Driving Forces for the Marsh Wetland Degradationin the Honghe National Nature Reserve in SanjiangPlain, Northeast China

Demin Zhou & Huili Gong & Yiyong Wang &

Shahbaz Khan & Kuiyi Zhao

Received: 5 November 2006 /Accepted: 14 December 2007 / Published online: 19 January 2008# Springer Science + Business Media B.V. 2007

Abstract In the study, we analyze and assess quantitativelythe spatial pattern of vegetation and its ecological degrada-tion information in the Honghe National Nature Reserve(HNNR), a Ramsar-designated site in Northeast China.Statistics from historical survey data are used to measurethe degradation of marshes over time and changes in thehydrological regime. Long-term statistical data are alsoemployed to analyze both natural and human impacts onthese changes. Both the wetland degradation model and itsmechanisms are discussed in this paper. The research findsthat the loss of water and other types of degradation in thevegetation habitat caused by the rapid deterioration of thehydrological regime has threatened the status of HNNR as a“storage area of natural genes.” Scientifically constructedstrategies are urgently required to ensure sustainableeconomic benefits that do not adversely affect this naturereserve.

Keywords Marsh wetland . Degradation . Driving force .

Flood plain

1 Introduction

“Wetlands are areas of marsh, fen, peatland or water,whether natural or artificial, permanent or temporary, withwater that is static or flowing, fresh, brackish or salt,including areas of marine water the depth of which at lowtide does not exceed six metres” [19]. The global wetlandarea is estimated to be 8.6×106 km2, constituting 6.4% ofthe land surface of the Earth [16]. Wetlands in China cover6.594×105 km2. This is a total of 6.5% of its land mass, thefourth largest area of wetland of any country. The existenceand functioning of wetlands is crucial for adjacentterrestrial and aquatic ecosystems. Wetlands are character-ized as rich biological resources and as areas that arecapable of high food production. Not only do wetlandsprovide a service as a habitat for highly endangered wildlife, but they also provide important functions such asnutrient cycling and climate change mitigation. For thesereasons, wetlands are described as a “storage area of naturalgenes” and the “kidney of nature” [4, 16].

The degradation of wetlands and the loss of wetlandbiodiversity have received much attention from scientists[16]. Less stability in natural land ecosystems due towetland degradation will inescapably threaten the sustain-able development of human beings. In Sanjiang Plain, a keyreason for wetland degradation is the lack of water in thewetland, which is imposed by extensive human activities, alocally warming climate, and decreasing precipitation. Thelack of adequate moisture means that, ultimately, marsheswill contain a lower level of vegetation species richness; inthis way, becoming just a wet meadow. Most marsh plants

Environ Model Assess (2009) 14:101–111DOI 10.1007/s10666-007-9135-1

DO09135; No of Pages

D. Zhou :H. Gong :Y. Wang :K. ZhaoKey Laboratory of Wetland Ecology and Environment,Northeast Institute of Geography and Agricultural Ecology,Chinese Academy of Sciences,Changchun 130012, People’s Republic of China

D. Zhou :H. Gong (*)Key Laboratory of Resource, Environment and GIS in Beijing,Capital Normal University,Beijing 100037, People’s Republic of Chinae-mail: gonghl@263.net

D. ZhouGraduate University of Chinese Academy of Sciences,Beijing 100039, People’s Republic of China

S. KhanCSIRO Land and Water,Griffith, NSW 2680, Australia

will suffer poor physiological health, and some of them willbe in danger of extinction. Animal habitats in the wetlandswill be under severe threat due to the damage of thewetland plants, which will bring about a loss of biodiversityand the degradation of the natural wetland function.

The “wetness” is the fundamental characteristics of awetland. Yearly or seasonally abundant water is an essentialelement, which controls the ecological characteristics of thewetland and its process of succession. Ecohydrologists wishto understand and analyze the correlation between ecologyand hydrology in the riparian areas and fresh water plainsand hope to establish quantitative modeling of the inter-actions of the processes [1, 20]. Their attempts includeseeking a hydrological mechanism for specific ecologicalspatial patterns and succession processes, and analyzingplant structures, spatial patterns, and succession processesthat are largely controlled by variations in topographicfluvial processes in the wetlands [23, 25]. One keyobjective of hydroecological research is to further under-stand the moisture characteristics of the wetland planthabitats, the relationship between the ecological pattern andits hydrological mechanism, from which we can predict theecological consequence caused by a hydrological alteration.By doing such research, a better assessment of wetlandsand their wiser use can be approached. Ultimately, this willlead to the maintenance, health, and repair of damagedecosystems [21]. The technical development of remotesensing (RS) and geographical information system (GIS)promotes a convergence between the contributing areaconcept developed by hydrologists and the wetlandlandscape structure approach used by landscape ecologists[2, 7, 15].

