Conceptualizing ‘green’ in urban and regional planning – the cases of Oslo and Helsinki

ABSTRACT In recent decades, nature has been increasingly acknowledged in the urban environment for its importance to people’s well-being and quality of life, as well as for its role in building sustainable cities. The idea of nature in cities and the conceptualization of ‘green’ (e.g. green structure, green fingers, green infrastructure, parks and ecosystem services) are correlated in planning approaches. This study explores the conceptualization of green by analysing the concepts used in the two regions of Oslo and Helsinki, and by investigating their current master and regional plans through quantitative and qualitative analyses. The findings exhibit a variety of green concepts and complementary features (between planning concepts introduced earlier and newer ones). Over the years, and in the light of evolving ideas of nature, the master and regional plans of both regions have set up a multi-functionality framework, more recently influenced by ecosystem services approaches. The study contributes to understanding the evolving conceptualization of green in urban and regional planning approaches. The discussion is linked to place-specific contexts and regulatory practices, and connected – to some extent – to the wider international debate and planning ideas that incorporate nature.


Introduction
The interpretation of nature and its relationship with the city and people's well-being has influenced urban and regional planning approaches and objectives over decades.Since human ideas of nature continue to evolve over the time, older green concepts (namely those introduced in earlier plans) tend to weave new meanings in response to the challenges faced in different historical periods, (Duvall et al., 2018) and be intertwined with newer green concepts.Some green concepts have evolved historically and locally, according to specific political, landscape and spatial pressures, such as green belt (London), green heart (Amsterdam) and green finger (Copenhagen).For example, the green belt initiative in the UK has had a complex evolution in terms of content and function.It was originally conceived to supply food for several towns, while some decades later, it aimed to manage densities and define boundaries between neighbouring towns, as well as to support recreation (Amati 2008).While parks and urban green spaces constitute a large group of well-established spatial concepts (Littke 2015), the newer concepts of green infrastructure (GI), ecosystem services (ES) and nature-based solutions can pursue wide-ranging ecological, social and economic benefits derived from nature (Mell 2016).These concepts can be broadly applied to services provided by the green spaces themselves, in the light of their multi-functionality (Hansen and Pauleit 2014;Littke 2015).Multi-functionality refers to the combination of ecological, social, economic, abiotic/biotic, and cultural functions of green and blue spaces, including natural and semi-natural public and private green spaces (Hansen and Pauleit 2014;Ahern 2007).The multi-functional approach can be valid for an entire GI, or across individual green spaces as components of a GI 1 which provides ES (regulative, supporting, provisioning and cultural services, TEEB 2011).
Several studies have focused on analysing concepts which have been used for categorizing green objects and areas.In a Swedish case, Lövrie (2003) considered more than 300 concepts by analysing 41 green plans, which showed significant variation in their contents (Littke 2015, referring to Lövrie 2003).The conceptual understanding of 'green' is related to the specific functional characteristics of various green elements, and is compounded by differences in everyday practice and professional language (Littke 2015, referring to Lövrie 2003).For example, some formal green concepts are used in juridical contexts (e.g.master and regional plans), while other terms referring to outdoor environments and neighbourhood parks are used in urban design projects (Littke 2015).Some green concepts, however, are not regulated, but are mentioned in municipal and regional plans as 'recommended' frameworks or approaches.
The conceptualization of green is also related to understanding by experts, practitioners and policy makers in their discourses on 'green', as well as the geographical and planning contexts, and corresponding green regulatory frameworks within which they operate (Nordh and Olafsson 2021;Di Marino et al. 2019).Furthermore, concepts can be complementary, or interlinked with each other, thus weaving new meanings in response to contemporary challenges (e.g.social, economic and climate adaptation challenges).In this way, the 'green' can acquire new multi-functional purposes (Duvall et al. 2018;Littke 2015).
Thus, this study addresses the following RQ: How does the evolving conceptualization of 'green' in urban and regional planning reflect place-specific contexts and regulatory practices, as well as the wider international debate on nature in planning?
This study builds on two Nordic cases: the regions of Oslo (Norway) and Helsinki (Finland), in which local academics and practitioners have long debated the conceptualization of green in planning strategies and practices (see, e.g.Hautamäki 2019;Jørgensen and Thoren 2012).The study includes a review of studies focusing on conceptualization of green in the earlier and contemporary plans of Oslo and Helsinki, as well as an investigation of green concepts in current plans of the two regions.Since this is a qualitative study of two cases, the results naturally cannot be generalized to all contexts; instead, the study contributes to understanding the evolving idea of nature (adapted as per Duvall et al. 2018), and the related conceptualization of green in the planning domain.

