Int. J. Environ. Res., 4(2):361-372,Spring 2010ISSN: 1735-6865

Received 25 Jan. 2009; Revised 5 Dec. 2009; Accepted 15 Dec. 2009

*Corresponding author E-mail: bgohar@ut.ac.ir

Improving the Natural and Built Ecological Systems in an UrbanEnvironment

Aminzadeh, B.1* and Khansefid, M.2

1 Faculty of Urban Planning, College of Fine Arts, University of Tehran, Tehran, Iran2Department of Environmental Design, Graduate Faculty of Environment, University of

Tehran, Tehran, Iran

ABSTRACT: This study investigates the application of landscape ecology in planning and designof urban ecological systems. The ecological approach to landscape planning and the concepts ofdesigning and implementing ecological systems have gained increasing attention in the last twodecades. However, the ecological systems of urban environment need more research to considerbuilt and natural patches and corridors together and to provide proper and applicable strategies thatmeet all of the diverse aspects of planning and designing sustainable urban systems. This approachcould help in defining sustainable landscape development, aiming for a balance between bothphysical and natural systems in urban areas. This research is focused on Tehran’s metropolitan areaas a case study to provide a relationship between landscape ecology and urban planning anddesign to propose a model for analyzing and providing strategies and policies for conserving andresorting urban ecological systems. The spatial structure of green and natural areas are studied andcategorized based on the patch-corridor-matrix model. Overlaying the selected layers helped pro-vide strategies for conservation and reclamation, and policies to improve the structure and functionof urban landscapes. The strategies to restore the ecological structure and to develop its functionin Tehran metropolitan area are based on structural congruence, aggregate with outliers, local com-pensation and indispensable patterns.

Key words: Ecology, Landscape, Natural, Built, Systems, Tehran

INTRODUCTIONIn the recent years ample attention is paid to

the ecological system in urban areas (Aminzadeh& Ghorashi, 2007; Bahraini & Aminzadeh, 2007;Micarelli, et al., 2007; Vahadj et al., 2007; Yavari,et al., 2007; Micarelli & Pizzioli, 2008). Systemrefers to a regularly interacting or interdependentgroup of items forming a unified whole, a group ofinteracting bodies under the influence of relatedforces, an organized or established procedure andharmonious arrangement or pattern. These mean-ings provide a good basis to use the term systemfor a more holistic approach towards urban envi-ronment. The urban ecological systems can bridgethe conflict between reserve conservation, fixingnature in space and time and development. Theyhelp to focus on an effective spatial scale as well.

As the coherence of an ecological system is basedon ecological processes it may be single purposeor multipurpose (Jongman, 1995). The multi-ob-jective systems goes beyond ecological improve-ments of the city and habitat needs of wildlife, toaddress recreation and beautification, promotingurban flood damage reduction, enhancing waterquality and other urban infrastructure objectives.Extending the ecological system concept withmultifunctional indicators is a promising step to-wards sustainable city. Ecological systems, asnatural or built potentials, play a leading role inachieving sustainable urban environment. Byfocusing on structures, functions and transforma-tions of the environment, landscape ecologyapproach is an attempt to find patterns and inter-relations between landscape elements, built and

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natural patches, corridors and the matrix (Forman,1995; Ingegnoli, 2002). Ideas such as urban openspace network (Turner, 1995; Cranz & Boland,2004), park systems (Jongman & Pungetti, 2004;Maruani & Cohen, 2007) and greenway networks(McHarg, 1969; Ahern, 1995; Little, 1999; Fabos,2004; Turner, 2006) are developed as initiatives tointerweave the natural and built systems in eco-logical landscape design and planning (Makhzoumi& Pungetti, 1999). Urban environmental qualityand the landscape structure of Tehran metropoli-tan area and utilizing natural river valley corridorsfor ecological restoration of urban environment inlandscape scale and other ecological features werestudied to improve the ecological structure (Yavariet al., 2007) and consequently mitigating some ofthe environmental constraints the city encountersin an increasing rate. Based on the literaturereviewed , the main objectives of this study are 1)to apply landscape ecology approach as could beinterpreted in urban ecological planning, 2) to de-termine the current situation and analyze the natu-ral and built elements of the ecological systemsof Tehran which faces numerous environmentalproblems and pollutions due to its rapid growth, 3)to suggest strategies for structural and functionalimprovement of natural and built urban ecologicalsystems of the case under study, and 4) to pro-pose a model for the application of ecology inlandscape scale.