Research into wetland degradation in China presentlyfocuses on the dynamic change of the landscape patterncharacterized by widespread wetland fragmentation causedby human beings [12]. The prevalent method is to obtain

information on the dynamic change on specific wetlands bythe interpretation of multitemporal RS images or comparablehistorical survey data, from which investigators analyze thecharacteristics of the wetland fragments and its processesbased on landscape theories supported by GIS. In general,most investigators emphasize quantitative analysis of thefragmented wetland spatial pattern on the scale of valley, orabove [8, 11–13]. These research results clearly describe thefragmentation process of wetlands on a large scale. However,not only in China but worldwide, few research programshave been designed to discover the mechanism or drivingforces that degrade wetlands, or explore quantitatively thehydrological mechanisms that control the ecological struc-ture and spatial patterns of wetlands [17, 25]. Consequently,the characteristics of the degraded plant community that arelinked with the altered hydrological system are poorlyunderstood [8].

2 Materials and Methods

2.1 Study Area

Honghe National Nature Reserve (HNNR; 133°34′38″–133°46′29″E and 47°42′18″–47°52′N) is located in theNortheast portion of the Sanjiang Plain, an extensive plainbetween three big rivers: the Heilong River, the SonghuaRiver, and the Wusuli River (Fig. 1). HNNR covers251 km2. Two rivers enter the reserve, the Nongjiang Riverat its north boundary and the Woyalan River through thecentral, core zone. Widespread inundation by floods isfacilitated by a network of cross channels on the lowtopographic gradient of the area (average slope grade ofless than 1:10,000). Low gradient areas are favorable forwetlands. HNNR is on the International Important Wetlandlist for being a typical inland wetland and fresh water

Fig. 1 Location of the HNNR

102 D. Zhou, et al.

ecosystem in the North Temperate Zone. It has also beenRamsar-declared wetland since 2001. Presently, HNNR has16 orders, 43 families, and 174 species of waterfowl,including 10 species of nationally rare and endangeredwaterfowl, and 1,012 species of plants, which include 6species of nationally endangered plants [14].

2.2 Materials

Data used in this research are as follows: three 1/4 cloud-free scenes Landsat TM 7 images of the study area acquiredduring the growing season on September 12, 2001, June 5,2004, and August 1, 2004. An original contour map waspublished in 1994 by the Land Survey of HelongjiangProvince at scale of 1:10,000 with 1 m elevation intervals.A reference map of land use type and a map of wetlandtype were produced by the Institute of Natural Resources ofHeilongjiang Province in 1987 by survey. Data forgroundwater level were produced by using an observationwell in the buffer area of HNNR from1997 to 2002. Datafor the surface water table were generated by usingOdyssey 2.0 at the site of the Woyalan River in the corearea of HNNR in 1993, 2002, and 2005. Climate data from1982 to 2002 at Honghe came from the climate stationsupported by the Field Station of Wetland Ecology of theChinese Academy of Sciences and Honghe Farm 17 kmsouthwest from our study site. Climate data from 1957 to2002 in the Jiansanjiang area came from the climate stationsupported by the Jiangsanjiang Farm 90 km southwest fromour study site. The former is a climate station using theGeneral National Standard of the Chinese Weather Bureau,while the later is a regional central climate station using theBasic National Standard. In the climate stations, the WQG-11 dry–wet bulb thermometer in a thermometer screen wasused to measure the air temperature, and the SKM-6 raingauge was used to measure precipitation. Statistical data forthe crop land area and rice land area from 1966 to 2002came from the statistical yearbooks of local farms. Maps oflocal canal networks surrounding HNNR in the two specificyears (1982 and 2002) were provided by the local farmadministration.