Evolving ideas of nature
The evolving ideas of nature have permeated urban and regional planning strategies and practices within various historical periods and in response to different challenges.During the industrial revolution, cities growth increasingly polluted and unsanitary (Duvall et al. 2018).Urban parks and garden movements were the planning-base response to those conditions (Duvall et al. 2018).In this context, nature was gradually romanticized as relief and amenity (Duvall et al. 2018) (Figure 1).The possible negative consequences of the urban sprawl have been tackled with initiatives such as the green belt, the green ring and related concepts -all of which have emphasized the spatial separation of nature from the city (see 'nature as boundary' in Figure 1), and more recently through the compact city model (Duvall et al. 2018).Between the 1960s and 1990s, the focus was on 'the global environment and sustainability (climate change mitigation and adaptation, reduced resources and energy consumption, economic benefits and ecological modernization)' (Duvall et al. 2018, 482).This was acknowledged in the so-called ecourbanism movement in the 1980s (see 'nature as greening' in Figure 1).In the 1990s and early 2000s, there was a growing awareness of human and urban pressures on ecosystems (with the emerging concepts of ES and GI), and related environmental and sustainable concerns about urban growth (see 'nature as systemic' in Figure 1).Current environmental issues such as climate change emphasize the importance of ecosystems, multi-functionality and the role of urban nature within planning concerns (see 'nature as infrastructure' in Figure 1).In this context, new meanings of green concepts and new planning approaches should be recognized and analysed in urban and regional planning discourses (see the case of Ireland in Duvall et al. 2018).
The meaning of some green concepts can be partly explained by focusing on the specific and dynamic contexts in which they are used (Healey 2012).More recently, Reimer and Rusche (2019) stated that 'These concepts are substantiated by the diverse understandings and attributes used for various reasons by different actors that are embedded in different political and planning contexts' (1543).The same authors (2019, referring to Healey 2012) suggested that GI can be understood as a global narrative and a 'travelling concept'.Nonetheless, knowledge of distinct performance aspects within the local implementation of GI is crucial for city planners today.However, the meaning of various concepts may remain vague or subject to different interpretations within local contexts (Healey 2012).
New interpretations of nature first emerged as objectives in what were future planning exercises, but past and contemporary interpretations of nature and related green concepts may continue to co-exist in current city planning approaches (Hansen et al. 2015;Duvall et al. 2018;Lövrie 2003).

Multi-functionality as part of the evolving idea of nature
Multi-functionality is one of the key aspects of 'nature as infrastructure' (Figure 1), which is operationalized through GI and related concepts.Multi-functionality has played a major role in high density cities as an approach to fostering synergies between various benefits, which can be combined effectively in the smallest of green spaces and compact areas (Hansen et al. 2019).It also aims to combine different functions more effectively in both large and small green spaces (Hansen and Pauleit 2014).Multi-functional green spaces should provide benefits to humans (e.g.human health and social cohesion), as well as secure ecological systems (Hansen and Pauleit 2014;Tzoulas et al. 2007).
Initially, green spaces were identified in local plans for recreational and leisure purposes, as well as to promote nature conservation.Gradually, further functions of green spaces have been identified, including recreational opportunities, a variety of green networks, enhancement of cultural scenery, mitigation of the impacts of climate change, preservation of biodiversity, and controlling run-off water.Further, water in the form of small streams, ponds and lakes -as well as their shorelines -promotes hybrid areas between green and blue spaces (Hannikainen 2019).
Green areas in cities are diverse in terms of size, access, ecological values, and recreational possibilities for residents, all of which form part of a healthy ecosystem and well-functioning hydrologic circle (Jaakkola 2012;Viinikka et al. 2023).To this end, there is increasing discussion today on the ways in which green areas can promote sustainability by responding to climate change issues, cooling the local climate, cleaning and filtering water and air, providing habitats to encourage biodiversity, as well as enabling people to recover from mental fatigue and commuting routes (Jaakkola 2012).
During the 1980s, the concepts of green structures and greenways were accorded significance in urban planning (Thorén and Saglie 2013).The concept of green structure embraces both the structural and functional connections between green spaces themselves, and between them and the city and its inhabitants (Lövrie 2001).The same author states that The purpose of the concept of green structure when it was launched was, in addition to creating a collective term for green areas such as parks, gardens, cemeteries, natural areas, etc., also to emphasise a structural perspective on these elements in the urban environment.(54) The notion of green structure is also related to the idea of a compact city, and future city development within an existing built-up area; while in general, the greenway concept is less concerned with urban density and sprawl (Thorén and Saglie 2013).
Originally, the multi-functional approach of both green structures and greenways was based on Olmsted's thinking (Mell 2016).Olmsted's ideas were about a comprehensive multi-functional (multi-purpose) park and boulevard system that would provide areas of special interest.In addition to the relevance of parks for public health and the role of trees in soil drainage and air purification, the Olmstedian approach focuses on the aesthetic and scenic dimensions of landscapes and nature (Mell 2016).The greenways concept has been used as a strategy to safeguard integrated green linear systems.
The integration of multi-functionality in urban green planning initiatives is stressed significantly within GI and ES approaches.For example, GI is also intended as a conceptual tool for designing and managing a large variety of ES.Regulative services (for example, the prevention of urban flooding) depend on the interplay between built and unbuilt areas, including the necessary supporting technical infrastructure.These services are grouped with supportive services that highlight the importance of ecosystems in providing habitats for various species (CICES v.4.3 sections, in TEEB 2011).Green spaces can also contribute to provisioning services (e.g. the supply of food, clean air, water and materials) (TEEB 2011).Cultural services are also often available, through a combination of urban and natural heritage factors, as well as commercial or public services supporting their use (Costanza et al. 2017).
The capacity of urban green spaces to provide multiple benefits is largely acknowledged among scholars (Haaland and Konijnendijk 2015).Nonetheless, it is important to understand to which degree cities are currently facing challenges related to urban densification and their efforts to provide multi-functional green spaces (Hansen et al. 2019).Scientific approaches to multi-functionality (assessing social, ecological and economic benefits) have not been directly transferred into planning practice, so it is important to further embed the multi-functionality potential of green spaces into local planning goals, practices and tools (Hansen et al. 2019).

