Key Enablers of and Barriers to the Uptake and Implementation of Nature-Based Solutions in Urban Settings: A Review

Abstract

Climate change and urbanization have resulted in several societal challenges for urban areas. Nature-based solutions (NBS) have been positioned as solutions for enhancing urban resilience in the face of these challenges. However, the body of conceptual and practical knowledge regarding NBS remains fragmented. This study addresses this gap by means of a systematic review of the literature, to define NBS as a theoretical concept; its broader significance with respect to societal challenges; the key stakeholders in NBS planning, implementation and management; and major barriers to and enablers of NBS uptake. The results of this review reveal that, despite a lack of consensus about the definition of NBS, there is a shared understanding that the NBS concept encompasses human and ecological benefits beyond the core objective of ecosystem conservation, restoration or enhancement. Significant barriers to and enablers of NBS are discussed, along with a proposed strategic planning framework for successful uptake of NBS.

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Review
Key Enablers of and Barriers to the Uptake and
Implementation of Nature-Based Solutions in Urban
Settings: A Review
Shahryar Ershad Sarabi 1, * , Qi Han 1, A. Georges L. Romme 2, Bauke de Vries 1and
Laura Wendling 3
1
Information Systems in the Built Environment (ISBE) group, Department of Built Environment, Eindhoven
University of Technology, 5612 AZ Eindhoven, The Netherlands
2
School of Industrial Engineering, Eindhoven University of Technology, 5612 AZ Eindhoven, The Netherlands
3VTT Technical Research Centre Ltd., 02150 Espoo, Finland
*Correspondence: s.ershad.sarabi@tue.nl; Tel.: +31-402-475-403
Received: 3 June 2019; Accepted: 29 June 2019; Published: 30 June 2019


Abstract:
Climate change and urbanization have resulted in several societal challenges for urban areas.
Nature-based solutions (NBS) have been positioned as solutions for enhancing urban resilience in the
face of these challenges. However, the body of conceptual and practical knowledge regarding NBS
remains fragmented. This study addresses this gap by means of a systematic review of the literature,
to define NBS as a theoretical concept; its broader significance with respect to societal challenges;
the key stakeholders in NBS planning, implementation and management; and major barriers to and
enablers of NBS uptake. The results of this review reveal that, despite a lack of consensus about the
definition of NBS, there is a shared understanding that the NBS concept encompasses human and
ecological benefits beyond the core objective of ecosystem conservation, restoration or enhancement.
Significant barriers to and enablers of NBS are discussed, along with a proposed strategic planning
framework for successful uptake of NBS.
Keywords: NBS; nature-based solutions; systematic review; barriers; enablers; strategic planning
1. Introduction
Climate change already significantly affects urban ecosystems [
1
] and this impact is expected
to increase in the future [
2
]. In addition to climate change, rapid urbanization has accelerated the
degradation of urban ecosystems via increases in the size and density of built areas, consumption of
natural resources, and habitat loss [
3
,
4
]. The majority of the world’s population lives in urban areas
and significant further urbanization is anticipated in the next two decades [
5
]. By 2050, an estimated
66% of the world’s population will reside in cities [
6
]. Conversely, urbanization is a multifaceted
process that yields efficiency in the usage of space, promotes economic development, and facilitates
technological innovation [3].
In the last few decades, several ecosystem-based approaches have been devised to re-nature
urban areas, in an effort to enhance the resilience of urban systems [
4
]. The concept of nature-based
solutions (NBS) is one of the more recent concepts proposed for this purpose. NBS harness natural
capital to deliver ecosystem services, along with a range of other benefits, which serve to address
key social, environmental, and economic challenges [
7
]. The initial focus of the NBS concept was on
enhancing resilience in the context of climate change [
8
], but the broader potential for NBS to address
socioeconomic challenges along with environmental issues has been increasingly recognized [7].
While NBS have been conceived as practical solutions for urban resilience [
7
], the uptake of the
concept has been limited to date. In this respect, the NBS concept remains unclear both conceptually
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and practically, which fuels the idea that NBS may simply be another ‘buzzword’ that is easily
misused [
8
,
9
]. The present review aims to map what is known about barriers to and enablers of the
uptake and implementation of NBS in urban environments. To address the ambiguous nature of the
NBS concept, we undertook an analysis of the existing literature on NBS, to help clarify the overarching
concept of NBS as well as to identify the key barriers to and enablers of successful NBS uptake. As
such, this review study contributes to building a body of knowledge on NBS, which should enable
city administrators, policy makers, startups that offer NBS solutions, and many other stakeholders
to overcome key barriers to the adoption and implementation of NBS. Moreover, considering the
findings of the review, a strategic planning framework will be developed to support the uptake and
implementation of NBS.
2. Materials and Methods
A systematic literature review was conducted to provide an overview of research to date related
to the uptake of NBS. A search for publications addressing NBS as a theoretical concept, as well as
NBS adoption, management, planning and implementation, was conducted in March 2019 using the
Scopus search engine. Scopus was selected due to its broader coverage compared to other academic
search engines [
10
]. The term “nature-based solutions” was used to search the “title”, “keyword”, and
“abstract” fields of the indexed literature. The initial search yielded a total of 250 publications.
In the second step, the abstract and introduction sections were read and papers entirely focused on
technical and physical dimensions of NBS (e.g., biophysical studies) were eliminated from the sample.
This step served to reduce the number of reviewed publications to 68 (see also Figure 1). Additional
screening of the entire text of these publications was undertaken to identify those that were relevant
for our research questions regarding the barriers to and enablers of NBS. As a result, a final dataset of
41 publications was obtained.
The selected papers were all published between 2015 and 2019, which underlines that NBS are a
relatively young concept. In the final set of studies, 22 papers were empirical. Out of 41 papers, 32
were published in academic journals and 9 are chapters in books. Geographically, 23 studies address
(some part of) the EU context, 15 studies are global in nature, one study is conducted in Asia, one in
the US and another one in Australia.
The primary goal of the analysis was to map the diversity in conceptualizations and to explore
which specific issues are studied more or less. We analyzed the papers qualitatively by full text
analysis to identify how the authors have conceptualized NBS, objectives of NBS, key stakeholders in
developing NBS, and the barriers and enablers for implementation and uptake of NBS (see Figure 1).
We provided categories for these different dimensions and queried the set of publications based on
these categories. To ensure the consistency of the data extraction and analysis we developed a data
extraction spreadsheet (see Supplementary Materials).

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Figure 1. representation of the review process.
3. Results
In this section, the main results are described, starting with the fundamentals of the NBS concept.
Subsequently, relevant actors and the barriers to and enablers of NBS are identified.
3.1. Fundamentals of the Nature-Based Solutions Concept
As a relatively new concept, NBS is not yet clearly defined and thus there is a lack of
understanding regarding what NBS are and are not; this increases the risk that the concept is misused
[9]. In addition, questions can be raised regarding the necessity of the concept, its added values in
comparison to alternative approaches, and the applicability of NBS to specific objectives. In this
section, current definitions and typologies of NBS are first discussed, and then the necessity of the
concept is investigated by exploring the added values and various objectives of implementing NBS.
3.1.1. NBS: What does it mean?
Various definitions have been proposed for NBS. Table 1 provides several examples, and thus
illustrates that the definitions used tend to differ significantly, both in content and in the jargon used.
There are two definitions that are often cited and may thus serve as key reference points. These
definitions were proposed earlier by the International Union for the Conservation of Nature (IUCN)
[11] and the European Commission (EC) [7], respectively. These two broad definitions, reproduced in
the last two rows of Table 1, are both formulated to embrace a variety of approaches and
interventions. IUCN’s definition [11] emphasizes the importance of nature conservation and
restoration, whereas the EC [7] has a broader perspective and simultaneously considers the three
pillars of sustainability [12,13].
Table 1. Definitions proposed for NBS.
NBS are…
Reference
“any transition to a use of ecosystem services with decreased input of non-
renewable natural capital and increased investment in renewable natural
processes.”
Maes and
Jacobs [14], p.
123
“multifunctional green interventions delivering upon the social, economic
and environmental pillars of sustainable development.”
van der Jagt et
al. [15], p. 265
Figure 1. Representation of the review process.
3. Results
In this section, the main results are described, starting with the fundamentals of the NBS concept.
Subsequently, relevant actors and the barriers to and enablers of NBS are identified.
3.1. Fundamentals of the Nature-Based Solutions Concept
As a relatively new concept, NBS is not yet clearly defined and thus there is a lack of understanding
regarding what NBS are and are not; this increases the risk that the concept is misused [
9
]. In addition,
questions can be raised regarding the necessity of the concept, its added values in comparison to
alternative approaches, and the applicability of NBS to specific objectives. In this section, current
definitions and typologies of NBS are first discussed, and then the necessity of the concept is investigated
by exploring the added values and various objectives of implementing NBS.
3.1.1. NBS: What does it mean?
Various definitions have been proposed for NBS. Table 1provides several examples, and thus
illustrates that the definitions used tend to differ significantly, both in content and in the jargon used.
There are two definitions that are often cited and may thus serve as key reference points. These
definitions were proposed earlier by the International Union for the Conservation of Nature (IUCN) [
11
]
and the European Commission (EC) [7], respectively. These two broad definitions, reproduced in the
last two rows of Table 1, are both formulated to embrace a variety of approaches and interventions.
IUCN’s definition [
11
] emphasizes the importance of nature conservation and restoration, whereas the
EC [
7
] has a broader perspective and simultaneously considers the three pillars of sustainability [
12
,
13
].
Table 1. Definitions proposed for NBS.
NBS are . . . Reference
“any transition to a use of ecosystem services with decreased input of
non-renewable natural capital and increased investment in renewable
natural processes.” Maes and Jacobs [14], p. 123
“multifunctional green interventions delivering upon the social,
economic and environmental pillars of sustainable development.” van der Jagt et al. [15], p. 265