2.3 Methods

In the study, multitemporal remotely sensed images wereemployed to generate digital vegetation information at theplant community scale. We then coupled vegetationinformation with hydrological zonation produced from adigital elevation model (DEM) of the study area by a GIShydrological analysis method. We used vegetation surveydata to calibrate the digital vegetation information generat-ed by the RS method and observed hydrological data forthe digital hydrological zonation data generated by the GIS

method. We then quantitatively analyzed present vegetationcharacteristics and their close relationship with the hydro-logical regime in wetlands. Statistics from historical surveydata were also used to measure the degradation of marshesand the historical change of the hydrological regime. Bothnatural and human factors were discussed in this paper forseeking driving forces that degrade marsh wetland inHNNR (Fig. 2).

2.3.1 Wetland Vegetation Mapping

Remotely sensed data have been widely used in past studiesand have been proven an effective tool in vegetationmapping [7]. In this research, the natural vegetation in thestudy area was classified into five ecosystem types. Theclassification encompassed 11 community level categoriesand an open water category (Table 1) with a focus ontypical marshes. Agroecosystems were considered in thespecial category of artificial ecosystems. Landsat TM 7images were used for mapping wetland vegetation at thecommunity level according to the classification scheme.Supervised classification using the maximum likelihoodalgorithm was carried out using the Erdas 8.6 platform tointerpret the enhanced preprocessed image (from June 5,2004) with color composite (bands 5, 4, and 3 allocated tored, green, and blue, respectively). To carry out thesupervised classification, intensive ground truthing wasconducted in the region to provide an accurate trainingsample. Multitemporal image referencing and GIS wereused to improve the precision of the interpretation. Theclassification map of 13 wetland communities was calibrat-ed from both a land use map and a vegetation classificationmap that had already been generated from previoussurveys. The final classification map (Fig. 3) was validatedusing an error matrix, and a 85.87% classification accuracywas achieved. Using ArcGIS 8.3, a classification mapdisplaying six ecosystem types was also produced in whichthe five marsh community categories were merged into oneecosystem type.

2.3.2 Hydrological Zonation

Hydrogeomorphological zonations were generated by adigital analysis method according to accepted wetlandecological principles. They indicated that marshes aremostly connected to saturated areas of the river networkor other depressions and areas of low elevation [3]. Despitethe lack of a field map to delineate potentially saturatedareas, the development of computer terrain analysis toolsand the increasing availability of digital terrain models(DTM) have provided us the ability to derive the extent ofthese saturated areas. Using the gridded DEM, bothdepressions and river networks were then generated by

Driving forces for the marsh wetland degradation 103

the hydrological analysis module within ArcGIS8.3. Rivernetworks that were produced by the analysis were thenvalidated with both GPS waypoints and the relief map. Thevectorized DEM data from the original contour map werethen used to delineate the yearly saturated zone – where thewater table reaches an average depth deduced from recordsof gauge readings – and the connected area above anaverage height was defined as the yearly unsaturated zone.The area between yearly saturated and yearly unsaturatedwas then assigned to the seasonal saturated zone. The studyarea is thus divided into three hydrogeomorphologicalzones. The low elevation zone is equivalent to the yearlysaturated zone located in the low elevation area, the yearlyunsaturated zone is located in the high elevation area, andthe seasonal saturated zone is located in the cross areamedium elevation area (Fig. 4).

3 Results and Analysis

3.1 Analyses on the Degradation Characteristicsof Wetlands

Our research results showed that, by percentage, Calama-grostis angustifolia–Carex spp. is the most dominant of all

the individual communities in Table 1 and constitutes inexcess of one third of the study site. As for ecosystemtypes, wet meadow constitutes 39% of the area; therefore,the wet meadow area is now bigger than the marshland by a0.5 area ratio, making it the dominant ecosystem type in the

Table 1 Scheme for wetland classification in HNNR

Ecosystemtype

Community type Code

Forestswamp

Quercus mongolica–Populus davidiana–Betula platyphylla

10

Marsh Carex pseudocuraica–Carex lasiocarpa 12Carex lasiocarpa 6Glyceria spiculosa 5Carex schmidtii–Carex meyeriana 4Phragmites australis 9

