Introduction

The governing regime of Türkiye has been a republic since October 29, 1923. Since then, there have been numerous military interventions, including the May 27, 1960 military coup d’etat; the March 12, 1971 military memorandum; the September 12, 1980 military coup d’etat; the February 28, 1997 postmodern coup d’etat; the July 15th, 2016 military coup d’etat attempt (Tatlıoğlu et al. 2018). At the time, Türkiye was a newly established republic, still adapting to new system of governance. The nation has experienced four military interventions and one intervention attempt. During this period, the parliamentary system faced several setbacks (Yıldırım 2013). The July 15, 2016 military coup attempt was thwarted by the retroaction of the people. The manifested will of the people demonstrates the Turkish people’s content with the regime type and their steadfast support for democracy.

Military zones are estimated to cover approximately 6% of the world’s land area. However, research on how these military zones affect the landscape and biodiversity remains quite limited (Svenningsen et al. 2019; Zentelis and Lindenmayer 2015). Recently, military zones are frequently brought up as a discussion topic due to their security related vulnerabilities in terms of their location. The relocation of military zones from city centers to the outskirts has become a prominent issue for reasons such as the city’s growth direction, its borders and security concerns. No concrete conclusions have been reached on the subject. Understanding the potential uses of these military zones if they are relocated to the outside of a city is critical. In the downtown area of the capital city of Ankara military zones often come up as a hot topic due to their strategic locations and the vast area they cover. Present-day Ankara is affected by the pressure exerted by military zones in its peripheral areas and the commercial zones. Additionally, the significant amount of space these military zones occupy within Ankara limits the variety of land uses aimed at meeting the needs and expectations of urban residents.

The purpose of this study is to highlight the actual urban green space allocated per individual in Ankara City by examining the state of existing green space and population. Furthermore, the study presents the potential to reach the European standard in terms of urban green space allocated per individual by using military zones, which are stuck in the former outer periphery belt, now mid-periphery belt of the city, and metropolitan parks. However, it is known that after the failed coup d’etat attempt on July 15, 2016 there are multiple military zones in İstanbul which have been turned into settlement areas after they were approved for construction. In case of a similar situation in Ankara not only will Ankara’s peripheral memory cease to exist but, the potential to increase the amount of green space allocated per individual will also be missed. Will Ankara experience a similar case to Istanbul, where 21 military zones were relocated to the outside of the city after the coup d’etat attempt on July 15, 2016 by the decision of the Ministry of Environment and Urbanization? What function will the transformed military zones serve in Ankara after possible relocation of military units to the city’s outskirts? Will the urban green space needs of the population that lives in Ankara be met after the military zones are turned into metropolitan parks? These are the questions that the study seeks to answer.

Two fundamental periods have dominated urban planning in Türkiye during the last 44 years. The first period, which lasted from 1980 to 2002, was characterized by the decentralization of authorities. The second period, which began in 2002, was marked by re-centralization, which dominated planning processes. The practice of urbanization was dominated by the processes of deregulation and liberalization after 2002 (Balaban 2008). TOKİ (Housing Development Administration of the Republic of Türkiye) is the leading institution in Türkiye regarding the transition of military zones. Under bilateral agreements with the National Defense Ministry, TOKİ constructs infrastructure for the Turkish Armed Forces in exchange for land (İnan 2019).

For instance, 10% of the total area belonging to Istanbul Province is occupied by military zones according to a study conducted by the Istanbul Chamber of City Planners in 2016. The military zones were built on areas in the outer periphery belt of the city; eventually as the city expanded, they ended up inside the settlement area. Some of the areas belonging to the military were used during the coup d’etat attempt on July 15, 2016. This led to a national discussion on security concerns related to military zones within Ankara (BBC Türkçe 2023).

The military zones in Türkiye have been transitioned for various reasons. These reasons include natural disasters, reconstruction of areas not in line with zoning plan, alignment with the European Union Acquis, earthquake preparedness, and state security. After the failed coup attempt on July 15, 2016, a series of decree-laws (KHK) were issued, leading to the closure of several military education facilities. Several military zones were moved to the outskirts of the city as well. How these former military zones, which are empty and serve no particular purpose, are going to be utilized and what function they will serve has not been addressed yet (Kuşkonmaz 2021). Military zones should not be seen as ‘empty areas’ within the city region. The natural and artificial landscape value of these areas should be determined with proper techniques and protected as such. With large-scale planning, military zones could be transformed into a green belt that spans the city, addressing the congestion of settlements within the urban periphery (Şahin 2016).

Military zones are seen as reserve plot portfolios, which are the regions first to be transformed into functional areas or new settlement regions in metropolitan cities. The third clause of “Act Concerning the Transformation of Areas Under Risk of Disaster” dated May 16, 2012 has paved the way for the transfer of forbidden military zones, security areas and unused estates belonging to the military to the municipalities and TOKİ. Therefore, the act facilitated the takeover of military zones that will move outside of the urban area, by the National Treasury first and the Ministry and municipalities second (Alp 2016). Utilization of military zones without turning them into settlement areas and while protecting the existing biodiversity would serve as a buffer within the dense urbanization (Svenningsen et al. 2019). The public was not given opportunities to actively participate during the replanning processes following the relocation of military zones. Thus, these circumstances brought about constructions that are unplanned and/or not in accordance with the needs of the people and transformations based on political gain along with it (Fig. 1). The private construction companies, landowners, and central government backed by foremost institutions and establishments and the central government’s tributaries all played their roles during the aforementioned process (Ural 2019).

