A Classification and Interpretation of Methodological Approaches to Pursue Natural Capital Valuation in Forest Research

Abstract

This paper reviews natural capital (NC) valuation approaches in the context of woodland, forest, and riparian ecosystems, emphasising the need for participatory methods to take priority over neoclassical economics approaches. Focusing on research carried out in Scotland, the study analyses findings according to a classification of natural capital initiatives that we have developed, building on ideas proposed by the UK ENCA initiative, a guideline proposed to help researchers and practitioners understand NC and take it into account in valuation, decision-making and policy. We have found that landscape-scale initiatives that address the relationships between people and place to inform value and decision-making beyond the economic (monetary) benefits generated by ecosystem services (ES) are becoming popular. For instance, recent methods employed to capture stakeholders’ non-utilitarian preferences include the use of participatory GIS mapping, scenario planning, and other participatory methods to identify, explore and quantify less tangible cultural ecosystem services (CES). The review shows that many studies provide information relevant to the formulation of a place-based NC approach, working towards the integration of contextual and relational values into land management decisions to help formulate management strategies that maximise ES delivery. Conversely, we have not found evidence of the integration of shared values arising from an eco-centric perspective of nature valuation into the more classical, instrumental value lens. Such an approach would help inform broader, overarching aspects of woodland and forest management that may foster more effective conservation and help to manage conflicts.

1. Introduction

There is a high degree of recognition of the importance of conceptualising the natural environment as natural capital (NC) to help promote more sustainable policies and decision-making. Bateman and Mace [1] define natural capital as: “those renewable and non-renewable natural resources (such as air, water, soils and energy), stocks of which can benefit people both directly (for example, by delivering clean air) and indirectly (for example, by underpinning the economy)”. In other terms, NC provides the flows of “ecosystem services” (ES) from which people derive benefits [1]. The concept of NC is rooted in economics, which treats environmental resources as economic assets (like reproducible, manufactured capital) that must be protected in order to sustainably maintain the ES upon which all life depends [2]. We adopt, in this paper, a more extensive view, where NC also holds importance for societal wellbeing and encompasses consideration of the landscape, geographic, place and livability roles of the environment in shaping human relationships [3].

According to the traditional view of NC embedded in the concept of capital assets, natural resources can be treated under accounting rules by the formulation of balance sheets and risk registers [4]. The implementation of an NC accounting approach is certified by hundreds of policy documents and initiatives of local, regional, and international scope. These have been launched and promoted by various offices of national statistics to test accounting rules for resources and ecosystems in line with the United Nations System of Environmental Economic Accounting (SEEA) [5]. UN SEEA follows the system of National Accounts to present information about the contribution that NC makes to economic activity, to recognize the full value of natural resources such as soil, vegetation, animals, water, and biodiversity [6]. The application of this framework at corporate scale (The Natural Capital Protocol), for example, represents an attempt to understand business dependencies and their impacts on nature [7,8].

Furthermore, embedding NC accounting into standard frameworks for capital accounting contributes to the formulation of “inclusive wealth indicators”, a new measure of economic progress that justifies the benefits from investing in natural assets more appropriately than GDP [9]. The Dasgupta Review [9] stresses that humanity underestimates the values of nature, resulting in its “overconsumption”, and promotes NC accounting as a necessary approach to improve the design, implementation and monitoring of policies (and practices) aimed at the sustainable use of NC and biodiversity conservation, as well as a move to advance relevant policies for the correct pricing of natural resources and their correct funding [10], management and use. However, concerns around the economic valuation and accounting of NC are particularly expressed where values connected to people and landscapes cannot be reflected in purely utilitarian metrics and appraisals [11], which typically are used in cost–benefit analysis, but are considered insufficient and ineffective in solving “wicked problems” [12]. In addition, economic valuation alone is not always considered to be a sufficient condition for setting strategies to protect land, or valorise citizens, landowners, and land managers as environmental stewards [3]. Therefore, improvements in NC valuation to underpin decision-making [13] and for orientating policies addressing climate [14] and biodiversity concerns [15] are required.