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Table 1. Cont.
NBS are . . . Reference
“soft engineering approaches that are aimed at increasing the resilience
of territories and societies affected by meteorological events and
therefore reducing the economic, functional, cultural, and social damage
disruption that such events cause.”
Short et al. [16], p. 242
“actions that alleviate a well-defined societal challenge
(challenge-orientation), employ ecosystem processes of spatial, blue and
green infrastructure networks (ecosystem processes utilization), and are
embedded within viable governance or business models for
implementation (practical viability).”
Albert et al. [12], p. 12
“conscious use of nature to help urban inhabitants address various
environmental, social and economic challenges.” Kronenberg et al. [17], p. 295
“actions to protect, sustainably manage and restore natural or modified
ecosystems that address societal challenges effectively and adaptively,
simultaneously providing human well-being and biodiversity benefits.”
Cohen-Shacham et al. [11], p. 2
“Nature-based solutions are actions inspired by, supported by or copied
from nature and which aim to help societies address a variety of
environmental, social and economic challenges in sustainable ways.” EC [7], p.5
To clarify which perspective is more common, we classified the publications reviewed into two
groups in Table 2. The first group of publications conceptualizes NBS as actions that are designed
to conserve and restore nature, placing biodiversity at the heart of the NBS concept (in line with
IUCN’s definition), whilst the second group of publications conceptualize NBS as actions designed to
address environmental, social and economic challenges simultaneously by maximizing generation of
ecosystem services (the definition from the EC). Table 2shows that nine studies are in line with the
former definition and 27 were based on the latter definition. The other publications did not exhibit an
explicit inclination toward one of the two viewpoints.
Table 2. Groups for defining NBS.
NBS as . . . Focus Number of Papers References
Solutions to major societal challenges
while improving natural capital and
biodiversity
Nature conservation and
restoration 9 [16,18–25]
Solutions which meet environmental,
economic and social objectives
simultaneously
Sustainable development
27 [8,12–15,17,26–46]
The result of this analysis shows that the sustainability perspective is more common among the
reviewed publications. In other words, NBS are more often considered as solutions that provide
benefits to the environment and humans simultaneously rather than focusing on nature conservation
and restoration. This result is aligned with the views of Nesshöver et al. [
13
] who suggest that
NBS do not inherently conserve nature or enhance the biodiversity, and that the specific aim of NBS
development should be explicitly recognized in NBS projects. This is important as the provision of
ecosystem services is not always positively correlated with biodiversity enhancement outcomes [8].
Another way to map the territory of NBS is to cluster solutions based on the level of ecosystem
intervention, drawing on the typology proposed by Eggermont et al. [
9
]. These authors identified three
types of NBS: Type 1 are NBS with minimal or no interventions including protection and conservation,
urban planning and monitoring strategies; type 2 are management approaches to develop sustainable
ecosystems and optimize the generation of chosen ecosystem services, like integrated water resource
management plans or installation of apiaries, and; type 3 include highly intensive management
approaches, including those aiming at the creation of entirely new ecosystems, which constitutes the

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most visible type of solution in the area of NBS. We analyzed the set of publications to assess which
type of NBS was referenced and used in each publication. Table 3shows which studies refer to one of
the three types defined above or to multiple types.
Table 3. Types of NBS.
Types of NBS Number of Articles References
Type 3 19 [15,17,23,25–30,32–34,38,40,43,44,47,48]
Type 2 3 [16,35,36]
Type 1 2 [18,20]
Multiple types 11 [9,12,13,19,22,24,31,37,41,46,49]
Table 3points out that type 3 of NBS, characterized by a high level of managerial intervention,
has received most attention in the literature. In fact, actions involving less managerial interventions
were only rarely identified as NBS (see type 1 and 2 in Table 3). In addition, publications that address
multiple types of NBS primarily deal with types 2 and 3. The focus of the reviewed literature on
type 3 and to a lesser extent type 2, implies a greater alignment with the three-pillar sustainability
perspective underpinning the EC’s definition of NBS [
9
]. However, this focus in the publications
reviewed may result from a reporting bias; for instance, type 1 of NBS is possibly reported less in
scientific publications than in popular publications or on social media.
The EC’s phrase “actions inspired by, supported by or copied from nature”, a key element of
their NBS definition [
7
], has added to the confusion. Krauze and Wagner [
37
] attempted to clarify
this phrase from the perspective of ecohydrology, by describing the notion of ‘mimicking nature’ as
“introducing biophysical structures into blue-green infrastructure and urban-green infrastructure”, and
‘manipulating nature’ as the “introduction of agents external to the indigenous system”. In addition,
Krauze and Wagner [
37
] classified NBS based on city management zones. According to this framework,
the role of NBS changes from preserving nature to enabling nature as the location of NBS moves from
outer parts of the cities toward the city center. By combining the NBS typology of Eggermont et al. [
9
]
with Krauze and Wagner’s [
37
] framework, one can argue that the shift from type 1 to type 3 of NBS
converges with a decreasing emphasis on the ‘natural’ character of the urban environment and an
increasing emphasis on the proximity of NBS to the city center (Figure 2). This is not to say that type 1
NBS cannot be found in the inner parts of a city, but the general pattern observed is that the level of
managerial intervention required in NBS increases when moving (closer) to the center of an urban area.
Figure 2illustrates the change in perspective of NBS from nature-oriented to a sustainability orientation.
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Table 3. Types of NBS.
Types of NBS
Number of Articles
References
Type 3
19
[15,17,23,25–30,32–34,38,40,43,44,47,48]
Type 2
3
[16,35,36]
Type 1
2
[18,20]
Multiple types
11
[9,12,13,19,22,24,31,37,41,46,49]
Table 3 points out that type 3 of NBS, characterized by a high level of managerial intervention,
has received most attention in the literature. In fact, actions involving less managerial interventions
were only rarely identified as NBS (see type 1 and 2 in Table 3). In addition, publications that address
multiple types of NBS primarily deal with types 2 and 3. The focus of the reviewed literature on type
3 and to a lesser extent type 2, implies a greater alignment with the three-pillar sustainability
perspective underpinning the EC’s definition of NBS [9]. However, this focus in the publications
reviewed may result from a reporting bias; for instance, type 1 of NBS is possibly reported less in
scientific publications than in popular publications or on social media.
The EC’s phrase “actions inspired by, supported by or copied from nature”, a key element of
their NBS definition [7], has added to the confusion. Krauze and Wagner [37] attempted to clarify
this phrase from the perspective of ecohydrology, by describing the notion of ‘mimicking nature’ as
“introducing biophysical structures into blue-green infrastructure and urban-green infrastructure”,
and ‘manipulating nature’ as the “introduction of agents external to the indigenous system”. In
addition, Krauze and Wagner [37] classified NBS based on city management zones. According to this
framework, the role of NBS changes from preserving nature to enabling nature as the location of NBS
moves from outer parts of the cities toward the city center. By combining the NBS typology of
Eggermont et al. [9] with Krauze and Wagner’s [37] framework, one can argue that the shift from
type 1 to type 3 of NBS converges with a decreasing emphasis on the ‘natural’ character of the urban
environment and an increasing emphasis on the proximity of NBS to the city center (Figure 2). This
is not to say that type 1 NBS cannot be found in the inner parts of a city, but the general pattern
observed is that the level of managerial intervention required in NBS increases when moving (closer)
to the center of an urban area. Figure 2 illustrates the change in perspective of NBS from nature-
oriented to a sustainability orientation.
Figure 2. Schematic representation of range of NBS (Type1: NBS to improve use or protection of
natural ecosystems, Type2: NBS to improve managed ecosystem sustainability or function, Type3:
Design and management of newly-created ecosystems); adapted from [9] and [37].
In the reviewed publications, in particular those referring to type 3 NBS, other terms such as
blue-green infrastructure and ecological engineering, were occasionally used interchangeably with
NBS. This highlights the need to more explicitly characterize how NBS and the processes through
Figure 2.
Schematic representation of range of NBS (Type1: NBS to improve use or protection of natural
ecosystems, Type2: NBS to improve managed ecosystem sustainability or function, Type3: Design and
management of newly-created ecosystems); adapted from [9] and [37].