Fig. 1: Transformation of military zones in Türkiye.
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The concept of a ‘regional park’ in Ankara, which was proposed by the Ankara Metropolitan Municipality, first emerged in 2012 and has been under discussion ever since. The plan aimed to create a regional park by consolidating small-scale parks in the Çukurambar Neighborhood of the Çankaya District. The Ankara Department of the Chamber of Urban Planners was the very first to object to this plan. They argued that the plan would lead to political gains, prompting the court to rule in favor of halting the project. (İlkay 2017; İlkay 2016).

Urban settlements spread out from their founding core to their surrounding environment. Ankara City is an ancient settlement and was founded around the Ankara Castle in its core. The city, which was included in the administrative borders of different civilizations over its history, spread as a settlement from the surroundings of its castle. Thus, the core of Ankara City is made of Ankara Castle and its surrounding environment. The core hasn’t had much development up until the declaration of the republic. With the declaration of the republic on October 29, 1923 a new political function was attributed to the city with the phenomenon of being the capital of the nation, its development accelerated. During the following periods the development of both unplanned shed-slum structures, which were around the old Grand National Assembly of Türkiye (TBMM) building and planned projects such as Bahçelievler contributed to the growth.

The periphery belt studies are critical for showing what kind of development a settlement goes through with different plans and practices in its axis over time. Furthermore, periphery belt areas are usually portrayed as urban heritage and/or ecological corridors. This feature is also vital for a city to display a preservative barrier against the negative effects of urban development on existing natural areas and ensure ecological sustainability (Kubat and Hazar 2018). In a historical context the city settlements will undoubtedly cause an emergence of periphery belt areas regardless of whether they are old or recent. An old historical city could have an observable presence of all three inner, middle, and outer periphery areas, whereas a recently emerged city could have none of the aforementioned three. The emergence period of the middle and outer periphery belts of an older city and the inner and middle periphery belts of a recently emerged city might be simultaneous (Conzen 2009).

The periphery belt areas can be defined as areas that are further from the city center and have wider open spaces (Conzen 2009). The periphery belt zones emerge naturally and uniquely in every city due to their development features. The periphery belt areas are located in the peripheral zones of the urban settlement. The need for vast and cheaper lands outside of the city downtown is influenced by geographical features such as remoteness and attractiveness (Kubat and Hazar 2018).

To analyze the periphery belt zones in Ankara City, differentiating them into six distinct periods is essential. These periods are: The Pre-planned Period (the pre-1924 period), The Lörcher Plan (the 1924–1932 period), The Jansen Plan (the 1931–1957 period), The Yücel-Uybadin Period (the 1957–1970 period), The 1990 Regulatory Plan (the 1970–2006 period), and The 2023 Master Plan (Tiryaki and Kubat 2023). The reason these periods are analyzed is that every single plan that has been put into effect for Ankara to become an exemplary planned settlement, resulted in differences regarding the development phases of the city (Fig. 2).

Fig. 2: The growth of Ankara City according to the planning periods.
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This figure is covered by the Creative Commons Attribution 4.0 International License. Copyright © the authors, all rights reserved. (Altaban 1986:141, Ankara Metropolitan Municipality Zoning Plan, Google Earth Images).

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After Ankara became the capital, several plans for the city to become a planned and exemplary urban settlement have been put into effect. The very fabric of old Ankara’s development after the declaration of the republic was significant. However, when deciding the location of the new Republic-era institutions, selecting the Atatürk Boulevard, which connects the old Ankara to the new urban area, affected the growth direction of the city (Günay and Kubat 2022). A 1924 map, scaled at 1:4000, depicted the land use, including cemeteries, marshes, parks, gardens, churches, mausoleums, and mosques. The cemetery and marsh zones around Ankara Castle clearly show distinctions when considering the current fabric of the city. In this period the inner periphery belt region was Ankara Castle and its immediate surroundings. Areas such as the Bent River, marshes and agricultural areas located in the north of the city at that time, and the agrarian areas, marshes and cemeteries in the opposite direction are evaluated as the periphery belt zone due to their function as limiters for the Ankara’s settlement area and their distinct cultural fabric (Tiryaki and Kubat 2023). Initially, the Lörcher Plan was introduced in 1924. With the Lörcher Plan the planned growth direction for the city was to the south of the historical city fabric. Currently, the development around Kızılay and its surroundings has its base in the decisions taken while this plan was in effect (Gökçe 2007). The periphery belt zones, which emerged in the period called the Unplanned Period named after the effect of Lörcher’s plan, lost their peripheral identity due to their transformation into residential areas (Tiryaki and Kubat 2023). The Lörcher Plan not only allowed the city to grow towards the south but the decisions taken in this period tried to keep the population of Ankara around the old city core (Cengizkan 2010). Then in 1927 the shortcomings and narrowness of the Lörcher Plan were observed. In the same year, an international competition for a new zoning plan for Ankara was organized and decided upon. In the aftermath of the competition, the plan of Prof. Dr. Hermann Jansen was agreed upon. After the Second World War, the increase in trend of migrating from rural areas to urban areas was also seen in Türkiye just like the rest of the world. The Jansen Plan that was put into effect in 1932 aimed to preserve the fabric of the old city. Additionally, the plan’s other aim was to direct the city’s growth towards new areas such as Çankaya and Kızılay. Furthermore, the Jansen Plan also sought to expand urban green space with a plan to change the main city growth form an East-West orientation to a North-South direction (Gökçe 2007). With the forwarded proposals introduced during the Jansen Plan, changes were seen in the periphery regions of the city. Before this plan the periphery zones of the city were made up of fields, marshes and graveyards located to the north, east and west of the city. Ankara’s periphery belt zones were made up of the mentioned areas. However, these areas underwent a change in functional land use and lost their periphery belt zone features within the scope of the Jansen Plan. Ankara’s old periphery belt zones became inner belt zones placed in between the old urban fabric and the new urban fabric (Tiryaki and Kubat 2023). Moreover, the Jansen Plan caused the urban core to change and develop in the direction of Çankaya (Günay and Kubat 2022). The large and bare terrains around the Ankara City’s core were an attractive opportunity for migrations. Thus, the plan was deemed insufficient around the 1950’s with Ankara City’s population being drastically higher than what was predicted by the Jansen Plan. There was a decisive demand for a city development plan for Ankara City presented to the competitors in 1927. What was demanded of the competitors was to create a plan that would include a projection of the population that the city could support for the next 50 years. For the authorities of the republic at that time the sole city that could serve as a role model was İstanbul. What misled them was the fact that the contemporary population of İstanbul at that time was 700,000, which was tenfold the amount Ankara had at that time. The population of İstanbul despite the background of hundreds of years and the fact that Ankara was a still recently developing city led to the prediction that Ankara could only reach a population of 300,000 for the next 50 years (Tankut 1993). With the need for a new zoning planning in effect a new international competition was arranged in 1955. Nihat Yücel and Raşit-Uybadin’s plan won the contest and thus became the new zoning plan of Ankara. The new plan, called the Yücel-Uybadin Plan projected that the population of Ankara would reach 750.000 by 1985. The plan was created with this projection at its core. However, by 1965, Ankara had already reached the projected population. (Tankut 1993; Günay and Kubat 2022; Tiryaki and Kubat 2023; Gökçe 2007).

