Oasis land-use change and its environmental impact in JintaOasis, arid northwestern China

Shan-Zhong Qi & Xiao-Yu Li & Hui-Ping Duan

Received: 30 October 2006 /Accepted: 23 January 2007 / Published online: 1 March 2007# Springer Science + Business Media B.V. 2007

Abstract Land use change resulted in land degrada-tion is a focus of research on global environmentalchanges and plays a significant role in the stabilityand economic development of oases in arid regions ofChina. Jinta Oasis, a typical oasis of temperate aridzone in northwestern China, was investigated toassess land-use change dynamics during 1988–2003with the aid of satellite remote sensing and GIS, andto explore the interaction between these changes andoasis environment. Six land-use types were identified,namely: cropland, forestland, grassland, water, urbanor built-up land, and barren land. The results indicatethat cropland, urban/built-up land, and barren landincrease greatly by 30.03, 13.35, and 15.52 km2,respectively; but grassland and forestland areas de-crease rapidly by 58.06, and 1.76 km2, respectively.These results also show that obvious widespread

changes in land-use occur within the whole oasisover the study period and result in severe problems ofenvironmental degradation (i.e. land desertification,decline of groundwater, and vegetation degeneracy).

Keywords Land use change . Oasis environmentalchange . Land degradation . Jinta Oasis . Aridnorthwestern China

Introduction

Land use/cover change is a focus of global environ-mental change research (Turner et al. 1994). It isdirectly relevant to such issues as water and soilquality (Bushchbacher et al. 1988; Dalal and Mayer1986) and food security (Wilson 1988). Effects ofland use change on land degradation resulted frompopulation pressure and land use intensification (Chenand Tang 2005; Mundia and Aniya 2006), have beenreported elsewhere. It often resulted in nutrientdepletion, soil organic matter reduction (Guggenbergeret al. 1995), soil quality degradation (Lal et al. 1999;Solomon et al. 2000), biodiversity decrease and soilerosion acceleration (Warkentin 1995). Landscapechanges are thought to be driven by the complexinteractions of socioeconomic (anthropic) and envi-ronmental (physical) factors (Forman 1995; Zonneveld1995). Human activities in response to various socialand economic factors define patterns of land use/cover and resource use (Blasi et al. 2003; Irwin and

Environ Monit Assess (2007) 134:313–320DOI 10.1007/s10661-007-9622-5

S.-Z. Qi :H.-P. DuanCollege of Population, Resources and Environment,Shandong Normal University, No. 88 Wenhua East Road,Jinan 250014, Shandong Province,People’s Republic of China

S.-Z. Qie-mail: qshzhsd@yahoo.com.cn

X.-Y. Li (*)Institute of Applied Ecology, Chinese Academy Sciences,No. 72 Wenhua Road,Shenyang 110016, Liaoning Province,People’s Republic of Chinae-mail: lixy76@163.com

Geoghegan 2001; Wear and Bolstad 1998). So far,land use/cover change has received more attentioninternationally (Chen et al. 2003; Mas 1999; Yangand Lo 2002). The International Geosphere–Bio-sphere Program (IGBP) and International HumanDimensions Program (IHDP) were launched in themid-1990s to study land use/cover change at the globalscale. These programs aimed at understanding themain driving force behind the change (Verburge et al.1999), which could include climatic, biological, andsocio-political forces (Reid et al. 2000). With therapid growth of human population, such alternationsare taking place at unprecedented rates, magnitudes,and spatial scales (Turner et al. 1994). Human-induced changes in land use/cover form an important

component of global environmental change. Therefore,it is important to study the changes of land use/cover.