Conceptualizing 'green' in early master and regional plans of Oslo and Helsinki (from the 1910s until the 2000s)
The framework developed by Duvall et al. (2018) has been applied in interpreting the green in the early master and regional plans of Oslo and Helsinki 2 The idea of 'nature as relief' influenced Oslo's plans in the early 1900s.The built-up area was surrounded by natural forested land that many people still feel attached to.These areas were later called Marka and have remained important for outdoor recreation.Winter sports, including cross-country skiing, became popular as a cultural phenomenon and an important part of the identity of the new nation of Norway (Syse 2012).Oslo is surrounded by five Marka: Nordmarka, Sørmarka, Østmarka, Lillomarka and Vestmarka 3 , which constitute around 170,000 hectares of forested land surrounding Oslo on the north, east and west, while the southern part of the city meets the fjords (Syse 2012) (Figure 2).
The idea of nature as relief (and providing amenities) permeated the 1929 master plan (designed by the city architect Harald Hals), in which the idea was to secure access to the Marka through a system of parks for recreation, consisting of continuous unbuilt areas, enabling people to walk from inner-city areas to the Marka (Hals 1929).These paths or roads for walking (or skiing) are called turveier (Figure 2).Hals' ideas were inspired by Olmsted's Park systems, in particular, the Emerald Necklace in Boston, USA, and he was also influenced by Alhpand's and Haussmann's plans for Paris, and Howard's garden city ideas (Thoren and Araldi 2010; Jørgensen and Thoren 2012).Plans produced in the 1950s kept together the two concepts of nature as relief and boundary, with the Marka becoming borders to demarcate urban expansion around Oslo (Markagrensen) (Alsvik 1998).The master plan of 1950 focused on placing housing for the growing population mainly in the outer zones of the city, with the objective of creating sub-centres connected by green corridors (Jørgensen and Thoren 2012).The idea of 'nature as greening' permeated the plans of the 1970s and 1980s, in which one of the priorities was to improve the quality of life by maximizing levels of fresh air and sunlight, and outdoor recreation opportunities in order to promote people's well-being and health.
In 1994, a landscape architect and an ecologist -Thorèn and Nyhuus -introduced the 'green structure' concept in Norway (Thorèn and Nyhuus 1994).This created a new shift to 'nature as systemic', which was emphasized throughout plans at the time.The principles of connectivity and multi-functionality framed plans for green structures, linked to: (1) cityscape and aesthetic conditions; (2) recreation, play and quality of life; (3) nature and biodiversity; (4) biological production related to forestry and agriculture; (5) technical matters related to storm-water management and local climate; and (6) 'soft' transport (biking, walking) (Thorén and Nuhuus 1994).Densification had become a national strategy for urban development, which in turn, prompted concerns about sustainability, while also considering the need to protect inner-city green spaces.Securing 'green structures' was viewed at the time as being just as important as increasing density; accordingly, in 1994, the city planning office produced the first Green Plan for Oslo (Falleth and Saglie 2012).However, in the 2000s, master plans focused further on the densification of the city, in the name of climate change and sustainable development (Jørgensen and Thoren 2012).
The incorporation of nature into cities was exemplified in Helsinki in 1918 by Jung and Saarinen who developed the Pro Helsingfors plan which introduced the radial notion of 'green fingers' -green areas on shorelines and green zones between suburban areas (Hautamäki 2019).These green fingers consist of parks and a forest network from the centre to the west, north and east (Figure 3).In a way, this is an inversion of the famous 'finger plan' of Copenhagen (Denmark) in which the 'fingers' refer to urban structures and areas for further urban growth along existing roads and rail connections, to other town centres (the Copenhagen Plan from the 1960s - Caspersen and Olafsson 2010).
Both perspectives of nature as relief and nature as boundary framed the interpretation of green in the master plans of Helsinki until the 1960s.As reported by Hautamäki (2019), from the 1940s, there was a new perspective on planning green areas influenced by the international garden city ideology (see the development of Helsinki's neighbouring municipality of Tapiola) (Hautamäki and Donner 2022).In 1960, Helsinki's master plan stressed the importance of recreational routes in green zones, and in 1970, the plan focused on recreational areas and cultural environments (Hautamäki 2019).
The idea of 'nature as greening' started permeating Finland in 1978, when the Ministry of the Environment ratified a local master plan (osayleiskaava) for the longest and largest green finger, called Keskuspuisto (Central Park) (Eronen 2004).Another green finger (Viikki-Kivikko) crosses the Viikki neighbourhood and reaches the Vanhakaupunginlahti Bay (Lipsanen 2006), while another stretches from the Uutela peninsula in Vuosaari to the Mustavuori area in the city of Vantaa (Figure 3).Four smaller green fingers follow minor rivers (Figure 3).Green fingers promote diversity by each having a distinct character, according to their situation in the landscape and the surrounding urban structure (Jaakkola 2012;Hautamäki 2019).They are also intended to function as an important green structure at the regional level, connecting the national parks of Nuuksio in the west and Sipoonkorpi in the east, to the green areas within Helsinki (Eronen 2004) (Figure 3).The perspective of 'nature as systemic' framed the master plans of 1992, when green structures became important, including green fingers and green spacestogether with their interconnections, and preservation of the landscape (Hautamäki 2019).The notion of 'nature as infrastructure' started framing the interpretation of green in 2002, when the green fingers were clearly delineated in the master plan, with the help of a team of landscape architects (Eronen 2004), and are still included in a thematic map (Recreation and Green Network 2050) of the current master plan (City of Helsinki 2016).The discourses on the densification of the city, in name of providing a good living environment and a functional traffic, as well as creating attractive urban spaces, have permeated the city plan (City of Helsinki 2016).
To conclude this section, we remark that there is an evolving conceptualization of green in the master plans and the use of green concepts (such as the park system in Oslo in 1917-1918and green fingers in Helsinki in 1918)).Some of the concepts continue to be used in the later plans, gaining even stronger connotations (such as Marka and turveier in Oslo, and green fingers in Helsinki).Other concepts such as the cultural environment, fragmentation of the landscape, and the optimization of outdoor areas permeated the plans produced during the 1970s and 1980s, in both cities. Green structure, multi- functionality and connectivity framed the prevalent interpretation of open spaces in both regions from the 1990s onwards.We also note that the idea of nature as infrastructure permeated the master plans of both Oslo and Helsinki during the early 2000s.However, explicit and implicit references to the concept of ES appear only in the current master and regional plans (see Section 5.1, 5.2.1 and 5.2.2).