Conceiving of NC accounts from an ecosystem perspective offers a basis for monitoring the effects of policies on natural assets and socio-ecological systems, and whether these are properly embedded in the right measurement tools, programmes, and pilots. A number of recent studies on the role of these initiatives in the policy cycle process [16] demonstrate practical cases of using NC accounting in different geographic areas, at different spatial (and temporal) scales, and in different policy domains [17].

In the UK, NC is embedded in several national policies and in the devolved regional governments. For example, the Scottish Government has clearly stated its aspiration to increase the contribution of NC to a broader range of economic and social benefits in policies such as the third Land Use Strategy (2021–2026) [18] and Scotland’s Forestry Strategy (2019–2029) [19], just to mention a few. In the latter strategy, forests have been the object of revisions towards multifunctionality and protection, to be achieved by the inclusion of deliberative processes in decision-making. A recent paper on the integration of NC and ES approaches in 224 Scottish policy-relevant documents has summarised the situation as “good levels of conceptual integration of the concepts but persistent difficulties in turning the patchy knowledge of ecosystem functioning into proactive policy intervention and concrete measures” [20]. Such conceptual integration is a useful precursor to more tangible or specific changes, although such changes cannot be taken for granted.

Considering the interest in embodying NC in policies, the formulation of NC approaches in national- [21,22] and landscape-scale initiatives for governing private sector investments in NC through Regional Land Use Partnerships [3,23], and the difficulties in generating impacts [20], we explored what approaches might be most effective in influencing decision-making, reviewing recent research methods and strategies in support of monetary and non-monetary NC valuation approaches for place-based decision-making. To do this, the paper proposes first an overview of the “academic climate” in NC studies targeting the woodland and forest context at the international scale, and then summarises findings from methodological approaches to pursuing integrated NC valuation in forest research in Scotland. The goal is to report on the identification of state-of-the-art knowledge and highlight gaps in NC valuation, emphasising the importance of valuation for participatory and democratic deliberative approaches [24,25] to decision-making. Findings from the review are used to suggest, in the discussions, a new democratic approach to valuation to guide local decision-making in practice.

The paper is structured as follows. As Scotland is set as the geographic scope of the study, the policy landscape relevant to using natural capital approaches in this country is presented first. A methodological section follows, describing how the literature has been selected and analysed. The results show descriptive statistics of the prevailing methods and NC themes considered in the most recent and relevant scientific literature. The discussion contextualises the results in the light of research emerging in other environmental sectors, and proposes the most widely addressed themes, highlighting knowledge gaps and the reasons why the introduction of participatory methods into NC valuation is necessary and timely. Conclusions ensue.

2. The Policy Landscape for Natural Capital Valuation: A Scottish Perspective

The study uses Scotland as a basis for review, and therefore, we begin by outlining the current policy landscape in this country. This is important for understanding the role of NC valuation in developing a more sustainable management approach and use of Scottish forests, and how NC is operationalised through regulatory approaches and private finance mechanisms.

The main institution responsible for forestry policy, support, and regulations is Scottish Forestry. This agency deals with the crucial role trees play in tackling climate change and nature loss, supporting the economy and the people of Scotland’s wellbeing. They provide expert advice to Ministers on forest policy, and support and work with landowners, forestry professionals, communities and a wide range of stakeholders interested in forestry across Scotland. Importantly, Scottish Forestry emphasises their incorporation of stakeholder perspectives into new strategies to secure a green recovery for Scotland on its path to net zero, and describe efforts to translate the social capital created through participation in research and knowledge exchange into the more effective implementation of forest policies on the ground.

These activities are in line with the Science and Innovation Strategy for Forestry in Great Britain [26], which highlights a prioritisation of research across forest policy, practice, and academia on NC concepts, with natural capital accounting described as relevant to “monitoring progress towards environmental goals”.

