Applying the Landscape Services Concept in Landscape Research: A Review

Considerable attention has been given to the concept of landscape services since the development of research on ecosystem services. However, from the landscape perspective, there are numerous challenges and unanswered issues regarding landscape services. The objective of this paper is to provide a comprehensive review about the state-of-the-art concept of landscape services and its corresponding approaches while trying to set up a foundation for further discussions. First, the definitions and classifications of ecosystem services and landscape services are presented. Second, the relationship between ecosystem services and landscape services, and the studies that integrate ecosystem services into landscape research, are discussed. Finally, an overview is provided concerning research conducted at multiple scales, and the various assessment and quantification methods used for mapping and studying landscape services, even though there are many challenges in establishing a comprehensive approach for such quantification and mapping.


Introduction
The ecosystem services (ES) approach is an effective way to strengthen the link between ecosystems and human well-being.Since the late 1960s (Odum and Odum, 1972), ES have been receiving significant attention in the scientific community.The terminology 'ecosystem services' was first used by Ehrlich and Ehrlich (1981).It represents a critical research agenda in the trans-disciplinary field of ecological economics, aiming to bridge the gap between ecosystem ecology and environmental and resource economics (Costanza et al., 2017) to gain public interest in biodiversity conservation, the societal and economic value of natural assets is emphasised.The mainstreaming of ES was marked by two key publications: Daily (1997) and Costanza et al. (1997).In the two decades since its development, an extensive list of publications has been generated regarding key issues such as definitions, classification, valuation and assessments, modelling, and mapping approaches.Furthermore, various associated topics have become key issues in multidisciplinary fields of research.The concept of landscape services (LS) is one of them.
The terminology 'landscape services' (LS) is becoming increasingly popular because it is always regarded as a synonym for ES, especially when referring to landscape research.However, these terms are not always the same.ES act as a bridge between ecosystems and human well-being.However, the landscape is a socionatural system -a holistic, appreciable and dynamic entity (Antrop, 2000) -that changes based on interactions with human activities.This means that landscapes involve natural ecosystems and total human ecosystems.Landscape science helps better understand the effects of the spatial distribution of human activities on landscape processes and structures through which services are derived (Müller et al., 2008).LS, focusing on the relationship between human interactions and landscape processes and structures, are topical issues in the context of landscape ecology and sustainability (Termorshuizen and Opdam, 2009).
There are many arguments supporting the importance and application of LS in landscape research.For example, the effective use of LS for land use management and planning (De Groot and Hein, 2007), such as the analysis of landscape patterns, processes, and functionality as a premise for land use planning, which is an established process in Central and Eastern Europe.Another application is during policy-making processes and landscape planning, i.e., the assessment and planning of urban green infrastructure (Gulickx et al., 2013).It also supports the development of landscape sustainability (Wu, 2013).
However, there are still many obstacles concerning LS, such as the typology, the relationship with ES, evaluation and visualisation approaches, and practical application in landscape planning and research (De Groot et al., 2010).Several reviews have been published to clarify the development of ES, but not LS.The need to differentiate LS from ES in landscape research using a coherent and unified approach is essential, especially because this confusion can lead to the formation of a non-standard discipline with a blurred boundary.Additionally, LS alone should be treated as the common ground for interdisciplinary research.
This study aims to provide a thorough knowledge base that distinguishes LS from ES and seeks solutions for incorporating the concept of LS into landscape planning and decision-making processes while contributing to the ongoing discussions.Section 2 presents the state-of-the-art concept of LS (definition and classification).Section 3 provides a coherent knowledge base regarding the relationship between ES and LS (similarities and differences), and the integration of ES into landscape research.A research overview of LS is provided (Section 4), incorporating multi-scale studies, and different assessment and mapping methods.In conclusion, future development prospects are discussed (Section 5).