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In the reviewed publications, in particular those referring to type 3 NBS, other terms such as
blue-green infrastructure and ecological engineering, were occasionally used interchangeably with
NBS. This highlights the need to more explicitly characterize how NBS and the processes through
which they are created, implemented and managed, differ from other theoretical concepts or actions
designed to achieve similar socioecological objectives.
3.1.2. Why are NBS Important? What are the Objectives for Developing NBS?
Nature-based solutions are gaining increasing attention from scientists and practitioners as
potential solutions to enhance ecological, social and economic urban resilience [
13
,
48
]. The multiple
co-benefits of NBS support increasing resilience of urban socioecological systems through the creation
and enhancement of the system’s capacity to accommodate and adapt to disturbances such as
flooding, heatwaves, coastal erosion, etc. [
48
]. While, renaturing urban areas to enhance urban
ecological resilience and sustainability is not a new concept [
21
], there are specific factors that make
NBS an innovative concept. For instance, Pauleit et al. [
21
] introduced NBS as a multidisciplinary
umbrella concept that combines the lessons learned from previous ecosystem-based approaches, and
Nesshöver et al. [
13
] emphasized the transdisciplinary nature of the NBS concept. As discussed in
both studies, NBS not only combine different bodies of knowledge, but also incorporate knowledge
of actors from multiple levels, especially citizens who have context-based knowledge. Davies and
Lafortezza [
45
] mentioned the focus of NBS on applicability of solutions as an important added value.
Overall, cross-sectoral multifunctionality is the main factor that makes NBS interesting for stakeholders
and a strong investment option for sustainable urban development [8,9,13,15,27,36].
Based on an analysis of 20 case studies in European cities, Raymond et al. [
27
] proposed ten
challenge areas to which NBS can contribute. These challenge areas are: climate change mitigation
and adaptation; water management; coastal resilience; green space management; air quality; urban
regeneration; participatory planning and governance; social justice and social cohesion; public health
and well-being; and economic opportunities and green jobs. An analysis of the empirical studies (i.e.,
22 of the 40 publications) serves to identify which challenges have been addressed in the literature (see
Table 4).
Table 4. Objectives for developing NBS.
Objectives Number of Papers References
Climate Change Mitigation and Adaptation
10 [12,17,20,24,26,35,38,41,43,50]
Water Management 14 [12,16–18,20,22–24,26,29,38,39,41,50]
Coastal Resilience 2 [18,23]
Green Space Management 7 [15,20,34,35,43,44,49]
Air Quality 4 [17,38,46,49]
Urban Regeneration 8 [15,24,26,31,35,44,46,49]
Participatory Planning and Governance 8 [15,16,26,31,35,39,46,49]
Social Justice and Social Cohesion 9 [15,16,26,31,35,39,43,46,49]
Public Health and Well-being 10 [15,17,26,29,31,34,35,39,43,49,51]
Economic Opportunities and Green Jobs 5 [15,16,20,29,43]
Among the biophysical challenges identified by Raymond et al. [
27
], the NBS literature focuses
primarily on water management and enhancing water resilience. In this area, the role of NBS is mainly
to improve connectivity of the water cycle, increase water retention and infiltration, and manage
surface run-off. The contribution of NBS to climate change adaptation and carbon sequestration is
also cited frequently. Moreover, our analysis reveals considerable attention to the socioeconomic
benefits of NBS. Several of the reviewed publications provide evidence for the potential of NBS to bring

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stakeholders together and initiate social innovations [
15
,
24
,
35
,
46
]. In particular, NBS have been noted to
be highly effective in enhancing ecosystem stewardship and sense of place among affected populations,
especially vulnerable people and low-income groups who are typically under-represented [
26
]. This
benefit is especially acknowledged in relation to urban gardens and urban agricultural areas, where
citizens directly participate in the management, maintenance and monitoring of NBS [
15
,
35
,
36
,
49
]. The
role of NBS in providing health and well-being benefits such as improved mental health, e.g., [
51
],
and encouraging healthy and dynamic life styles, e.g., [
39
] were also emphasized in the reviewed
publications. While the EC [
7
] maintains a particular focus on the potential of NBS to create job
opportunities, this benefit is hardly or not considered in any of the reviewed studies. The economic
benefits of NBS are typically limited to the cost effectiveness of specific solutions, e.g., [
29
] and the
job creation potential of NBS is only explicitly articulated in the context of urban agriculture [
15
,
36
].
Notably, the results of this analysis might possibly have been more in favor of biophysical challenge
areas, if we would have included studies drawing on a more technical perspective. Nonetheless, our
review clearly shows that the concept of NBS emphasizes the importance of enhancing both social and
ecological resilience in urban areas.
In sum, by mapping the concept and objectives of NBS, this section served to clarify that the
scope of NBS goes beyond nature conservation, and the NBS concept equally emphasizes its potential
benefits to social and ecological resilience. In the next section, the NBS concept is discussed from a
more practical perspective.
3.2. Nature-Based Solutions in Action
In this section, we analyze the key actors in developing NBS, and explore the barriers and enablers
of NBS identified in the selected papers.
3.2.1. Who are the Key Actors?
Review of the selected NBS literature identified four levels of actors relevant for NBS development
(Table 5). Micro-level actors include citizens, landowners, business owners, citizen groups, and
non-governmental organizations (NGOs). Meso-level actors work at the city level, and include
municipal departments, water boards and similar local actors. The macro-level actors work at regional,
national and international levels, and include regional and national authorities, and international
organizations. Transboundary actors transcend these geographical levels and organizational
boundaries, by fostering relationships and networks among producers and users of NBS.
Table 5. Stakeholders in NBS development.
Actors Number of Papers References
Micro 28 [8,13,15–17,20,22,24,26–36,40,44–46,48–50,52]
Meso (city level) 27 [8,13,15–17,20,22,24,26–29,31–36,40,43–46,48–50,52]
Macro (regional, national or international)
12 [14–17,20,23,28,33,36,40,43,52]
Transboundary 7 [15–17,26,31,45,50]
Meso-level and micro-level actors are the most recognized groups in the reviewed literature and
are typically identified as the key actors for uptake and implementation of NBS. Micro-level actors
constitute the most diverse category of actors and are the primary beneficiaries of NBS [
36
]. The role of
this group also varies in different cases from end-users with little decision-making power (top-down
management) to the initiators of NBS innovations with genuine power to make decisions (bottom-up
management) [
26
,
31
]. Micro-level actors are core to the NBS concept and contribute essential contextual
knowledge and experience to management actions. This group of actors are usually active in the
level of parcels or single NBS elements e.g., [
15
,
26
], with short-term goals and actions [
8
]. The role
of meso-level actors (municipal departments) can vary in different contexts from initiators of NBS

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e.g., [
35
], to monitoring, supervisory, and supportive roles e.g., [
15
]. This group of actors are identified
as critical mainly due to their role in providing the required institutional context and providing land
and financial support for development of NBS e.g., [
26
]. The benefits that this group receives from
NBS include improving the image of the city and increasing municipal income e.g., [
44
]. This group of
actors are active at the city scale and are characterized with longer-term perspectives in comparison to
the micro-level actors. Among macro-level actors, the role of the EC is emphasized [
33
,
36
], especially
for providing incentives to accelerate the transition toward NBS e.g., [
17
], along with a framework
for NBS demonstration and knowledge exchange [
33
]. National and regional level actors are also
mentioned as effective stakeholders, particularly through provision of an appropriate institutional
context [23,28,43].
An important group of actors whose role is emphasized in the literature reviewed are transboundary
actors, also known as change agents or knowledge brokers. These actors are important as their actions
diffuse knowledge of NBS among multiple stakeholders and facilitate mainstreaming the concept into
urban planning practices, by engaging disparate groups to form networks centered on NBS [
16
,
45
].
Depending on the context, different actors can play this role. For example, NGOs and scientists
functioned as transboundary actors in a Polish green roof initiative [
17
], whereas a project officer,
appointed by the local district council, played this role in the case of a NBS project focused on flood
management in the UK [
16
]. Frantzeskaki et al. [
31
] argued that the role of transboundary actors is
central to NBS innovation diffusion.
3.2.2. Barriers to Successful Development of NBS
We analyzed the reviewed NBS literature to recognize the barriers mentioned for successful
implementation and uptake of NBS. Six major barriers were identified. The results are presented in
Table 6.
Table 6. Barriers to successful development and uptake of NBS.
Barriers Number of Papers References
Inadequate financial resources * 9 [22,24,27,31,32,34,36,39,40]
Path dependency * 7 [8,17,31,40,43,45,50]
Institutional fragmentation * 6 [8,22,31,34,50,52]
Inadequate regulations * 6 [17,20,22,36,40,52]
Uncertainty regarding
implementation process and
effectiveness of the solutions *** 18 [8,9,12,13,15–18,20,22–25,27,28,31,32,35,
37,39–41,52]
Limited land and time availability **
7 [12,23,27,31,36,37,52]
*=socio-institutional barriers, *** =hybrid barriers (both socio-institutional and biophysical), and ** =
biophysical barriers.
Inadequate financial resources can be a significant barrier to NBS implementation. Specific
funding opportunities to facilitate the implementation of NBS are limited. In addition, many of the
co-benefits associated with NBS can be realized only in the long-term whereas funding schemes tend
to be short-term in nature [
31
]. Municipalities have limited resources, and autonomy in deciding
how to allocate the expenditures [
32
]. Sole reliance on governmental and municipal resources to
finance solutions places a great deal of pressure on these institutions and highlights the critical need
for additional exploration of economic opportunities related to NBS in order to encourage private
investment [24].
The other identified barrier to uptake and implementation of NBS is the so-called ‘path dependency’
of organizational decision making, which confines decision makers by their active memory based
on past experiences and often leads to resistance to change [
45
]. This barrier can be linked to what
Kabisch et al. [
8
] referred to as the ‘paradigm of growth’. Urban stakeholders are accustomed to using