This activity is translated into policies through which the Scottish Government manifests aspirations to expand wooded cover and increase the contribution of NC to a broader range of economic and social benefits, as proposed in the third Land Use Strategy (2021–2026) [18] and Scotland’s Forestry Strategy [19]. Both policies target the multifunctionality of forests, to be achieved by the valorization of a range of ecosystem services and their integration with economic, human, and social capitals.

In addition, the Scottish Government is active in embedding NC in policies across scales. These range from national accounting initiatives adhering to the standard practices of the Office of National Statistics [22,27] to placed-based projects that recognise people’s motivations, perceptions, and relationships with nature [28]. For example, public initiatives promoted by the Scottish Environment Protection Agency guide the valuation of NC at the landscape scale, while NatureScot has proposed a suite of NC accounts to inform place-specific rural and climate change policy [29], including those associated with woodlands.

The incorporation of NC, as a national indicator for economic success, into the National Performance Framework (NPF) suggests that the Scottish Government [30] is considering alternative metrics to traditional GDP as the main measure of economic success. These indicators focus on different measures of wealth, building on a wellbeing economy approach, and follow the inclusion of the conception of wealth proposed by the Office of National Statistics [22] in the UK National Accounts. New policy developments mark an expectation that the collection and use of NC data will be mainstreamed into secondary policy [31]. This indicates fundamental changes in their way of thinking, which may function to influence the direction of Scottish policy, especially of those policies associated with land use, land use change and forestry.

A number of avenues are being explored by the Scottish Government to operationalise NC approaches. These include a variety of mechanisms offering technical, knowledge-based or financial support to those seeking to use these approaches on the ground, via, for example, the Scottish Rural Development Programme funded Farm Advisory Service [32]. In addition, the Regional Land Use Partnerships (RLUPs) facilitate NC-led collaborations [33] involving government, communities, landowners, managers, private sector representatives and wider stakeholders. With the implementation of the RLUPs, a new mode of multi-level governance is proposed to navigate the protection of NC via complex public and private schemes [11,23].

Importantly, efforts to attract private investment in natural capital are being observed. “Scotland’s Forestry Strategy Implementation Plan: 2022–2025” [34] discusses NC at a conceptual level, drawing links with the Interim Principles for Responsible Investment and highlighting government ambitions for a “values-led, high-integrity market for responsible investment in natural capital” (Interim Principles for Responsible Investment in Natural Capital. Available at https://www.gov.scot/publications/interim-principles-for-responsible-investment-in-natural-capital/, accessed on 25 July 2024). This implementation plan goes beyond the creation of woodlands, and pursues the protection of Scotland’s rainforests by the inclusion of deliberative processes in decision-making and the rolling out of projects that highlight the wellbeing and (mental) health benefits stemming from woodlands. The “Interim Principles for Responsible Investment in Natural Capital” [35] outlines how policy can align with private initiatives and financing to create ethical natural capital markets.

The Scottish Forum on Natural Capital carries out activities to facilitate pathways for private funding, while the Scottish Government’s Green Investment Portfolio [36] considers opportunities for private investment in NC projects. The number of emerging private payment schemes for ecosystem services is growing [3], with the ambition to overcome barriers to scaling up investments in NC, caused by the undervaluing of nature as public goods, for which there is otherwise no clear incentive to pay. These schemes are supported by public investments to address mechanisms that make nature restoration projects attractive for private market investors (FIRNS, The Facility for Investment ready Nature in Scotland—https://www.nature.scot/funding-and-projects/firns-facility-investment-ready-nature-scotland/firns-aims-outcomes-and-eligibility).