Oases are the specific and unique intrazonal land-scapes that exist with deserts in arid and semi-aridregions of the world. In China oases are mainlydistributed in temperate and warm temperate desertareas between the west of the Helan Mountain and thenorth of Qinghai-Tibet Plateau, which are connectedwestward with those of the Middle Asian region (Jiaet al. 2004; Zhang et al. 2003). Unlike other regions,the landscape structure and change in this area aremainly manifested by the desert-oasis-river landscapepattern, simple composition, coarse grain size, highcontrast of heterogeneous landscape mosaics, andhigh dependence on water sources (Cheng et al.1999). Although oases take up only 4–5% of the totalarea of the region, over 90% of population and over95% of social wealth are concentrated within theoases (Han 2001). Oasis is not only the mostconcentrated area of human activities in arid regionbut also the largest area where artificial disturbancesoccur at the regional scale. Therefore, study of landuse change within oases and its impacts on thestability of oases are essential for sustainable devel-opment in the arid regions. However, there were fewresearches to analyse land-use change and its impactson the oasis environment for Chinese arid region (Jiaet al. 2000; Luo et al. 2005). The study area, JintaOasis, is a very typical artificial oasis in drylandregion of China and is set as one of the national landresource developing and representative areas in Chinabecause the oasis is vast stretches of soils and easy toreclaim for agriculture. It is located in the northeast ofJiuquan District, north side of middle of HexiCorridor, in which the center of satellite launch is

Fig. 1 Location map of Jinta Oasis in arid northwestern China(98°39′–99°08′E, 39°56′–40°17′N)

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Fig. 2 Changes of gross yields of provisions in Jinta Oasisfrom 1988 to 2003

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Fig. 3 Area of crop planting and amount of fertilizerapplication during 1988–2003 in Jinta Oasis

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located. It could serve as an example for exploringoasis land-use change patterns, their driving forces,and their impacts on the stability of oases and theecological safety of the national defence constructionof China.

The objective of this study is to detect changes inland-use and to assess its impacts on the environmentin Jinta Oasis. It attempts to document land coverchanges since 1986 using two sets of multispectralTM (thematic mapper) images (1988 and 2003) todetect trends in land-use in the late 1980s and early2000s. This study is specifically concerned with theanalysis on the assessment of related environmentalimpacts and socioeconomic consequences withinoasis ecosystem.

Materials and methods

Study area

Jinta Oasis, between 98°39′–99°08′E and 39°56′–40°17′N, is located in the lower reaches of HeiheRiver Basin of arid China, with total area of 1,652.2 km2

(Fig. 1). The total annual average precipitation isabout 59.5 mm and annual potential evapotranspira-

tion is about 2,567 mm. Most region of Jinta Oasis isflat, and its soil potential for agriculture is very goodmainly including mud soil, tide soil (meadow soil),wind sand soil, and typical gray brown soil whichdistributed around the edge of Jinta Oasis. BecauseJinta Oasis was once thought to have relativelyabundant water resources (Chen 2002), it had beenused as an important commodity grain productionbase in the northwestern China and experienced rapidsocioeconomic development, fast population growth,and agricultural production increasing (Figs. 2 and 3).

Data and methods

The primary data source of this study is the LandsatTM images taken in 1988 and 2003. The data frombands 4, 3, and 2, obtaining the Landsat™ data fromthe Institute of Remote Sensing Application (IRSA),Chinese Academy of Sciences, were used (Deng et al.2003, 2004; Liu 2002). The maximal spatial resolu-tion of the data used is 30 m. By modifying the USGeological Survey Land-use/Land Cover Classifica-tion System (Chen 2002) applicable to the studyarea, land use was classified into six types, namely:cropland, forestland, grassland, urban/built-up land,water, and barren land (Table 1). The area measure-

Table 2 Transition matrix of land use types from 1988 to 2003 (unit: km2)

2003

1988 Cropland Forestland Grassland Urban/built-up land Water Barren land Increase Net change

Cropland – 12.98 35.59 1.62 0.00 55.96 106.15 +30.03Forestland 13.64 – 10.30 0.29 0.03 3.78 28.04 −1.76Grassland 43.12 8.05 – 0.17 0.03 28.41 79.78 −58.06Urban/built-up land 5.94 0.14 1.67 – 0.03 8.05 15.84 +13.35Water 0.00 0.58 0.14 0.00 – 0.35 1.07 +0.92Barren land 13.41 8.05 90.14 0.40 0.06 – 112.06 +15.52Decrease 76.12 29.80 137.85 7.27 0.14 96.54 342.93 –

