Introduction

Connecting children with nature has attracted increasing attention in the field of education due to its multiple benefits to children’s health (McCormick, 2017), socio-emotional development (Mygind et al., 2021), and educational outcomes (Mann et al., 2021). Among these benefits are enhanced concentration, improved academic performance, reduced aggression, and a lower risk of obesity among children (Faber Taylor & Kuo, 2011). In this context, nature-based learning (NBL) has emerged as an approach that integrates principles of nature into educational practice while enhancing the overall learning experience for children. NBL is defined as “learning through exposure to nature and nature-based activities, [which] occurs in natural settings and where elements of nature have been brought into built environments” (Jordan & Chawla, 2019, p. 2). This is distinct from nature-based play (Miller et al., 2021), which refers to unstructured activity in nature, where the extent of the nature experience cannot be assumed (Raith, 2017). While we recognise that “nature” is an ambiguous concept, in this paper we adopt a definition rooted in the practical application of nature as a medium for learning outside the classroom: “all the animals, plants, and other things in the world that are not caused by people” (Collins English Dictionary, 2023).

Nature-based learning can be facilitated in multiple ways, including by using nature for supporting the teaching of curriculum subjects (Chawla, 2018). Embedding nature in the mainstream educational curriculum has the advantage of providing opportunities for regular experiences in nature to children in urban environments, thus mitigating inequity of children’s access to nature (Stevenson et al., 2020). A NBL approach to the curriculum fosters knowledge and affective domains simultaneously (Palmberg & Kuru, 2000), both of which are important to motivate environmental action (Liu et al., 2020). This study makes the assumption that to achieve this combination of elements, NBL must occur in a nature-based environment outside the classroom where the experience has the potential to be immersive. This assumption stems from an ecological psychology framework that views the most effective learning in a learning context as that which emerges from a person-environment relationship and utilizes both the functional and relational properties of this environment (Sharma-Brymer et al., 2018). This also relates to Gibson’s theory of affordances and the properties of an environment that support development (Khan et al., 2020). Since the quality of nature in the indoors classroom is limited in complexity, unpredictability, multi-sensoriality and multi-dimensionality, it cannot provide the depth of experience necessary for NBL. At the same time, educators may not easily be able to access immersive nature spaces that are suitable for NBL, and there is evidence of considerable inequity in school-based access to nature (Baró et al., 2021; Fernández et al., 2022; van Velzen & Helbich, 2023), with related social justice implications.

This study focuses on the role that school grounds can play in addressing the disparity children face in their access to nature. Use of school grounds has the potential to ensure children’s regular access to a natural setting (Collado & Evans, 2019; Wallace, 2019; White et al., 2018), while eliminating costs (financial, environmental, or time-related) of trips to and from destinations outside school. In this way NBL on school grounds directly reflects the concept of nature-based solutions, i.e. solutions inspired and supported by nature which are cost-effective, provide environmental, social and economic benefits, and bring more, and more diverse, nature and natural features and processes into cities (European Commission, n.d.). However, despite growing interest in green schoolyards and in the NBL approach (Danks, 2010; Jansson & Mårtensson, 2012; Van Dijk-Wesselius et al., 2020), there is a lack of clarity about how school grounds can be designed to enable effective NBL. Furthermore, there has been little explicit exploration of the link between specific design features of nature spaces in school grounds and specific desired outcomes (e.g., cognitive-academic, physical, emotional benefits). This is important in view of the fact that implementing changes to school grounds to support NBL requires financial investment and trade-offs that make it important for school administrators and policy-makers to know whether particular design features are linked to desired benefits. This is especially relevant to schools sited in urban areas, which are often built on small footprints, with limited open spaces. Such schools may be making choices between different options for the use of limited open spaces, further underlining the need for a framework to guide design. Indeed, it is of note that while many studies have highlighted the benefits of greening school grounds (Jansson & Mårtensson, 2012; Sedawi et al., 2021; Wells & Lekies, 2006), the natural settings described in several studies are unlikely to be available to small, urban schools. In this context, there is a need to empirically explore whether and how effective NBL learning spaces can also be created within urban schools.