In addition to the theoretical bases based onlandscape ecology, the below experiences arehelpful to develop an ecological framework forimproving the ecological systems in Tehran met-ropolitan area (Table 1).

Adopting a new ecological view of the met-ropolitan landscape in designing New Yorkgreenspace system (Flores et al., 1998) suggestsa framework that emphasizes a dynamic view ofa biologically rich urban environment with a focuson interactions among multiple sites across tem-poral scales. This approach is defined by present-ing five key ecological principles as follows:

a) Content: a wide spectrum of ecosystemfunctions that are strongly linked to ecosystemstructure

b) Context: a combination of localities that resultsin considerable variability in the kind of ecologicalcontext specific to each site

c) Dynamics: suggests that with structuralchanges, ecosystem function also changes

d) Heterogeneity: means ecosystems need not bepristine, only flexible, connected, and diverse withcomplement of species to generate the genetic,biological, and biogeochemical capacity to adaptand respond to a changing environment

e) Hierarchy: help manage ecological complexityby organizing it into discrete functional compo-nents operating at different scales

The application of these principles resulted increating regional water reserves that provide theregion with fresh drinking water, protectingharbor (the area’s most significant ecosystem),and delimiting the outward expansion of the region’surbanized core. Establishing large regional reservesshould be of a sufficient size to withstand the im-pact of different disturbances without disruptingits main functions. A full-scale reinvestment inurban parks, public spaces and natural resourcesto improve the environmental quality of our cities,provide a fair share of park land to urbanresidents, and help cities attract businesses andresidents.

Comprehensive concept plan of urban green-ing based on ecological principles, a case study inBeijing, China (Li et al., 2005) attempts toanswer how to establish an urban greening planat the regional, city and neighborhood levels toachieve long-term sustainability. This three-levelsystem constitutes an integrated ecological net-work for urban sustainable development of Beijing.For future development of the city, urban parks,forestry, agriculture, water and infrastructureshould be planned and designed in an integratedway. It has the prospect of achieving the long-term goal of developing Beijing towards an Eco-City. Ecological principles and requirements forurban greening of Beijing define the temporal andspatial scale of greenspace planning. Three spa-tial scales have to be considered. At the regionalscale, the entire area of Beijing Province is con-sidered. Even the relationship to the neighbor-cityTianjin is included in the plan. At the city scale,the urban area of Beijing with its suburbs and thesurrounding peri-urban zone is taken into account,and at the neighborhood scale, some selected andtypical areas within the fourth ring road are

Aminzadeh, B. and Khansefid, M.

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Table1. The natural and built ecological systems in 3 metropolitan areas

Strategies Ecological Principles Region

creating regional reserves

invigorating green spaces in highly urbanized

environmentscreating a regional network of green spaces

content

context

dynamics

heterogeneity

hierarchy

New York

(Flores et a l. , 1998)

integrating isolated greenspace into a network clarity and

consistency of greenspace system enhance ecosystem

services

br idge separa ting elements

spatial scales

time-scales

Beijing

(Li et al., 2005)

creating networks of open space and ecological corridors

establish networks of ecological space, greenways and

parkways

connectivity

connectedness

London

(Turner, 1995)

considered.The plan distinguishes between threetime-scales for implementation. The ecologicalprinciples and requirements for the urban green-ing in Beijing are as follows:

a) Structure and function: changing the functionof fragmented and isolated greenspaceb) Clarity and consistency: an easily-communi-cable long-term vision and an integratedgreenspace

c) Functional and ecological diversity: combiningseveral ecological functions and are not mono-functional

d) Biodiversity and eco-services: enhancing eco-system services by high greenspace quality anddiversity and improve specific conditions for en-dangered species

e) Distribution of greenspace: creating publicparks close to high-density residential areas andno pollution in fresh air-generation zones and freshair corridors, establishing big forest areas and eco-logical buffer belts at the regional scale and verti-cal greening for high-density settlement

f) General acceptance and implementation of theplan: publicizing the concept through the media,involving decision makers and the public as astrong driving force to promote green space de-velopment.