In the early 1960’s, a new plan for Ankara was called for. During the 14th year of the Yücel-Uybadin Plan, the Ankara Metropolitan Area Regulatory Plan Bureau (AMANPB) under the Ministry of Public Works and Housing was established by cabinet decree. As a result of the work that had been done during the years 1970–1975 the plan for the next 20 years was concluded. In 1982 a new plan under the name Ankara 1990 Regulatory Plan came into force. Ankara’s continued rapid growth brought about emerging needs in terms of planning. In 1986 a research team headed by the METU Department of City and Regional Planning conducted a new plan that would last until 2015 (Gökçe 2007). The continuous growth in Ankara’s population calls for new areas to mitigate the housing needs. This situation could call necessitate a change in the purpose of land use certain areas to address these needs. The Yücel-Uybadin period and the period in which Ankara’s population exploded correspond to each other. The primary catalyst for this explosion was the migrations from rural areas to urban ones. The increase in population caused Ankara to grow rapidly and unforeseeably in a way that city planning couldn’t anticipate. In this period the structures that emerged in terms of shanties and slums in Etlik, surroundings of Keçiören, south of Çankaya, were not anticipated by the Jansen Plan. In the Yücel-Uybadin plan, the foundation for Ankara’s future growth was based on highway planning, particularly the Konya-Samsun, which remains important today (Gökçe 2007). The outer periphery belt zones of Ankara at that time, which emerged during the Jansen Plan, lost their peripheral features during the Yücel-Uybadin Plan. The former inner belt zones became buried within the city, transforming into inner urban zones. The expansive service areas that emerged in the southern and western parts of the city became central periphery belt zones. These belt zones also limited the growth of the city in their directions. Additionally, the defunction of the outer belt zones, which was present at north of the Ankara Castle, maneuvered the growth direction of the city to that axis (Tiryaki and Kubat 2023). The Yücel-Uybadin Plan also aimed to develop and integrate the city along the suburban railway line, stretching from Sincan in the west to Kayaş in the east. To achieve this, an employment-housing relationship has been established with the founding of the Ankara Sugar Factory in Etimesgut. The plan also sought to curb the spread of slums by meeting the housing needs of workers, particularly those employed in the military factories around Kayaş (Gökçe 2007).

Ankara’s development largely took place around the topographical depressions where the city was originally founded, a pattern that continued until the implementation of the 1990 Regulatory Plan. However, as the population kept rising, solutions were needed to alleviate the pressure on the city center and to expand the city into more spacious areas. To address this, the 1990 Regulatory Plan focused on creating large-scale residential projects and industrial zones in the western areas of Ankara. As a result, housing estates such as Batıkent and Eryaman were developed in line with this plan (Gökçe 2007). The concept of expanding the city to the west, known as the Western Corridor, led to significant morphological changes in the structure of the city. In this period the inner periphery belt zones of the city continued to exist. In the Yücel-Uybadin plan, the barren areas to the west of Ankara formed the city’s outer periphery belt zones. Under the 1990 Regulatory Plan, these barren lands were transformed into green spaces, becoming a key feature of the middle periphery belt zone (Tiryaki and Kubat 2023).

Periphery belt zones illustrate the boundaries embedded within cities and the borders of the historical city core over time. These areas form either ecological corridors or buffer zones as cities develop. Thus, they are essential for sustainability in the urban natural areas of a city. An urban natural area has an effect that decreases the urban heat islands as they mainly consist of open and green spaces (Hazar and Özkan 2020). Discussions on the functional land use that makes the periphery belt zones are still ongoing. According to Barke (1982) green spaces, urban agricultural areas, industrial areas, areas that belong to corporate use, residential areas with low density and recreational areas could be considered as components of a periphery belt zone. Other areas such as agricultural production areas, urban gardens, urban parks, preservation areas, harbors and public usage areas of also belong to periphery belt zones (Kubat and Hazar 2018). According to Conzen (2009), Military zones may also be regarded as a part of periphery belt utilization as well.

