e c o l o g i c a l m o d e l l i n g 2 0 2 ( 2 0 0 7 ) 540–546

avai lab le at www.sc iencedi rec t .com

journa l homepage: www.e lsev ier .com/ locate /eco lmodel

The integrated eco-environment assessment of thered soil hilly region based on GIS—A case study inChangsha City, China

Li Zhong-Wu ∗, Zeng Guang-Ming, Zhang Hua, Yang Bin, Jiao ShengCollege of Environmental Science and Engineering, Hunan University, Changsha 410082, People’s Republic of China

a r t i c l e i n f o

Article history:

Received 15 January 2006

Received in revised form

27 October 2006

Accepted 6 November 2006

Published on line 12 December 2006

a b s t r a c t

The development of remote sensing (RS) and geographic information system (GIS) provides

an effective means for studies of regional eco-environmental changes. Aiming at the red

soil hilly region with an extremely vulnerable ecosystem, supported by GIS, this study estab-

lished the environmental information system database for red soil hilly region, and evalu-

ated the eco-environment quality in a typical area of this region—Changsha City. Based on

the database, the study integrated Delphi, AHP and Integrated Eco-environment Assessment Index

Method into the eco-environmental quality assessment in the study area. The results showed

that only 7% of the total land area in Changsha (approximately 827.64 km2) is maintaining

Keywords:

GIS

AHP

Changsha City

Red soil hilly region

a higher or the highest grade of the eco-environmental quality. However, 52.4% of the total

area (approximately 6187.14 km2) is of a worse or the worst grade of the eco-environmental

quality. It was concluded that the entire eco-environmental quality of Changsha City has

degraded rapidly due to the highly intense human activities in recent years.

Therefore, supported by GIS, using AHP method (Bantayan

Eco-environment assessment

1. Introduction

The regional eco-environment quality is the base of the sus-tainable development, while the universal assessment foreco-environment quality is helpful to find out the regionalcurrent condition of sustainable development. As a result,the universal assessment of regional eco-environment qual-ity is a research focus at home and abroad. The analyticalhierarchy process (AHP) was put forward by Satty (1977)in 1970s, and is a systematic engineering method syn-thetically integrating qualitative analysis with quantitativeanalysis (Jin et al., 2004). As the AHP method can quan-tify qualitative analysis from subjective judgments, it was

applied in the quantitative research of many research fields,including nature, society and economy. (Lin and Yang, 1996;Ramanathan and Ganesh, 1995; Fahmy, 2001; Lai et al., 2002).

∗ Corresponding author. Tel.: +86 731 8640078; fax: +86 731 8822829.E-mail address: lzhongwu@hotmail.com (Z.-W. Li).

0304-3800/$ – see front matter © 2006 Elsevier B.V. All rights reserved.doi:10.1016/j.ecolmodel.2006.11.014

© 2006 Elsevier B.V. All rights reserved.

It is also becoming a common means of eco-environmentquality assessment at present (Wang et al., 1994; He et al.,2004; Solnes, 2003; Kurttila et al., 2000). Geographic informa-tion system (GIS) is a modern information technique thatemerged in the 1960s, with powerful functions of storing, dis-posing, analyzing and visualizing (Wu et al., 2002). Althoughit has almost 40 years’ history, GIS has been used in natu-ral resources management and eco-environment assessmentonly in the last 20 years (Ouyang et al., 1996; Lan et al.,2004; Aspinall and Pearson, 2000; McKinney and Cai, 2002).It is also able to consider time as the fourth dimension toresearch dynamic change of regional environment quality.

and Bishop, 1998; Dai et al., 2001), the research appraised theeco-environment quality of a typical frail ecosystem: red soilhilly region.

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In fact, because of its many good features, manyesearchers focused on using the GIS model approach in envi-onmental quality assessment and environment modeling.spinall and Pearson (2000) integrated eco-hydrological mod-ling, remote sensing, and landscape ecological analyses intoIS to develop some indicators to evaluate water basin healtht a regional scale. That sort of GIS model is very complicated,ecause it involves programming and interfacing between GISnd the environmental model. As a result, it is not suitable foreneral users. Matejicek et al. (2003) used the remote sensingRS) and GIS integrated with an ecological model to obtain anDVI index and simulate N pollution. However, GIS was only

egarded as a tool to display the results, which is only a pri-ary utilization of GIS in environmental modelling. Xu et al.