Emphasis has been placed on planning veg-etated urban fields in London. Other types ofgreen space have been neglected (Turner, 1995).This attempt has distracted planners’ attentionfrom the vital task of creating networks of envi-ronmentally pleasant open spaces. The onlycontinuous ecological corridors in London are therivers, which constitute another layer to the GreenStrategy. As London is conceived to have websof public open space, it would have been possibleto plan for more diverse habitats and natural pro-cesses. The greenway theory and parkways areintroduced as parts of this ecological system andurban rivers are converted into blue-ways, byopening up access to the banks of rivers. Eco-ways are established networks of ecological spacein cities by using and merging urban water courses,public utility corridors, parklands and private gar-dens into a single integrated system of ecologi-cally important components.

Urban ecological systems can link terrestrialecological, physical, and socioeconomic compo-nents of metropolitan areas (Pickett et al., 2001)in an ecological approach to landscape planning(Sanderson & Harris, 2000; Steiner, 2000) in ur-ban environment. The experiences and theoriesdemonstrate that ecological patches and corridorsplay a crucial role in the sustainability of urban

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Table 2. Considerations for structural and functional improvement of patches, corridors and matrix in theurban landscape context

Improvement considerations for patches, corridors and matr ix in the urban landscape context

Large pa tches

P rotec ting large patches with high ecological value am id the urban built environment often

surrounded by other conflicting land uses

1

Small pa tches

Integrating the sma ll patches for be tter functioning of the ecologica l systems especially in densely

built-up and popula ted areas

2

M ore patches

M aking more patches for fa cilitate the penetr ation of the ecological flows into the urban fabric

3

Patches vicinity

Creating close patches for increasing the ir ecological functions, m ore convenient and less

obstructed flows be tween the pa tches

4

Patc

h

Corr idors Connectivity

Connectivity of the corridor s will bene fit the individual and overa ll ecological func tions of them

5

Corr idors branching patterns

The inte rwoven structura l pa ttern of both branching natural or circuit built corridors in their

hie rarchical order and the ir interac tions directly influence their e cological func tions

6

Cor

rido

r

P atches and corridors

Connecting patches through natural or m anmade corridors for higher ecological performance

7

Integrity

Interconnections betweens the ecological patches and corridors in the urban natural and built

ma tr ix to enhance and protec t integr ity of the c ity and ecologica l flows

8

Regional perspective

Consider ing the ecological systems beyond the city lim its where the ecological flows a re

continued or originated

9

Mat

rix

environments and their transformations directlyinfluence the ecological functions of the city. Somegeneral points for structural and functional im-provement of patches and corridors in the urbancontext are categorized in Table 2.

The application of landscape ecology inimproving urban ecological systems based onpatch-corridor-matrix model depends on the localand regional ecological conditions. The case ofTehran metropolitan area will help to recognizethe natural and built systems’ potentials and

restrictions and the ways by which the urban eco-logical structure and function could be improved.

MATERIALS & METHODSThe data required for the research has been

gathered from Tehran planning organizations andprior researches, reports and plans, satellite im-ages and aerial photos regarding the city naturaland urban context. The data has been analyzedbased on patch-corridor-matrix model to come tothe ecological structure of the city.

The environmental potentials and restrictionsof the natural and built ecological systems are fol-

Natural and Built Ecological Systems

lowed by considerations and suggestions for struc-tural and functional improvement of urban eco-logical systems in Tehran metropolitan area.

The base layers of data maps are overlaid toanalyze the overall ecological structure and func-tion of the city, natural and built patches includ-ing open and green spaces, due to their funda-mental role in the ecological structure of the cityare recognized. Hydrological networks are stud-ied as main ecological corridors in the urban land-scape context which vary from natural rivervalleys to manmade surface or subsurface wa-ter flows. The main hydrological corridors influ-ence energy, air and nutrients flow through thecity. Main access of roads, highways and streetsas main structural elements and ecological cor-ridors in urban context, especially in the denselybuilt up urban fabric, as connecting elements ofthe ecological patches and as structural elementsof the ecological systems. The three mentionedlayers have been analyzed to locate the main andmost effective ecological patches and corridorsin the city matrix. The overall ecological struc-ture of the city is then obtained by merging thelayers of natural or manmade ecological patchesand corridors into one single map which containsall the effective features in the structure of thecity (Fig.1).