The aim of this study was to determine the current state of knowledge with respect to design of school grounds for NBL. A systematized review of peer-reviewed literature was carried out to answer the following questions:

  1. 1.

    What evidence-based guidance exists for designing school grounds to achieve NBL through the primary school curriculum?

  2. 2.

    To what extent is such guidance applicable to schools in urban areas and/or with space constraints?

  3. 3.

    Are specific design features of green school grounds linked to specific desired outcomes?

The remainder of this paper is structured as follows. The next section elaborates on the contribution of NBL to ecological citizenship through nature connectedness. The following section explains the methods adopted for the systematized review, with results presented in the subsequent section. This is followed by a discussion of significant implications and key conclusions.

Nature-based learning: fostering motivation towards environmentally-responsible behavior

Chawla, (2018) notes that “teachers today work in a changing climate” (p. 1), raising the question of how educators will respond to the considerable challenges of global environmental change. NBL has emerged as an approach that, in addition to offering various direct benefits to children (as outlined above), also has the potential to contribute to “the development of informed and motivated ecological citizenship” (Chawla, 2018, p. 3), particularly through its ability to foster enhanced nature connectedness. The term connectedness with nature (CN) is used in this paper in a broad sense to refer to the ways in which people identify themselves with the natural environment and the relationships they form with nature (Restall & Conrad, 2015).

Nature connectedness has the ability to generate intrinsic motivation to engage in pro-environment behaviors (Martin & Czellar, 2017; Rosa et al., 2018) by creating an emotional affinity with nature that allows individuals to view its destruction as self-destruction (Müller et al., 2009). In fact, it has been identified by several authors as a strong predictor of environmentally-responsible behavior, thus aiding a transition to more eco-friendly and sustainable practices (Alcock et al., 2020; Geng et al., 2015; Ives et al., 2017; Molinario et al., 2020; Restall & Conrad, 2015; Yang et al., 2018). The provision of environmental knowledge is also an essential component of environmentally responsible behavior. However, it alone is not sufficient in triggering positive behavior towards the environment because it lacks the affective element that stimulates motivation (Tamashiro et al., 2013). While it would be amiss to assume that CN is the only factor motivating environment-friendly behavior (Barrable & Booth, 2022), research has demonstrated that it is essential for mitigating environmental impacts (Otto & Pensini, 2017; Whitburn et al., 2020).

Furthermore, childhood is an important age for developing nature connectedness (Chawla & Gould, 2020) since early intervention tends to be more effective (Barrable & Booth, 2022) and maximizes the potential for the experience to have lifelong impact (Kollmuss & Agyeman, 2002; Liefländer et al., 2013). This is also the developmental period where integration in the social context occurs (Sobel, 1999) and where the motivation to behave in environmentally friendly ways is likely to be formed and to have lifelong impact (Evans et al., 2018; Pinder et al., 2020). Connecting children with nature in today’s urbanized societies is increasingly challenging, even as it becomes more relevant (Chawla & Gould, 2020): there are currently more people living in urban areas than in rural areas (United Nations, 2018). As experiences in nature decline, children’s interest in nature is likely to diminish (Soga et al., 2016), with various theories predicting a decline in people’s opportunities to interact with nature (Soga & Gaston, 2022), increased nature apathy (Kesebir & Kesebir, 2017), a progressive decline in knowledge of nature (Gerl et al., 2021), and a progressive loss of daily interactions with nature (Pyle, 2002). The loss of such a connection is not inevitable and CN can potentially be fostered through various means, amongst which are experiential learning approaches such as place-based education (Smith, 2002; Sobel, 2008), of which NBL is often a component (Anderson, 2017). However, there does seem to be ample evidence supporting the presumption of a general decline in human-nature interactions within urbanised environments.