Ecosystem Services
Many researchers have discussed the definition of ES (Costanza et al., 1997(Costanza et al., , 2017;;De Groot et al., 2002;MA, 2005), but a unified definition is still unavailable.Various definitions have been proposed in a multidisciplinary context.De Groot (1992) explained ES as 'the capacity of natural conditions and processes to sustain human needs', emphasising ecological processes and structures.Cairns (1997) believes that ES are functions that promote human survival and development.However, Boyd and Banzhaf (2007) presented ES as biological components, rather than invisible ecological processes and functions, directly utilised for human well-being.Similarly, Fisher, Turner and Morling (2009) proposed that ES are 'the aspects of ecosystems utilised (actively or passively) to produce human well-being' (p.645).
Currently, the definition of ES proposed by the Millennium Ecosystem Assessment (MA) may be the most widely used and recognised; ES are defined as 'the benefits from ecosystem functions and processes, which are favourable for human well-being, directly or indirectly' (MA, 2005, p. V).The term 'services' is used to denote goods, functions, and services.Regardless of the existing controversy, an extensive discussion has been triggered globally about ecosystem functions, goods, and services.Besides, the TEEB (The Economics of Ecosystems and Biodiversity) study defined ES as "the direct and indirect contributions of ecosystems to human well-being" (TEEB, 2010).

Definition of Landscape Services
The concept of LS has introduced a new approach for studies on multi-functional landscapes and spatial heterogeneity at the landscape scale.For instance, such alternative methods can be used to tackle the issue of quantifying invisible services (e.g., cultural services / aesthetic values).This concept was first used in a paper about the urban agricultural sector (Leones, 1994).Termorshuizen and Opdam (2009) proposed the terminology 'landscape services' to link landscape ecology and sustainable development, defining LS as 'a spatial human-ecosystems that offers additional ecological, social, and economic values based on human activities and landscape changes'.This concept considers the relationships among the locals, stakeholders, and the environment, promoting further collaboration across scientific disciplines and highlighting landscape patterns.
Currently, even though there are numerous corresponding publications, ambiguous boundaries still exist due to the lack of a unified theory about LS.Some of the key relevant arguments on the definition of LS can be seen in table 1, which aims to clarify the advance in the understanding of LS.This table shows that most researchers consider ES and LS as synonyms; the only difference being the matter of scale, rather than anything fundamental.However, from the perspective of specific disciplines (landscape planning / landscape ecology) and different stakeholders, 'landscape service' is a distinct term.Therefore, a clear dichotomy between the ES and LS concept is essential.