Oslo and Helsinki regions
The two case study regions are presented in Table 1.In the Oslo region, fjords and woodlands are important natural reserves, together with waterways and agricultural fields (Oslo Region 2015).The landscape of the Helsinki region is dominated by many forests, coastlines, lakes, rivers and islands.There is an abundance of green and agricultural areas, even in the most urbanized areas (Helsinki-Uusimaa Region 2020).In both regions, green structures are clearly visible.
Today, similar to the City of Oslo (Oslo Kommune 2015), the City of Helsinki is tackling the pressure of transforming the city and its parts, while at the same time, preserving greenness (Hannikainen 2019).In Helsinki, greenery encompasses 40% of the city's land surface area (216.5 km 2 ) (Hannikainen 2019), while the comparative figure in Oslo is 29.2% of the total land surface area (454 km 2 ) (Venter et al. 2020).

Materials and methods
This study analysed the current master and regional plans of the two case cities (Table 2).In both Norway and Finland, planning is structured in a hierarchical manner.The  national and regional authorities seek to influence the master plans through 'soft' guidance, as well as more 'hard' legal instruments, such as statutory plans.
'Planning and policy documents can capture and represent the discourses of a city and/or region, as well as their planning strategies and practices at certain points in time' (Hansen et al. 2015, 231).Document analyses with regard to the conceptualization of green have been conducted in recent years (Hansen et al. 2015;Duvall et al. 2018).The content analysis of planning documents was conducted to examine current conceptualizations of 'green' (in terms of green concepts and their frequency).The conceptualization of green is related not only to green and natural areas and elements, but also to other concepts that are associated with anthropogenic environments -such as cultural landscapes and playgrounds -that often include green areas and contribute to the production of ES.This analysis encompasses green space categories (such as parks and nature conservation areas), more conceptual and site-specific concepts (such as green structure, green fingers and green networks), as well as blue-green factors and other approaches and tools (such as ES).The multi-functionality and ecosystem services approach (as part of the evolving idea of 'nature as systemic' and 'nature as infrastructure' in planning discourses -see Figure 1), and legislative/regulatory framework are also addressed in the planning documents which were analysed in this study.

Conceptualizing 'green' in the current master and regional plans of Oslo and Helsinki
A broad spectrum of green concepts is used in the current plans in both regions (Figures 4 and 5).In the Oslo city and region, the most predominant concepts used in the plans refer to open spaces (n = 276), urban woodland (n = 235), green structure (n = 227), parks (n = 120), and park trails (n = 76).The use of the newer blue-green concept is still rather infrequent (n = 6).In the Helsinki city and region, the frequently used green concepts are recreation areas (n = 223), green connections (n = 112), nature conservation areas (n = 101), green areas (n = 85), and green structure (n = 80).
The master and regional plans of Helsinki refer to the ES concept (n = 30) (Figure 5).In the case of Oslo, the ES concept itself is not mentioned in either the regional or master plans.However, several services provided by ecosystems are mentioned under other green concepts.For example, several recreational green areas along Oslo Fjord are identified as nature reserves, providing natural and cultural heritage values (comparable to provisioning and cultural services).
Concepts that are commonly used in both regions (in either master or regional planning) are those that are rather traditional: green structure (n = 307), parks (n = 162), natural values (n = 100), green areas (n = 87) and biodiversity (n = 87) (Figure 6).

