the use of fertilizers and pesticides. So far, there are a few research findings about Chinese farmland’s ecological functions, but only a part of ecological functions is discussed in this article. At present, an integrated research is needed in order to get a comprehensive understanding of cropland ecosystem. This article gives a primary result of ecological functions and their monetary values in Chinese cropland ecosystem. The results showed that the total monetary value of ecological functions provided by Chinese cropland ecosystem was 1912.18 billion yuan RMB in 2003 (present price in 2003); the positive value was 2233.41 billion yuan RMB and negative was -321.23 yuan billion RMB. The value per hectare was 18960.60 yuan RMB/hm2, of which the value of crop products was 14788.70 yan RMB/hm2 and others were 4171.90 yuan RMB/hm2. The ecological functions in the farmland vary with regions. The values ranged from 8.68 to 505.08 billion yuan RMB, and HHHR and MLRYR were higher than those of the other ecological zones. The values per hectare ranged from 515.90 to 3498.43 yuan RMB/hm2, and SC and MLRYR were higher. Keywords: Chinese cropland ecosystem; ecological function; monetary value

1

Introduction

Cropland is one of the important terrestrial ecosystems. In contrast to forests, grasslands, and other terrestrial ecosystems, cropland has some special ecological functions under human intervention. For example, cropland not only provides people with food, but also plays a role in controlling soil erosion and groundwater contamination. Till now, the researches on cropland’s ecological functions are relatively few and most of them focus only on a part of functions or describe the trends only (Costanza, et al, 1997; Xiao et al, 2004; Björklund et al, 1999; Wier et al, 2000). Some researchers adopt directly or indirectly Constanza’s results as parameters to evaluate cropland’s ecological functions (Wang et al, 2004; Zhao et al, 2004), and few of the researchers explore the regional differences in the ecological functions exhibited by the cropland ecosystem. On the basis of these, the article evaluated the ecological functions and regional differences exhibited by Chinese cropland ecosys-

tem with respect to these functions in 2003.

2 Ecological functions and their values in Chinese cropland ecosystem 2.1 Function of production Cropland provides people with abundant crop products which are necessary for their survival. Furthermore, its by-products and crop stalks are the primary support for Chinese farmers’ special subsidiary production, such as handicraft, livestock, and poultry feeding. For the production function of cropland, the study adopted a direct market method to assess its monetary value. The data of crop output value come from China Statistical Yearbook 2004, and for evaluation of by-products, the article adopted the 700 farm households’ survey data conducted in six provinces by the authors from 2003 to 2005. Table 1 lists the output and value of crop products in each agroecological zone of China. The results showed that grain

Received date: 2007-03-20. * Corresponding author. E-mail: [email protected] Copyright © 2007, Chinese Society for Sustainable Development and Research Center for Sustainable Development of Shandong Province. Electronic version published by Elsevier Limited. All rights reserved.

Sun Xinzhang et al. / China Population, Resources and Environment, 2007, 17(4): 55–60

production is mainly concentrated in the middle and lower reaches of the Yangtze River (MLRYR), Huang-huai-hai Region (HHHR), Northeast China (NEC), and Southwest China (SWC), where 78.8% of the grains of whole of China was produced in 2003; production of oil plants is mainly concentrated in MLRYR and HHHR, where 63.9% of the edible oil of the whole of China is produced; cotton is mainly produced in HHHR, MLRYR, and Xinjiang (XJ); and fruits mainly in HHHR and MLRYR. The monetary values of crop products are higher in HHHR and MLRYR, which accounted for 53.0% of China’s total planting output value. 2.2 Function of social security At present, cropland not only provides Chinese people with crop products, but also plays the role of providing social security for rural people. In China, there are approximately 480 million rural laborers, of which 160 million have been employed in nonagricultural sectors. However, many of the rural laborers still doing agriculture actually are semi-employed because the number in the agricultural sector exceeds greatly the number needed. According to a survey conducted by the Ministry of Agriculture, China’s agricultural production actually needs only 170 million laborers, but there are 320 million working on it. This means that approximately 46.8% of the labor force in the agricultural sector is unemployed. However, these unemployed laborers are out of national unemployment compensation system, unlike the urban unemployed people, because they have cropland and have a job, theoretically. This is the main reason why we think that cropland plays the role of providing social security to the rural population of China. Furthermore,