2001) used the GIS overlay operation based on raster to eval-ate the degree of lake eutrophication. This approach usedome GIS modules (e.g. spatial analysis module), and did notntegrate the environmental model into GIS. This approachad two obvious benefits: it fully implemented the GIS func-ions, and was easily utilized. The approach had been usedn similar research (Valavanis et al., 2004; McNeil et al., 2006).ence, researchers used this GIS model approach to evaluateco-environmental quality.

The red soil hilly region is of low ecological stability andigh fluctuation in biological system and productivity, sensi-ive to the activities of humans, and sudden disasters. Thehysical environment always tends to being more and moreerious, and being against human being’s survival (Cao andhang, 1995). The distribution of red soil hilly regions is broad,

ncluding 11 provinces and 619 counties in southern China,ccupying an area of 1.13 million km2 and accounting for 11%f the total land of China (Lu and Shi, 2000). Here, the sub-ropical monsoon climate gives the region sound bioclimatic

onditions (annual rainfall of 1400–1700 mm, mean annualemperature of 16–19 ◦C) and a strong potential for producingnormous quantities of biomass. Due to the long-term excessevelopment of natural resources, red soil hilly region has

Fig. 1 – Study si

2 ( 2 0 0 7 ) 540–546 541

become one of the most vulnerable eco-environment regionsin China (Cao and Zhang, 1995), characterized by serious ero-sion, heavy floods and droughts, degressive land productivity,and degraded ecological stability. The integrated analysis ofthe vulnerable eco-environment in the red soil hilly regionwill prompt the development of regional economics and theimprovement of human habitats.

The objectives of this study are expected to disclose themain factors affecting eco-environment quality, and to find agood approach to universally assess the environment qualityin red soil hilly regions.

2. Methods

2.1. Study site

The study site for this research is Changsha City (Fig. 1).The Changsha City is the capital of Hunan Province, China,located in the eastern part of the province, spanning over111◦53′–114◦15′E and 27◦51′–28◦40′N. It is composed of fivedistricts (Furong, Tianxin, Yuelu, Kaifu and Yuhua), threecounties (Changsha County, Wangcheng County and Ningxi-ang County) and Liuyang City, with a total area of 11,819.5 km2.Changsha City is a low hilly region with its elevation descend-ing from south to north, varying from 23.5 to 1607.9 m.Mountain, hill, hummock and plain account for 29.5, 17.2,23.3 and 25.3% of the total area of Changsha, respectively. Asubtropical monsoon climate gives Changsha City an annualrainfall of 1483.6 mm, which is mainly from April to July. Forthe features of topography of Changsha City, this region canbe regarded as an example of a red soil hilly region.

2.2. Data disposing

Maps with different scales and from various governmentaldepartments were scanned and/or digitized into a computer.

te location.

i n g

542 e c o l o g i c a l m o d e l l

By using ArcGIS 8.1, maps were reprojected into the standardprojection system (Transverse Meacator) that was used in theNational 1:250,000 Basic Terrain Database, and converted intothe form of 100 m × 100 m grid. Related TM images were inter-preted with Erdas Imagine 8.5 to get the information of landuse in Changsha City by Supervised Classification, integratedwith outdoors investigations in some typical regions.

3. Assessment model

3.1. The establishment of index system foreco-environment quality assessment

Eco-environment system is a complex system with multi-subjects and multi-levels. It is composed of natural andman-made environments. Because of “red desertification”, theland resource is scanty and also very important in ChangshaCity. As a result, land resource is the most important factoraffecting eco-environment quality. At the same time, humanactivity is also an important factor of eco-environment quality,especially for red soil hilly regions, and we selected society andeconomics factors as representatives of man-made environ-ment. Finally, the water and creature factors are regarded asrepresentatives of other natural factors, and should be takeninto account. Based on the analysis, in our research, the eco-environment system of Changsha City was divided into threesubsystems—biology and water resource (B1), land resource(B2) and society and economics (B3). Choosing proper assess-ment factors is the key to establishing the index system foreco-environment assessment. The factors should be able torepresent the features of the system and be related to the mainenvironmental problems in the corresponding area. Further-more, access or familiarity with the required data should alsobe considered in choosing factors. The research selected rep-resentative and sensitive factors considering three aspects asfollows:

(i) Integrating actual conditions of nature, society and econ-omy in Changsha City.