Land use/cover types Type features

Cropland All agricultural land, including arid lands and irrigated landsForestland Arbor, shrubbery, sparse woods and tree nurseryGrassland Grassland which coverage is more than 5%Urban/built-up land Including city, industry, traffic land and mine, and rural settlementWater Including lakes, ponds, reservoirs etc.Barren land Including desert, Gobi, exposed soil and rock, and gravel land

Table 1 Land use/covertypes in Jinta Oasis

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ments of land-use types were made using thestatistics function of GIS according to the details ofthe satellite image processing methodology andprocedures (Li et al. 2004; Liu et al. 2005). Todefine the transition of land-use types in the studyarea, the ArcView software and its spatial analysismodule were used to calculate the transition matrixes(Table 2).

On the other hand, to identify and assess environ-mental impacts caused by land-use change, fieldinvestigation was carried out in the whole oasis andthe following data during 1988–2003 were collected:(1) the records from meteorological station distributedin the study area; and (2) the statistical data of thenational economy and social development of JintaCounty.

Results and discussion

Overall land-use changes in Jinta Oasis

Change in different cover types is one of the majorindicators to show general changes of the landscape.The areas of cropland, urban/built-up land, water, andbarren land increased, and forestland and grasslanddecrease from 1988 to 2003, respectively (Fig. 4,Table 3). The relative increase of urban/built-up landwas the greatest (up from 7.67 to 21.03 km2).However, the relative decrease of grassland was thegreatest (down from 206.61 to 148.55 km2) (Table 3).Cropland (324.90 km2 in 1988 and 354.93 km2 in2003), grassland (206.61 km2 in 1988 and148.55 km2 in 2003), and barren land (1,576.47 km2

in 1988 and 1,591.99 km2 in 2003) were the mainland use/cover types in Jinta Oasis, which accountedfor more than 15, 7, and 73%, respectively.

Results from the transition matrix reflected the areaincrease or decline of each land use type (Table 2).Between 1988 and 2003, cropland and barren landexperienced the largest gains from other uses, by106.15 and 112.06 km2, respectively (Fig. 4), although76.12 km2 of cropland and 96.54 km2 of barren landwere lost to other uses, respectively. Of this increasedcropland and barren land, the areas mainly convertedby both grassland (35.59 km2) and barren land(55.96 km2), and by grassland (90.14 km2), respec-tively. The other significant growth of area was inurban/built-up land, mainly derived from cropland(5.94 km2) and from barren land (8.05 km2). How-ever, grassland experienced the highest net decreaseof 58.06 km2 (Table 2). In gross terms, 90.14 and35.59 km2 were converted into barren land and crop-land respectively. The other significant loss to grass-land occurred in the form of conversion to forestlandat 10.30 km2.

Fig. 4 Land use/cover maps of 1988 and 2003 in Jinta Oasis

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These changes in cropland, urban/built-up land,and grassland have the following reasons. Bothnatural conditions and human activities are responsi-ble for the land use/cover changes in Jinta Oasis. Thedirect driving force for increases of cropland andurban/built-up land mainly was population growth inthe oasis. With the population growth (Fig. 2), foodand buildings obviously became the important prob-lem for survival in the oasis, thus gaining the area netincreases of cropland (30.03 km2) and urban/built-upland (13.35 km2), respectively. Also, the increase ofurban/built-up land area was related to populationgrowth and improved quality of life since the open-upto outside world and reform policy adopted in China.Local residents were poor before early 1980s underthe socialism planned economy and their economicsituation had been improved dramatically since mid-1980s. The increase of urban/built-up land reflects thechanges of the economic condition.