for those who are employed in nonagricultural sectors, the use of cropland ecosystem also ensures them against unemployment because they can go back to their hometown and engage in farm production over again. The valuation method of the social security function is shown as follows: V=N×M×r where V is the monetary value of social security function (in yan RMB); N is the number that is ensured by cropland; M is the minimum subsistence allowance in urban China; and r is the ratio of consumption level in rural China to that in urban China. Table 2 listed the number and monetary value in each agroecological zone. The results showed that at present there are 130 million people who rely on cropland and the monetary value is 73.31 billion yuan RMB. In other words, the unemployment number will be increased by 130 million and governments need to increase 73.31 billion yuan RMB per year for these people’s unemployment compensation if there was a lack of social security functions by cropland. 2.3 Atmosphere regulation function 2.3.1 CO2 sequestration and O2 emission Crops sequestrate CO2 and release O2 by photosynthesis, which is helpful for control of global warming and for fresh air supply. The study quantified the CO2 sequestrated and O2 emitted by China’s cropland ecosystem each year according to net primary production (NPP) and photosynthesis equation, and then assessed the value of CO2 sequestration by carbon trade price (51.21 yuan RMB/t CO2) and the value of O2 emission by the industrial cost of oxygen production (400 yuan RMB/t O2).

Table 1 Output and value of crop products in 2003 Oil plants (103 t)

Fruit (103 t)

Output value (109 yuan RMB/a)

4

10 068

1438.5

1 023

5

1 233

336.0

7 755

501

1 600

4 083

482.8

HHHR

95 701

8 412

1 874

53 137

3 872.3

LP

29 868

1 369

231

13 787

913.8

QTP

1 834

312

0

35

55.0

MLRYR

113 928

9 554

1 118

32 910

4 015.5

SWC

67 165

3 574

0

7 985

1 784.2

SC

38 133

1 733

0

21 936

1 972.0

Total

430 695

28 110

4 860

145 174

14 870.1

Agroecological zones

Grain (103 t)

NEC

62 702

1 632

IM

13 607

XJ

Cotton (103 t)

Notes: Northeast China (NEC)(including Heilongjiang, Jilin and Liaoning); Inner Mongolia(IM); Xinjiang(XJ); Huang-huai-hai Region(HHHR)(including Beijing, Tianjin, Hebei, Henan and Shandong); Loess Plateau(LP)(including Shanxi, Shannxi, Ningxia and Gansu);Qinghai-Tibet Plateau(including Qinghai and Tibet); Middle and Lower Reaches of Yangtze River(MLRYR)(including Shanghai, Jiangsu, Zhejiang, Anhui, Jiangxi, Hunan and Hubei);Southwest China(SWC)(including Yunnan, Sichuan, Guizhou and Chongqing); South China(SC)(including Guangdong, Guangxi, Hainan and Fujian) .

Sun Xinzhang et al. / China Population, Resources and Environment, 2007, 17(4): 55–60

The NPP of cropland in China can be estimated using the following equation:

model. According to the research results and planting structure in 1990, we can calculate the flux of the emission of greenhouse gases by cropland, and then calculate the emitted quantities of greenhouse gases in 2003 and total GWP. From the results (Table 3), we can see that China’s cropland is a source of carbon as a whole. However, this considerably differs with the agroecological zones. The zones of cropland taking on a carbon source are NEC, IM, and XJ, especially NEC; the zones where carbon emission and sequestration are almost equal include SC, SWC, and MLRYR; the zones of LP, QTP, and HHHR are weak carbon sinks. The total monetary value of cropland’s atmosphere regulation function is 142.917 billion yuan RMB per year. NEC has the most fertile soil and is also one of the three main grain production zones (others are HHHR and MLRYR) of China. However, crop production in the zone also declined. The soil carbon sank when it provided Chinese people with abundant food. According to the results, NEC emitted 86% of the total 362 million t CO2 (CH4 and N2O have been converted to CO2 according to GWP) in China’s cropland ecosystem.

n

NPP =

∑ P /R ×(1−W ) i

i

i

i=1

where Pi is economic yield of i crop; Ri is harvest index of i crop; Wi is water content of i crop; i = 1, 2, …8, represent cereals, beans, potatoes, oil plants, cotton, sugar crops, tobacco, and vegetables, respectively. For the NPP of orchards and tea gardens, the article uses the data of forestland in the same agroecological zone as a substitute. 2.3.2 Emission of Greenhouse gases Cropland soil also emits CO2, CH4, and N2O, which have an important effect on global warming. In the study, we used Global Warming Potentials (GWP) to convert the quantity of CH4 and N2O into the quantity of CO2 that had the same greenhouse effect as CH4 and N2O did, and then evaluated them using carbon trade price. Li et al (2003) calculated the quantities of CO2, CH4, and N2O emitted by China’s cropland in 1990 using DNDC

Table 2 Social security function and its value in cropland ecosystem Minimum subsistence allowAgroecological zones

ance in urban China(yuan

R

RMB/month)

Number

Monetary value

(103 person/yr.)

(108 yuan RMB/ yr.)