The main effective element in the ecologicalstructure and function of Tehran are natural andbuilt patches, corridors and matrix.The abundantlands, remnant natural patches, the existing hillsand high lands are located in central and south-east Tehran. Where the micro climatic conditionsallow, these patches are covered by bushes, lowshrubs and dispersed trees. The natural patchesare under constant pressure of urban development(Fig.2).

The urban forests, parks, gardens, orchardsand other built green areas in all shapes and sizeswith interrelations with the whole landscapeelements are named as built patches. They varyaccording to their sizes; two large urban forestsin east and west side of the city are the main builtpatches with high ecological functions, small builtpatches of urban parks are scattered in the urbanfabric.The seven river valleys, north-south, arecharacteristic of natural corridors of Tehran land-scape structure. They are fertile habitats that sup-

port a variety of flora and fauna and play a sig-nificant role as catchments and a place for en-ergy and winds flows to remove air pollutions fromthe city environment, providing opportunity ofconnectedness with the natural upland-lowlandnatural context.

The natural hydrological corridors along theriver valleys face more destructing factors andhave less ecological functions from north to southbecause of their structural modifications (Fig.3).The natural corridors connect many natural or builtpatches that are scattered along them. The natu-ral corridors are mostly oriented toward north-south. The east-west ecological connections arerestricted due to morphological structure of city.Built corridors include linear parks along the rivervalleys, roads and highways and their boundaries,parts of the city greenbelt, tree lines along av-enues, canals and gutters and subterranean hy-drological flows of Quanats. The built corridorsfollow the hierarchy dictated by the main roadswhich are oriented toward east-west. Natural-builtmatrix is the most dominant element of the Tehranlandscape which varies from natural mountain-ous to the urban context, then the patches ofnature in the centre and finally the agricultural land-scape and the desert edge in the south.

RESULTS & DISCUSSIONThe overlaid map illustrates both natural and

built structural elements of Tehran ecologicalsystems, the main constrains in Tehran ecologicalcontext is land use change, the invasion of urbandevelopment to the remnant patches of nature,the destruction and obstruction of the natural rivervalley corridors, and the gradual separation ofurban fabric and green areas as a result of thedisregarding urban ecological flows and processesand lack of comprehensiveness in developmentalplans.

The remnant natural and manmade ecologi-cal patches are under constant pressure of urbandevelopment due to scarcity of land in the increas-ingly heavily built-up metropolitan area. Some ofthem most important ecological patches such aslarge remnant natural patches in the center, largepatches of built urban forests in the east and westand the natural corridors of the seven north-southriver valleys and their hydrological flows which

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Fig. 1. overall ecological structure of Tehran

(A) The green and open space patches as main manmade or natural ecological patches(B) The hydrological corridors as main natural ecological corridors(C) The main access of roads, highways and streets as main manmade ecological corridors(D) The existing ecological patches and corridors in the manmade-natural matrix of Tehran forming the ecologicalstructure of the city

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Fig. 2. The green patches as main manmade or natural ecological patches, under constant fragmentation anddestruction pressure of construction and urban development

have been already fragmented by transportationcorridors or disturbed by urban development andother changes in land use.

As Fig.4 shows remnant natural patches inthe middle(a), manmade forests in the east(b), theremnant mountains of south east(c), the manmadepatches of green amid the urban matrix(d), high-ways and roads as main manmade corridors inthe urban matrix(e), agricultural lands in the south,south east and south west(f), manmade forests inthe west(g), the river valleys as main naturalcorridors(h), and mountainous lands in the northas the natural matrix(i), are the most important

Fig. 3. The river valleys as main natural ecological corridors, fragmented, obstructed or transformed todrainage canals

natural and built elements of Tehran ecologicalsystems.