Classification Systems of Landscape Services
Significant efforts have been made by researchers to develop a clear catalogue for ES assessment, valuation, modelling, and policy-making (i.e., Daily, 1997;Syrbe and Walz, 2012), after Costanza et al. (1997) provided a list of seventeen services.Classification systems for ES mainly depend on ecosystem processes and functions.The typology put forth by MA is classified into four broad types of ES: provisioning, regulating, supporting, and cultural services (MA, 2005).However, the typology of ES does not consider the spatial pattern, and landscape elements and characteristics.A systematic typology and comprehensive framework for LS are currently lacking.LS are defined as 'the capacity of ecosystems to provide goods and services that satisfy human needs'.
They consider ES and LS the same, without fundamental differences, mainly a matter of scale.Willemen et al. (2012); Willemen (2010) LS are 'the flow of goods and services provided by the landscape to society'.
A modelling approach is elaborated to visualise the regional spatial and temporal dynamics in the LS provided.Syrbe and Walz, (2012) The term 'ES' is enlarged to 'LS'.LS are a broader perception manner and highlight the spatial characteristics and relationships.
The LS assessment through landscape metrics integrates three different service provision areas.Wu (2013) 'ES provided by multiple landscape elements in combination as emergent properties'.
LS are the core of landscape sustainability science in a changing landscape.But this narrow definition of LS refers to ecological services generated by landscape patterns or configurations (Bastian et al., 2014).Bastian et al. (2014) ES and LS are synonyms.LS are 'the contributions of landscapes and landscape elements to human well-being'.
They proposed that spatial aspects, landscape elements and characteristics, and landscape planning impact the LS provision.Hermann et al. (2014) 'All goods and services that landscapes provide for well-being'.
They argue that LS are more related to human habitats and cultural patterns, rather than natural processes and conservation.Vallés-Planells, Galiana and Van Eetvelde (2014) LS involve 'the social dimension of landscapes and the spatial pattern resulting from both natural and human processes in the provision of benefits for human well-being'.2014) developed a categorisation that is built on the CICES and combines the social dimension of landscapes, including three categories: provisioning, regulation and maintenance, and cultural and social life fulfilment services.Human wellbeing, as well as social and cultural dimensions have been considered at the landscape scale.More specifically, it emphasises the all-inclusive nature of landscapes and the benefits for human welfare, while considering human satisfaction.For example, health, enjoyment, self-fulfilment, and social fulfilment are included in the cultural and social services (See Table 2).Bastian et al. (2014) recommended a typology for LS (or ES), including provisioning, regulating, and social-cultural services, which clearly considers spatial aspects, and landscape characteristics and elements related to landscape planning and landscape ecology.ES and LS are considered to be the same only when the landscape dimension has been carefully considered.
Table 2 shows a comparison (differences and similarities) between the selected four ES and two LS classification systems.In this table, Costanza et al. (1997) classified ES into seventeen specific services.From the first column to the fourth column (Costanza et al., 1997;MA, 2005;TEEB, 2010;Haines-Young and Potschin, 2010a), different classification systems of ES are shown.Vallés-Planells, Galiana and Van Eetvelde (2014) and Bastian et al. (2014) developed LS classification systems based on ES systems that refer to landscape related aspects.Besides, in some cases, a particular category serves two purposes and hence, the additional service theme is mentioned in parentheses.
It should be noted that these systems are broadly similar, especially the ones related to ES.Since the classification systems for LS are generally derived from the ES typology, it is essential to seek a unique, practical, scientific, and rational classification system for LS.On one hand, landscape features, distinct service delivery processes, their relationship to human values, and the application in decision making should be taken into account for an effective classification system.This means that landscape patterns and spatial characteristics are essential.On the other hand, apart from being pleasant and joyful amenities (Haines- Young and Potschin, 2010b), cultural services are also essential when considering services that fulfil personal and social human satisfaction.Furthermore, it is hard to evaluate cultural services without information on spatial patterns and landscape functions.
Table 2: Comparison (differences and similarities) between seven selected main classification systems for ecosystem services and landscape services applied in many research areas (Costanza et al., 1997;MA, 2005

Similarities and Differences
The ES concept is an essential part of research on ecological economics.Assigning monetary value to the services provided by nature is not an innovative idea.McCauley (2006) argued that the term 'service' is a utilitarian approach towards nature, because only the goods and products that are considered valuable for human beings, and not for the landscape or ecosystems, are considered.However, owing to the fact that humans and other species all belong to the biosphere, Costanza et al. (2017) emphasised that ES should not only focus on human beings alone, but also consider other species in the world.Furthermore, ES recognise that human well-being and survival are closely related to nature; therefore, humans should show the appropriate understanding and gratitude towards nature.
The LS evolve from ES, but they do not have an owner-member relationship (Figure 1).A landscape includes different kinds of ecosystems (usually a mix of ecosystems), indicating that LS are a mixture and/or a superimposition of ES, with different functions at different scales (e.g., aesthetic attractiveness).
Furthermore, when compared to an ecosystem scale study, a regional ecological landscape is the most practical scale to conduct research on sustainable processes and mechanisms (Wu, 2013).It is also the bridge that links landscape ecology and sustainability science.However, landscape sustainability science is still in its formative stages, and few researchers have systematically studied the theories and methods related to regional ecological landscapes.
Both LS and ES highlight the link between ecosystems and human values and focus on the human dimensions of ecosystems.However, LS can describe the benefits provided by both natural and artificial landscapes, whereas ES focus on natural systems.The research on ES emphasizes the functional relationships between ecological processes and composition, but the spatial relationships between landscape structure and patterns are neglected.LS highlight the importance of spatial patterns and the spatial relationship between service providers and beneficiaries (Sun et al., 2018).It also underlines the society property, since landscapes provide social benefits to human beings.
There is a visible indication to see the rapid development of ES research, which is the soaring quantity of literature.A search using SCOPUS on November 11, 2018, produced 19,461 papers using the term 'ecosystem service' in the title, abstract, or keywords between 1994 and 2018.There are over 2,000 papers from 2015 to 2018, and over 2,800 from 2017 to 2018 alone.The papers typically focus on valuation, quantification assessments, and mapping.Contrarily, there are only 99 papers employing the term 'landscape services' in the title, abstract, or keywords between 1994 and 2018 (SCOPUS, Figure 2), of which 86 papers were published in the last decade.
The number of publications on LS is only 0.5% of those on ES.An increase in the number of publications since 2005 can be observed in figure 2. Most of the papers with the term 'landscape services' in the title, abstract, and keywords, were published in Ecological Indicators and Landscape Ecology.Each of these journals published nine articles since 2009, followed by the Shengtai Xuebao Acta Ecologica Sinica (5 papers) and the Sustainability Switzerland journal (5 papers).Four papers were published in Horttechnology (2013 -2016).The most important topics addressed were landscape planning, and the effects of landscape structure and patterns on the scale.Based on the data presented, collaborative efforts in LS research are absolutely imperative.Sining Zhang