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gray infrastructure for addressing challenges and enhancing the built-up areas for the purpose of
economic growth. Changing the mindset of stakeholders toward NBS can be a difficult process, and
breaking the ‘path dependence’ requires changing individual and societal behavior [43].
Institutional fragmentation (‘sectoral silos’) is another important barrier mentioned in the literature.
Different departments usually work in line with their own vision, legal frameworks and procedures,
and use their own sectoral language [
31
]. Different responsibilities distributed among multiple agencies
and departments are a barrier for the production of benefits from NBS, and limit the opportunities
for incorporating novelty in the NBS planning and management process [
52
]. The split among
responsibilities can cause confusion about who is the owner, and who should operate and maintain the
NBS in the long-term [50].
Regulations supporting NBS implementation are scattered [
52
]. In general, the prevailing
regulations have been developed from gray infrastructures as the main, or only available, option to
address given challenges. In other cases, the principle of ecosystem protection may not underpin
regulations, or legislation may not encompass all environmental components, as is the case in
China where farm ponds are not covered in the environmental regulations [
20
]. On occasion, even
when appropriate regulations and policies exist, a lack of law enforcement can limit the uptake of
solutions [22].
Lack of information, or the uncertainty regarding NBS implementation processes and benefits, is
frequently mentioned in the literature as a critical barrier limiting the uptake of NBS by decision makers.
As innovations dealing with complex social-ecological systems, NBS are characterized by multiple
uncertainties [
8
]. The lack of comprehensive information regarding the creation, implementation and
management of NBS as well as the dearth of evidence regarding NBS effectiveness across widespread
spatial and temporal scales may lead to a great deal of uncertainty, particularly among the public [
37
],
or even invoke conflict among actors [
22
,
35
]. The body of knowledge regarding NBS has remained
largely academic [
52
], with limited diffusion which has negatively affected the level of acceptance of
NBS by the public [16,22].
Limited space (land) and time are additional barriers mentioned in the reviewed literature.
In general, NBS require more land and time to provide the expected benefits than conventional
gray infrastructure approaches [
23
]. Limited available space, especially in urban areas, can restrict
development of NBS. This barrier is particularly apparent in the inner parts of the city where land is a
scarce and expensive resource [
37
]. In many cases, the benefits of NBS may be fully realized only in the
long-term, limiting their acceptance to local level actors with shorter-term agendas. The successful
implementation of NBS requires long-term collaborative efforts among multiple stakeholders [
12
], thus
there is a need to view NBS and the benefits delivered from a longer-term perspective.
3.2.3. Enablers for Successful Development of NBS
Previously we have discussed the multiple functions that NBS provides and the barriers for
developing these solutions. However, to realize the multifunctionality of NBS and to address the
barriers, various approaches, mechanisms, or actions can be adopted. Several enablers have been
mentioned in the reviewed literature (Table 7).
Table 7. Enablers for successful implementation of NBS.
Enablers Number of Papers References
Partnership among stakeholders * 27 [8,9,12,13,15–17,19,20,22,24,26–28,30–
36,43,45,46,48–50]
Knowledge sharing mechanisms and
technologies * 9 [8,13,20,23,27,33,35,43,45]
Economic instruments * 9 [14,15,32,33,36,39,40,44,52]
Plans, acts and legislations * 9 [15,20,28,35,36,43–45,49]

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Table 7. Cont.
Enablers Number of Papers References
Education and training * 8 [16,20,27,31,36,43,45,50]
Effective monitoring and Valuation
systems for implementation process and
benefit *** 16 [8,9,12–14,16,19,20,26–29,32–34,42]
Open innovation and Experimentation ***
5 [15,16,26,31,34]
Combining NBS with other urban
elements and gray infrastructures ** 8 [12,22,23,27,28,37,43,45]
Appropriate planning and design ** 5 [26,30,34,37,48]
*=socio-institutional enablers, *** =hybrid enablers (both socio-institutional and biophysical), and ** =
biophysical enablers.
The most frequently identified socio-institutional enabler is the partnership among stakeholders
and organizations from multiple levels (vertical cooperation) as well as from the same level (horizontal
cooperation). NBS are designed to deal with challenges that are affected by or affect multiple
stakeholders, and partnerships are required to ensure the generation of multiple benefits [
15
].
Nesshöver et al. [
13
] identified three specific benefits that partnerships with stakeholders can bring to
the NBS development process: 1) ‘Substantive’ benefits by providing local perspectives and improving
the planning; 2) ‘instrumental’ benefits to bring support for the plan, and; 3) ‘normative’ benefits by
increasing the legitimacy of the process. Through face-to-face partnerships, stakeholders can generate
shared visions of and understanding of the solutions and nature [
16
], while open dialogue can foster
greater acceptance of NBS, and break the ‘path dependence’ [22].
Partnerships with local actors especially community groups can encourage trust, while facilitating
ecosystem stewardship and social learning as critical factors for socioecological resilience [
24
,
35
].
Citizens can empower the NBS planning and management process by their local knowledge and
catalyze the “tailoring to local context” of NBS, which substantially increases the likelihood of a
successful outcome [
31
]. Several successful examples of partnerships with NGOs can be found
among papers. For instance, a partnership between an NGO and municipality led to development
of the first community garden in Szeged [
15
]. The private sector can also bring substantial benefits,
mainly due to limited technical and financial resources of municipalities [
32
]. The private sector
can offer essential support to the NBS implementation process by sharing experience during project
implementation as well as through the contribution of financial resources. Public-private partnerships
(PPP) are encouraged as they combine the top-down regulation of the government sector with the
flexibility of the private sector [
24
]. Partnerships between businesses and other urban stakeholders
is key to showcase the potential and value of NBS for economic prosperity and human well-being.
Partnerships and collaborations should also form among departments and institutions. Support of
a single department that derives benefits from NBS implementation and is directly responsible for
developing the solutions is insufficient in the long term. In particular, due to the multidisciplinary
nature of NBS multiple departments that receive benefits from the NBS should be involved in the
projects [
32
]. Frantzeskaki [
26
] emphasized an inclusive narrative of the mission for NBS to bridge the
knowledge across different city departments.
There are different approaches mentioned to facilitate partnership among stakeholders. As
van Ham and Klimmek [
24
] mention, the key to successful partnerships is developing a shared
understanding of NBS and their benefits. Using place-based approaches to engage the local actors [
35
],
or any initiative similar to the Million Trees NYC project in New York [
43
], serves to generate a
shared understanding. The role of the transboundary actors in providing this shared understanding is
important, as they can speak the language of different groups and connect them with one another [
31
].
The level of partnership varies in different cases and contexts with different property types [
46
].
There are cases like communal gardens, characterized by self-governance, where micro-level actors

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(e.g., citizens, gardeners, etc.) manage the ecosystem, and the role of the municipality is mentioned
as the provider of land and the required institutional context [
15
]. In contrast, in cases of allotment
gardens the green areas have been developed using a more top-down form of governance [
46
]. NBS
with relatively more inclusive systems of property management, including engagement of varied
groups of people, is believed to facilitate social learning and generation of ecosystem stewardship [
46
].
Knowledge sharing mechanisms and technologies are also identified as important enablers for
NBS development. These technologies in urban areas are typically used for sharing ideas, getting
feedback or mapping NBS issues. They enable the involvement of bigger groups of stakeholders
and are faster and cheaper than physical partnerships. For instance, using e-governance, the city of
Melbourne has supported successful implementation of place-making strategies through effective
incorporation of citizens’ knowledge in the planning process [
35
], or in the case of Tempelhof park in
Berlin where consultation through an online platform served to engage 68,000 users and around 2500
idea contributors participated in the planning process [24].
Sharing experiences and lessons learned among different contexts using knowledge sharing
technologies has also been mentioned as an enabler. For instance, knowledge repositories like
Oppla (http://oppla.eu/) and ThinkNature (https://think-nature.eu/) or the Natural Infrastructure
for Business platform (https://naturalinfrastructureforbusiness.org/) are instrumental in sharing
experiences and best practices in implementing NBS [
33
], which in turn may promote investments in
natural infrastructure [24].
In several cases, the use of economic instruments and incentives has been referred to as an enabler.
Droste et al. [
32
] introduced three types of economic instruments including, price instruments, quantity
instruments, and fiscal instruments. The first two instruments focus on the private actors by changing
the fees and charges of using ecosystem services (price-based instruments), or limiting the activities
affecting the nature (quantity instruments). The third one focuses on the decision makers in the public
sector by creating incentives for developing green infrastructures and NBS through the inclusion of
ecological criteria in fiscal transfer processes. Using economic instruments can encourage stakeholders
to uptake and implement NBS as the alternative that can provide the best value for money to them.
The economic instruments can also be in form of grants, like in the case of Szeged where a European
grant aid enabled an NGO to initiate a community garden [15].
Plans, programs and legislations can be a barrier as well as an enabler. The role of meso- and
macro-level actors is central in providing supportive and clear legislation. For example, the Edinburgh’s
Community Empowerment Act 2015 empowered the community to manage public lands [
15
] and
legislation, such as the EU flood directive which appears to support NBS development [
23
]. At a local
level, legislation similar to the strategic green infrastructure plan developed by the Barcelona city
council [
49
] can facilitate mainstreaming the NBS concept by considering its social-ecological system
perspective. Other examples of legislation as an enabler of NBS implementation include the Federal
Law in Switzerland where agencies are required to apply the ‘Swiss Landscape Concept’ [
28
], and the
“National Planning Policy Framework” in the UK that embraced sustainable urban drainage (SUD)
legislation requiring municipalities to implement SUDs in residential developments with ten or more
homes and in major commercial and mixed use developments [52].
Education and training programs for stakeholders from different institutional scales including
citizens, and professionals is also mentioned as an enabler to decrease the uncertainties regarding the
functionality of solutions and to provide public support for NBS. As Davies and Lafortezza [
45
] mention,
training programs on NBS should be scaled up and equal study time, as is currently dedicated to gray
infrastructure, should be dedicated to NBS education. Besides infrastructure professionals, educating
the public through formal education in classrooms, and informal education through newspapers,
television, radio, and the internet can facilitate uptake of the NBS concept [20].
Evaluation of the multiple benefits yielded by NBS, especially the social benefits, has not been fully
developed to date [
16
]. Effective evaluation systems, or development of a standardized system of NBS
evaluation considering the spatio-temporal dynamics of benefits, have been mentioned as an enabler to