The Oslo region
Today, the main objective of the master plan for Oslo is to ensure sustainable and climate-neutral urban development that safeguards and further develops the city's urban, natural and historical qualities (Oslo Kommune 2015).The plan indicates that the functions delivered by green spaces serve ecological and socio-cultural purposes, while providing improved spatial connectivity.The grønnstruktur (green structure) aims to manage biological diversity in a sustainable way and to protect cultural landscapes and cultural heritage for future generations.The plan emphasizes that: 'The city's biological diversity is dependent on varied and continuous nature areas.Oslo has several nature areas of a high degree of importance for both population and biological diversity' (Oslo Kommune 2015, 33).Under the separate heading of 'blue-green structure' (n = 35), the plan states that development of green areas must also take into consideration recent increases in levels of precipitation.Such recommendations expand the functions of the green structure in responding to climate adaptation challenges such as storm water regulation and flood protection.In the master plan for Oslo, the multi-functional green structure has a regulatory role.It has been introduced as a land-use category, including its sub-categories of nature areas, open spaces, parks and green areas for walking (turdrag).Marka is not a land-use category, whereas turveier (park trails) are (see Table 3).The Planning and Building Act of 2008 (Ministry of Environment, Norway 2023) delegates most formal planning authority to the regional and municipal levels.It states that grønnstruktur (green structure) is one of the main aims that should be considered in area plans with regard to transport facilities, infrastructure and buildings, regardless of their purpose.This change in the law means that 'green structure' is now a recognized legal term in the planning legislation of Norway and is required to be an integral part of all master plans.The intention is that the legislation will provide better legal anchoring for the planning of green structures, and have a broader impact on the management of municipal land use.At the same time, the concept of green structure is embedded in comprehensive statements such as it must be considered to set requirements for necessary technical infrastructure, blue-green structure, social infrastructure, public spaces (streets and squares), energy supply, Figure 5. Green concepts used in the master and/or regional plans of Helsinki.
conversion/cabling of high-voltage lines, outdoor recreation areas, as well as play and sports areas, and cultural functions.Blue-green structures, including storm water management, vegetation and outdoor areas, must be considered before a use permit is granted.(Oslo Kommune 2015, 21) In addition to green structure, park trails (turveier, n = 76) continue to play an important role.The major focus of the turveier -which is not a binding concept -is about spatial and ecological connectivity, with continuous park trails being developed mainly along rivers and the sea front (Oslo Kommune 2015).In order to meet recreational goals, there are numerous mentions in the plans of turveier, as well as 'parks and open green areas in new developments' (Oslo Kommune 2015, 33).The concept of Marka (urban woodland) is mentioned the most (n = 235); these woodlands have formed a boundary and green ring surrounding Oslo since the 1950s and serve multiple functions by providing recreational areas and biodiversity protection.
In Oslo's master plan, a reference to the grønne nettverk (green area network, n = 1) and its multi-functional framework (by including biotic and abiotic functions) is rather significant: Areas along waterways are similar to the hiking trails, being important for nature experiences and for creating coherent green networks in the construction zone.The waterways are also important as breeding and spawning areas for fish and other biological diversity.Open corridors are also essential for local climate and local air quality.(Oslo Kommuneplan 2015, 56) This latter statement refers implicitly to the regulating/supporting/recreational ES provided by open spaces.Under 'guidelines', the master plan refers to the blå-grønn faktor (blue-green factor, n = 6) and grønn arealfaktor (green area factor, n = 4) as indicative methods to ensure the provision of sufficient blue-green areas, together with the management of their water and Table 3. Binding and non-binding green concepts used in the Oslo and Helsinki master and regional plans.
Binding green concepts and green elements that are legally binding into the master plan and regional plan Non-binding green concepts that are not regulated in the planning but used as framework / approaches into the master plans and regional plan Not present in the plan

Green concepts
Master plan Oslo

Regional plan Oslo
Master plan Helsinki x Rivers, river valleys, riversides [1]  x x x Sea and waterways, coastlines, beach zones x x x Streams, water and ponds x x x Agriculture and forestry, nature and outdoor recreation (LNF) [2]   x Blue-green factor (BGF) x Blue-green structure x x Green areas for walking x Green border x x Green area factor (GAF) x x Open spaces x Park trails x Urban woodland (Marka) [3]  x Agriculture, urban agriculture x x Areas dominated by forestry, which is large, uniform and significant from the point of view of the ecological network