With the population and the irrigated area increas-ing (Fig. 2) as well as the increasing of crop plantingarea (Fig. 3), the amount of consumed water hasincreased by 2.2×108 m3 in the recent 10 years (Liand Zhao 2003). Additionally, the grassland haddecreased in the study period because of the unrea-sonable utilizations of water resources in Jinta Oasis.Owing to the over-exploitation and utilization ofsurface water and groundwater in the middle andupper reaches of Heihe River Basin (Qi and Luo2005), vegetation had been seriously degraded ordestroyed. There are many dry riverbeds with degrad-ed vegetation, and the hydrophytes and swampvegetation that once grew in large areas have declinedor dried out. For example, according to the recentdata, the degraded area of grassland has accounted for52.0% of the area of available grasslands in JintaCounty (Li and Zhao 2003). Besides, the pollutedwater quality due to the fertilizer application (Fig. 3)

(e.g. the biological oxygen demand (BOD) content inthe Beidahe River in Jiuquan Region was higher thanthe National Water Quality Standards of China(GB3838-88) by 140%; and the area with salt contentof 3.0–5.0 g l−1 in groundwater in the Jinta district ofBeidahe River Basin has been extending upstream-ward at a rate of 2.0–6.0 km2 per year (Qi and Luo2005), is also one of the important reasons for thedecay and decease of forest and pasture, thus resultingin the degradation of grassland in Jinta Oasis.

On the other hand, the precipitation change is alsoa direct driving force for the decreases of grassland inthe study area (Fig. 5). In arid northwestern China,precipitation is a most critical climatic variable thatcontrols the distribution of grass and vegetation.Owing to the decrease of precipitation in the oasis,the grass and vegetation faded and perish. Moreover,irrational use of natural resources (e.g. overgrazing)(Table 4), led to heavy damage of grassland andresulted in the decrease of grassland area (Li andZhao 2003). To confine the cropland area and to limitthe water use volume for agricultural irrigation and

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Fig. 5 Precipitation and number of water supplying wells inJinta Oasis from 1988 to 2003

Land use/cover 1988 2003

Area (km2) Proportion (%) Area (km2) Proportion (%)

Cropland 324.90 15.1 354.93 16.5Forestland 34.84 1.7 33.08 1.5Grassland 206.61 9.6 148.55 6.9Urban/built-up land 7.67 0.4 21.03 0.9Water 0.23 – 1.15 –Barren land 1,576.47 73.2 1,591.99 74.2

Table 3 Areas and propor-tions of different land use/cover types in 1988 and2003

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provide more portions for grasslands and forestlandscould avoid the decreases of them.

Impacts on the oasis environment

Oasis ecosystem in arid and semiarid regions isdisproportionately prone to ecological damage frominappropriate forms of land uses. The problem of landdegradation with the oases is due to a combination offour factors: (1) over-using inland river water and/orover-drawing groundwater leading to the shrinkage ofoases, including the decline and death of naturalvegetation, the decline of groundwater, drainage oflakes, etc.; (2) poor irrigation management leading tosalinization; (3) over-reclamation, over-cutting forfirewood, and over-grazing which leads to grasslanddegradation; and (4) failure to maintain shelterbelts inand around the oasis areas, which leads to the invasionof wind-blown sand (Wu and Ci 2002). According tothe field investigations and data analysis, differenttypes of land-use change, from better ecologicalconditions to worse ones, corresponded to degreesof environmental degradation severity in Jinta Oasis.