To establish, enhance and complete the eco-logical networks in Tehran, the city faces somerestrictions and posses some potentials both cre-ated by natural environment or caused by humanactivities and the built environment which havebeen classified by the source of initiation. Thenatural and built potentials and restrictions ofTehran ecological systems are descr ibedbelow.Natural Potentials include the river valleysfacilitating upland-lowland flows and make con-nections north-south, natural uplands in the north,

Int. J. Environ. Res., 4(2):361-372,Spring 2010

Fig. 4. Natural and built elements of Tehran ecological structure

north, east and south-east, the remnant naturalpatches in the north and the middle of the city, thenatural hydrological flows as hierarchical naturalstructures.

Built Potentials consist of highways and roadsas main network and connecting elementsbetween the patches east-west, the patches ofbuilt green areas scattered among the built-upareas, the built hydrological flows along main roads,highways and streets.Natural Restrictions includethe high and steep lands in the north and east withlimited water supplies and soil depth as restric-tions to establish patches of ecological functionsand the dry climatic conditions.

Built Restrictions consist of the densely popu-lated urban areas make penetration of ecologicalcorridors into these areas difficult, the destructionof ecological networks especially along the rivervalleys and the natural hydrological flows, frag-mented built patches and pollutions and their det-rimental effects on living conditions.The main prin-ciples to restore the ecological structure and todevelop its function in Tehran metropolitan areaare structural congruence, aggregate with outli-ers, local compensation and indispensable patternswhich are described below.

It signifies that transformations should notcancel the spatial relationships between geo-morphology, vegetation, hydrology and land uses.Creating an integrated system of major naturalcorridors and patches within and outside the city,connecting the built green patches in the heavilybuilt-up urban context such as parks and othergreen patches and improving the ecological fea-tures citywide will help the integrity of naturaland built systems by establishing dynamicallystable ecological systems or networks in poorvegetation conditions of river banks and hills andsteeps next to the highways to providing the ba-sis for the natural systems to thrive and flourishusually regarded as naturalization of urban eco-logical systems.

Land containing humans is best arranged eco-logically by aggregating land uses, yet maintain-ing small patches and corridors of nature through-out developed areas, as well as outliers of humanactivity spatially arranged along major boundaries.Preserving the large remnant natural patches andcreating urban forests in the hilly land will help toarrange the structural elements of Tehran eco-logical network in a more sustainable way. Creat-ing a new system that did not formerly exist andproducing ecosystems in connection to existing

Natural and Built Ecological Systems

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hydrology and morphology which will include in-terruptions in manmade patches and corridors withhigh ecological values in densely built-up and popu-lated areas in the city centre and enhancing theactivities undertaken to improve existing environ-mental quality at some places with limited watersupplies or other constraining factors such as dryuplands or land with poor drainage conditions.

Serious transformations which alter manycharacters of a landscape have to be compen-sated through an ecologically balanced therapyinside the same unit. Regarding the existing hi-erarchy of ecological patches and corridors inthe urban context, the urban green infrastruc-ture, and following natural rules will help the lo-cal compensation. Naturalization of river banks,reclamation the disturbed or obstructed naturalpatches or corridors in the urban or suburbanenvironment to meet the recreational needs ofthe citizens and the ecological needs of the city,providing water supplies to establish vegetationin a specific area lacking water such as dry up-land areas in Tehran greenbelt, and constructingnew parks, water features and ponds, greenwaysand establishing park systems will benefit thelocal and regional compensation in Tehran eco-logical systems.

Ecological rehabilitation or partial recovery ofecosystem, not necessarily reestablish the pre-dis-turbance structure where alterations in natural andbuilt patches and corridors are seen. Mitigatingdefined as site restoration to an environmentallyand socially acceptable condition, but not neces-sarily natural, for drainage problems in the southbecause of the low-land situation, water pollutionsand sewage disposal. Reclamation or series ofactivities intended to change the biophysical ca-pacity of an ecosystem in the disturbed or ob-structed natural patches or corridors in the urbanor suburban environment face severe adversetransformations.

It is necessary to leave wider possibility ofconnections and fluxes regarding the whole land-scape, especially top-priority patterns and thosewhich are more sensitive to the surrounding envi-ronment. Preserving large remnant patches andlarge green patches in the urban fabric, preserv-ing the upland mountainous and lowland agricul-tural land from development and using them as

connectors to ecosystems beyond the city bound-aries through establishment of dynamic ecologi-cal systems or networks could help in unify theecosystems within and outside city.