NEC

152

0.298

8 521

46.3

IM

121

0.298

2 283

9.9

XJ

124

0.298

1 652

7.3

HHHR

175

0.298

30 901

193.4 48.9

LP

128

0.298

10 682

QTP

129

0.298

926

4.3

MLRYR

169

0.298

34 223

206.8

SWC

141

0.298

26 122

131.7

SC

188

0.298

16 942

113.9

Total

155

0.298

132 252

733.1

Table 3 Atmosphere regulation functions and their values of cropland Total GWP

CO2 sequestration

O2 emission

Total value

(106 t/yr.)

(106 t/yr.)

(106 t/yr.)

(106 yuan RMB/yr.)

NEC

385.20

72.41

53.29

37.86

IM

89.22

16.37

12.05

10.81

XJ

31.96

13.63

10.03

30.93

HHHR

61.93

125.66

92.49

404.57

Agroecological zone

LP

32.82

36.85

27.12

102.26

QTP

−0.25

2.38

1.75

8.39

MLRYR

165.17

142.74

105.06

397.95

SWC

81.88

80.32

59.12

235.84

SC

72.96

68.52

50.43

200.57

total

920.89

558.88

411.34

1429.17

Sun Xinzhang et al. / China Population, Resources and Environment, 2007, 17(4): 55–60

2.4 The water and soil conservation functions 2.4.1 Soil conservation function China’s cropland ecosystem has many positive effects on soil and water conservation, although unreasonable farming activities have led to increased soil erosion. First, soil erosion could be reduced when the soil was covered with crops. Second, many types of measures leading to the retention of soil and water were devised by Chinese farmers over the long period of production practice, which produced excellent results with regard to soil and water conservation, such as terrace and check-dams. The soil conservation function of cropland ecosystem can be calculated as follows: Qs =A×(Ep−Er) where Qs is soil quantity retained by cropland ecosystem; A is cropland area; Ep is potential erosion modulus; and Er is present erosion modulus. The monetary value of the soil conservation function of cropland ecosystem can be estimated from the functions of reducing abandoned farmland and by alleviating sedimentation, and methods of opportunity cost and shadow engineering are adopted, respectively. 2.4.2 Water conservation function The water conservation function of cropland ecosystem can be calculated as follows: Qw = A×J×R J = J0×K R = R0−Rg where Qw is water retained by cropland compared with naked land; A is cropland area; J is mean rainfall produced runoff each year; J0 is mean total rainfall each year; K is the ratio of rainfall produced runoff to total rainfall; R is the efficiency of cropland retaining rainwater compared with naked land; R0 is the ratio of rain runoff in naked land; and Rg is the ratio of rain runoff in cropland. The K value is determined based on characteristics of rain in each agroecological zone (Zhao et al, 2004) and R value based on some related documents (Sun et al, 2005). The function of water conservation is mainly embodied in regulating flood and in supplying fresh water. Here, we calculated its value by adopting reservoir-building cost in China (1.17 yuan RMB/ m3). The results showed that the degrees of soil conservation are higher in NEC, LP, and SWC, but the monetary values are higher in SWC, HHHR, and MLRYR; the capacity of water conservation in south zones is stronger than that in north zones (Table 4). 2.5 The function of environmental decontamination There are many circular production patterns in Chinese conventional farming system, which leads to cropland ecosystem playing an important role in environmental decon-

tamination. Dung and some living garbage often are used as organic manure, which not only sustains soil fertility but reduces expenditure to dispose these rejectamenta. For the function of environmental decontamination, we use garbage disposal cost in China (108 yuan RMB/t) as an index to estimate its monetary value. The results showed that Chinese cropland decontaminates 3604.79 million ton rejectamenta each year, and total value is 389.32 billion yuan RMB; the decontaminating capacity is stronger in HHHR and MLRYR than that in other zones (Table 5). 2.6 Function of water consumption Irrigation raises cropland’s productivity, which improves people’s survival ability in arid and semiarid areas. However, irrigation also leads to some environmental problems in China, such as falling of groundwater level in HHHR and drying up of the Tarim River in Xinjiang. Water used for irrigation accounted for 64.5% of the total 532.0 billion m3 water consumption in whole China’s production in 2003. The monetary value of water consumption by Chinese cropland ecosystem can be assessed as follows: Vw = W × R × Cw where Vw is the value of water consumption; W is the amount of water used for cropland production; R is water rate; and Cw is reservoir-building cost. The results are shown in Table 5. We can see that Chinese cropland needs 174.15 billon m3 of water each year and its monetary value is 203.75 billion yuan RMB. MLRYR, SC, and HHHR are the main water-consumption zones. 2.7 Function of environmental pollution With the rapid development of agricultural modernization, organic manure, weeding by hand and some other measures which are beneficial to environment are gradually being substituted by chemical fertilizers, herbicides, and pesticides. These chemicals increase crop yield as well as induce a series of environmental problems, such as air pollution, eutrophication, nitrate accumulation in farm products, and pesticide residue. Theoretically, the negative value of environmental pollution induced by cropland ecosystem should be the loss of human welfare caused by chemical fertilizers and pesticides. However, it is almost impossible to quantify the losses because a reasonable method and sufficient data are unavailable. Hence, the study adopted the following method to assess it: Vp = M×(1−r)×p where Vp is the negative value of environmental pollution caused by chemical fertilizer and pesticide; M is utilization amount of fertilizer and pesticide; r is their utilization rates; and p is their current prices. Chen et al (2002) surveyed utilization rate of fertilizers