One solution to addressing these challenges in a global setting is for the connection with nature to be integrated into the schooling experience. This can not only contribute to enhanced CN but can also foster enhanced ecological literacy, defined in this context as an enhanced ablity to understand the organizational principles of natural ecological communities and to apply these to human communities (McBride et al., 2013). Primary schooling is a highly appropriate global context for CN intervention since education is compulsory across regions and in 192 countries (UNESCO Institute for Statistics, 2004), with most countries having a minimum curriculum of five or six years of primary schooling (UNESCO Institute for Statistics, 2004). Furthermore, the school environment offers the possibility of frequent and regular contact with nature, both of which are characteristics that have been shown to affect development of CN (Cleary et al., 2020), especially in younger children (Kals et al., 1999). The emotional affinity towards nature has also been shown to become stronger the more concrete and specific the contact with nature (Soga et al., 2016). In this context, facilitation of NBL through the formal school curriculum offers a convenient and reliable context for regular and frequent engagement with nature, because it provides a wide subject range of opportunities for the educator to create such experiences.

Methods

Study scope

This review focused on the following:

  • NBL that is curriculum-based, allowing regular and sustained contact with nature.

  • NBL that targets primary schools and their age cohort of children aged 5 – 11. This age bracket was selected as it most commonly corresponds with years of compulsory schooling (UNESCO Institute for Statistics, 2004); these are also the most critical years for developing CN.

  • NBL that is facilitated outside the classroom, within school grounds. While there is interest in integrated school design, which seeks to harmoniously blend both indoor and outdoor environments (e.g. Grietēna, 2015; Monsur, 2013), empirical research to support such holistic design remains limited and most NBL programmes presently remain focused on the outdoors.

  • NBL that reflects a conceptualisation of nature rooted in the natural sciences, excluding applications such as agriculture. Agricultural practices often involve landscape simplification, which may result in the loss of biodiversity through biotic homogenization, reduced diversity of landcover types, and reduced configurational landscape heterogeneity, all of which have been shown to have ecological filter effects (Gámez-Virués et al., 2015). These may in turn have a detrimental impact on the human-nature connection (Sedawi et al., 2021).

Search strategy

Data were gathered through a systematized review (Grant & Booth, 2009). To the extent possible, PRISMA guidelines on the transparent reporting of systematic reviews and meta-analyses (Page et al., 2021) were followed (Fig. 1).

Fig. 1
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PRISMA flowchart

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A list of search terms was produced in relation to the theme of green school grounds in the context of nature-based learning and design. In order to ensure that the review comprehensively captured relevant literature, we first carried out a general search for terms associated with i) nature-based learning programs and ii) green school grounds. It was found that school grounds are also referred to as “schoolyards” and specific programmes can be carried out in “school gardens”. NBL can be referred to in a variety of ways; however, the scanned literature always contained the words “nature” and “learning/education”. Most of these terms carry broad interpretations. For example, while NBL is sometimes classified as “environmental education”, this term covers a broad field of learning that does not necessarily include direct experience in nature. Likewise, “school gardens” are created for a variety of reasons and may be linked with horticulture or healthy eating, or physical activity, rather than with nature-based learning. Terms were thus adjusted and Boolean operators employed to obtain more focused coverage. The following terms were ultimately used for the systematized search: “green schoolyards”, “green* school grounds”, “school gardens”, “nature-based learning”, “garden-based learning”, “nature-based learning” AND (school grounds OR schoolyards), “nature-based education” AND (school grounds OR schoolyards), “outdoor classroom”. “outdoor classroom” AND design*, "designing school grounds”. No date restrictions were applied, i.e. all studies meeting the search criteria were included, regardless of their date of publication. The search was carried out using a search platform with access to 173 databases (Appendix 2), including Scopus, ScienceDirect, SpringerLink, Education Collection (Proquest), and ERIC.

Eligibility criteria

In line with the study scope, the following inclusion criteria were applied:

  1. 1.

    Scientific papers: only peer reviewed studies involving primary research

  2. 2.

    English language literature

  3. 3.

    Studies related to primary school ages (5 – 11 years)

  4. 4.

