Prompted by fast and extensive landscape changes throughout the world, landscape ecology aims to provide policy relevant information about landscape change and form the base for landscape management, design and policy (Wu 2013; Mayer et al. 2016). The discipline has a long tradition in reaching out and building bridges to fields of action such as landscape sustainability (Wu 2010), landscape approach (Reed et al. 2016), landscape design (Nassauer and Opdam 2008) and regional and landscape planning (Forman 2008). The contribution of landscape ecology to inform planning and research management has been addressed in conceptual and empirical studies (see e.g., Ahern 1999; Pedroli et al. 2006; Opdam et al. 2013; Wu 2013; Milovanović et al. 2020). Few studies have also analyzed how landscape ecology has been used in landscape planning practices and plan making (e.g., Termorshuizen et al. 2007; Bjärstig et al. 2018; Trammell et al. 2018).

How landscape ecology has reached out to landscape planning, i.e., the focus of this research, is especially interesting. Landscape ecology is an interdisciplinary scientific discipline that focuses on spatial pattern and heterogeneity, and specifically their characterization and description over time, their causes and consequences and how humans manage those (Turner et al. 2001). The conceptual and theoretical core of landscape ecology links natural and social sciences to understand landscapes as arenas where structural features and social construction converge (Pinto-

Landscape planning is prominent across the world as an integrated, collaborative practice on a regional scale (Steiner 2008; Selman 2012) and benefits from landscape ecology in manifold ways. It focuses often on rural areas or open landscapes, where conflicts between urban sprawl and recreational landscape values, agricultural production and nature conservation, and renewable energy production and aesthetics dominate (Mann et al. 2018). Landscape planning greatly varies from place to place and can be integrated into the institutions (e.g., in Germany), provide an input into strategic spatial planning (e.g., in Switzerland), be conducted as an ad hoc initiative (e.g., in the USA) or be largely missing (e.g., in Romania) (Hersperger et al. 2020).

Landscape planning as an academic field is undertheorized, as evidenced by the fact that very few scientific journals are devoted to landscape planning (with the notable exception of “Landscape and Urban Planning”). However, landscape planning has a strong tradition in addressing procedural aspects that has led to established planning procedures. They operationalize the planning process through a sequence of steps and are well suited to investigate the link between landscape ecology and planning. Well-known examples are Steiner’s Ecological Planning Model (Steiner 2008), Steinitz’ Framework for Landscape Planning (Steinitz 2012), and Ahern’s Framework Method for Sustainable Ecological Planning (Ahern 1999). In this line of work are also proposals that explicitly address landscape ecological planning (Wang et al. 2001; Hersperger 2006; Miklós and Špinerová 2019). The pragmatic conceptualization of the planning process into a sequence of steps should not undermine the fact that landscape planning, like any kind of spatial planning, must be accepted as an ongoing political activity that is geared towards negotiation and conflict resolution between different public and private actors, within an arena of dynamic multi-level power relations and funding regimes (Oliveira and Hersperger 2019).

Landscape ecological concepts hold a great potential for integrating landscape ecological knowledge into landscape planning (Botequillha Leitao and Ahern 2002). We understand “concept” in line with Merriam-Webster’s online dictionary as representing an abstract or generic idea generalized from particular instances (Merriam-Webster 2020). In the case of landscape ecology, these ideas can refer to the representation and organization of landscape elements (e.g., in terms of connectivity), to landscape characteristics (e.g., patterns) or to frameworks for landscape analysis (e.g., landscape services). Most of these concepts have an intrinsic spatial nature. The goal of this paper is to review recent publications to assess the use of landscape ecological concepts in planning. Specifically, we address the following research questions:

1. Landscape ecological concepts: What are they? How frequently are they mentioned in current research?
2. 2.How have landscape ecological concepts been integrated into landscape planning?
3. We present results on the identified landscape ecological concepts, their prevalence and integration into planning. The discussion centers on the use of landscape ecological concepts and on promising opportunities for landscape ecological concepts in planning.

4. Methods

   Data collection

   To collect our data, we adopted the PRISMA approach for systematic review (Moher et al. 2009). Four key journals in the field of landscape ecology were selected to conduct the analysis, respectively Landscape Ecology (LE), Landscape Online (LO), Current Landscape Ecology Reports (CLER), and Landscape and Urban Planning (LUP). The choice was based on (1) the relevance for landscape ecology science and (2) the clear linkages between landscape science into planning, based on aim and scope descriptions (for details see Supplementary material 1). All articles published in the four journals in the period 2015–2019 were downloaded and served as a basis for the analysis (n = 1918). The five years period was considered long enough to prevent distortions caused by special issues and short enough to keep the workload manageable.