Integrating Ecosystem Services into Landscape Research
In the last decade, researchers have tried to integrate the concept of ES into landscape research.Using the search terms 'ecosystem services' and 'landscape' in the title in SCOPUS (November 11, 2018), 333 relevant papers were found, published between 2008 and 2018, with over 50 papers per year from 2016 to 2018 (Figure 3).225 papers tackled case studies across the globe.
In general, ES and LS are considered synonyms only in the field of landscape planning (De Groot et al., 2010).An abundance of research has been carried out on integrating ES and landscape planning, such as the impact of climatic and land-use change on ES (Lautenbach et al., 2011), the impact of changes in landscape patterns on ES (Duarte et al., 2018), the development and planning of green infrastructure (Liquete et al., 2015;Zhang and Muñoz Ramírez, 2019), and, the advances in landscape planning (Ahern, Cilliers and Niemelä, 2014).LS are inevitably mentioned in these topics, because the LS concept is the key to analysing the relationship between spatial patterns and scales related to human activities.

Research Conducted at Multiple Scales
ES demonstrate a dominant role only at specific spatial-temporal scales (Hein et al., 2006), as observed in studies on the supply, demand, and flow of ES are in a dynamic state at the different spatial (local, regional, national, and global) and temporal (short, medium, and long term) scales.It is important for stakeholders to analyse these scales in terms of varied interests and gain an insight into the applicable institutional scales for ecosystem management decisions.There is an increasing awareness of the significance of spatialtemporal scales when analysing and evaluating ES.For instance, Syrbe and Walz (2012) investigated the spatial characteristics of ES and their relationship with quantified measures of landscape structure.Hein et  However, when ES are applied at the landscape scale, many functions are often lost or degraded, due to an excessive emphasis on landscape functions (Costanza, 2008).For example, an overemphasis of recreational functions may result in the destruction of historical heritage and biodiversity loss.Therefore, it is important to balance various landscape functions while exploring the relationship between the delivered services.In order to explain and analyse the complicated relationships of LS at various scales, it is essential to know the association relationship of different LS at different spatial scales (Aertsen et al., 2012).Also, it is necessary to consider the dominant services at the same spatial-temporal scale, and the coordination of services and functions at multiple scales that contributes to meeting various community demands.
Landscapes are constantly changing, resulting in a change in LS provision.Each of the LS has spatial heterogeneity.For example, climate regulation services, at the local scale, are presented as services that relieve urban heat island effects and maintain favourable weather (Niemelä et al., 2010;Young, 2010).At the regional scale, it has a positive influence on maintaining a habitable environment for residents and good weather conditions for food production (Serna-Chavez et al., 2014).On the global scale, it plays a crucial role in controlling carbon emissions and reducing global warming.
Therefore, before applying LS to landscape research and further decision-making processes, it is essential to consider LS in different scales at the same time.The transmission mechanisms of multi-scale ES and LS analysed with a spatial-temporal perspective requires further investigation.