Ankara’s city core first developed around the edges inside of a topographical pit. Later, the development spread outside of the topographical pit. Consequently, inside of the peripheral belts military zones also had their locations changed. Currently the population increase in Ankara City’s center is still ongoing. As the population increases, the structuring of the city center of Ankara not only increases vertically but also widens towards the periphery belt zones (Günay and Kubat, 2022). Military zones in the city center were located on the outer borders of the periphery belt zone during the Yücel-Uybadin Plan and the 1990 Regulatory Plan. In the 2023 Master Plan, the military zones are located in the middle periphery belt zone (Tiryaki and Kubat, 2023).

The formation of periphery belt zones is influenced by physical features, socioeconomic activity, and social factors affecting a city. These areas were part of the peripheral belts at the beginning. During the following periods they succumbed and got buried inside the city. The periphery belt zones primarily experience two processes. They first experience the formation and then the modification processes depending on the development of the city. Periphery belt zones only become perpetual if they first form naturally, then if they preserve their initial function. Once periphery belt zones become perpetual, they experience what is called a fixation or consolidation (Soylugüzeloğlu and Kubat 2022). Military zones in the city center of Ankara were once located at the vast and barren fields in the outer periphery belt zones when they first emerged. During their foundation period they were part of the outer peripheral belt of the city and were limiting the development of the city. Presently, they are part of the middle peripheral belt due to continuous development. As their initial function endures as of today, they are heading to the consolidation process.

Another way for periphery belt zones to oversee a change is through translation. In addition, if the function of the peripheral belt succumbs to the pressure of population increase, it gives way to residential development, the belt experiences alienation (Soylugüzeloğlu and Kubat 2022). In the case of the relocation of military zones located in the middle peripheral belt zone of Ankara, a translation will occur. Additionally, if these now-relocated zones turn into residential areas then alienation will occur.

Methods

In this study a satellite image belonging to Landsat concerning the year 2023, zoning plans provided by the Ankara Metropolitan Municipality, population data for the year 2022 obtained from the Turkish Statistical Institute, previously conducted research data, sources on the study field and, field expeditions have been used. Two field expeditions dating 2023, April and 2023, September have been conducted to observe the districts of Altındağ, Çankaya, Etimesgut, Keçiören, Mamak, Sincan, and Yenimahalle. Another observation on the existing vegetation in military zones has been conducted as well. Furthermore, their location in relation to the city’s transportation routes has been examined.

First the borders of military zones were defined from the zoning plan obtained and then these borders were exported to the ArcGIS 10.5 program in the study. Afterwards, using the currently effective zoning plans, high-resolution satellite images from Google Earth Pro, and field expeditions, the localization of urban green spaces was conducted. The localized urban green spaces were then exported to the ArcGIS 10.5 program and digitized. To conduct the distributional analysis of urban green spaces, an index analysis using the band data of Landsat satellite imagery has been used. The analyses carried out are Landsat Normalized Difference Vegetation Index (NDVI), Normalized Difference Moisture Index (NDMI), Normalized Difference Built-up Index (NDBI) and Normalized Impervious Surface Index (NISI) (Table 1).

Table 1 The analysis indexes on vegetation satellite imagery and the formulas used in the study.
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The density of urban green space within the districts was examined through the index analyses applied in the study area. Afterwards, a comparative evaluation of how the military zones could contribute to the urban green space potential was conducted. Then through the population data obtained from the Turkish Statistical Institute, the distribution of population density in the districts was produced. Additionally, building density was analyzed using the zoning plan data. The findings. The from the index data were compared with the population and building density of each district. Through the findings from analyses, the analyses, it is anticipated that the military zones in central Ankara could transform into urban green spaces. Therefore, their contribution to this phenomenon regarding districts has been analyzed with various data.

In the study field not only the contribution of military zones to the urban green spaces was calculated, but also an accessibility analysis for military zones anticipated to transform into urban green spaces, including the service radius of these spaces. To conduct the accessibility analysis, the Service Area tool from the Network Analyst module of ArcGIS 10.5 was used. The calculations were conducted both in terms of service radius and walking distance. GIS technologies have been used heavily in relation to land use, land use availability, city modelling, education, accessibility to green spaces and health institutions. (Topuz and Deniz 2023, Deniz 2024) (Fig. 3).

Fig. 3: Methodological window of the study.
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Results

Nowadays, urban settlements are treated as a social, historical and cultural norm. Nonetheless, this behavior is not correct. Cities in their fundamentals are an ecological community and an ecological norm beyond historical accumulation (Bookchin 2017). The 21st Century has caused various environmental problems. Air pollution due to industry is a prime example of this issue. Air pollution emitted by the industrial complexes causes heat islands in the city due to the increasing number of residential buildings and green spaces being replaced by concrete structures. With the influence of effects mentioned previously for cities to sustain their ecological structure, green spaces are vital. Urban green spaces are one of the important services that cities offer to their residents. These green spaces not only offer a landscape view but are also important for urban sustainability (Rojas et al. 2016).

According to the report presented by the World Health Organization (WHO) for a city to be considered accessible, healthy and secure, the minimum amount of green space offered by the city should be 9 m2 per individual, and the ideal amount should be at 50 m2 per individual (Morar et al. 2014). In terms of a standard based on these figures, countries vary significantly worldwide. The amount of green space per individual changes from one city to another. For instance, in Europe cities such as Stockholm, Copenhagen and Hamburg, which bear the title of “Green Capital”, the amount of green space allocated per individual in these cities is between 20 and 40 m2 (Ercoşkun 2012).