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facilitate increased uptake of NBS [
42
]. At present, the most commonly accepted evaluation framework
for NBS is EKLIPSE [
27
] developed by an expert working group under the auspices of the European
Commission [
33
]. The EKLIPSE framework uses the ten challenges outlined by Raymond et al. [
27
]
as the basis for evaluating NBS benefits. The innovative aspect of this framework is that synergies
and tradeoffs among the challenges are considered as an important part of the assessment process.
Nesshöver et al. [
13
] emphasized the necessity of nested multiscale assessment systems, as different
NBS, and functions operating at different spatio-temporal scales. In addition, Thorslund et al. [
18
]
emphasize the importance of viewing interactions among NBS from a broader scale. Several examples
of methods to look at NBS from larger scales have been mentioned. For instance, Chen et al. [
20
]
refer to inventory mapping as a method to monitor farm ponds on a larger scale. Other approaches
considered useful for assessment and evaluation of NBS performance include multi-criteria analysis
for integrated evaluation of NBS methods considering social, environmental and economic aspects
from the viewpoints of multiple stakeholders, for example [29].
Collaborative monitoring approaches have also been encouraged by the literature. By using
Internet of Things technology, the knowledge of local actors who interact daily with the urban ecosystem
can be used to enrich the NBS monitoring systems [
20
]. Collaborative monitoring can provide valuable
information for decision makers regarding how different groups recognize NBS functions, and can
provide contextual information regarding the implementation and impact efficiency of the projects [
13
].
Experimenting with NBS has been mentioned as an effective strategy for implementing and
evaluating solutions in a controlled environment. Artmann and Sartison [
36
] state that “residents
doing urban gardening experience a sense of belonging”. Experimentation provides an opportunity to
identify optimal strategies for NBS development and to learn from mistakes without significant losses,
and thus encourages appreciation for and acceptance of the solutions: “Experiments show a visible and
tangible action that is accessible, invites discussions and can alter thinking and perceptions” [
26
]. For
example, in the case of introducing perennial urban meadows in the UK, an experimentation strategy
provided the maintenance staffand apprentices the opportunity to gain new skills [34]. Urban living
labs (ULL) have been increasingly used, particularly in European countries, as an experimentation
strategy for developing NBS. Experimentation provides opportunities for stakeholders from different
levels to meet and interact, and as such facilitates innovation diffusion [
15
]. Experimentation strategies
can thus turn a passive experience ‘of nature’ into an active experience ‘with nature’ [31].
Although the importance of bringing nature to urban areas is acknowledged, NBS should not be
considered solely as an alternative to gray infrastructures in an ‘either-or’ sense. “Hybrid solutions that
blend nature-based applications with engineered systems may provide the optimal impact considering
environmental footprints, land requirements and cost expenditures” [
43
]. For instance, providing
protection in face of extreme floods, or water cleaning functions in urban areas with high density cannot
be accomplished solely through NBS implementation in most cases. Effective combination of NBS and
gray infrastructure, or green-gray integration, can facilitate breaking the path dependency toward gray
infrastructure in communities while retaining functional gray infrastructure [
45
]. Pontee et al. [
23
]
provide detailed examples of hybrid solutions for improved coastal resilience. In some cases, using
gray infrastructures with a relatively small physical footprint can be combined with implementing
NBS in the remaining space [
12
]. For example, SUDs that combine green and gray solutions provide
the opportunity to decrease flood risk and minimize the risk of pollution diffusion to downstream
areas while providing several additional co-benefits [52].
In order to ensure solutions are fully implemented, they should be designed and located
appropriately. For instance, Andersson et al. [
48
] emphasize that the size of a solution should be
appropriate to the level of disturbance in case of extreme events, and Frantzeskaki [
26
] notes the
importance of paying attention to the aesthetical aspects of NBS, critical for their successful uptake by
the public. The other important issue is where NBS should be located. Andersson et al. [
48
] argue
that “the insurance is achieved by the NBS providing a ‘buffer’ between the exposed area and the
potential risk” and Hoyle et al. [
34
] recommend to locate perennial meadows in semi-rural parts of

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urban areas to provide optimal performance. It is important to consider NBS placement at a strategic
level and plan for NBS from the landscape scale, in order to assess the interaction between NBS and
urban setting and optimize the synergies and trade-offs between them [
30
]. Krauze and Wagner [
37
]
emphasized the importance of looking at an urban area as an integrated system, by introducing the
concept of a continuum of ecosystem services and focusing on NBS planning, to provide ecological
corridors and transfer ecosystem services across different city zones. These considerations highlight
the advantages of NBS planning as a component of urban development rather than as an ‘added extra’
arising from land use planning.
4. Strategic Planning for Nature-Based Solutions
4.1. Background
The results of our review, outlined in the previous section, provides an understanding of the
state-of-the-art knowledge regarding the uptake of NBS. We discussed what NBS are, what their
objectives are, which barriers arise in the development of NBS, and how to overcome these barriers. In
addition, we identified the key actors in the NBS development process. Considering these different
findings, we are going to propose a (preliminary) NBS strategic planning framework. In describing
the various elements of this framework, we will also identify a number of areas where more research
is needed.
The framework presented in this section is mainly relevant for cities that are planning to incorporate
NBS and are looking for ways to decrease the risk of failure as much as possible. This framework
includes three main steps (Figure 3), vision development, identification of appropriate solutions, and
identification and prediction of barriers and enablers. It also provides general guidelines regarding
how actors can interact in each step. The framework emphasizes the inclusion of multiple actors from
different institutional levels, starting at the early stages of the planning process [
8
,
13
]. In addition, the
iterative refinement of the plan regarding the barriers to and enablers of NBS uptake is another added
value of this framework in comparison to conventional planning approaches. In the remainder of this
section, we discuss each step separately.
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4. Strategic Planning for Nature-Based Solutions
4.1. Background
The results of our review, outlined in the previous section, provides an understanding of the
state-of-the-art knowledge regarding the uptake of NBS. We discussed what NBS are, what their
objectives are, which barriers arise in the development of NBS, and how to overcome these barriers.
In addition, we identified the key actors in the NBS development process. Considering these different
findings, we are going to propose a (preliminary) NBS strategic planning framework. In describing
the various elements of this framework, we will also identify a number of areas where more research
is needed.
The framework presented in this section is mainly relevant for cities that are planning to
incorporate NBS and are looking for ways to decrease the risk of failure as much as possible. This
framework includes three main steps (Figure 3), vision development, identification of appropriate
solutions, and identification and prediction of barriers and enablers. It also provides general
guidelines regarding how actors can interact in each step. The framework emphasizes the inclusion
of multiple actors from different institutional levels, starting at the early stages of the planning
process [8,13]. In addition, the iterative refinement of the plan regarding the barriers to and enablers
of NBS uptake is another added value of this framework in comparison to conventional planning
approaches. In the remainder of this section, we discuss each step separately.
Figure 3. NBS strategic planning framework (i.e., the thick arrows represent the primary planning
process and other arrows refer to feedback relations between various steps).
4.2. Vision Development
In the first step, the vision is developed in terms of the challenge areas and objectives for using
NBS. In our literature review, we showed the high potential of NBS for addressing not only
biophysical but also social challenges. Accordingly, NBS are able to address environmental, economic
and social challenges simultaneously and give equal attention to these three aspects. Therefore, to
realize the added values of NBS, one should not focus on a single challenge. For example, the
municipality of Dresden cooperates with citizens, gardeners, and companies to develop a shared
vision that not only covered ecological challenges but also focused on providing opportunities for
Figure 3.
NBS strategic planning framework (i.e., the thick arrows represent the primary planning
process and other arrows refer to feedback relations between various steps).