    Primary research about NBL programs using green school grounds as part of the formal curriculum experience (subject-based learning), and/or green spaces in school grounds in relation to the curriculum (program or outcomes)

Details of searches showing numbers of search results, and included/excluded studies are given in Appendix 1, Tables 1-3.

Selection process

The filters “peer reviewed journals”, “articles” and “children” were applied to reduce the number of irrelevant studies that focused on community urban greening outside schools. The first author read titles and abstracts and screened whole articles where abstracts showed relevance to the inclusion criteria or if relevance was unclear. The second author independently screened two randomly selected samples of 50 results each (comprising 41% of all relevant studies). No disagreements were recorded.

Data extraction

Data from the studies that met the inclusion criteria were extracted by the first author, with results entered manually in Microsoft Excel© 2021 under the following headings:

  • Search term

  • Database

  • Author/s and source of publication

  • Included / Excluded (+ reason)

Additional data collected for included studies are indicated in Table 1. Extracted data were then checked by the second author.

Table 1 Data collected for included studies
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Results were imported into Zotero (6.0) and organised under the tag ‘included’ if the studies were relevant, or where excluded, under the relevant exclusion tags (Appendix 1 – Table 3). Several excluded studies carried multiple tags. As noted above, in this study we adopted a natural science-based definition of nature; activities and school grounds spaces that focus exclusively on harvesting crops were therefore omitted from the review.

Limitations

While this review adhered to the parameters set by the search protocol, it is possible that relevant studies might have inadvertently been excluded. In particular, the empirical focus of this review excludes grey literature, that is, research material not formally published through traditional academic publishing channels, even though it is noted that there is a considerable, and growing, practice of NBL in schools initiated by organisations and the state sector worldwide (e.g., among others: Nature Friendly Schools, and Learning through Landscapes in the U.K.; Natural Start Alliance, and International School Grounds Alliance in the U.S.; Nature Classrooms, and Aranyaka Upanishad Forest School in India; Learning through Nature in South Africa). Additionally, this research excludes literature not in English.

Results

Included studies

A total of 295 studies were found through the systematized search. Following the removal of 50 duplicates identified by Zotero, 245 studies remained, of which 11 were found to be relevant or partially-relevant (Fig. 1). Details of the 11 included studies are presented in Table 2.

Table 2 Results of systematised search: included studies
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Design of school grounds for Nature-based learning

A key aim of this study was to determine whether there is evidence-based guidance for designing school grounds to achieve NBL through the primary school curriculum. None of the 11 studies reviewed include explicit design guidance or made reference to such, with school grounds seemingly designed on an ad hoc and case-by-case basis. All studies espouse a philosophy consistent with the view that green school grounds lead to improved student outcomes. However, only three of the study aims or programmes are linked with a particular green feature; hence, while there are random details of school grounds green spaces, none articulate a design framework. Table 3 thus presents elements of the green spaces described in these studies, rather than clear design parameters. The most common elements referred to are: trees, gardens, water features, and plants (n = 5). The most indicative insights as regards specific causal relationships are from Khan et al., (2019), who emphasise that the outdoor classroom or gathering space must be surrounded by natural elements for access during lessons, from Sivarajah et al., (2018), who conclude that diverse tree cover is the most significant vegetation factor contributing to academic performance, from Puhakka et al., (2019), who focus on exposure to biodiversity leading to improved physical and mental states, and from Zaballa et al., (2021), who deliberately introduce plants to increase children’s knowledge and understanding of them. The age ranges of the sample populations in these studies, however, vary widely.

Table 3 Features of natural areas mentioned in included studies
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This study also seeks to examine what knowledge is available specifically to guide the implementation of NBL in small, urban schools. However, none of the included studies is based in school grounds with small footprints, as can be evidenced by the descriptions of natural spaces provided, though most studies (n = 7) are carried out in urban schools, often in poorer neighborhoods. In fact, the research aims in several of these studies are related to the effect of school grounds nature on children in urban schools (Camasso & Jagannathan, 2018; Khan et al., 2019, 2020; Sivarajah et al., 2018; Tucker & Izadpanahi, 2017; Zaballa et al., 2021). Two of the included studies’ school grounds appear to have extensive and diverse spaces with pathways connecting multisensorial destinations (gardens, water themed areas, loose parts, opportunites for active learning and passive reflection). White et al., (2018) provide no description of the school grounds; however, by inference from the fact that the program’s key focus is birdwatching, the school has natural spaces large enough for urban birds to frequent or may be surrounded by natural areas or gardens.