The study area consists of the central districts of Ankara City in terms of administration, which are Yenimahalle, Çankaya, Altındağ, Keçiören and Sincan, and it also consists of neighbourhoods of Etimesgut and Mamak districts, where both population and residential density are highest. According to the Metropolitan Neighborhood Act of 2012 numbered 6360, urban areas of metropolitan cities now include rural areas. These areas are not included in this study during definitions of the borders. The population of the study area was 4.351.764 at the time the data was collected (Fig. 4).

Fig. 4: Study area, military zones, parks and recreational areas according to Ankara metropolitan municipality, 2023.
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According to the NDVI analysis conducted on the study area, the maximum value found was 0.60 while the minimum value found was −0.32. The findings show that the districts of Yenimahalle, Sincan and Etimesgut have negative average values and therefore exhibit more sparse vegetation. The average NDVI analysis value in these districts is calculated to be −0.10. The NDVI values in other districts vary between 0.1 to 0.6. Thus, in these districts, the green space coverage is higher than in Yenimahalle, Sincan and Etimesgut districts. According to the NDMI analysis conducted on the study area, the maximum value found was 0.51 while the minimum value found was −0.38. The surface humidity values of Sincan, Keçiören, Mamak and Altındağ districts are calculated to be relatively low since their vegetation density is sparse. Çankaya District on the other hand has a higher value of NDMI since it has denser vegetation. According to the NSIS analysis conducted on the study area, the maximum value found was 0.73 while the minimum value found was −0.07. NDBI values on the other hand were calculated to be 0.39 when on maximum and −0.51 when on minimum value. Higher urban green space and lower artificial space coverage in the Çankaya District resulted in higher surface permeability according to the findings of NISI, NBDI and NDVI analyses. According to the results of NDVI analysis the urban green spaces are denser in Çankaya and less dense in Keçiören, Yenimahalle and Etimesgut districts. Additionally, the data from NDMI analysis shows parallels with data from NDVI analysis. This situation indicates that especially in Çankaya District where green spaces are more dense vegetation humidity density also increases. Data from NDBI analysis, which highlights the artificial areas existing in the study, shows that every district has some places where artificial areas are denser. Especially Keçiören, Etimesgut and Sincan districts stand out in terms of artificial area density. Impermeable surfaces, which occur from surface deformation in cities and ferroconcrete structures, show a negative correlation with existing green spaces. Thus, when NISI data was examined in Yenimahalle, Sincan, Etimesgut and Keçiören districts existing impermeable surfaces were observed to be denser (Fig. 5).

Fig. 5: Index analyses of the study area.
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The index used in the analysis: (a) NDVI analysis result (b) NDMI analysis result (c) NDBI analysis result (d) NISI analysis result (Altaban 1986:141, Ankara metropolitan municipality zoning plan, google earth images). This figure is covered by the Creative Commons Attribution 4.0 International License. Copyright © the authors, all rights reserved.

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According to the NDVI analysis results of the districts, mean values are highest in Çankaya District with 0.175 and lowest in Yenimahalle District with 0.136 in Ankara City. Thus, the situation indicates that the amount of green space is highest in Çankaya District and lowest in Yenimahalle District. When NDVI results are examined according to the maximum and minimum values in districts, it is seen that the maximum values were from Çankaya District and minimum values were from Altındağ District. When the difference between maximum and minimum NDVI values was examined two outlier values of Altındağ District with 0.88 and Yenimahalle District with 0.63, were noticed. The amount of green space in Altındağ District reflected the lightest and the darkest colours in the electromagnetic spectrum’s wavelength considering visibility. Furthermore, the difference between maximum and minimum values was high in the Altındağ District. On the other hand, in the Yenimahalle District the difference between values was low.

When data from the index analyses and population density were compared it was found that in Mamak and Keçiören districts neighborhood-based population density was higher however, green spaces were lower according to the index analyses conducted in the districts. In other districts it is observed that neighborhood-based population density was centered around district centers. Additionally, it is also observed that green spaces have a density towards the areas in the center. The findings indicate that the existing green spaces should be increased significantly, especially in Mamak and Keçiören districts.

Considering military zones as empty spaces in urban areas is a grave mistake. Natural and landscape values of these areas should be defined with suitable index analyses, and they should be put to the most proper use (Şahin 2016). When the existing military zones turned into green spaces model was analyzed with the data from the index analysis if the current land cover is preserved, Mamak district will obtain more green space contribution. However, when analyses are conducted on the scenario of existing military areas undergoing transformation and turning into active urban green space, the Etimesgut, Mamak and Sincan districts will also acquire vast amounts of urban green space.

When population density calculations were conducted areas added by the Metropolitan Neighborhood Act of 2012 numbered 6360, the rural and urban population divide was not regarded. The district with the densest population was Keçiören with 151,1 (person/ha). Among the contributing factors to this is the fact that Keçiören is one of the smaller districts in the study area only larger than Altındağ, and the fact that Keçiören is only second after Çankaya in terms of population number. Keçiören’s population density is followed by Mamak with 83.1 and Mamak is followed by Altındağ with 70.0 (Table 2, Fig. 6).