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4.2. Vision Development
In the first step, the vision is developed in terms of the challenge areas and objectives for using
NBS. In our literature review, we showed the high potential of NBS for addressing not only biophysical
but also social challenges. Accordingly, NBS are able to address environmental, economic and social
challenges simultaneously and give equal attention to these three aspects. Therefore, to realize the
added values of NBS, one should not focus on a single challenge. For example, the municipality of
Dresden cooperates with citizens, gardeners, and companies to develop a shared vision that not only
covered ecological challenges but also focused on providing opportunities for learning and enhancing
ecosystem stewardship [
31
]. Resources are often limited and each city has different needs; it may
therefore be critical to prioritize the challenges to be addressed in the planning process [8,9].
Multi-criteria decision analysis (MCDA) can be used to prioritize identified challenge areas.
Meerow and Newell [
53
] provide an example of MCDA use, whereby challenge areas were prioritized
with a view to the implementation of green infrastructure in Detroit. Explicitly considering the
perspectives of multiple stakeholders strongly supports development of a shared and publicly
acceptable vision. However, inclusion of many different stakeholders can be highly challenging, as
macro- and meso-level actors are likely to provide more strategic input while micro-level actors tend
to adopt a more practical and project-based point of view. This is where transboundary actors play
a key role based on their ability to speak the language of different groups and develop a shared
understanding. For example, transboundary actors played an important role in co-creation actions
in Stockholm by networking among local government and civil society and exploiting the synergies
among different challenge areas [31].
4.3. Identification of Potential Solutions
The second step for cities is to find out how they can reach their vision. Cities should identify
potential solutions that can contribute to the challenges selected. Our review suggests that NBS
should be recognized as combination of elements and strategies, including all three types of NBS,
as addressing challenges usually needs a cascade of NBS [
41
]. For example, in the case of Lambhill
Stables in Glasgow, constructed wetland, urban agriculture, and bioremediation pond elements form
an integrated solution to restore the minefield and provide areas for environmental education [
26
].
The results of the MCDA applied in the previous step can be used to prioritize protentional solutions
based upon the documented performance of various types of NBS, although knowledge gaps remain
concerning the performance and impact of various NBS implemented at different scales and across
a range of environments. As observed earlier, the current literature largely focuses on NBS type 3,
characterized by a high level of intervention (see Table 3). Additional research is required to fully
characterize the performance and impact of all types of NBS, but particularly those with a lower
level of intervention (i.e., Type 1 and 2). The choice of NBS is closely connected with the target
location(s), and knowing the answer to the question of “where” can help each city find potential
solutions. Here, the NBS literature does not currently provide a single standardized technique or
tool for identifying the optimal location for NBS. Green infrastructure planning methods can also
be relevant for identifying optimal NBS locations within a given urban area [
53
–
55
], although the
additional sociocultural, socioeconomic and institutional/governance dimensions associated with NBS
compared with green infrastructure are not fully considered by these extant techniques.
Bringing the perspectives of multiple stakeholders together is critical in this step. Macro- and
meso-level actors can enrich this step by their broader view of the longer-term and large scale
benefits arising from NBS, while micro-level actors can enrich the process with their local ‘grassroots’
knowledge about shorter-term needs and preferences [
56
]. It is the role of transboundary actors
to ensure alignment between objectives across temporal scales, supporting design of shorter-term
actions to foster achievement of longer-term goals. The importance of transboundary actors is further
discussed by Andersson et al. [56], Olsson et al. [57] and Borgström et al. [58].

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4.4. Identification and Prediction of Barriers
Step 3a in Figure 3explores and predicts the barriers for the uptake and implementation of NBS.
In the review, we identified six major barriers. Four of these are socio-institutional barriers and one
barrier was both socio-institutional and biophysical, which is consistent with previous studies [
8
,
59
,
60
].
The most frequently observed barrier was uncertainty regarding the implementation process and the
benefits arising from NBS, followed by inadequate financial resources, land and time availability, path
dependency in decision making, institutional fragmentation, and inadequate regulations.
Every city will face a unique set of barriers, which highlights the importance of including multiple
actors in all stages of the planning process. Meso-level actors are likely to be more familiar with the
political and institutional barriers that may occur, while micro-level actors are more familiar with
project-specific barriers. Transboundary actors can help by identifying the connections and interactions
among different barriers, as well as strategies to overcome them. Methods like interpretive structural
modeling (ISM) have been used to model barriers and identify the interactions among them in complex
situations [
61
,
62
] and can thus also be relevant in the context of NBS. Past experiences in the same
city or other cities can help to identify and predict potential barriers [
8
]. The process of barrier
identification may result in changes to the initial vision and/or preferences for particular solutions,
illustrating the iterative nature of the NBS planning process (see Figure 3). Future research on NBS
should further explore the process of barrier identification to formalize a standard methodology aimed
at the development of a best practices approach to overcome commonly identified barriers.
4.5. Identification and Prediction of Enablers
Step 3b illustrates the identification and prediction of enablers of NBS. Previously, we identified
nine enablers for successful uptake and implementation of NBS. Five are socio-institutional enablers,
two are hybrid in nature, and the remaining two are biophysical enablers; previous studies found
similar results [
59
,
60
]. Developing partnerships between stakeholders appears to be the most frequently
observed enabler, followed by effective monitoring, knowledge sharing, financial instruments, plans
and legislations, education and training, combining with gray infrastructures, open innovation and
experimentation, and appropriate planning and design. As in step 3a barrier identification, the
presence of multiple actors can enrich the identification of enablers. Meso-level actors can readily map
institutional and organizational enablers, while micro-level actors are better positioned to identify
project- and design-related enablers. Transboundary actors drawing upon a multi-dimensional
perspective are key to the identification of new, or innovative potential enablers and important in the
definition of the most appropriate actions.
The ISM method has been frequently used to model the drivers and enablers in complex
situations [
63
,
64
]. Iteration of previous steps to refine outcomes can also be important at this stage. For
example, if an enabler is characterized by high cost or can only be realized in the long term, this may
affect how actors prioritize the challenges and solutions. In Section 3, we provided several examples of
how a specific enabler may alleviate a particular barrier. However, the body of knowledge explicitly
addressing interactions among barriers and enablers is limited at present. The compilation of extant
knowledge regarding interactions among barriers and enablers, including specific examples as case
studies, could underpin practical guidelines about effectively overcoming barriers to NBS uptake
and implementation.
5. Concluding Remarks
NBS are increasingly recognized as a promising means to address a number of societal challenges
arising from climate change and urbanization, with multiple social, environmental and economic
co-benefits. The present review shows that NBS have the potential to transform the concept of “urban
nature” from a real or perceived barrier to sustainable and inclusive socioeconomic development
to a necessary element of development planning and implementation. To date, the NBS literature

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has focused largely on NBS requiring relatively higher levels of intervention (i.e., type 3 NBS). Types
of NBS characterized by a relatively greater management component compared with restoration or
creation components have received lesser attention in the scientific literature. Further investigation of
all types of NBS, including not only the co-creation but also the co-implementation and co-governance
aspects, is necessary in order to derive a comprehensive understanding of NBS performance, impact
and cross-sectoral benefits in both the short- and long-term. In particular, the contribution of NBS to
social-ecological resilience requires additional examination as a function of NBS type across a broad
range of sociocultural, socioeconomic and environmental contexts.
Systematic co-planning and co-management of NBS is necessary to fully exploit the potential
value of NBS in any context. Herein, we identified the primary barriers to and enablers of the uptake
and implementation of NBS. Based on the review results, we proposed a strategic planning framework
for NBS that minimize the risk of failure and reduce the level of uncertainty associated with NBS
adoption. This framework also advocates the participation of multiple actors in the early stages of the
planning process to maximize the capture of relevant barriers and enablers.
Limitations of the present review include focus on publications using the keyword “nature-based
solution(s)”, whilst related literature discussing similar approaches such as “green infrastructure” or
“ecosystem-based adaptation” may also be relevant and potentially enrich the results of this study.
Despite its acknowledged limitations, the results obtained in the present study highlight several
knowledge gaps related to NBS. Foremost, additional research is needed regarding the barriers,
opportunities and co-benefits associated with different types of NBS as well as the synergies and
trade-offs among them. In-depth analysis of barriers and enablers in each documented case of NBS
uptake is required to build a reference based to identify and predict barriers to and enablers of
NBS uptake and implementation. Finally, future work should study the interactions among specific
barriers and enablers, as well as the influences they have on, and how they are in turn influenced by,
various actors at the macro-, meso-, micro- and transboundary levels. This analysis could support the
derivation of user-specific guidelines regarding the means by which a particular enabler may alleviate
or overcome a given barrier, further promoting the widespread uptake and implementation of NBS.
Supplementary Materials: The following are available online at http://www.mdpi.com/2079-9276/8/3/121/s1.
Author Contributions:
S.E.S. conducted the review and wrote the first version of the manuscript, and Q.H.,
A.G.L.R., B.d.V. and L.W. provided feedback on earlier versions of the manuscript and edited it.
Funding:
This research has received funding from the European Union’s Horizon 2020 Research and Innovation
Programme under Grant Agreement No. 730052.
Acknowledgments:
We would like to thank Elke den Ouden and Rianne Valkenburg for comments and feedback
on previous versions of this paper. We are grateful for UNaLab partners and especially to Tom Hawxwell and
Sophie Mok who shared their ideas and perspectives with us during the development of this paper.
Conflicts of Interest: The authors declare no conflict of interest.
References
1.
White, P.; Pelling, M.; Sen, K.; Seddon, D.; Russell, S.; Few, R. Disaster Risk Reduction: A Development Concern.
A Scoping Study on Links between Disaster Risk Reduction, Poverty and Development; Report to UK Department
for International Development (DFID): London, UK, 2004.
2.
European Environmental Agency. Climate Change, Impacts and Vulnerability in Europe 2012: An Indicator-Based
Report; European Environmental Agency: Copenhagen, Denmark, 2012.
3.
McDonald, R.I.; Marcotullio, P.J.; Güneralp, B. Urbanization and Global Trends in Biodiversity and Ecosystem
Services. In Urbanization, Biodiversity and Ecosystem Services: Challenges and Opportunities; Springer: Dordrecht,
The Netherlands, 2013; pp. 31–52.
4.
Haase, D.; Larondelle, N.; Andersson, E.; Artmann, M.; Borgström, S.; Breuste, J.; Gomez-Baggethun, E.;
Gren, Å.; Hamstead, Z.; Hansen, R.; et al. A Quantitative Review of Urban Ecosystem Service Assessments:
Concepts, Models, and Implementation. Ambio 2014,43, 413–433. [CrossRef] [PubMed]