CONCLUSIONThe process to provide a model for urban eco-

logical systems based on landscape ecologyapproach should take all natural and built struc-tural elements into consideration. The process ofimproving the ecological systems is illustrated inFig.5.

The remnant natural patches and corridors inthe urban environment are to be preserved andrestored to increase their ecological functions ofthe city so that the natural flows can continue andpenetrate into the built environment. The builtpatches and corridors within the urban context canact as main elements to make an ecologically func-tional system. The built patches are most influen-tial factor in the densely built-up and populatedcity regions, and the built corridors can act as mainconnecting elements between the natural and builtpatches. Protecting the integrity between struc-tural elements, preserving the original pattern ofecological systems, will help to establish and en-hance the ecological processes and flows in theurban and suburban environment.

The built and natural ecological features ofTehran do not seem to have complementary in-teraction and urban development in many caseshas led to destruction or obstruction of ecologicalflows of natural corridors in the city context. Theriver valley corridors and remnant natural patchesin the middle and built green patches in the eastand west are considered as main structuralelements in Tehran urban ecological system. Cat-egorizing the building elements of the ecologicalstructure of the city into natural and built with land-scape ecology approach and patch-corridor-ma-trix model will help to clarify the current situationand classify future improvement policies and ac-tivities.

Based on suggestions for structural and func-tional improvements of the Tehran ecological sys-tems and the major problems that the city faces,some of the activities for improving Tehran eco-logical systems are as follows.

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Considerations for structural and func tiona l improvement of patches, cor ridors and matrix in the urban landscape

Description of urban ecological systems in the urban context

Potentials and restr ictions of urban ecological systems

Suggestions for improvement of ecological systems in the urban context

S tructural congruence

Implications of landscape ecology approach in urban natural and built systems

Aggregate with outliers

Local compensation

Indispensable patterns

Natural patches

Built patches Natural cor ridors

Built corridor Natural-built matrix

Fig. 5. The process for improving the natural and built ecological systems in the urban environment based onlandscape ecology approach

a)Restoring the natural form and structure of theriver valleys, natural matrix connectivity, and sen-sitive built areas such as roads crossing the rivervalleys.

b)Cultivating vegetation and penetration of thenatural and built ecological patches and corridorsinto the urban fabric as ecological rehabilitationactivities.

c)Improving rules and regulations against the al-terations of ecologically important features forpreservation purposes.

d)Removing the pollutants through physical, chemi-cal and biological processes and assisting vegeta-tion growth through bioremediation techniques tomitigate some of environmental problems.

e)Naturalizing the environment and optimizing themicroclimatic conditions, providing the basis forthe natural systems to thrive and flourish.

f)Creating new or ecologically important featuressuch as small green patches in the urban fabricestablishing greenways along main roads and ahierarchical system of linear parks in the urbancontext.

Aminzadeh, B. and Khansefid, M.

g)Providing water supplies to establish andenhance vegetation in specific areas such as dryupland and hilly lands in the center and providingbetter drainage in low-lands of the south.

h)Preparing suitable conditions in landfills in thesuburban areas and the abandoned mine lands andforsaken industrial lands to reclaim the disturbedor obstructed natural patches or corridors.

The contributions of ecological systems willdirectly modify landscape elements in form andconsequently improve them in ecological func-tions. The ecological systems in the urban con-text will act as main supporting features toachieve and ensure dynamism and sustainabilityin the city. The application of landscape ecologyapproach as interpreted in urban ecological sys-tems planning based on the current situation,description and analysis of the natural and builtelements of the ecological features in Tehranmetropolitan area and the suggested policy mak-ing issues and strategies for structural and func-tional improvement of urban ecological environ-ment and the considerations for structural andfunctional improvement of patches, corridors andmatrix in an urban context can be generalizedbut some of the policy making issues and strate-gies for improvement of urban ecological sys-tems may vary or diversify according to localnatural and manmade landscape elements andgeomorphologic and hydrological varied condi-tions and the landscape structure of the construct-ing elements of the ecological features in theurban environment.

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