Outcomes of NBL programmes and links with design features

Three studies mention specific curricular outcomes (Camasso & Jagannathan, 2018; Khan et al., 2019, 2020), i.e., improved student performance in mathematics and/or science, though this result relates to older primary or even post-primary children. While the age range of the study by White et al., (2018) is fully within the inclusion criteria, it is unclear whether the six-week bird-feeding and monitoring project is related to the curriculum. Sivarajah et al., (2018) report improved general academic performance, although the age range does not correspond fully with the target age bracket of this research.

Only one of the studies (Khan et al., 2020) provides empirical evidence of links between green school grounds features and specific outcomes, in that it describes a design philosophy and how it translated into elements of the outdoors classroom (Table 3). None of the three studies that record improved outcomes in mathematics and science provide a description of the design elements that are potentially linked with these outcomes (Camasso & Jagannathan, 2018; Khan et al., 2019, 2020). The only descriptors of the green space where these studies are conducted are vague (e.g. “outdoor environment”, “direct nature experience”), and general categories of elements (leaves, seeds or sticks from nature) of the natural areas (Table 3). Sivarajah et al., (2018) note tree cover as being a better predictor of children’s academic performance than other vegetation, while Zaballa et al., (2021) describe improved comprehension of plants and plant diversity in the school with green areas over the control school, though it is not stated whether this knowledge is part of science lessons. None of these studies specifically refers to CN outcomes.

Among results that mention CN-related outcomes (Table 3), the study by Puhakka et al., (2019) is more of a preschool study but has been included in the review since it includes 5-year-olds and describes a program of learning activities; however, the activities mentioned are commonly associated with preschool learning, such as exploration, play, and multisensory experience rather than primary school traditional curriculum subjects. While Tucker & Izadpanahi’s, (2017) study includes nature in the school grounds as part of its sustainability design ethos, the study is not designed to distinguish between the effects of the physical design aspects and the natural design aspects on the study’s outcomes related to environment attitudes and behaviors.

Study characteristics

The evidence base produced by this review does not cover all primary school ages equally. Participant ages across the 11 studies (Table 3) mostly lie within the upper primary bracket, that is, 7 or 8 years and older (Camasso & Jagannathan, 2018; Green & Rayner, 2022; Khan et al., 2019; Sivarajah et al., 2018; Tucker & Izadpanahi, 2017; White et al., 2018), with only three studies focusing on early to middle primary (Loureiro & Dal-Farra, 2018; Puhakka et al., 2019; Wallace, 2019; Zaballa et al., 2021).

Research methodologies across the 11 studies also vary greatly, with most employing mixed methods techniques (Camasso et al., 2018; Khan et al., 2019; Green & Rayner, 2020; Khan et al., 2020; Loureiro & Dal-Farra, 2018; Puhakka et al., 2019), two studies using quantitative methodology (Sivarajah et al., 2018; Tucker & Izadpanahi, 2017), one qualitative study (Zaballa et al., 2021), and one study applying experimental design (Camasso et al., 2018). Some studies are carried out over an extended period (Camasso et al., 2018; Green & Rayner, 2020), others hold post-intervention studies (Puhakka et al., 2019) and two studies are based on pre- and post-intervention research (Khan et al., 2020; White et al., 2018). The authors of one study base their main research on images, specifically children’s drawings (Zaballa et al., 2021). Validity and generalizability of results also vary across the studies, with sample sizes ranging from one class in one school, to a large number of schools within a city or region.