3. Methods

The papers screened in this manuscript were selected from the ISI Web of Science Catalogue and the Google Scholar web engine. We have principally targeted research carried out in forest, woodland and landscape contexts promoting the formulation of NC strategies for valuation and decision-making. We carried out two main searches. The first was a scoping analysis of peer-reviewed studies exploring the role played by NC in the forest ecosystem by using the key string (“natural capital” OR “ecosystem services”) AND (“woodland”) for the period 1991 (date from the term NC becomes relevant) to 2022. In total, 3415 papers were returned by the Web of Science catalogue. The results from this analysis are important to understand the context and discover the areas of natural and social science that have had a significant influence on the concept of NC and its valuation. They were also used to refine the criteria for a second search, which was more comprehensive as regards the role that landscape can play in NC approaches, which was performed in the same web engines by using the key strings (“natural capital” OR “ecosystem services”) AND (“woodland” OR “forest” OR “landscape”). This second search covered the period until December 2023, and Web of Science returned 19,942 papers. Because our goal was to build a broad view of the typology of valuation methods proposed, we have not added to our search strategy any key words referring to the most common approaches used in mainstream economics for valuing goods and services from nature, such as “contingent valuation method”, “choice experiment” or “travel cost method”.

We screened papers referring to the Scottish territory (75 in total), considering any form of economic or social valuation, and providing implications for decision-making. Papers were discriminated based on auditing the title, abstract and introduction of each paper, leading to the selection of 37 titles. We also conducted a Google Scholar search using the same search strings and explored the first 10 pages (100 hits were consulted). Excluding duplications and papers not addressing valuation approaches clearly in the title, keywords and abstract, 17 papers were selected. In addition, a further search was carried out to consider recent research affecting the implementation of natural capital approaches in riparian woodland using the following string: (“natural capital” OR “ecosystem services”) AND (“riparian woodland” OR “riverwood”). Nine papers were found and four were included in the database. Of these studies, only one was carried out in the UK (Wales), showing a shortage of research in this area. Figure 1 reports the flow chart of the selected papers.

Finally, to build a discussion and allow a comparison with other sectors, we extended the analysis of the valuation of NC and ES to the marine sector. The search of Web of Science returned 46 papers, from which 17 were chosen for the discussion. Internal judgement from within the research team led to the use of 21 additional papers for the discussion, addressing the role of forests and woodlands as catalysts of social innovation, that were not initially retrieved by our search in the online catalogues.

The papers selected for the review (Figure 1) were collated in a spreadsheet and coded using an inductive approach by considering the goals, methods, and typologies of NC approaches implemented in each case study. We have formulated a subjective classification of NC approaches (

Table 1. Categories of NC approaches used to classify the literature. Our elaboration on ideas proposed by [37].

Classification	Description
NC accounting	Papers implementing accounting (biophysical and monetary quantification) to forests and woodlands
Monetization of ES	Papers valuing ES in monetary terms under welfare approaches for forests and woodlands, including non-use values
Understanding ES	Papers referring to the broad range of investigation into the ES and benefits generated by forests and woodlands beyond monetary values
Importance of collaboration	Papers suggesting innovation in the reduction of conflicts between stakeholders by using NC and ES emerging from the analysis of forests and woodlands
Emerging tools	Papers proposing tools for the analysis of NC and ES in forests and woodlands
Importance of geography	Paper emphasising how the valuation of NC and ES is affected by the space where forests and woodlands are located
Contribution to sustainability	Papers emphasising the sustainable management of forests and woodlands
Nature in relation with multiple capitals	Papers addressing NC in relation to other capital domains (human, social, manifactured, economic, financial)
Liveable places and place-based approaches	Papers emphasising how the locality counts in the emergence of relational and other cultural aspects

) that suits the reviewed case studies and builds on the knowledge summarised in the guidance suite “Enabling a Natural Capital Approach” (ENCA) [37], produced to help policy and decision makers when considering NC values. The classification of NC approaches that we propose reflects the goal of the ENCA initiative [37]—to produce knowledge that informs practitioners around the NC framework, provide monetary and non-monetary valuation of the environment, and build on NC accounting principles and methods. We consider that our proposal fits well with the ENCA ambition of searching and collecting public-facing knowledge to inform policy, as well as public, private and third-sector decision-making, with tools and guides for conducting assessments, NC accounting and spatial mapping. Importantly, also, our classification follows the ENCA recommendations in emphasising the use of deliberative methods and “social and cultural assessment” [37] in decision-making. We recognize the limitations of purely economic NC valuations that do not account for the wide range of social, spiritual, well-being and health benefits offered by forests.