Shallowwater

Pond 7

Wetmeadow

Calamagrostis angustifolia 3Calamagrostis angustifolia–Carex spp. 1

Shrubwetland

Betula fruticasa 2Salix brachypoda 11Alnus sibirica 13

Cultivatedland

Crop 8

Plant Ecological Survey

Sample survey

VegetationClassification

Characteristics of Ecological Degradation in HNNR

RS Interpretation

HNNR Boundary

Vectorization

Comparable Historical Data

Multi-temporal

RS Images

Hydrological Observation

Surface water

Ground water

Coupling Hydro-ecologicalAnalysis

Analyse onDriving forces

Hydrological Zonation

Vegetation Mapping

Rice Plantation Irrigation Establishment Decreasing Precipitation Warming Climate

Hydrological Pattern GIS

Hydro-analysis

DEM Generation

Local Relief MapFig. 2 Overview of the projectof analyzing driving forces forwetland degradation

104 D. Zhou, et al.

area. Within the present six wetland ecosystem types,typical marsh constitutes only 38% of the area. Accordingto the data from HNNR in 1998, Ni and Li [18] suggest thatthe typical marsh was the dominant ecosystem typecovering 48% of the area. Consequently, this means thatthere has been a 10% reduction in the typical marsh areaover the past 7 years. With this present degradation rate, themarsh landscape in HNNR will disappear entirely withinthe next 30 years. By coupling landscape patterns withhydrogeomorphology for analysis, this study also suggests

that the present marsh areas have shrunk into the narrowriverways that are situated in the central core area aroundthe Woyalan River and the edge of the Nongjiang River inthe north of HNNR.

Besides ecological degradation, some marsh plants havealso been degraded physiologically. With an average heightof 74 cm in the past, Carex lasiocarpa was tall and strongas a local dominant plant, and it lived with a strong rootfloor under the deep water. Presently, C. lasiocarpa hasbecome small and thin due to the loss of a suitable habitat.The field survey data from 2003 to 2004 in HNNR indicatesthat C. lasiocarpa is now 40 cm high on average – areduction of almost 50% within the past 50 years – and itspresent average biomass is now only 403 g/m2 – a 30% losscompared to 653 g/m2 50 years ago. The plant speciesrichness has also decreased rapidly with only 6.7 species persquare meter on current average. This is a reduction ofaround one species per square meter over the past 50 years.

3.2 Analyses on Driving Forces to Degrade MarshWetlands

In the Sanjiang Plain, the degradation of the “suitablemoisture of wetland habitats” plays a key role in thedegradation of marsh wetlands. The ‘T’-shaped backwaterFig. 4 3-D map of surface water system in HNNR

Fig. 3 Category map of plantcommunities in HNNR

Driving forces for the marsh wetland degradation 105

between the Woyalan River and a branch of the NongjiangRiver causes annual flooding from the Nongjiang River tothe Woyalan River that maintains the wetlands. However,the extensive irrigation establishment presently makesflooding less frequent. Therefore, considerations have tobe made for the hydrological impacts issuing from the localirrigation systems that are becoming increasingly commonin the surrounding area. Although no long-term hydrolog-ical data are available, some limited observational dataindicate that there have been significant changes in shallowgroundwater in the past few years in HNNR. Water tabledepths of the Woyalan River have decreased from 1.2 m in1993 to 0.6 m in 2002, and 0.48 m in 2005 with an annualmean reduction of 6 cm. Similarly, the shallow groundwaterdepth in the buffer zone of the site has decreased to almost4 m between 1997 and 2002, an annual mean reduction of80 cm over the 5-year period [14].

Figure 5 shows the historic change of waterscapes at thesame Woyalan Riverway site, which indicates the obviousloss of wetland habitat in the core area caused by the loss ofsurface water in HNNR. In contrast to the wide riverway 2or 3 years ago, the present riverway has been disconnected,and its surface water has become overgrown by plants dueto the rapidly falling water level. This confirms our

observation data that indicates the rapid decline of bothgroundwater and surface water levels in HNNR.