(ii) Integrating main environmental problems in Changsha

City.

(iii) Integrating features of Changsha City as a typical red soilhilly region, the selected index should be highly represen-tative and sensitive.

Fig. 2 – Index system for integrated assessment of

2 0 2 ( 2 0 0 7 ) 540–546

Finally, nine factors were chosen for the integratedanalysis, including water resource, vegetation cover, soil pen-etrability, soil nutrient, terrain slope, geology conditions,residential density, GDP of per capita and population density(Fig. 2).

3.1.1. Creature and water resource subsystem (B1)For the creature and water resource subsystem, water resource(C1), vegetation cover (C2) and soil penetrability (C3) wereselected as the factors of B1. Water resource is key to thebalance of the ecological system. Vegetation cover is theimportant medium between city and nature, and is alsoan important factor for protecting biological diversity andimproving environment quality. Soil penetrability can beregarded as the indirect factor of sensitivity of groundwaterto pollution, and the bigger the penetrability is, the easier it isfor the groundwater to be polluted. The vegetation cover andsoil penetrability are related to water resource.

3.1.2. Land resource subsystem (B2)The soil nutrient (C4), terrain slope (C5) and geology conditions(C6) were selected as the factor of B2. Slope is a crucial factorto construction control and soil erosion. In general, the biggerthe slope is, the more the plantation is. In fact, there is goodvegetation cover in mountain area with steep slope in Chang-sha City. Soil nutrient and geology conditions also had closerelations to the regional land use and construction intensity,respectively. They also affect the soil penetrability (C3) andvegetation cover (C2).

3.1.3. Society and economics subsystem (B3)For B3, residential density (C7), GDP of per capita (C8) and pop-ulation density (C9) were selected. They indicate the degreeof development of land resources, and also reflect the changeor deterioration of the ecological system. For instance, pop-ulation density in the city zones of Changsha City is over2000 km−2, while only 260–520 in the suburban zones. It is thehigh population density that directly results in traffic jams,environmental pollution and other serious problems in thecity zones.

3.2. Determining weights of assessment factors

Analytic hierarchy process was adopted to determine theweight of each factor. AHP is a simple systematic engineering

eco-environmental quality of Changsha City.

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ethod to quantitatively analyze non-quantitative objects. Itannot only fully consider the researcher’s subjective judg-ent during the quantitative and/or qualitative analysis, but

lso expresses the complex system in a hierarchic structurerom interrelation between inside and outside of the system,nd by analyzing step by step, helps the decision-makingrocess to be systemic, numerical and modelling. Due to itsbility of assigning proper weights to various factors of com-lex systems, AHP was also called an analytic multi-levelalue process (Tang et al., 1999). As a complex system withulti-subjects and multi-levels, eco-environment system was

uitable to employ AHP. The detailed analytic process was asollows.

.2.1. Establishment of the hierarchic structurehe entire eco-environmental system was broken down into

hree layers—A, B and C, denoting Objective Layer, Middleayer and Factor Layer, respectively (Fig. 2). Each layer in thisierarchic structure was compared in pair-wise comparisonselative to each of the elements in the level directly above.

.2.2. Establishment of comparison matrixayer A was broken down into Layers B and C to establishhe pair-wise comparison matrix. Relative importance of B1,

2 and B3 were analyzed by Delphi method, also called Expertudgment. In the research, we invited experts with ecologicalackgrounds to give the relative importance of each factor,espectively, then universally analyzed all the opinions, andnally, got the rank of relative importance for each factor.onclusions are:

. Erosion was crucial to ecological issues, and terrain slopewas an important indicator for the degree of erosion. InChangsha City, the mountain area of both sides of the city(eastern and western part) has big slopes and is sensitiveto environmental change. Therefore, weight of B2 is thehighest.

. The serious impact to the eco-environment was inducedby human beings. The research area was composed of cityand town with a high population density. Therfore, B3 hasthe relatively high weight.

. Comparing B3 and B2, B1 was less important. But it can-not be ignored, for the vegetation cover and water resourceare related directly to local climate, ecological issues andeconomic development.