The 11 studies present a diversity of aims, with dependent variables ranging from academic performance, to physical activity and wellbeing levels, to interest, empathy and attitudes towards the environment. Study aims are reflected in program aims, which either focus on academic subject performance, physical wellbeing, or knowledge and understanding of nature and the environment, with some studies more concerned about a phenomenon related to green school grounds than a specific program. When study aims are matched with results, the outcomes that show the clearest links with NBL are: improved academic performance, specifically in mathematics and science; increased physical activity and play; improved well-being; increased awareness, interest, and understanding of natural elements or the natural environment; and improved relationships with the environment in terms of attitudes and behavior (Table 2).

All relevant studies are relatively recent, having been published since 2017. Since there was no date restriction on the review, the implication is that there is increasing interest in the subject area. However, the evidence base remains small and studies are currently too inconsistent to provide a clear framework for the design of such spaces. Studies also have limited cultural and geographical representativeness. While countries span quite diverse geographical contexts (Fig. 2), not all continents are represented and few countries are represented, mostly by single studies.

Fig. 2
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Studies by geographical region and frequency

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Discussion

The eleven included studies provide an indication that there are positive benefits of curricular NBL amongst primary-school children. These results are encouraging and suggest that investment in NBL may well be worth pursuing. At the same time, it is amply clear that there is a need for more evidence. The small number of included studies and the fact that these are representative of a wide variety of geographical contexts limits generalizability. It is also worth noting that climate and ecology are key determining factors for green school grounds design but vary widely across the world. For example, water features (lakes, rivers, fountains) were present in five of the studies in this review, but such features may not be available or sustainable to maintain in arid or semi-arid climatic contexts. In such contexts, an alternate feature leading to the same desired outcomes would therefore need to be sought. If for example, a lake provides an aesthetically pleasing/relaxing effect in one geographical context, it might be replaced by rows of graceful palm trees in a drier context. In this review, Sivarajah et al., (2018) suggest that a varied tree cover is a better predictor of children’s academic performance than other vegetation types, raising the question of whether there are natural elements that would generate the same outcome in urban schools that may not have adequate space for a variety of trees, or in climatic contexts where tree growth may be constrained. A third pertinent example from a study by Paddle & Gilliland, (2016) reveals that children perceive the restoration offered by schoolyard trees as being influenced by seasonal changes in foliage, a result that is only applicable where deciduous trees are native to the geographical region. While it is possible that NBL applied through different locally-adapted natural features would have the same effect on children’s CN and other NBL outputs, as evidenced by the improvements in outcomes of the different variables tested in the review studies, there nevertheless remains a need for a wider and stronger empirical evidence base that is better representative of different climatic and ecological realities.

Context is also important given evidence that NBL practice is mediated by cultural influences (MacQuarrie, 2018). According to Vygotsky’s zone of proximal development theory, a child’s psychosocial transformation is mediated by the social context and interaction with the adults in it (Gredler, 2012). For instance, a school that employs a traditional reductionist curriculum (separate subjects) might need a different design approach than a school that adopts a forest school philosophy, where the environment is an integrated context that stimulates cross-curricular learning. Adapting an outdoor education approach necessitates careful cultural consideration, an argument also made in a critique of forest schools in the UK by Leather, (2018). Culture plays a determining role in creating the learning context and in assisting the child in the learning process that appropriates meaning and enacts competencies found in the learning context (Ferreira, 2014). While much of the nature connectedness literature represents Western perspectives, the human-nature relationship itself is very much a cultural product, and manifests itself differently among different cultural groups (Krettenauer et al., 2020; Sedawi et al., 2021). For instance, while cultural and societal beliefs about education and family backgrounds have been identified as potential barriers to the acceptance of outdoor education and NBL practice (Dyment, 2005; Oberle et al., 2021; Rickinson et al., 2004), this may not be the case in countries traditionally associated with forest schools, such as Denmark. Nevertheless, this review provides little insight into how cultural variables may manifest in different programs and the green school grounds design that would support them, with cultural influences not explicitly addressed.