Biodiversity
x Blue network x Ecological network x Ecosystem services (ES) x x Forest network x Green connection, need for a green connection x x Green finger [4]  x  4) Some of the green fingers are spatially presented in the regional plan, but not as a concept in the planning documents or on the map.
vegetation.These factors do not play any regulatory role, but the idea behind them is to plan infill developments in a more sustainable way by providing more permeable surfaces and vegetation.This approach is being used as a norm for new construction projects in Oslo and neighbouring municipalities (such as Baerum).In addition to stormwater and micro-climate regulation, these factors can contribute to increasing aesthetics and carbon sequestration, thus supporting a healthier urban climate.
In the Oslo regional plan, the multi-functional green structure is used as a conceptual approach rather than a regulatory one (as in the Oslo master plan) (see Table 3) to portray a broader picture of the region (Oslo Region 2015).Five main objectives are depicted in the regional plan: growth and protection; long-term green borders; accessibility to green areas for more varied social groups; regional green structures to promote biologisk mangfold (biodiversity, n = 12); and friluftsområder (outdoor recreational areas within the LNF category, 4 n = 58) connecting densely populated areas (Oslo Region 2015).In pursuing these objectives, the Oslo Regional Plan uses the concepts grønne korridorer (green corridors, n = 2) and naturområder (natural areas, n = 2).The preservation of large contiguous natural areas with green corridors between them is clearly important for connecting the dense built-up areas (Oslo Region 2015).The Oslo regional plan also defines other green concepts which are non-binding and should be used for more participatory processes and dialogue among municipalities.These include grønne grenser (green borders, n = 2), 'where cities and small municipalities end and where protection begins in order to secure green interests from continued urban sprawl' (Oslo Region 2015, 29).'The green border should be the subject of a further local process and dialogue with current actors' (Oslo Region 2015, 29).The socalled blå-grønnstruktur (blue-green structure, n = 12) is acknowledged as a unique requirement that 'easily comes under pressure with strong urban growth and is especially important to take care of when the priority growth areas are more densely developed' (Oslo Region 2015, 29).
In the Oslo region, Marka have gained particular legal status in the so-called Markaloven (The Act of Marka of 2009) (Oslo Region 2015).However, Marka is not a legal category according to the Planning and Building Act (2008) (Ministry of Environment, Norway 2023), and is thus non-binding when mentioned in master and regional plans (Table 3).According to the Planning and Building Act of 2008, the main part of each Marka should be set aside as landbruksområder (agricultural areas within the LNF category, n = 58) and friområder (open spaces n = 276).The Marka law aims to promote the multi-functionality of green spaces in several ways by supporting outdoor activities among local communities, while protecting the borders of Marka themselves, as well as their rich, varied landscape and cultural heritage.These multiple functions delivered by the green spaces which form the Marka have been recognized by the municipalities as important values to uphold.