Resources 2019,8, 121 17 of 20
5.
United Nations. World Urbanization Prospects, The 2011 Revision; United Nations Department of Economic
and Social Affairs: New York, NY, USA, 2012.
6.
United Nations. World Urbanization Prospects: The 2014 Revision (Highlights); United Nations Department of
Economic and Social Affairs: New York, NY, USA, 2014; Volume 32.
7.
European Commission. Towards an EU Research and Innovation Policy Agenda for Nature-Based Solutions &
Re-Naturing Cities: Final Report of the Horizon 2020 Expert Group on Nature-Based Solutions and Re-Naturing
Cities; European Commission: Brussels, Belgium, 2015.
8.
Kabisch, N.; Stadler, J.; Korn, H.; Bonn, A.; Frantzeskaki, N.; Pauleit, S.; Naumann, S.; Davis, M.; Artmann, M.;
Haase, D.; et al. Nature-based solutions to climate change mitigation and adaptation in urban areas. Ecol.
Soc. 2016,21. [CrossRef]
9.
Eggermont, H.; Balian, E.; Azevedo, J.M.N.; Beumer, V.; Brodin, T.; Claudet, J.; Fady, B.; Grube, M.; Keune, H.;
Lamarque, P.; et al. Nature-based solutions: new influence for environmental management and research in
Europe. GAIA Ecol. Perspect. Sci. Soc. 2015,24, 243–248. [CrossRef]
10. Yang, K.; Meho, L.I. Citation Analysis: A Comparison of Google Scholar, Scopus, and Web of Science. Proc.
Am. Soc. Inf. Sci. Technol. 2007,43, 1–15. [CrossRef]
11.
Cohen-Shacham, E.; Walters, G.; Janzen, C.; Maginnis, S. Nature-Based Solutions to Address Global Societal
Challenges; IUCN: Gland, Switzerland, 2016.
12.
Albert, C.; Schröter, B.; Haase, D.; Brillinger, M.; Henze, J.; Herrmann, S.; Gottwald, S.; Guerrero, P.;
Nicolas, C.; Matzdorf, B. Addressing societal challenges through nature-based solutions: How can landscape
planning and governance research contribute? Landsc. Urban Plan. 2019,182, 12–21. [CrossRef]
13.
Nesshöver, C.; Assmuth, T.; Irvine, K.N.; Rusch, G.M.; Waylen, K.A.; Delbaere, B.; Haase, D.; Jones-Walters, L.;
Keune, H.; Kovacs, E.; et al. The science, policy and practice of nature-based solutions: An interdisciplinary
perspective. Sci. Total Environ. 2017,579, 1215–1227. [CrossRef] [PubMed]
14.
Maes, J.; Jacobs, S. Nature-Based Solutions for Europe’s Sustainable Development. Conserv. Lett.
2017
,10,
121–124. [CrossRef]
15.
Van der Jagt, A.P.N.; Szaraz, L.R.; Delshammar, T.; Cveji´c, R.; Santos, A.; Goodness, J.; Buijs, A. Cultivating
nature-based solutions: The governance of communal urban gardens in the European Union. Environ. Res.
2017,159, 264–275. [CrossRef] [PubMed]
16.
Short, C.; Clarke, L.; Carnelli, F.; Uttley, C.; Smith, B. Capturing the multiple benefits associated with
nature-based solutions: Lessons from a natural flood management project in the Cotswolds, UK. L. Degrad.
Dev. 2019,30, 241–252. [CrossRef]
17.
Kronenberg, J.; Bergier, T.; Maliszewska, K. The Challenge of Innovation Diffusion: Nature-Based Solutions
in Poland. In Nature-Based Solutions to Climate Change Adaptation in Urban Areas: Linkages between Science,
Policy and Practice; Kabisch, N., Korn, H., Stadler, J., Bonn, A., Eds.; Springer International Publishing: Cham,
Switzerland, 2017; pp. 291–305. ISBN 978-3-319-56091-5.
18.
Thorslund, J.; Jarsjo, J.; Jaramillo, F.; Jawitz, J.W.; Manzoni, S.; Basu, N.B.; Chalov, S.R.; Cohen, M.J.; Creed, I.F.;
Goldenberg, R.; et al. Wetlands as large-scale nature-based solutions: Status and challenges for research,
engineering and management. Ecol. Eng. 2017,108, 489–497. [CrossRef]
19.
Bridgewater, P. Whose nature? What solutions? Linking Ecohydrology to Nature-based solutions. Ecohydrol.
Hydrobiol. 2018,18, 311–316. [CrossRef]
20.
Chen, W.; He, B.; Nover, D.; Lu, H.; Liu, J.; Sun, W.; Chen, W. Farm ponds in southern China: Challenges and
solutions for conserving a neglected wetland ecosystem. Sci. Total Environ.
2019
,659, 1322–1334. [CrossRef]
[PubMed]
21.
Pauleit, S.; Zölch, T.; Hansen, R.; Randrup, T.B.; Konijnendijk van den Bosch, C. Nature-Based Solutions and
Climate Change—Four Shades of Green; Springer International Publishing: Cham, Switzerland, 2017; pp. 29–49.
22.
Santoro, S.; Pluchinotta, I.; Pagano, A.; Pengal, P.; Cokan, B.; Giordano, R. Assessing stakeholders’ risk
perception to promote Nature Based Solutions as flood protection strategies: The case of the Glinšˇcica river
(Slovenia). Sci. Total Environ. 2019,655, 188–201. [CrossRef] [PubMed]
23.
Pontee, N.; Narayan, S.; Beck, M.W.; Hosking, A.H. Nature-based solutions: Lessons from around the world.
Proc. Inst. Civ. Eng. Marit. Eng. 2016,169, 29–36. [CrossRef]

Resources 2019,8, 121 18 of 20
24.
Van Ham, C.; Klimmek, H. Partnerships for Nature-Based Solutions in Urban Areas—Showcasing Successful
Examples. In Nature-Based Solutions to Climate Change Adaptation in Urban Areas: Linkages between Science,
Policy and Practice; Kabisch, N., Korn, H., Stadler, J., Bonn, A., Eds.; Springer International Publishing: Cham,
Switzerland, 2017; pp. 275–289. ISBN 978-3-319-56091-5.
25.
Arkema, K.K.; Griffin, R.; Maldonado, S.; Silver, J.; Suckale, J.; Guerry, A.D. Linking social, ecological, and
physical science to advance natural and nature-based protection for coastal communities. Ann. N. Y. Acad.
Sci. 2017,1399, 5–26. [CrossRef] [PubMed]
26.
Frantzeskaki, N. Seven lessons for planning nature-based solutions in cities. Environ. Sci. Policy
2019
,93,
101–111. [CrossRef]
27.
Raymond, C.M.; Frantzeskaki, N.; Kabisch, N.; Berry, P.; Breil, M.; Nita, M.R.; Geneletti, D.; Calfapietra, C. A
framework for assessing and implementing the co-benefits of nature-based solutions in urban areas. Environ.
Sci. Policy 2017,77, 15–24. [CrossRef]
28.
Xing, Y.; Jones, P.; Donnison, I. Characterisation of Nature-Based Solutions for the Built Environment.
Sustainability 2017,9, 149. [CrossRef]
29.
Liquete, C.; Udias, A.; Conte, G.; Grizzetti, B.; Masi, F. Integrated valuation of a nature-based solution for
water pollution control. Highlighting hidden benefits. Ecosyst. Serv. 2016,22, 392–401. [CrossRef]
30.
Emilsson, T.; Ode Sang, Å. Impacts of Climate Change on Urban Areas and Nature-Based Solutions for
Adaptation. In Nature-Based Solutions to Climate Change Adaptation in Urban Areas: Linkages between Science,
Policy and Practice; Kabisch, N., Korn, H., Stadler, J., Bonn, A., Eds.; Springer International Publishing: Cham,
Switzerland, 2017; pp. 15–27. ISBN 978-3-319-56091-5.
31.
Frantzeskaki, N.; Borgström, S.; Gorissen, L.; Egermann, M.; Ehnert, F. Nature-Based Solutions Accelerating
Urban Sustainability Transitions in Cities: Lessons from Dresden, Genk and Stockholm Cities. In Nature-Based
Solutions to Climate Change Adaptation in Urban Areas: Linkages between Science, Policy and Practice; Kabisch, N.,
Korn, H., Stadler, J., Bonn, A., Eds.; Springer International Publishing: Cham, Switzerland, 2017; pp. 65–88.
ISBN 978-3-319-56091-5.
32.
Droste, N.; Schröter-Schlaack, C.; Hansjürgens, B.; Zimmermann, H. Implementing Nature-Based Solutions
in Urban Areas: Financing and Governance Aspects. In Nature-Based Solutions to Climate Change Adaptation in
Urban Areas: Linkages between Science, Policy and Practice; Kabisch, N., Korn, H., Stadler, J., Bonn, A., Eds.;
Springer International Publishing: Cham, Switzerland, 2017; pp. 307–321. ISBN 978-3-319-56091-5.
33.
Faivre, N.; Fritz, M.; Freitas, T.; de Boissezon, B.; Vandewoestijne, S. Nature-Based Solutions in the EU:
Innovating with nature to address social, economic and environmental challenges. Environ. Res.
2017
,159,
509–518. [CrossRef]
34.
Hoyle, H.; Jorgensen, A.; Warren, P.; Dunnett, N.; Evans, K. “Not in their front yard” The opportunities and
challenges of introducing perennial urban meadows: A local authority stakeholder perspective. Urban For.
Urban Green. 2017,25, 139–149. [CrossRef]
35.
Gulsrud, N.M.; Hertzog, K.; Shears, I. Innovative urban forestry governance in Melbourne?: Investigating
“green placemaking” as a nature-based solution. Environ. Res. 2018,161, 158–167. [CrossRef]
36.
Artmann, M.; Sartison, K. The Role of Urban Agriculture as a Nature-Based Solution: A Review for
Developing a Systemic Assessment Framework. Sustainability 2018,10, 1937. [CrossRef]
37.
Krauze, K.; Wagner, I. From classical water-ecosystem theories to nature-based solutions — Contextualizing
nature-based solutions for sustainable city. Sci. Total Environ. 2019,655, 697–706. [CrossRef] [PubMed]
38.
Engström, R.; Howells, M.; Mörtberg, U.; Destouni, G. Multi-functionality of nature-based and other urban
sustainability solutions: New York City study. L. Degrad. Dev. 2018,29, 3653–3662. [CrossRef]
39.
Blau, L.M.; Luz, F.; Panagopoulos, T. Urban River Recovery Inspired by Nature-Based Solutions and Biophilic
Design in Albufeira, Portugal. Land 2018,7, 141. [CrossRef]
40.
Denjean, B.; Altamirano, M.A.; Graveline, N.; Giordano, R.; van der Keur, P.; Moncoulon, D.; Weinberg, J.;
M
á
ñez Costa, M.; Kozinc, Z.; Mulligan, M.; et al. Natural Assurance Scheme: A level playing field framework
for Green-Grey infrastructure development. Environ. Res. 2017,159, 24–38. [CrossRef]
41.
Keesstra, S.; Nunes, J.; Novara, A.; Finger, D.; Avelar, D.; Kalantari, Z.; Cerd
à
, A. The superior effect of nature
based solutions in land management for enhancing ecosystem services. Sci. Total Environ.
2018
,610–611,
997–1009. [CrossRef]