With the continuous increase in population andlivestock (Table 4), the area of cropland and built-upland has risen but the grassland area has decreasedsignificantly during the study period. These changeshave caused land desertification development exhibit-ing spatial and temporal differentiation and the

changes of regional groundwater resources in thestudy area (Li and Zhao 2003; Lu et al. 2002). Owingto the increase of cropland in Jinta Oasis and overusesof surface water resources in the upper and middlereaches of Heihe River Basin (Luo et al. 2005; Qi andLuo 2005), widespread extraction of groundwaterresources is inevitable. For example, the area ofcropland increased from 324.90 km2 (1988) to354.93 km2 (2003) (Table 3), and the number ofwater-supplying wells in Jinta Oasis increased from1,053 (1988) to 1,570 (2003) (Fig. 5). The irrigatedareas of agriculture and forestry increased from173.3 km2 in the early 1980s to 242.4 km2 in 1995,a net increase of 40% (Yu 2005). These resulted in thedecline of groundwater resources, at a rate of 0.30–1.70 m yr−1 (Wang and Cheng 1999).

Water being a limiting factor in plant growth,decreases in the water resources and decreasing ofgrassland in the oasis have resulted in concomitantdecreases in the number of plant species, along withtheir density, coverage and yield or biomass (Qi andLuo 2006), thus inducing the degradation of naturalvegetation and oasis desertification in the study area.Because vegetation has been seriously degraded ordestroyed, along with the decrease of precipitation inthe oasis (Fig. 5), 90.16 km2 of grassland wasconverted into the barren land in the study period.There are many dry riverbeds with degraded vegeta-tion, and the hydrophytes and swamp vegetation thatonce grew in large area have declined or dried out.Based on the collected data, the area of degradedgrassland, sandy grassland, and grassland sufferingfrom sand blown by wind, accounted for 52.0, 28.0,and 29.0% of the area of available grassland in JintaOasis, respectively (Editorial Committee of JiuquanYearbook 2000).

Conclusions

During the period from 1988 to 2003, widespreadchanges in land use/cover took place in Jinta Oasis.Grassland and forestland decreased by 58.06 and1.76 km2, respectively. By comparison, cropland,urban/built-up land, and barren land expanded by30.03, 13.35, and 15.52 km2, respectively. Changes tograssland occurred in the form of conversion tocropland, barren land, and forestland. As a result ofland use changes and human activities, especially the

Table 4 Tendencies of population and livestock in Jinta Oasisduring the period from 1988 to 2003

Year Population (×104) Livestock (×104)

1988 11.85 2.6021989 11.98 2.6361990 12.53 2.6461991 12.83 2.6811992 13.04 2.7461993 13.01 2.7771994 13.13 2.8691995 13.20 2.8881996 13.39 3.0361997 13.50 3.0511998 13.62 3.3321999 13.78 3.4472000 13.76 3.6452001 13.94 3.6912002 14.00 3.8522003 14.17 3.864

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latter, severe environmental degradation (i.e. landdesertification, decline of groundwater, and vegeta-tion degeneracy) occurred in the whole oasis from1988 to 2003. These changes had, in turn, impactedon the regional sustainable development of JintaOasis. Therefore, more attention had to be paid tothe effect of land development on ecological environ-ment in land use planning and management of oasisecosystem in future.

From these results obtained in this study, eco-environmental managers in local government must beaware that human activities bear an interactiverelationship with environment. It is insufficient topay attention to the impact of human activities onenvironment. We must direct our attention to theoverall environment under which certain humanactivities can take place. Besides, environmentalconsequences of human activities could occur at ornear the site of action, but could be felt thousands ofkilometers away. When examining the potentialimpact of human activities, these off-site effects mustbe taken into consideration as well. In order to keepthe environmental health and sustainable developmentof oases in arid regions, a spatially holistic approachto the environmental or resource allocation problemshould be adopted and a holistic overview of theeconomy, ecology and society in these regions shouldbe developed to encourage ultimate efficiency.

Acknowledgements The study was sponsored by the Na-tional Natural Science Foundation of China (Grant No.40501068) and the Doctoral Foundation of Shandong NormalUniversity, Shandong Province (Grant No. 304010). Weespecially thank the anonymous reviewers who read a firstdraft of this paper for their constructive comments to furtherimprove the manuscript.

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