The Helsinki region
The current master plan for Helsinki aims to link recreational and green areas (n = 117) into a network (City of Helsinki 2016) formed by the green fingers (n = 39) and other wider green areas that continue throughout the region, as well as parks (n = 39) and transverse green connections (n = 26).The diverse uses of green environments provided by parks, cultural environments, forest networks -as well as maritime, nature and recreation services -are seen as an integral part of good and healthy environments (City of Helsinki 2016, 76).
Nature conservation areas are binding green concepts at both municipal and regional levels, most often based on the Nature Conservation Act of 1996, reformed in 2023 (Ministry of the Environment, Finland 2023).In the master plan, the objectives for conservation areas (n = 16) most often refer to preserving them and ensuring ecological connections to and between them, but also developing their recreational and ecosystem services (City of Helsinki 2016, 99, 194).
The vihersormi (green finger) concept (n = 39) appears only in the master plan for Helsinki.The concept is descriptive, with green fingers being spatially presented as green and recreational areas (n = 117) as part of the legally binding master plan map (Table 3).Further, the parts of the fingers belonging to nature conservation areas are protected by the law.The plan highlights the multi-functional nature of the fingers: 'The green fingers include many integrated areas of landscape and heritage value, large functional areas for recreation, such as sports parks and neighbourhood parks, as well as conserved areas like Natura areas'.(City of Helsinki 2016, 46).The notion of continuity which is attached to green fingers in the plan, is mainly recreational, since pedestrian bridges or underpasses may be provided, thus ensuring that the connections are not broken by transport infrastructure.
The non-binding concept of viherrakenne (green structure, n = 9) is used in the master plan in a limited way; instead, the plan mentions various types of networks (e.g.green, forest, meadow and blue networks) (City of Helsinki 2016, 16).The related concept of viheryhteys (green connections, n = 26) in the master plan refers to 'transverse recreation routes that strengthen east-west connections and improve the accessibility of recreation services from residential areas' (City of Helsinki 2016, 98).Thus, these green connections connect the green fingers into a network.The plan includes a schematic illustration of a multi-functional realization of the green connections between different kinds of parks, waterways, a nature conservation area, an urban forest, a playground, urban agriculture, cultural landscapes etc. (City of Helsinki 2016, 100).Unlike green fingers and networks, the concept of green connections appears in the legally binding master plan map.However, the exact location of each connection is advisory, and 'the nature of the connection can vary from built to park-like or natural' (City of Helsinki 2016, 98).
There are several references to an ekosysteemipalvelut (ES) framework in the master plan (n = 12).However, the related objectives are rather general: they are seen as 'important for human well-being' and should be 'developed' (City of Helsinki 2016, 8, 99), for example, 'when building new constructions or planning new parks' (City of Helsinki 2016, 76).
The concept of 'cultural landscapes' (n = 15) often relates to the objective of preserving local identity attached to cultural environments (City of Helsinki 2016, 77).The cultural landscapes in Helsinki often represent urban parks, private green spaces and gardens; green areas that are essential to the history of the city.They 'describe the city's development and design solutions from different eras and tell about Helsinki's garden and park culture and leisure activities' (City of Helsinki 2016, 166).Preserving 'nationally valuable landscapes' (n = 3) is a legal requirement in Finland, as stipulated by the Land Use and Building Act 132/1999 (Ministry of the Environment, Finland 1999).There are a couple of such landscapes within the city of Helsinki, including the agricultural landscape of Vantaanjoki river valley.
In the Helsinki-Uusimaa Regional Plan, one of the key objectives and planning principles concerning green environments emphasizes the diverse benefits they can provide: 'nurturing the values and coherence of the green structure and cultural environments by securing areas and connections that are significant for biodiversity, landscapes, cultural environments, natural resources and recreation' (Helsinki-Uusimaa Region 2020, 19).The regional plan's objectives for cultural landscapes (n = 15) are linked in terms of attractiveness, recreation and tourism but also of climate change mitigation and adaptation and biodiversity (Helsinki-Uusimaa Region 2020, 53, 156).Practicing traditional rural businesses in rural cultural landscape areas is recognized as a means to maintain the region's cultural landscape values (Helsinki-Uusimaa Region 2020, 163).
The regional plan recognizes the concept of nature conservation areas (n = 85) in the form of national parks and nature parks under the Natura2000 label, and these areas are marked accordingly as binding in the regional plan.The regional plan orders that measures may not be planned for an area designated as a nature conservation area that endanger or weaken the natural and environmental values on the basis of which the area has been formed as a protected area, or the aim of which is to establish one.(Helsinki-Uusimaa Region 2023, 21) In addition to this, cultural heritage and recreational opportunities, or even developing tourism potential (Helsinki-Uusimaa Region 2020, 143).
Whereas green fingers (vihersormet) are one of the most important concepts in the master plan, the concept does not occur at all in the regional plan.Instead, viherkehä (green ring, n = 55) is frequently mentioned in the regional plan.This non-binding concept of a green ring includes nature conservation and recreation areas, green connections, and cultural environments (Helsinki-Uusimaa Region 2020, 164), thus embracing a diversity of functions.It was included in the plan in order 'to underline its significance to residents' well-being and the image of the region' (Helsinki-Uusimaa Region 2020, 164).On the one hand, the objective of the green ring is to identify environmental values that support biodiversity, recreation and nature tourism.The brand value of the concept for local actors is also acknowledged (Helsinki-Uusimaa Region 2020, 166).On the other hand, the green ring aims at steering new construction projects within the existing infrastructure (Helsinki-Uusimaa Region 2020, 164).The spatial extent of the ring is shown by other markings in the plan; the concept of a green ring is not used on the map.
As with the green ring, the descriptive concept of green structure (n = 71) is indicated by other (legally binding) markings in the regional plan: nature conservation areas, green connections, recreation areas and 'areas dominated by forestry, which are large, uniform and significant from the point of view of the ecological network' (MLY-alue 5 ) (Helsinki-Uusimaa Region 2020, 131).At the regional level, the legally binding concept of preserving or creating viheryhteystarve (green connections, n = 86) requires specific consideration.In particular, the objective is to preserve or realize green connections 'in a way that secures movement possibilities for species, recreation and outdoor activities, and maintains landscape and nature values' (Helsinki-Uusimaa Region 2023, 21).Thus, multi-functionality is also recognized for this concept in regional planning.
Enhancing the provision of ES (n = 18) is one of the sub-objectives for 'responding to climate change and the sustainable use of nature and natural resources' in the regional plan (Helsinki-Uusimaa Region 2020, 16).In particular, the areas with the most potential to produce ES are specified.Objectives at the regional level cover mostly cultural ES, but there are also references to regulating ES in relation to nature conservation areas, and provisioning services such as food production and the management of groundwater (Helsinki-Uusimaa Region 2020, 148, 163, 186).Table 3 summarizes and compares the appearance and regulatory role of different green concepts used in the current master and regional plans for Oslo and Helsinki.