Some investigations [3, 22] have demonstrated that thedistribution of ecosystem type follows a specific patternalong a hydrogeomorphic gradient. In HNNR, over 70% ofthe typical marsh plants are distributed in the yearlysaturated zone, about 25% in the seasonal saturated zone,and only about 5% in the yearly unsaturated zone. Thisindicates that the distribution of marshes is distinctly underthe control of the wetness gradient. The alteration of thewetness gradient definitely brings about a change of bothecological pattern and structure of wetlands, and thedecreased area of marsh wetlands is a response tothe change of the wetness gradient. Figure 6 illustrates theecological degradation model of wetlands caused by lesswetness in freshwater wetlands within HNNR. The modelis described as follows: the decrease of both floodingfrequency and its extent makes the wetness gradient fallback along the geomorphological gradient, which holdsdown the area of marsh habitats with suitable moisture.Consequently, nonmarsh plants expand along the geomor-phological gradient by replacing typical marsh plants. Thedistribution of typical marsh is accordingly shrunk into thelimited shallow riverway or low-lying land.

Fig. 5 Change of waterscape ofthe Woyalan Riverway in thecore area of HNNR

Fig. 6 Degradation model of wetlands along the geomorphologicalgradient in HNNR

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Fig. 7 Temperature change in the Jiansanjiang Area from 1957 to2002

106 D. Zhou, et al.

In general, the degradation of marsh wetlands in HNNRis mainly caused by the alteration of the hydrologicalregime, which is attributed to the four principle drivingforces as follows:

3.2.1 Change of Local Temperature

Some researches [5] have reported that Northeast China hasbeen a warming area since the 1970s. Yan et al. [24]pointed out that the average temperature in Sanjiang Plainhas risen for the past half century. The warming centers arelocated in the plain areas where the average temperature isup from 1.2°C to 2.3°C for the 45 years between 1955 and1999. The observation data from the Jiansanjiang ClimateStation confirms that local temperatures have risen from1957 to 2002. A linear regression on yearly averagetemperature data indicates that it warms up at a rate of0.342°C per 10 years for the past 45 years (Fig. 7); thetrend of temperature change in Honghe is almost similarwith that of Jiangsanjiang from 1982 to 2002 with a linearregression on yearly average temperature data showing thatit warms up at a rate of 0.374°C per 10 years since 1982

(Fig. 8). Variations in temperature affect evaporation. Thecontinuous rise in temperature contributes to a biggersaturation vapor pressure on the water surface, whichgenerates a greater evaporation due to the bigger saturationdeficiency; therefore, a local warming temperature speedsup the evaporation process, which shrinks wetland areas byreducing its water capacity [9].

3.2.2 Change of Local Precipitation

Research results from Yan et al. [24] also indicate that theyearly precipitation has generally decreased in the SanjiangPlain for the 45 years from 1955 to 1999. A linearregression on yearly precipitation data indicates a slowdrying from 1955. Yearly precipitation data from theJiansanjiang Central Climate Station confirms the decreas-ing trend from 1957 to 2002. A linear regression analysison that data indicates that local yearly precipitation hasdecreased at a rate of 1.586 mm per year for the past45 years (Fig. 9). A similar trend appears in Honghe for thepast 20 years during which the yearly precipitation hasdecreased within a limited range. A linear regressionanalysis on that data indicates that local yearly precipitationhas decreased at a rate of 2.039 mm per year since 1982(Fig. 10). Although there has been only a limited decreasein precipitation, the negative impact is likely to be long-term. Wetland habitats are degraded due to less precipita-tion and, hence, less water supply. Utilization of naturalprecipitation for crops will be less efficient due to lessaverage precipitation, coupled with a greater yearly varia-tion, which makes local agriculture turn to groundwater forirrigation.

3.2.3 Change of Local Crop Structure

Grain production is always a key issue in China because itis a developing country with the largest population of any

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1982 1986 1990 1994 1998 2002Date /Year

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rage

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The measured value The value of 5 year running mean The rectilinear trend

Fig. 8 Temperature change in HNNR from 1982 to 2002

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Fig. 9 Precipitation change in the Jiansanjiang Area from 1957 to2002

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Fig. 10 Precipitation change in HNNR from 1982 to 2002