Additional documents such as the ENCA Services Databook [38], the ENCA Case studies [39] and the ENCA Services Asset Databook [40] sit alongside the ENCA guidance offerings [37] to collate studies of economic valuations of ecosystem services and their impacts across the UK.

From each source selected to discuss the classification proposed in Table 1, a narrative has been extracted, with coding for the information proposed in

Table 2. Information coded for each paper included in the literature review—for details see Supplementary Material.

Authors	2. Title of the publication	3. Journal/book	4. Goal
5. Methods	6. Details of the methods	7. NC approach classification (Table 1)	8. Provisioning services
9. Regulating services	10. Cultural services Location	11. Payment for ecosystem services	12. Country
13. Location	14. Policy goal	15. Theme

. The typologies of NC approaches are explored in the results section, below, and contextualised in the discussions. For information extracted from the papers reviewed on the codes listed in Table 2, it is suggested to consult the section on Supplementary Material.

4. Results

4.1. Evolution in the Numbers of Papers

This section describes the results on the trends in NC research in the forest and woodland sector, globally. According to our results, based on a Web of Science search, the first papers on the topic appeared in 1998, with the aim of broadening the framework for environmental impact assessment, and were associated with Australian environmental policy. During the 1990s and early 2000s, papers on the topic numbered under 50 units annually, which signals limited attention from researchers at that time. In the period 2005–2010, the number of papers on the topic slightly increased (over 50 papers annually). However, a clearly growing tendency can be seen from 2012/2013 onwards (over 100 papers annually). In the last five years, every year, circa 350–400 papers on the topic have been published, certifying a growing interest in the NC approach in forest research (Figure 2).

From Figure 2, it is possible to see an enormous increase in the number of papers produced on NC, ES and woodland in the last 5 years, with more than 50% of the papers returned published in the period 2018–2022.

When analysing individual countries (

Table 3. Top 20 countries with the most hits detected (1998–2022).

Ranking	Country	Number of Hits	Share of Hits (Out of 3415 Results for 1991–2022) (%)
1.	USA	839	24.6
2.	England	595	17.4
3.	China	423	12.4
4.	Australia	335	9.8
5.	Italy	262	7.7
6.	Germany	225	6.6
7.	Netherlands	177	5.2
8.	Canada	173	5.1
9.	Japan	170	5.0
10.	France	164	4.8
11.	Spain	164	4.8
12.	Scotland	161	4.7
13.	Sweden	122	3.6
14.	South Africa	117	3.4
15.	Brazil	81	2.4
16.	Switzerland	81	2.4
17.	New Zealand	76	2.2
18.	India	72	2.1
19.	Romania	65	1.9
20.	Denmark	63	1.8

), dominance of the USA (839 papers) and England (595) can be seen. Altogether, 42% of all the papers on NC, ES, and woodland were returned from these two countries alone. The third most productive country is China (423 papers), where research on the topic has been dynamically emerging since 2017/2018. The five most productive countries (USA, England, China, Australia, and Italy) produced almost three quarters (72%) of all the papers returned by the search.

Scotland globally ranked as the 12th most productive country in research on NC, ES and woodland, with the first paper, appearing in 1994, discussing economic decisions behind CO₂ compensations [41]. Romania (65 papers) is the only Eastern European country visible in the top 20. The only middle-income countries included in the top 20 (except, as already mentioned, China) are South Africa (117 papers), Brazil (81) and India (72). It is not surprising that not even one low-income country is represented in the top 20.