Discussion
The Oslo and Helsinki regions provide useful case studies for illustrating the evolving conceptualization of 'green', and the variety of green concepts and their roles in these regions -from the past to contemporary planning strategies and practices.Their current master and regional plans also recognize and demonstrate the importance of the multi-functionality and ecosystem services approaches (as part of the evolving idea of nature in planning approaches), while also providing an example of a regulatory/legislative framework for green.
Firstly, the findings confirm that both local and global debates around the idea of 'nature in the city' should be considered when exploring the conceptualization of green in urban and regional planning practices (Duvall et al. 2018).Some international approaches (e.g. the park systems of Olmsted, the garden city of Howard, green belt of London and fingers of Copenhagen) have influenced the development of green concepts and plans in the two regions to some extent (see Section 3) Some other well-known concepts, such as the green belt and the green heart, have not become popular in Norwegian or Finnish discourse -in fact, established words for these concepts do not even exist in those languages.The two cases shows that the use of green concepts in master and regional planning is linked to place-specific contexts (Healey 2012).Some concepts have been subjected to new interpretations and meanings.In Oslo, the concept of Marka has kept together the idea of 'nature as relief' (for recreational activities) and 'nature as boundary' (but indicating possibilities for expansion -see Figure 2).The use of the green fingers concept in Helsinki -which originally advocated the idea of 'nature as relief' -is different from the fingers in Copenhagen that refer to urban structures.The green fingers in Helsinki, on the other hand, are envisioned as linking with national parks (Figure 3).These concepts may not be equivalent to their counterparts in other planning contexts, but they have acquired a local meaning and enormous recognition within planning practices in the Oslo and Helsinki regions.
Secondly, the study show that today's use of green concepts demonstrates a more comprehensive understanding of the idea of nature (ranging from nature as relief to nature as infrastructure), as it includes both newer (e.g.multifunctionality and ES) and older concepts (e.g.green structure, recreational outdoor spaces and green fingers) which were introduced in early municipal and regional planning documents and have been retained (see Section 3).These threads form a sense of continuity in the planning domain, while also showing the evolution of ideas of nature in the field of urban development.Over the years, the green concepts of Oslo and Helsinki regions have embedded several well-known dimensions such as recreational and cultural activities (open spaces, parks and park trails in Oslo, and the cultural environment in Helsinki), as well as nature conservation, spatial and ecological connectivity, landscape and related concepts (agriculture, forestry, streams and natural values).More recently, the current Oslo and Helsinki master plans and regional plans have increasingly emphasized the multi-functionality framework of green spaces (influenced by the ecosystem services approach, both implicitly and explicitly).Other priorities are now emerging, such as climate adaptation, stormwater management, and air quality -which are being addressed by newer concepts (e.g.blue-green factors in Oslo) -and well-being (e.g.ES in Helsinki).The ES approach in Helsinki also supports the development of parks and new buildings.This demonstrates a strong recognition of the ability of urban green spaces to provide a variety of sociospatial and environmental benefits within a built environment (Hansen et al. 2019), as well as the ways in which multi-functionality is being operationalized through wellknown and newer green concepts.
Thirdly, the findings reveal that the use of some green concepts is -unsurprisingly -highly influenced by the institutionalized legal framework in each country.For example, the green structure in the city of Oslo, and nature conservation areas in Helsinki are binding concepts thus demonstrating a clear legal aspect in local planning practices (the Planning and Building Act of 2008 in Norway; and the Nature Conservation Act 1996 in Finland).Thus, it is not surprising that these terms have been retained in local planning documents, standards and practices.Other green concepts are used as a framework or approach, and it would require some time before they acquire legal status and local acknowledgement among planners and the public audience.In the meantime, they can still be used to envision future strategies and address upcoming challenges.
Further studies should consider other research methods, such as focus groups and interviews with several actors in order to reveal other planning discourses.It is also recommended to include the analysis of other planning materials, such as reports, impact assessments commissioned by planning authorities, council minutes, and decision documents.This would enable analysis of planning processes and decision-making phases between public authorities and developers.It would also yield further understanding of whether (and how) green concepts are embedded within negotiations and how they may influence sustainable urban transformation and planning discourses.

Conclusion
This study explored the evolving conceptualization of 'green' in two regions -Oslo and Helsinki -.It demonstrates the variety of green concepts which have been carried forward into contemporary planning, including the newer evolving concepts.The two cases show that the use of green concepts in master and regional planning is linked to place-specific contexts and regulatory practices.It is also connected, to some extent, to the wider international idea of nature in planning practices (from 'nature as relief' to 'nature as infrastructure') The study demonstrates a clear and increasing emphasis on the multi-functionality framework in the plans analysed, due certainly to the influence of ecosystem services approaches and ideas.The master and regional plans follow the regulatory framework for those green concepts which are binding, and therefore newer concepts (such as the blue-green factor and ES) remain as guidelines or approaches to be explored.
The study contributes to understanding today's use of green concepts, which should include both newer and older concepts (namely those introduced in earlier plans).This provides a sense of continuity in the planning process, while also displaying the evolving ideas of nature in cities.We need to think critically about advancing only a particular interpretation of nature (as might be suggested by other scholars) or adopting newer green concepts without a clear understanding of the conceptualization of green in precedent plans.Nevertheless, future studies should also focus on integrating newer green concepts into strategies and norms in order to address new challenges, such as flash floods, heatwaves and other effects of climate change.

Notes
1. GI is defined as an interconnected network of natural, semi-natural (e.g., waterways, wetlands, woodlands, greenways, parks and conservation areas), and artificial features (e.g.green roofs and green facades) (Hansen et al. 2019).2. See also Hautamäki (2022) for the case of Helsinki, in which the framework of Duvall et al. (2018) was used to analyse nature and related concepts.3. Vestmarka is the municipalities of Baerum, Lier and Asker (in the south-western part of the Oslo region).4. LNF covers agriculture and forestry areas, nature and outdoor recreational areas.These three elements are regulated within a unique land-use category.5.The MLY are forest areas with significant role for the ecological network.

Figure 1 .
Figure 1.The evolution of ideas about nature in planning discourses.Source: adapted from Duvall et al. (2018).

Figure 2 .
Figure 2. The green structure in Oslo (data extracted from the Byplankontoret, City of Oslo 1960, 38; and Oslo Kommune 2015) (Images annotated by the authors).

Figure 3 .
Figure 3.The green fingers in Helsinki (data extracted from the City of Helsinki, master plan 2016).(Images annotated by the authors).

Figure 4 .
Figure 4. Green concepts used in the master and/or regional plans of Oslo.

Figure 6 .
Figure6.The frequency of green concepts that are common in the master and/or regional plans of both Oslo and Helsinki.

Table 1 .
Geographical information on the two regions (Official Statistics of Finland 2022; Statistics, Norway 2022).

Table 2 .
Oslo and Helsinki planning documents selected for this study.