   Identification and prevalence of landscape ecological concepts

   Since we are not aware of a list of well-accepted landscape ecological concepts that would be suitable for our analysis, we resorted to an early publication that identified landscape ecological concepts when discussing landscape ecology and its potential application to planning (Hersperger (1994). To account for recent developments, we analyzed the sample of publications described above. Based on reading the title, abstract and keywords of all papers, an extensive list of concepts, topics and types of landscapes was extracted (n = 39). The high number can be explained by the fact that these concepts are often rather specific because their names have been taken directly from the paper. Each concept was assigned to a type (landscape ecology sensu stricto, ecology, land change science, planning/management, landscape perception). These types were used for a first grouping. We distinguished concepts from (1) topics, in the sense that the later are considered a theme addressed within the broader scientific discourse rather than abstract or generic idea in landscape ecology (e.g., climate change, sustainability), and (2) types of landscapes (e.g., agricultural landscapes, historic landscapes). The extensive list of concepts extracted from the first screening went through subsequent regrouping. Synthesizing led to the definition of seven additional concepts, where the detailed entries in the original list are often used to describe the concepts.

   Then, all 1918 papers went through a keyword search to identify the use of early and additional concepts. We used the “pdfsearch” package in R programming language, version 3.6 (R Core Team 2020; LeBeau 2018) and searched for singular and plural forms and different variations of the concepts, e.g., for “holism”, we also searched for “holistic”; and for “classification of landscape types”, we searched for “classification of landscape”, “landscape classification”, “landscape classes” (see Supplementary material 1, Table A). Results are reported as frequency of use per journal and/or period and can be interpreted as an indicator of how prevalent these concepts are.

   Integration of landscape ecological concepts into planning

   The title, abstract and keywords of the papers (n = 1918 articles) were screened to identify papers which might show how landscape ecological concepts are integrated into planning. A subsample of n = 131 papers was identified, which was further assessed for eligibility by full-reading. We retained 84 papers: 52 empirical papers and 32 overview papers for further analysis (see Supplementary material 4). The overview papers were further differentiated into reviews of scientific papers, evaluations of plans and projects, and frameworks and essays.

   Full reading of the empirical papers allowed us to evaluate how landscape ecology concepts have been integrated into each planning step of the planning cycle. The planning steps were derived from works by Steiner (2008), Steinitz (2012), and Botequillha Leitao and Ahern (2002) (see Table 1). To systematically collect the data, we used a protocol which addressed the following questions: (a) which type of planning is addressed by the paper?, (b) to which planning level does the paper refer to?, (c) which concepts are integrated in any of the planning steps described above? The insights from the overview papers on the integration of landscape ecological concepts into planning were synthesized after careful reading. To ensure systematic interpretation, all readers applied the protocol in two articles, and we calibrated the assessments and interpretation through detailed discussions (for more detail see Supplementary material 2).

   Landscape ecological concepts in current research

   Table 2a lists the eight concepts discussed by Hersperger (1994). GIS was also mentioned as a concept but was omitted from our analysis since it has developed into a widely used tool. Over time, many differentiations within the composite concept of Structure, function, change have been developed. The three components of the concept now form the basis of many quantitative landscape assessments, e.g., with landscape metrics (Costanza and Terando 2019), and change (Land change) became a science of its own. Thus, Structure, Function and Change will be treated as separate concepts in the quantitative analysis.

   Our analysis of the papers published in the past 5 years identified seven additional concepts (Table 2b). In the following paragraphs, the concepts are described, while the potential of the concepts for linking landscape ecology and planning will be explored in the discussion section.

   Landscapes as socio-ecological systems

   Socio-ecological systems, also called coupled human–environment (H-E) systems, provide a useful integrated analytical framework to understand the relationships between humans and environment (Holling 2001; Miyasaka et al. 2017). While heterogeneity, hierarchy, and feedback mechanisms are essential characteristics of socio-ecological systems, different integrated approaches have been developed to understand socio-ecological systems, including system dynamic models, spatial optimization models, spatial Bayesian Network models, and agent-based models (Liu et al. 2007; Le et al. 2012; Miyasaka et al. 2017).

   Landscape ecological concepts in current research

   Table 2a lists the eight concepts discussed by Hersperger (1994). GIS was also mentioned as a concept but was omitted from our analysis since it has developed into a widely used tool. Over time, many differentiations within the composite concept of Structure, function, change have been developed. The three components of the concept now form the basis of many quantitative landscape assessments, e.g., with landscape metrics (Costanza and Terando 2019), and change (Land change) became a science of its own. Thus, Structure, Function and Change will be treated as separate concepts in the quantitative analysis.

   Our analysis of the papers published in the past 5 years identified seven additional concepts (Table 2b). In the following paragraphs, the concepts are described, while the potential of the concepts for linking landscape ecology and planning will be explored in the discussion section.