Driving forces for the marsh wetland degradation 107

in the world and very limited cultivated land. The SanjiangPlain is the country’s largest area of cultivated land, whichmakes it the top base for producing merchandise crops inChina [8]. In the past decades, local rice fields haveexpanded rapidly while vegetable crops have declined dueto higher crop yields from rice bringing significanteconomic benefits. The lower cost and better performanceof the modern pump make it easy to realize such change ofcrop structure. Statistical data from local farms show thatthere were 3,781 km2 of crop field including 2,024 km2 ofrice field in the 15 farms surrounding HNNR in 2002. Thisis an increase of 10 times the crop area of and nearly40,000 times the rice area of that in 1996. Based on thealmost 40 years data in Fig. 11, two conclusions can bedrawn. Firstly, the area of crop fields continuouslyincreased until the 1980s, and since then, the rate ofincrease has slowed and then ceased in 1997. Secondly, thearea of rice fields increased rapidly from 1993 to 1998 andhas moved up and down since then. The local groundwater

level has declined rapidly due to a greater volume ofgroundwater being pumped for the irrigation of riceplantations and, hence, there are decreased moisture levelsin marsh wetlands. HNNR cannot withstand such anegative impact.

3.2.4 Change of Local Irrigation System

In the Sanjiang Plain, every local farm has established asystematic irrigation network, which greatly disturbs thelocal natural water system. Established reservoirs or dikeslimit water supplies from rivers to wetlands. Not only dothey cut off the hydraulic relationships between wetlandsand nearby rivers or lakes, water sources from the widecatchment to the wetland is also cut off by irrigation workssuch as dams, canals, and dikes used for flood control.Dams limit the dynamic hydrology within a river, reservoirsreduce the flooding frequency, and canalization of localrivers permanently prevents inundation of some plants [6].

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Fig. 11 Change of cultivatedareas in local farms surroundingHNNR

Fig. 12 Development of canalnetworks surrounding HNNR

108 D. Zhou, et al.

These human impacts mean that the wetland area in theSanjiang Plain has been significantly reduced.

The HNNR is surrounded by several large national farms(Fig. 1), which are supported by an extensive irrigationsystem. These irrigation networks have altered the hydro-logical conditions that are required for the maintenance ofmarsh wetlands in HNNR, such as for regular flooding tomaintain soil moisture and wetness [11]. Seven largedrainage channels and a dam have been constructed in theupstream areas of the Nongjiang River since 1988. From1996 to 2002, the density of the original canal work hasincreased substantially (Fig. 12) for the purpose ofimproving the local irrigation system. As a result of thesehuman modifications, the main source of water for HNNRhas now been cut off as the drainage channels bypass thesite and feed directly into the Heilongjiang River [14].

3.3 Degradation Mechanism of Marsh Wetlands on HHNRand Sanjiang Plain

Irrigation establishments are necessary facilities to supportthe local agriculture in Sanjiang Plain where waterloggingis natural due to the flat topography. However, the irrigationnetworks will redistribute local water resources. Localfarmers have changed radically from traditional crop fieldsto rice fields due to increasing demand for a higher yield[10]. Rice paddies demand extensive irrigation fromgroundwater sources during the growing season. As aresult, both surface water and groundwater have decreasedrapidly. This human interference is coupled with negativenatural impacts such as the local decreased temperature andwarming climate. The area of marsh habitats has conse-quently decreased and the wetland ecosystems have

gradually been succeeded by drier forms of ecosystem.The succession process has caused some endangered marshspecies to die out and has also degraded the marsh plantsystem ecologically. Some typical wetland animals will alsodisappear with the loss of their habitats (Fig. 13).

4 Discussions

4.1 Identification of Drive Forces for Wetland Degradation

Natural factors provide an inherent motivation for thedegradation of wetlands. Human factors, however, speed upthe degradation significantly. That is to say that wetlanddegradation is magnified by human factors being coupledwith natural factors. The natural driving forces such asdecreased precipitation or warming climate will degradewetlands slowly over a long-term rather than swiftly. Thedriving forces from human beings are more intensive thanthose from nature; furthermore, the role of natural factorscan be changed by human activity and some trends may bereversed. For example, the variation in yearly precipitationhas increased within the past 20 years (Fig. 9) and, hence,more efficient local irrigation facilities are required;however, the canalized river network reduces the watersupplies passing in and out of the wetlands. High runoff,generated by an extreme precipitation year, cannot becaptured in wetlands to carry out a regular floodingfunction. As a matter of fact, regular oscillation in theamount of precipitation is fundamental to form or maintainwetlands on the flood plain. The existence of drainagenetwork prevents flooding and degrades the wetland [3].