Resources 2019,8, 121 19 of 20
42.
Wendling, L.A.; Huovila, A.; zu Castell-Rüdenhausen, M.; Hukkalainen, M.; Airaksinen, M. Benchmarking
Nature-Based Solution and Smart City Assessment Schemes Against the Sustainable Development Goal
Indicator Framework. Front. Environ. Sci. 2018,6. [CrossRef]
43.
Santiago Fink, H. Human-Nature for Climate Action: Nature-Based Solutions for Urban Sustainability.
Sustainability 2016,8, 254. [CrossRef]
44.
Fan, P.; Ouyang, Z.; Basnou, C.; Pino, J.; Park, H.; Chen, J. Nature-based solutions for urban landscapes
under post-industrialization and globalization: Barcelona versus Shanghai. Environ. Res.
2017
,156, 272–283.
[CrossRef] [PubMed]
45. Davies, C.; Lafortezza, R. Transitional path to the adoption of nature-based solutions. Land Use Policy 2019,
80, 406–409. [CrossRef]
46.
Langemeyer, J.; Camps-Calvet, M.; Calvet-Mir, L.; Barthel, S.; G
ó
mez-Baggethun, E. Stewardship of urban
ecosystem services: Understanding the value(s) of urban gardens in Barcelona. Landsc. Urban Plan.
2018
,
170, 79–89. [CrossRef]
47.
Turkelboom, F.; Leone, M.; Jacobs, S.; Kelemen, E.; Garc
í
a-Llorente, M.; Bar
ó
, F.; Termansen, M.; Barton, D.N.;
Berry, P.; Stange, E.; et al. When we cannot have it all: Ecosystem services trade-offs in the context of spatial
planning. Ecosyst. Serv. 2018,29, 566–578. [CrossRef]
48.
Andersson, E.; Borgström, S.; McPhearson, T. Double Insurance in Dealing with Extremes: Ecological and
Social Factors for Making Nature-Based Solutions Last. In Nature-Based Solutions to Climate Change Adaptation
in Urban Areas: Linkages between Science, Policy and Practice; Kabisch, N., Korn, H., Stadler, J., Bonn, A., Eds.;
Springer International Publishing: Cham, Switzerland, 2017; pp. 51–64. ISBN 978-3-319-56091-5.
49.
Camps-Calvet, M.; Langemeyer, J.; Calvet-Mir, L.; G
ó
mez-Baggethun, E. Ecosystem services provided by
urban gardens in Barcelona, Spain: Insights for policy and planning. Environ. Sci. Policy
2016
,62, 14–23.
[CrossRef]
50.
Wamsler, C. Mainstreaming ecosystem-based adaptation: Transformation toward sustainability in urban
governance and planning. Ecol. Soc. 2015,20. [CrossRef]
51.
Vujcic, M.; Tomicevic-Dubljevic, J.; Grbic, M.; Lecic-Tosevski, D.; Vukovic, O.; Toskovic, O. Nature based
solution for improving mental health and well-being in urban areas. Environ. Res.
2017
,158, 385–392.
[CrossRef] [PubMed]
52.
Davis, M.; Naumann, S. Making the Case for Sustainable Urban Drainage Systems as a Nature-Based Solution
to Urban Flooding. In Nature-Based Solutions to Climate Change Adaptation in Urban Areas: Linkages between
Science, Policy and Practice; Kabisch, N., Korn, H., Stadler, J., Bonn, A., Eds.; Springer International Publishing:
Cham, Switzerland, 2017; pp. 123–137. ISBN 978-3-319-56091-5.
53.
Meerow, S.; Newell, J.P. Spatial planning for multifunctional green infrastructure: Growing resilience in
Detroit. Landsc. Urban Plan. 2017,159, 62–75. [CrossRef]
54.
Kremer, P.; Hamstead, Z.A. The value of urban ecosystem services in New York City: A spatially explicit
multicriteria analysis of landscape scale valuation scenarios. Environ. Sci. Policy
2016
,62, 57–68. [CrossRef]
55.
Norton, B.A.; Coutts, A.M.; Livesley, S.J.; Harris, R.J.; Hunter, A.M.; Williams, N.S.G. Planning for cooler
cities: A framework to prioritise green infrastructure to mitigate high temperatures in urban landscapes.
Landsc. Urban Plan. 2015,134, 127–138. [CrossRef]
56.
Andersson, E.; Barthel, S.; Borgström, S.; Colding, J.; Elmqvist, T.; Folke, C.; Gren, Å. Reconnecting Cities to
the Biosphere: Stewardship of Green Infrastructure and Urban Ecosystem Services. Ambio
2014
,43, 445–453.
[CrossRef] [PubMed]
57.
Olsson, P.; Folke, C.; Galaz, V.; Hahn, T.; Schultz, L. Enhancing the fit through adaptive co-management:
Creating and maintaining bridging functions for matching scales in the Kristianstads Vattenrike Biosphere.
Ecol. Soc. 2007,12. [CrossRef]
58.
Borgström, S.; Elmqvist, T.; Angelstam, P.; Alfsen-Norodom, C. Scale mismatches in management of urban
landscapes. Ecol. Soc. 2006,11. [CrossRef]
59.
O’Donnell, E.C.; Lamond, J.E.; Thorne, C.R. Recognising barriers to implementation of Blue-Green
Infrastructure: a Newcastle case study. Urban Water J. 2017,14, 964–971. [CrossRef]
60.
Ahn, Y.H.; Pearce, A.R.; Wang, Y.; Wang, G. Drivers and barriers of sustainable design and construction: The
perception of green building experience. Int. J. Sustain. Build. Technol. Urban Dev.
2013
,4, 35–45. [CrossRef]
61.
Singh, M.D.; Kant, R. Knowledge management barriers: An interpretive structural modeling approach. Int.
J. Manag. Sci. Eng. Manag. 2008,3, 141–150. [CrossRef]

Resources 2019,8, 121 20 of 20
62.
Winz, I.; Trowsdale, S.; Brierley, G. Understanding barrier interactions to support the implementation of
sustainable urban water management. Urban Water J. 2014,11, 497–505. [CrossRef]
63.
Nishat Faisal, M. Sustainable supply chains: A study of interaction among the enablers. Bus. Process Manag.
J. 2010,16, 508–529. [CrossRef]
64.
Rehman, M.A.A.; Shrivastava, R. An innovative approach to evaluate green supply chain mamagement
(GSCM) drivers by using interpretive structural modeling (ISM). Int. J. Innov. Technol. Manag.
2011
,8,
315–336. [CrossRef]
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