Assessment Framework and Quantification Mapping
The assessment and mapping of ES aims to understand the process of transforming data to visualise the results regarding the spatial distribution of ES with advanced GIS technology that has proved to be a great instrument in decision-making (Sherrouse, Clement and Semmens, 2011), and landscape planning (Zhang and Muñoz Ramírez, 2019).In the published literature, there are four main methodologies: (1) Literature survey method: It is based on the data applicability (Haines- Young and Potschin, 2009), but has high requisitions about the diversity and reliability of data.
(2) Modelling method (Nelson et al., 2009): Most cases using it that neglect the landscape patterns and spatial heterogeneity.
(3) Assessment index method: It uses criteria and indicators to evaluate and map ES, including monetary evaluation methods, e.g., the market-valuing method (De Groot et al., 2010), and, the value of monetization; and non-economic evaluation methods, e.g., the participatory, deliberative choice experiment approach (Kenter et al., 2011).(4) Land-cover based approach (Burkhard et al., 2015;Burkhard et al., 2009): This method considers the land use patches alone, but ignores the mosaics of boundaries, which are also important in landscape assessment (Martín de Agar, Ortega and de Pablo, 2016).Also, it does not support detailed evaluation and applies only to large scale data.
There are only 26 articles with a title that includes the term 'landscape services' (in SCOPUS search, on November 14, 2018).17 of them focus on assessment and (or) quantification mapping of LS, which is a critical topic.In order to merge with landscape research, the existing literature usually combines the four methods used for ES to assess LS.Compared to the ES assessment results, the results of LS assessments can provide more accurate and valuable information, therefore, providing a knowledge base for broader decision processes.There are several reasons illustrating the importance of LS assessment results.
First, LS assessment results are helpful for community/regional stakeholders and land managers.For example, Kienast et al. (2009) utilised expert-and literature-driven binary links in Europe, which generates a broad-scale multi-functionality assessment framework of LS for land managers.Additionally, the public participatory approach utilises the knowledge of community stakeholders (Fagerholm et al., 2012) to reach a collaborative, bottoms-up landscape management approach, and capture the non-utilitarian value of landscapes and sensitivity to cultural services.It is also used in land management by the American Indian tribes (Carver et al., 2009) and conservation efforts in the Amazon (Bernard, Barbosa and Carvalho, 2011).However, it is limited by the experience and knowledge of stakeholders.Wu et al. (2013) combined the results of a field survey with spatial index data that identify hotspots and the relationships between LS in Beijing and its surrounding areas, illustrating the importance of LS for stakeholders.
Second, LS can be used in broader decision-making processes, especially in landscape planning.Willemen et al. (2012) proposed a modelling approach, which tackles the multi-functional characteristics of a landscape, classifies different spatial levels, and proposes a spatially explicit method to show the potential relevance of LS for decision-making in Gelderse Vallei, Netherlands.Hermann et al. (2014) assessed and visualised an array of LS, considering different spatial scales and levels of services, to adopt three different approaches -the Broader Habitat Approach, the Socio-cultural Approach, and the Landform Approach.
They provide an efficient tool to support cross-border landscape planning processes.
Furthermore, in order to promote landscape sustainability research, a LS approach is necessary.Fang et al. (2015) provided the LS capability-flow-demand framework that can utilise LS for practical applications.
Nowak and Grunewald ( 2018) assessed the LS supply in seven different study areas in the Malopolska Province, and characterised landscape sustainability by combining a qualitative and a quantitative analysis.
In conclusion, the assessment and mapping approaches of LS are mainly derived from ES but have distinctive features.The former synthesizes various methods during the evaluation and visualization of LS in the landscape dimension to help meet human needs, enhances the participation of the public and stakeholders, promotes practical applications of the concept, and addresses landscape sustainability in the context of trans-disciplinary research.
However, some factors of LS (landscape patterns, heterogeneity, elements and features) are not fully understood.Additionally, there is insufficient research based on practical case studies.Furthermore, landscapes are always in a dynamic state, hence, ES and LS are also dynamic changes in the development process.The dynamics regarding LS are significantly relevant to environmental management and decision making.Therefore, identifying these dynamic changes and determining its possible critical thresholds will be among the challenges for future researchers.