Table 2 The size, populations and population densities of the settlements in the study area.
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Fig. 6: Districts by population density according to TURKSTAT, ABPRS.
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When the distribution of green spaces in regard to the districts is observed, the district with the highest amount of existing green space is Çankaya with 5.389.796.3 m2. Çankaya is followed by Yenimahalle with 4.569.999 m2 and Yenimahalle is followed by Keçiören with 3.129.779.5 m2 (Fig. 6). When the current situation is considered the district with the least amount of green space is Mamak with 1.029.350.1 m2. The City of Ankara’s highest amount of population and the second highest amount of population density in terms of districts belongs to the Keçiören District. The urban green space allocated per individual in the same district is calculated to be 5.2 m2 and deemed insufficient. The result is due to the population in the district being quite high and the settlement type in terms of building being attached (Keloğlu and Karabacak 2020).

According to the World Health Organization (WHO) the minimum amount of allocated urban green space per individual should be 9 m2. The amount of active urban green space in the study area is 21.236.076 m2. The average urban green space per individual is 4.9 m2. Among the districts included in the study area the district with the highest amount of urban green space per individual is Altındağ with 7.7 m2 and the district with the lowest amount of urban green space per individual is Mamak with 1.8 m2 (Table 3).

Table 3 Districts by population amount.
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The size of the study area is 71.880.84 ha. The number of buildings in the study area is 281.380. The density of the buildings in the study area is 3.9 (building/ha). The areas with the highest amount of building density are the south and southwest of Altındağ; the west and center of Mamak; and the east, north and west of Yenimahalle (Fig. 7). The migration which occurs from rural areas to the urban ones weakens the authority’s provision capacity in terms of the needs of people such as hygiene, transportation, and settlements (Gül et al. 2024). Nowadays, as the population of cities increases, the need for housing also increases. The demand for new residential areas is rising to meet the increasing housing needs. The urban green spaces are being covered by residential developments due to the growing number of built areas (Akerlund et al. 2006). One of the most tragic cases of this situation is observed in the United States of America. Every year, an average of 1.4 million ha of green space is covered and destroyed by the urban settlement areas (Mensah 2014). The term ‘urban green space’ contains elements such as urban forests, parks, gardens, urban green space corridors, playgrounds etc. (Dai 2011; La Rosa and Privitera 2013; La Rosa 2014). The increase in structures in urban areas that serve purposes such as settlement, industry and commerce falls short when meeting the needs of the people in terms of accessibility to the urban green space, distribution of area and size criteria (Ünal et al. 2016). For the population clustered in the city center of Ankara, accessibility to urban green spaces is a more dire case than the residential problem. For humans to remain healthy in both physical and spiritual contexts, the amount of urban green space located in city centers must be increased (Fig. 7).

Fig. 7: Distribution of building density in the study area according to Ankara Metropolitan Municipality, 2023.
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There is a correlation between the size of the districts and the distribution of building density. The district with the highest number of buildings is Çankaya with 65.106. Çankaya has a building density of 2.95 (building/area) due to its fairly large size. The district with the highest amount building density is Altındağ. The district, which has a building density of 7.86 (building/area), has a total of 39761 buildings. After Altındağ, Mamak has the second highest building density (Table 4).

Table 4 Distribution of building density by districts.
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Military zones shouldn’t be considered empty areas and should be designed with an upper-scale plan. They should be considered within the integrity of the urban area through urban natural threshold analyses conducted (Şahin 2016). The urban green space in the study area is 21.236.076 m2 in total. The total amount of land that belongs to military zones residing in the study area is 34.738.872.9 m2. The amount of urban green space per individual before adding the current military zones is 5.0 person/m². If military zones are evaluated as metropolitan parks then the total amount of urban green space adds up to 55.974.868.3 m2. Moreover, the total amount of green space per individual will add up to 14.3 person/m2. If a firsthand look is taken at the change in terms of area in districts, the district with the highest increase in urban green space is Etimesgut with 20.333.934.9 m2. Etimesgut is followed by Mamak with 12.097.625.1 m2. The main reason for these increases is the fact that these districts have the largest military zones. Districts that did not experience a change in terms of green spaces are Altındağ, Keçiören, Çankaya and Yenimahalle. However, when the newly created urban green spaces are included in service area calculations, the amount of green space per individual shows increases (Table 5, Fig. 8).

Table 5 Change in the size of urban green space when the currently existing military zones in the study area included.
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Fig. 8: Change in the size of urban green space when the currently existing military zones in the study area included according to TURKSTAT, ABPRS, Ankara Metropolitan Municipality (February, 2023).
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Since there are no military zones that could turn into metropolitan parks in Altındağ, Çankaya, Keçiören and Yenimahalle districts, a direct increase in urban green space cannot be observed. However, according to the standard related to the parks, the service radius of military zones in Etimesgut that are planned to turn into metropolitan parks will include the southern and the southwestern of Yenimahalle district and the northwest of Çankaya district. The service radius of the military zones in Mamak will include the population in the southern and southeastern of the Altındağ District. Keçiören district won’t be included in the service radius of the new metropolitan parks transformed from military zones. Nevertheless, considering the increase in vehicle ownership and the improvement in the quality of public transportation today the population of Keçiören district will easily be able to reach all of the new metropolitan parks (Fig. 9).

Fig. 9: Service radius of military zones when they turn into regional parks according to Ankara Metropolitan Municipality, 2023.
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Building random parks on green spaces gained from military zones in accordance with public policies would be improper. Additionally, the parks should not only be considered as playgrounds for children. There are criteria the parks should meet, such as the amount of population they will serve, the allocated area required per individual, and the overall space the park should have. Furthermore, every park has standards it must meet, including service radius, location within a certain walking distance, and accessibility within a specific time period. The parks are classified according to the following criteria. (Ersoy 2015, Table 6). Elements such as, city population, size of the military zones that will be converted into parks should be taken into account when planning is conducted based on the criteria defined in this classification.