Based on these conclusions, the pair-wise comparisonatrix is established for Layers A and B (Table 1).In order to gain the weights of the B1, B2 and B3:

Table 1 – Pair-wise comparison matrix for Layers A and B

A B1 B2 B3 Wi

B1 1 1/5 1/3 0.1045B2 5 1 3 0.6372B3 3 1/3 1 0.2583

2 ( 2 0 0 7 ) 540–546 543

(1) We must get the product of every row Mi:

Mi =3∏

j=1

bij, (i = 1, 2, 3)

(2) Get the cubic root of Mi:

Ni = 3√

Mi

(3) So, the weights of B1, B2 and B3 can be gotten by the fol-lowing formula:

wi = Ni∑Ni

, (i = 1, 2, 3)

Using this method, the weights of B1, B2 and B3 are 0.1045,0.6372, 0.2583.

3.2.3. Single rankingBased on corresponding pair-wise comparison matrix B, ele-ments in a level of the hierarchy were compared relative tosingle element in the level directly above and ranked by eigen-vector of the matrix (Zhang and Zhang, 1991). Eigenvector isderived from:

BW = �maxW (1)

�max is the maximum eigenvalue derived form:

�max =∑

(BW)inWi

(2)

W is the corresponding eigenvector of �max and Wi (i = 1, 2, . . .,n) is the weight value for ranking.

If matrix B is a consistent matrix, it means:

bij = bik

bjk, (i, j, k = 1, 2, . . . , n) (3)

�max of B should equal its number of order, and all the resteigenvalues should be zero. In research, �max = 3.0385. Consis-tence index (CI) was defined as:

CI = �max − n

n − 1(4)

In our research, CI = 0.0193, and average consistence index (RI)is 0.58. Random consistence index (CR) is defined as:

CR = CIRI

(5)

When CR ≤ 0.10, it means that the consistence of this matrixis acceptable. In this research, CR = 0.0332 ≤ 0.10 (Hou, 1992).

3.2.4. Total rankingBecause the pair-wise comparison matrixs of Layers B and Cis the same to that of Layers A and B, based on the results of aseries of simple rankings, the weights of all elements in a level

of the hierarchy relative to a whole level directly above can beobtained, which was total ranked, and was carried from theupper layer to the lower layer. After the above analytic pro-cess, weights of all indexes were determined for integrated

544 e c o l o g i c a l m o d e l l i n g 2 0 2 ( 2 0 0 7 ) 540–546

Table 2 – Weights of indexes for integrated assessment of eco-environmental quality of Changsha City

Subsystem B1 B2 B3

Weight of subsystem 0.1045 0.6372 0.2583C4

0.066

Factor C1 C2 C3

Weight of factor 0.0109 0.0666 0.0270

assessment of eco-environmental quality of Changsha City(Table 2).

3.3. Determining assessment valve

3.3.1. Dimensionless assessment factorsDue to great differences among values of different assessmentfactors, these factors must be dimensionless. After analyzingrelated data of each factor, their index values were determinedaccording to their relativity with eco-environmental quality.This aim was realized by:

Fij = 100Xij − Xmin,j

Xmax,j − Xmin,j(6)

In this equation, Fij means the dimensionless value of fac-tor j of grid i, varying from 0 to 1, while Xij, Xmin, j, and Xmax, j

mean the real, minimum and maximum value of factor j ofgrid i, respectively. All the factors are processed by this method(Zhen and Wang, 2000).

3.3.2. Integrated assessment of eco-environmental qualityof Changsha CityEco-environment was a large multi-element system, andexchanges of material, energy and information existed among

various subsystems of the large system. For better confidencelevels and accuracy, the Integrated Index Analysis for Environ-mental Quality was adopted (Liu et al., 2002), which means thatvalues of several indexes are overlaid in each grid and the

Fig. 3 – Map of integrated assessment of eco-

C5 C6 C7 C8 C9

6 0.4060 0.1646 0.0270 0.1646 0.0667

intersection value was used to determine the environmentalquality.

By using GIS software, the research area was divided into mgrids, and each grid had n factors. The integrated assessmentvalue of each grid was the sum of corresponding weight valuesof all the related factors, using the equation:

Pi =n∑

j=1

FijWj (7)

Pi is the integrated assessment value of grid i and Wj is theweight for factor j of grid i.

4. Results

Supported by the Spatial Analysis Module of ArcGIS, the inte-grated assessment value was calculated by Eq. (7) for eachgrid of research area, and then aggregated and reclassifiedto obtain the classification of eco-environmental quality ofChangsha City (Fig. 3; Table 3).