Conclusions and Recommendations
Although the concept of LS is derived from ES, and they are treated as synonyms in many studies, LS generate higher added value and provide a common ground unifying various disciplines (Termorshuizen and Opdam, 2009).Furthermore, LS can meet the demands of different stakeholders, promote broad-scale decision-making processes, and enhance landscape sustainability research.Hence, in future studies, LS should be regarded as a separate concept, instead of being a substitute for ES, and pursued in detail.
First, it is essential to develop and clarify the definition and typology of LS associated with landscape characteristics related to spatial patterns and the dimension of human activities.However, according to the typology of ES in the literature, one universal classification system does not exist since different disciplines and scientific purposes have led to different classification standards.Although Vallés-Planells, Galiana and Van Eetvelde (2014) and Bastian et al. (2014) have attempted to classify LS, it is still challenging to identify a fundamental category.
Second, the assessment and quantification methods for ES and LS are almost the same.Although in most studies on LS, several assessment methods are applied at the same time.Therefore, the next step would be to develop specific methods or tools to support the assessment and quantification of LS, and to establish a comprehensive framework involving socio-cultural, ecological, and economic values to support decisionmaking processes.
The existing literature has depended on the data on land use to ignore other choices.There is a large amount of data waiting to be explored.For example, mapping LS are not related to land use alone, but also to landscape features.The current maps of landscape functions and services include models and geo-statistical simulations (Ungaro, Zasada and Piorr, 2014), on-ground observations and spatial indicators (Gulickx et al., 2013), and the knowledge of community stakeholders about aerial images (Fagerholm et al., 2012).
Although the map of landscape functions should also show heterogeneity in the quantity and quality of services provision (Meyer and Grabaum, 2008), spatially explicit data on landscape heterogeneity is still unavailable.
Additionally, spatial and temporal scales are key issues in the assessment and mapping of LS, since the landscape perceptions of stakeholders, regarding both supply and demand, are varied at different scales.
The last but not least, at present, the world is seriously threatened by climate change, and scholars have begun to explore solutions based on ES.When it comes to concepts such as carbon sinks, it is necessary to mention mountain ES.Many current studies have assessed the trade-offs (Briner et al., 2013;Mina et al., 2017), and influencing factors (Arjjumend, Shibata and Fakana, 2018;Boix-Fayos et al., 2020), and Sining Zhang  (Briner et al., 2013).Therefore, continued scientific research and case studies are needed in order to achieve a comprehensive methodology to assess and map LS, with respect to landscape features, patterns, processes, and scales, as well as pay more attention to how to combine mountain ES with LS theory and methods.
In conclusion, the LS research community is still in the early stages.Further effort is required to improve this scientific knowledge bases and overcome obstacles.Taking the development of ES as a reference, more studies and projects on LS should be conducted, similar to the TEEB and the CICES project for ES.
They developed a classification for LS based on the Common International Classification of Ecosystem Services (CICES) and a review of the literature.Westerink et al. (2017) LS are delivered effectively by the biophysical landscape conditions, with a new role of enhancing social capital in landscape governance.LS are more suitable for studying social capital and ecological networks.In order to integrate ES at the landscape scale easily and to apply these services in landscape planning and decision making, researchers proposed classification systems for LS adapted from the classification systems for ES.De Groot et al. (2010) provided a categorisation similar to the ES classification since they consider ES and LS to be synonymous.Vallés-Planells, Galiana and Van Eetvelde (

Figure 1 :
Figure 1: Chart of relationship between ecosystem services and landscape services.portray the effects of human activities.

Figure 2 :
Figure 2: Comparison of published papers on ecosystem services and landscape services.Graphical representation based on SCOPUS search (November 11, 2018).
2006) analysed the spatial scales of ES and elaborated the framework that enhances the applicability of ES valuation for decision making in the De Wieden wetland in the Netherlands.Wang and Dai (2020) identified the main factors affecting ES in the Heng-duan Mountain region.

Figure 3 :
Figure 3: Number of published papers integrating the ecosystem services concept into landscape research.Source: SCOPUS search, November 11, 2018 temporal and spatial variations of mountain ES in the context of climate change.Even if the climate change factors are not considered in the assessment, the studies show that the trade-offs of MES in future scenarios are significantly affected by climate change