   Landscapes as socio-ecological systems

   Socio-ecological systems, also called coupled human–environment (H-E) systems, provide a useful integrated analytical framework to understand the relationships between humans and environment (Holling 2001; Miyasaka et al. 2017). While heterogeneity, hierarchy, and feedback mechanisms are essential characteristics of socio-ecological systems, different integrated approaches have been developed to understand socio-ecological systems, including system dynamic models, spatial optimization models, spatial Bayesian Network models, and agent-based models (Liu et al. 2007; Le et al. 2012; Miyasaka et al. 2017).

   Landscape ecological concepts in current research

   Table 2a lists the eight concepts discussed by Hersperger (1994). GIS was also mentioned as a concept but was omitted from our analysis since it has developed into a widely used tool. Over time, many differentiations within the composite concept of Structure, function, change have been developed. The three components of the concept now form the basis of many quantitative landscape assessments, e.g., with landscape metrics (Costanza and Terando 2019), and change (Land change) became a science of its own. Thus, Structure, Function and Change will be treated as separate concepts in the quantitative analysis.

   Our analysis of the papers published in the past 5 years identified seven additional concepts (Table 2b). In the following paragraphs, the concepts are described, while the potential of the concepts for linking landscape ecology and planning will be explored in the discussion section.

   Landscapes as socio-ecological systems

   Socio-ecological systems, also called coupled human–environment (H-E) systems, provide a useful integrated analytical framework to understand the relationships between humans and environment (Holling 2001; Miyasaka et al. 2017). While heterogeneity, hierarchy, and feedback mechanisms are essential characteristics of socio-ecological systems, different integrated approaches have been developed to understand socio-ecological systems, including system dynamic models, spatial optimization models, spatial Bayesian Network models, and agent-based models (Liu et al. 2007; Le et al. 2012; Miyasaka et al. 2017).

   Landscape and ecosystem services

   The Millennium Ecosystem Assessment (MEA) (2005) popularized the ecosystem services concept in the early 2000s. The mapping and assessment of ecosystem services have since been high on the agenda of many administrations. Like ecosystems, landscapes provide vital services to people (Keller and Backhaus 2020), i.e., the many and varied benefits to humans gifted by the natural environment. The ecosystem services concept is by far more prevalent in the scientific discourse than the landscape service concept. Some of the ideas that have inspired the development of the landscape service concept have been taken up by the broadening ecosystem services concept, as witnessed by the formulation “ecosystem services in the landscape context” and by the landscape approach. Termorshuizen and Opdam (2009) point out that in the context of landscape and ecosystem service discussions, “landscape” is used for all kinds of areas, whereas “ecosystem” is often associated with protected areas and biodiversity.

   Green infrastructure

   The concept of Green infrastructure refers to the network of green and blue elements such as remnant native vegetation, parks, private gardens, golf courses, street trees, and engineered options such as green roofs, green walls, bio filters, and rain gardens (Norton et al. 2015). Green infrastructure can promote ecosystem and human health in urban areas (Tzoulas et al. 2007). Unlike other types of public infrastructure such as roads, storm water systems, and schools, green infrastructure is often considered as amenity, not as a necessity (Benedict et al. 2006). Furthermore, the contribution of green infrastructure to mitigating high temperatures in urban landscapes, and to adapt to climate change more generally, has been widely recognized (Norton et al. 2015).

   Multifunctionality

   The concept of Multifunctionality highlights that landscapes tend to have multiple outputs and provides perspectives for “delivering joined-up policy where its core property of interactivity can be harnessed in ways that produce qualities valued by people” (Selman 2009). The concept developed from a feature of European agricultural landscapes (Otte et al. 2007) into an interdisciplinary concept which allows for understanding and analyzing landscapes from various perspectives, e.g., social, cultural, ecological, aesthetic (Bolliger et al. 2011). Landscapes serve multiple functions at the same time through (1) the same piece of land serving several uses, (2) an area being made up by many small areas dedicated to specific uses, and (3) interactions of uses (Otte et al. 2007). The concept is in line with the current shift from taming nature to reconnecting with nature, reflected by research directions on human-nature interactions, such as socio-ecological systems and human-wildlife coexistence (König et al. 2020).

   Land use

   Land use can be defined as “the total of arrangements, activities and inputs undertaken in a certain land cover type to produce, change or maintain it” (FAO 1997; Verburg et al. 2015). In other words, land use indicates the way geographic space is occupied by society and its activities. Typical land use categories include agriculture, grazing, forestry, transportation, residential, commercial, and recreation. The type of management and the intensity of land use affect stress and potential environmental degradation. The concept allows an integrated focus on structural and functional landscape aspects while addressing human agency.