4.1. Area with best or better eco-environmental quality

Areas with the best or better eco-environmental quality, which

have the strongest or stronger ecological sensitivity, the small-est or smaller intensity of human activities, and the most orbetter ecosystem services, and which also have the weakestor weaker ecosystem stability and were the most or more eas-

environmental quality of Changsha City.

e c o l o g i c a l m o d e l l i n g 2 0 2 ( 2 0 0 7 ) 540–546 545

Table 3 – Classification of eco-environmental quality of Changsha City

Grade Best Better Well Normal Worse Worst

Area (km2) 94.6 733.04 2828.5 1960.79 5042.35 1144.64–3.54.0

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ly disturbed by the environment, were located in mid andortheastern Liuyang County, western Ningxiang County andid western Wangcheng County, where mountains are dis-

ributed widely, such as Lianyun Mountain in Liuyang Countynd Wei Mountain in Ningxiang County. In these areas, theiround quality of eco-environment is due to fewer disturbancesy human beings, rich nutrients in the soil, high vegetationover and good soil penetrability. However, blocks of areas withormal or worse environmental quality were visible in thesereas, due to less forest protection and serious soil erosionesulting from steep slopes.

.2. Area with good eco-environmental quality

reas with good eco-environmental quality, which havetrong eco-sensitivity, small human activities, and importantcosystem service, included the whole of Liuyang County,id and western Ningxiang County and northern Changsha

ounty. Most land in these areas were farmland and forest,long with some grassland. Disturbance from mankind is rel-tively less, which makes the environment quality better.

.3. Area with normal eco-environmental quality

ost areas with normal eco-environmental quality, whoseco-sensitivity and human activity intensity are general, wereocated in Wangcheng County, Kaifu District of Changsha City,nd some parts of Ningxiang County and Liuyang County;hese areas are urban or suburban. The main land use typesn these areas are paddy fields and woodland. The eco-nvironment of these areas was affected by human activityore seriously, and the eco-environment quality was only

eneric. For this type of area, some environmental protectioneasures should be strengthened, including soil meliorating,

ree planting and pollution source management.

.4. Area with worse or worst eco-environmentaluality

reas with worse or the worst eco-environmental quality,hich have small eco-sensitivity, the biggest human activ-

ty intensity, and the best ecosystem stability, were locatedn Furong District, Yuhua District, Tianxin District, southernhangsha County, mid and northern Ningxiang County, andorthwestern Liuyang County. They accounted for over 50%f total area of Changsha City, indicating the eco-environmentuality was very serious. These areas were urban or town withhigh density of buildings, hard surface and limited vegeta-

ion cover, which increased the heat absorbed by land surfaceSchotten et al., 2001). Together with a high concentration ofreenhouse gases in the local atmosphere, temperature inhese areas was higher than that in the countryside, resulting

2–3 1–2 0–116.6 42.7 9.7

in “heat island effect”. Interpretation map of Satellite Imageryin May of 2000 showed that the maximum temperature of theurban area is 7.4 ◦C higher than the minimum temperatureof the suburban area, which illuminates, to some extent, thatenvironmental quality is the most vulnerable when affectedby activities of human beings.

5. Conclusion

Utilizing AHP method, the study utilized the GIS modelapproach to research the current condition of eco-environment quality for typical area of red soil hilly region.The result showed:

(1) The vegetation cover in creature and water resource sub-system, the slope in land source subsystem and the GDPper captia in social and economic subsystems are the mostimportant factors affecting eco-environment quality of redsoil hilly region, whose weight values were 0.0666, 0.406and 0.1646, respectively.

(2) The integrated assessment of red soil hilly region fora typical area of Changsha City showed that the worstarea of eco-environment quality in red soil hilly regionaccounts for more than half of the total area, which basi-cally accorded with the properties of frail ecosystem of redsoil hilly region.

(3) The result embodies the main benefit of the proposedapproach when compared with other different GIS mod-els. This methodology can easily use the spatial analysismodule to obtain the assessment results. Therefore,the method could be very interesting to policy makersinvolved in regional eco-environmental quality assess-ment, because it can allow decision makers to clearlyknow the current status of the quality of their regionalenvironment.

Acknowledgements

The study was funded by the National Foundation of Chinafor Distinguished Young Scholars (No. 50225926 and No.50425927).

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