Table 6 Standard regarding parks.
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From small scale to large scale, five military zones were addressed in the study area. Some of the addressed military zones are located fairly close to each other. The military zones that are close to each other could be considered as one. The population of the study area is 4.351.764 in total. The total amount of people that metropolitan parks could serve is 250.000 individuals according to the standards. In the case of military zones being transformed into metropolitan parks, the amount of people the parks could serve would increase by 1.250.000 individuals. However, there is a particularity here that is worthy of notice. The size of the military zones is well above the requirements of metropolitan parks. The total size of the military zones is 34.009.4 decare. Metropolitan parks require 5000 decares minimum. It is anticipated that with the size of military zones, seven metropolitan parks could be created. Therefore, the number of people the parks could serve is expected to reach 1,750,000 individuals.

According to the studies previously conducted, the distance a human can walk at a moderate walking speed is 11.88 meters per minute (Dal et al. 2010). People’s tendency to walk for inner-city transportation decreases due to an increase in vehicle ownership and an expansion in the diversity and network of public transportation. Nevertheless, when choosing a place for residence, walking distance to the reference points (school, market, shopping mall, park etc.) is still taken into consideration. The walking distance of metropolitan parks, which are planned to be developed from the military zones, has been detected alongside their service area. The walking distance of the metropolitan parks has been classified as ranging from 60 to 90 min. Three groups have been considered during the execution of walk analysis. These are 30, 60, and 90-minute groups (Fig. 10).

Fig. 10: Walk duration for the accessibility to metropolitan parks planned in place of the military zones according to Ankara Metropolitan Municipality, 2023.
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The metropolitan park planned in Mamak will serve those within 30 and 60 min of walking distance to Altındağ, and within 90 min of walking distance to the south of Keçiören and to the northeast of Çankaya in addition to the city center. The metropolitan park planned in Etimesgut will serve those within 30 min of walking distance to the southwest of Yenimahalle, 60 min of walking distance to the center of Yenimahalle and 90 min of walking distance to the north and northeast and east of Yenimahalle. Therefore, the metropolitan park in Etimesgut will be able to serve all of the Yenimahalle. The Çankaya district will also wholly benefit from the metropolitan park in Etimesgut. From the 30-60-90 min walking distances, the population in the north, northwest and west of Çankaya will benefit from the aforementioned metropolitan park. The metropolitan park in Sincan on the other hand, will only be able to serve its own population because of the small area it covers.

The size of the walking area that will be served by the metropolitan parks is 461.832.668.4 ha. The population of the effective walking area is 3.089.083 individuals. According to the standards of the World Health Organization the population of the effective walking area requires an urban green space service of 30.890.830.00 m2 in size. The total amount of space the military zones cover is 34.738.872.90 m2. According to the standards of the World Health Organization the urban green space gained from them is going to be more than 3.848.042.90 m2. However, according to the park standards the amount of land a metropolitan park needs for such a population is 617.816.600 m2. Thus, based on the same standard, there is a deficit of 27.042.787.8 m2 observed.

Conclusion

Ankara is a city that continues its urban development since its declaration as a capital and has evolved to this day. The city was, and still is, shaped according to the plans that were not always followed and implemented over time. Within the development of the city Ankara had different periphery belt zones and urban morphological memory when traced back to this day. The borders of urban periphery belt zones changed over time. The outer periphery belts became as middle periphery belts as the city grew. The initial military zones were located in the empty fields on the periphery belt outside of the city which were relatively cheaper and much more accessible compared to the city center. People who could not find a place to dwell during the migrations from rural areas to urban ones, built slums on the city periphery where the area was empty, relatively cheap and away from supervision. This phenomenon affected the development of the city periphery belt directly. The slums, which were located in the surroundings of the military zones, eventually started to be included in the urban transformation projects over time. Hence, the military areas which were initially founded on the outer periphery belt zone of the city eventually moved into the middle periphery belt zone. The development of Ankara City is still ongoing. The residential pressure stemming from the ever-increasing population creates a need for new residential areas.

Various propositions have been put forward on the fate of the military areas, as they remained in the city center after the July 15th 2016 coup d'état and raised concerns about security. In the event that military units move outside of the city center to surrounding districts, how the military zones will be used is critical for both the peripheral belt zone and the population that resides there. This is because Ankara’s morphological memory will be harmed in the case of military zones transforming into residential areas. Should the military zones transform into residential areas, which currently represent the middle periphery belt zone and previously to that the older outer periphery belt zone, these newly developed residential areas would become a part of the inner peripheral belt. However, if these military zones were repurposed as urban green spaces, the middle periphery belt zone of the city could be preserved. Furthermore, this would address the urban green space needs of the population.

Since military zones are exclusively reserved for military use and civilians are not allowed inside of them, an direct observation from inside the study area directly could not be conducted. The existing amount of green space was identified through analyses conducted in the study. Data regarding tree types and other vegetation within the area could not be accessed. Therefore, the evaluation is based on the findings from these analyses. More concrete evidence will become available if the military zones are vacated. Additionally, afforestation efforts will be carried out if these zones are converted into regional parks.

In most studies concerning accessibility, it is typically calculated using means of transport (Vîlcea and Şoşea 2020). However, the importance of assessing accessibility to green spaces via walking distance is expected to grow, given the increasing focus on reducing carbon emissions. The criteria, used for calculating accessibility to regional parks—such as the average distance of human steps and the distance traveled per unit time—are based on previously conducted studies. While these factors may vary from person to person due to physical differences, averaging them provides an approximate and practical result.