The most frequently represented areas of research are Environmental Sciences (1353 papers), Environmental Studies (990) and Ecology (893). In the “Economic” field, a lower number of papers (508) is found, while the “Forestry” category reports 149 papers, and the category of “Regional Urban Planning” returned 70 documents. It seems that mainly environmentally oriented research has been carried out so far, while fewer studies fall within the economics and planning area. Forestry seems to be a somewhat under-reported category, although this under-reporting may have been caused by the key search used. Neither “natural” nor “capital” are frequently used as keywords, while the most used words are “ecosystem” and “services”. The words “biodiversity” (496 papers), “conservation” (476), “management” (463) and “land-use” (253) are among the most frequented. The 8th most reported keyword is “climate change” (221 papers), the 9th “valuation” (220), and the 14th “carbon” (162), which highlights a focus in current research on the environmental crisis and possible solutions.

If we focus on words occurring in titles, there are, as expected, four leading words (“ecosystem”, “natural”, “capital” and “services”), while the term “sustainability” (or “sustainable”) seems to be by far the most used in titles (559 papers). The word “economic” occurs in the titles of 172 papers (although this is only the 17th most frequently used word).

4.2. Descriptive Statistics of the NC Approaches

Figure 3 reports the classification of papers based on the typologies and roles of NC approaches, as proposed in Table 1. It is observable that several approaches spanning from economic valuation to non-monetary, participatory, and mixed methods have been proposed to classify NC initiatives in the UK. Applying this categorisation to the screened literature, it is possible to observe that there is not any particular dominant area. Only a limited number of studies address economic valuation (as also emerged from the international review) using accounting procedures or cost benefit analysis (CBA). The majority of articles address a broader set of values using participatory approaches, eliciting non-anthropocentric values. Place-based initiatives are very well addressed (15%), along with the analysis and understanding of ecosystem services (15%) and the formulation of new solutions (15%). Each of these categories is second only to the category “Emerging tools” (19%).

4.3. Classification of NC Initiatives Emerging from the Literature on Forests and Woodlands in the Scottish Landscape

In this section, we describe the literature reviewed by summarising the goals and approaches of the papers reported for each of the NC categories shown in Figure 3.

I. Natural Capital Accounting. It is noticeable that the literature has contributed to disseminating natural capital accounting rules for a relevant number of sectors, including woodland and forest. Methodological guides on ecosystem accounts were prepared for protected areas in England and Scotland [42] by the Office for National Statistics, compiled in line with the guidelines recommended by the UN System of Environmental-Economic Accounting (SEEA)—Ecosystem Accounting principles, which are part of the wider framework of the system of national accounts [5] (https://seea.un.org/ecosystem-accounting) (accessed on 15 July 2024). More specific support for the Scottish NC accounts was produced in 2022 [43], looking at the forest ecosystem as a provider of timber, carbon sequestration, air pollution removal and recreational services.

Notwithstanding these experimental accounts, scientific papers assessing the baseline and variations in the extent and condition (quality) of the forest system under different land use strategies and scenarios are limited [44,45,46,47]. These studies used different methods, from reviews of data to syntheses of maps and facts (to address the conundrum of producing renewable energy whilst limiting impacts on pristine ecosystems such as forests and peatlands [47]), and the implementation of NC accounts to examine the impacts of land ownership on ES supply [45].

More articulated is the approach used by Allan et al. [44], who set out—both conceptually and practically—how NC can be integrated in a general equilibrium model to track the impact of disturbances on the economy and environment, as well as addressing policy implications. Such a method of modelling the interaction between nature and economics is expected in the longer term to comprehensively consider NC stocks and ES, and track the impact of disturbances on aggregated and sectoral economic activities [44].

II. Monetization of ecosystem services. Related to accounting is valuation, with various degrees of monetization of ES, such as flood regulation [48] or carbon sequestration [49,50]. Models like the Joint UK Land Environment Simulator (JULES) and experts’ judgement were used to estimate the additional volume of flood water potentially lost by woodland through evapotranspiration and retained by the hydraulic roughness of the floodplain woodland. The results from these models were integrated with CBA to value the impacts of afforestation on peak river flows, under climate change projections, and on other ES [51], or coupled to Bayesian Belief Network (BBN) models to explore synergies between the functioning of ecosystems and their values elicited by stakeholders preferences [52].