Sun Xinzhang et al. / China Population, Resources and Environment, 2007, 17(4): 55–60

much higher in SC, MLRYR, HHHR, and SWC, and lower in IM, NEC, QTP, and LP . From the results, we can see that the total ecological value provided by cropland in China is 1912.18 billion yuan RMB each year, of which direct production function is 1487.0 billion yan RMB, accounting for 77.8% of the total value, and indirect regulation values account for only 22.2%. Cropland ecosystem not only provides people with positive ecological services, but also exercises negative effects on living environment of humans. The losses caused by water consumption, fertilizer, and pesticide pollution are 321.23 billion yuan RMB each year. From the results, we can see that the ecological value per hectare cropland is 18960.60 yuan RMB/hm2, of which the value of production function is 14788.70 yuan RMB/ hm2, and other services total up to 4171.90 yuan RMB/ hm2; cropland ecosystem led to a loss of 3185.20 yuan RMB/ hm2 because of environmental pollution and water consumption.

around China. The article directly adopted their results. For the utilization rate of pesticides, the article estimated it according to some documents and agricultural household survey data. The results showed that approximately 28.4 million tons of fertilizers go to waste and 861.4 thousand tons of pesticides are not absorbed by crops each year, which cause a loss of 117.6 billion yuan RMB. The pollution caused by fertilizers and pesticides in HHHR and MLRYR are worse than that caused in the other zones, and at the same time the two zones are also the high agricultural productivity zones of China. 2.8 Brief summary The values of cropland’s ecological functions are higher in MLRYR and HHHR, and the total value of the two zones is 1004 billion yuan RMB each year, which accounts for 52.5% of the value provided by the whole cropland ecosystems in China; QTP, IM, and XJ are small, and SWC, SC, NEC and LP are intermediate. The values per hectare are

Table 4 Water and soil conservation functions and their values in cropland ecosystem

Agroecological zone

Quantity of soil conservation 6

(10 t/a)

NEC

Value of soil con-

Quantity of water con-

servation

servation

vation

(106 m3/a)

(108 yuan RMB/a)

(108 yuan RMB/a)

12.70

Value of water conser-

18.71

73.95

86.53 22.78

IM

2.88

2.97

19.47

XJ

1.42

3.68

1.81

2.12

HHHR

9.92

32.09

93.24

109.10

LP

13.77

21.88

41.66

48.74

QTP

0.41

0.56

1.49

1.75

MLRYR

9.00

31.77

367.42

429.88

SWC

18.75

49.89

213.17

249.41

SC

5.02

23.23

209.55

245.22

total

73.90

183.22

1 021.77

1 195.53

Table 5 Functions and their values in environment decontamination and water consumption of cropland

Agroecolgical zones

Quantity of rejectamenta de-

Value of rejectamenta de-

Water consump-

contamination

contamination

tion

6

8

8

3

Value of water consumption 8

(10 t/a)

(10 yuan RMB./a)

(10 m /a)

(10 yuan RMB/a)

NEC

344.20

371.74

185.72

217.29

IM

80.48

86.92

84.16

98.47

XJ

88.95

96.07

26.20

30.66

HHHR

933.21

1 007.87

255.74

299.22

LP

235.45

254.29

137.59

160.98

QTP

45.44

49.07

25.55

29.89

MLRYR

858.56

927.24

514.50

601.97

SWC

524.40

566.35

175.17

204.95

SC

494.10

533.63

336.83

394.09

total

3 604.79

3 893.17

1 741.46

2 037.52

Sun Xinzhang et al. / China Population, Resources and Environment, 2007, 17(4): 55–60

Table 6 Contaminated quantity and economic loss of fertilizers and pesticides

Agroecolgical zones

Fertilizers (104t/a)

Pesticides (104t/a)

NEC IM XJ HHHR LP QTP MLRYR SWC SC total

235.62 56.08 58.01 788.63 199.75 6.08 864.44 301.89 330.38 2 840.88

6.80 0.69 0.78 22.91 2.84 0.15 31.57 7.10 13.29 86.14

3

Losing value (108 yuan RMB/a) −99.38 −22.17 −26.63 −329.61 −80.45 −2.38 −356.31 −124.01 −134.68 −1 175.63

Discussions

increase, whereas indirect regulation values decrease after grassland or forestland is transformed to cropland.

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