Analyses are conducted on the population currently living in the Ankara City center and existing urban green space. The figures obtained through calculations will fluctuate over time due to ongoing migration and population growth. However, if military zones are transformed into regional parks, the standards set by the World Health Organization (WHO), which recommends 9 m² of urban green space per individual, will be significantly exceeded. According to the study’s findings, the urban green space per individual would be 14.3 m². Therefore, even with continued population growth, the WHO standards will remain above the threshold for a considerable time.

The study aims to present the regional park transformation potential of military zones located in the central districts of Ankara City by identifying their existing urban green spaces. Thus, several maps of the study area have been drawn for this purpose. Previously conducted similar studies have been searched and adapted into this study subsequently. The next step was to conduct analyses on the regional park transformation suitability of military zones. Furthermore, a Network Analysis was performed to determine the accessibility of the study area and its service radius. The study offers a proposal which will reorganize the empty areas in the city center so that they are useful for its population in case of military zones being relocated to the outer periphery belt zone areas.

Mougiakou and Photis (2014) discuss the evaluation and planning of urban green space network in their respective studies. With this context in mind, they suggested a plan that incorporates ecology, service, and bioclimatic considerations. Their studies align with the research focusing on the center of Ankara City.

According to some studies, findings related to the positive effect of military zones regarding their existing natural environment and biodiversity protection mission have been reported (Svenningsen et al. 2019, Perkov and Jukic 2023). This study also defends the positive contribution of military zones transforming into green spaces on biodiversity in case of functional transformation. The protection of certain areas during the development of urban settlements—thereby making them more functional in the future through urban green spaces—is also a fact (Önder and Polat 2012). The importance of military zones in terms of their protection of urban morphological development is massive. In the case of alternative functional uses for military zones, preferring this green space usage will help to protect the urban morphological integrity.

After the 1980 military coup d’etat, garrison and military zone constructions accelerated. Ankara City also experienced a similar transformation and the urban landscape changed. The overall area covered by the military zones in Ankara is approximately 40 million m2. In terms of percentage the coverage is around 13%. The military areas outside of the city center have been evacuated after the failed military coup d’etat attempt on July 15th, 2016. Conversely, the ones left standing in the city center on the other hand have been discussed heavily due to their security concerns. Relocation of these military zones will cause an urban fracture and urban morphological memory loss (Öztoprak and Çağlar 2021). A study conducted in İzmir highlighted the importance of military zones due to their protection of periphery belts. In that study, the military zones have been spatialized using GIS technologies, and their inclusion in green infrastructure plans was recommended in the interest of ecology and public benefit policies (Hazar ve Özkan, 2020). To protect urban morphology without interrupting it, the findings suggest using military zones as urban green spaces.

In case of relocation, ecological and landscape values of military zones with micro-level sensitivity should be presented with maps (Şahin 2016). Within this framework, analyses of NDVI, NDMI, NDBI and NISI have been conducted to show the existing vegetation and to determine its values. When the functional transformation of military zones has been in question, any other usage outside of a potential green space will bring environmental risks with it.

There are existing studies focused on the importance of military zones regarding the urban periphery belts (Öztoprak and Çağlar 2021, Hazar and Özkan 2020). Additionally, studies that concentrate on relocated military zones to be evaluated as green spaces in the interest of public policies are limited in the literature (Şahin 2016). For this reason, these studies provide information regarding the usage potential of public benefiting areas such as recreation and housing, which were previously military zones to local governments and decision-makers. The data produced in this study will serve as a basis for future studies and scientific analyses for local governments, which is the primary aim of this study. By proposing urban green space uses of military zones, this study will offer a practical benefit for society, local economies, and the protection of the natural environment.

The rural-urban population balance is disrupted in favor of cities all over the world. The population in Ankara is heavily on the urban side as well. Individuals who want to benefit from the economic and social advantages offered by cities are increasing. The need for recreational areas within the city is as important as the residential and employment concerns. The dense population living inside of the cities becomes a stress factor for individuals at some point. Reasons such as work life, heavy traffic, noise pollution, light pollution and air pollution cause people to be more stressed. At this point, the importance of urban green space, which could provide an escape for the people who want to stay away from the stress of city life, becomes clear.

The existence of urban green spaces is also important to prevent either the formation or to decrease the effect of heat islands. Roof materials, ferroconcrete structures and asphalted roads trap the sunlight and decrease the amount of sunlight redirected back to the atmosphere. The existence of urban green spaces helps to prevent overheating related problems in cities.

The housing need of the growing population is an important concern. However, the utilization of empty spots inside the city as housing areas only is an improper approach in terms of public benefit. People also require time spent in green spaces as much as housing areas in day-to-day life. It is important to increase the amount of urban green space in order to either protect or improve living conditions. In this context, the study prioritizes public benefit in front of the economic return or short-term benefit.

The purpose of the study is to use military zones as urban green spaces in order to protect the urban periphery belt zones in accordance with public policies. To remain focused on the aim of the study, other topics have not been addressed. However, for studies to be conducted in the future examination of areas, which were once military zones, by linking them with other green spaces located in Ankara City and how an east-west oriented green space corridor should be formed by connecting them in the city, could be explored. Moreover, in the case of military zones transforming into regional parks transformation to reduce the east-west oriented carbon emission in the city, bicycle road analyses could be conducted and examined. In the event that military zones are utilized as housing zones, future studies could examine how the urban heat island effect will change.