Another crucial constraint on greening school grounds is available space. The studies in this review predominantly illustrate examples of NBL in large areas: although there is no specific indication of the footprint occupied by different features, it is doubtful whether most of the features themselves (except for the kitchen garden in Wallace, 2019) can be accommodated in small spaces. Based on this review, there appears to be little guidance on how NBL can be implemented within schools with small footprints. However, while the included studies do not provide sufficient design guidelines for different types and footprints of primary schools worldwide, they nevertheless provide valuable insight into elements for inclusion in a design framework. This becomes particularly relevant if viewed through the lens of Gibson’s theory of affordances (Gibson, 2015), where the outdoor space can become a series of material possibilities and restrictions for the provision of meaningful experiences (Puhakka et al., 2019). The danger in this case would be to over-simplify the overall influence of a green space in favour of its individual elements as affordances: “Affordances exist in relation to the perceiver, but cannot be constructed subjectively by the perceiver” (Puhakka et al., 2019, pp. 2 – 3). Green school grounds are as much relational as they are situational. More research is thus needed on whether elements of green spaces in large schools can be selectively adapted to schools with a small footprint to achieve the same results. The more frequent features in the studies in this review (Table 3) could provide appropriate subjects for research.

The results of this review also indicate a dearth of research on the middle-to-early primary years in connection with NBL and outdoor learning. It is suggested that effective design of NBL spaces on school grounds should be informed by knowledge of the relevant pedagogy and developmental psychology pertaining to the intervention age besides other participant-related mediating variables (e.g. curriculum, attainment level, desired outcomes). Early years settings, for instance, tend to focus on free play and on viewing the environment as a third teacher that provides a multiliterate learning environment, after the Italian Reggio Emilia approach (Cortés Loyola et al., 2020). Older primary student teaching may tend to follow a subject-based curriculum based on subject learning outcomes. More progressive forms of curricular development adopt a cross-curricular approach or broader areas of learning (Wyse et al., 2018). Such considerations would be of crucial importance to primary schools that wish to implement whole-school NBL on their school grounds in limited spaces, possibly requiring zoning that is pedagogy, or development, sensitive. Again, the review results offer few insights on how this could be implemented in practice, suggesting avenues for further research.

Conclusion

This study sought to determine the current state of knowledge with respect to the design of natural spaces on primary school grounds for NBL. Key conclusions with respect to the three main research questions are as follows:

  1. 1.

    There is very little evidence-based guidance for designing green school grounds to achieve nature-based learning through the primary school curriculum. Only 11 relevant studies were identified through this review, and these vary widely in their scope, design and context.

  2. 2.

    Urban schools and/or schools that have small footprints are not well addressed within the identified 11 studies. There therefore appears to be a dearth of evidence-based guidance on whether and how NBL could be implemented within such contexts, which face particular challenges in accommodating natural spaces that can sustain teaching programs.

  3. 3.

    Available literature does not provide clear insights on the link between specific design features and programme outcomes. Although some design features are reported, these are often discussed in limited detail and there appear to be few to no studies that specifically consider the contribution of design elements to desired outcomes.

While recent years have seen an increase in research interest in school grounds for NBL, the design of school grounds for learning appears to be an under-addressed research area. The relationship between green school grounds design and mediating variables is complex, as indicated by this research, and as yet, there seems to be little to guide educators and school administrators in making informed choices and decisions when planning the design of available spaces on their school grounds. The provision of clearer and systematic design guidance could potentially provide a framework to guide implementation of NBL in practice, also allowing better comparability of different programs and thus a more robust basis for assessing NBL’s ability to contribute to specific outcomes. This therefore emerges as a priority for future NBL research, which also needs to better address a wider spectrum of geographical and cultural contexts. In particular, there is an urgent need for research that addresses the challenges of schools with small urban footprints, which increasingly represent a more common reality but that also face considerable challenges in implementing NBL. This is important not only to foster enhanced ecological literacy for all but also to address social injustices arising from inequitable nature access. Furthermore, it is important to recognise that efforts to implement NBL successfully also require parallel efforts across a variety of related research and practice domains, including teacher training, curriculum development and sustainable financing, among others.