Human

Activities

Pumping Groundwater

Key

Reduction ofWater in Wetlands

Degradationof a Suitable Moisture Natural succession

to Wet less

Physiological and Ecological

Changes on the Plant in wetlands

Grow

ingSeason

Protection On Farmland

During

Flooding

DecreasedPrecipitation

WarmingClimate

Draining Flooding water

Rice Plant

Lose of Animal & Plant Habitats

in wetlands

Wetland Biodiversity

damaged

Fig. 13 Degradation mechanism of marsh wetlands caused by human beings in the Sanjiang Plain

Driving forces for the marsh wetland degradation 109

The photographs in Fig. 5 were made in the same monthof different years in which precipitation data show very littleyearly difference. The contrast of water landscape in thephotographs illustrates that a loss of surface water has oc-curred despite similar natural climate and hydrologicalconditions. It indicates that the main driving force to degradethe marsh wetland in HNNR comes from human beings.

4.2 Probes into the Invalidation of Protection on Wetlands

Although HNNR is under high protection, severe degrada-tion has occurred due to extensive human activities in thesurrounding area. Similar changes of both hydrologicalregime and flora with reduction of marsh plants were alsoreported by Liu et al. [11] in the Small Sanjiang Plainwhere most wetland nature reserves are in a similarsituation of rapid ecological degradation. This indicatesthat the traditional management of nature reserves is beingchallenged for its poor efficiency. It is obvious thatproblems exist in the presently running constitution forthe Chinese nature reserve. One of the fundamentalproblems is that nature reserves in China are not managedin ways that account for their surrounding geography. Small,isolated reserves are strongly affected by the surroundinghuman activity, and currently, this is beyond the manage-ment of reserve administrators. Therefore, it is suggestedthat the nature reserve management be redesigned forintegrated strategies that unify agricultural activities andwater conservancy. Scientifically constructed strategies arenow urgently required to ensure sustainable economicbenefits that do not adversely deteriorate this nature reserve.

5 Conclusions

1 The spatial pattern of wetlands is very natural due tolimited interference from human beings within theHNNR, but ecological degradation has occurred be-cause of extensive irrigation from people living in thesurrounding area. There has been a 10% reduction inmarsh area over the past 7 years since 1998. With thepresent degradation rate, the marsh wetland in HNNRwill have disappeared entirely within the next 30 years.

2 The water supply and the geomorphological gradient arethe dominant factors, which control both the ecologicalpattern and the structure of wetlands in the study area.Marsh areas are increasingly restricted to lower lyingland as the water level falls; consequently, nonmarshplants expand along the geomorphological gradient byreplacing the typical marsh plants.

3 Agricultural activities in the surrounding area havechanged the physical characteristics of the local watersystem. The redistribution of regional water resources

due to human activity has had a negative impact on themarsh habitat in HNNR. The results of this studysuggest that the continuous degradation of suitablemoisture plays a key role resulting in the ecologicaldegradation of marsh wetlands in HNNR.

4 The impact intensity of natural factors to degrade marshwetlands is far inferior to that of human factors.Furthermore, the role of natural factors can be changedby human activity, and some trends may be reversed.The loss of water and other types of degradation in thevegetation habitats caused by the rapid deterioration ofthe hydrological regime has threatened the status ofHNNR as a “storage area of natural genes;” hence,scientifically constructed strategies are now urgentlyrequired to ensure sustainable economic benefits that donot adversely affect this nature reserve.

Acknowledgements This study was funded by the Direction Projectof the Chinese Academy of Sciences (KZCX2-YW-425), the NationalNatural Science Foundation of China (NSFC 40301001), and the FieldStation Foundation of the Chinese Academy of Sciences. Many thanksto the two anonymous reviewers and Ph.D. student Nicholas Car fromMelbourne University for their valuable work on the paper’s languagerevisions. We would also like to thank Ph.D. candidate Yanjing Loufor her friendly help to make the scheme of wetland classification andgraduate student Fenglin Wu for his kind help with some figures in thepaper.

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