III. Understanding ecosystem services. Most papers can be categorised in the group “understanding ecosystem services”. A greater number of studies addressed the problem of expanding the knowledge and use of ES. Participatory approaches were used to explore the ES associated with woodlands as they are viewed by individuals in Scotland, with the idea of reconciling objectives of multifunctionality with the legacy of past forestry systems that were not designed with multifunctionality in mind [53], and to facilitate mapping scenarios with key stakeholders to identify hotspots of ecosystem services and the landscape features underpinning such hotspots [54].

Qualitative and participatory methods such as interviews and workshops are often used to analyse ES and discover new benefits derived from NC, strongly drawing on stories of cultural or historical land use to argue for more material opportunities to create woodlands [55], and for co-planning exercises with managers to identify areas for potential woodland expansion, favouring mixed native woodlands with limited productive objectives [56]. Burton et al. [57] highlighted that, although woodland expansion is advocated by a number of Scottish policy documents, barriers to woodland creation remain, because of contested views on land use, along with concerns about trade-offs between ecosystem services and a lack of synergy between policies and plans. These issues were explored by implementing a mixed method approach combining document analysis, a stakeholder workshop, and semi-structured interviews. In another example, Bowditch et al. [58] described landowners’ concerns about the risks posed by forest expansion to gaming and recreational activities. Through the use of a participatory methodology, the landowners were able to see how forest expansion could create greater economic return throughout the life cycle, as well as to recognise its potential contributions to addressing climate change, landscape quality and a range of ES. In addition, Muñoz-Rojas et al. [59] showed how the implementation of the “landscape approach” could be used to examine potential conflicts in land use planning and between forest expansion, wind-farm development, and landscape protection.

IV. Importance of collaboration. The implementation of NC approaches in woodland contexts is also addressed in relation to reducing conflicts and facilitating knowledge formation. For example, Slee et al. [60] described how an NC approach was used to help resolve conflicts related to poor-quality farmland being designated for nature and landscape conservation, whilst the highest-quality farmland is often protected for food production. In some contexts, contrasting points of view between stakeholders have been addressed via participatory approaches to elicit non-monetary values emerging from forest restoration as a form of compensation for urban expansion [61]. Social innovation has also been promoted [62].

In addition, the analysis of NC has been aligned with new climate change information to shape decisions of forest planners [63], as well as to show discrepancies and gaps between scientists and land managers’ views related to knowledge co-production [64]. The NC approach could promote the role of private sector investment in public decision-making, and can be exercised through instruments such as biodiversity offsetting, philanthropy, voluntary carbon markets, sustainability funds, and climate bonds [65].

V. Emerging tools. In many circumstances, the implementation of approaches based on NC has contributed to the formulation of new tools for the analysis of natural resources and the support of decision-making. This is exemplified by the use of habitat suitability models investigating the effects of alternative land use change scenarios on landscape suitability for birds such as black grouse [66], and by the analysis of the impacts of farmers’ decisions on trade-offs between food, bioenergy production and the protection of passerine birds using agent-based modelling [67].

The evaluation of cultural services, based on the statistical analysis of pictures posted on social media, has recently been proposed to compare the spatial distribution of nature-based recreation to that of other ES, in order to understand where they overlap and what synergies and trade-offs emerge [68]. A tool to aid in the making of management decisions for recreation was implemented for the Cairngorms National Park (ESTIMAP-Recreation), parameterised by the knowledge of recreationalists, and validated by interviews with managers, residents, and visitors, asking if and how they considered the resulting maps useful [69].

Innovative solutions can be found in the analysis of participatory approaches dealing with the formulation of indicators and the mapping of cultural heritage [70], the production of indices for the monitoring of trends of natural capital (NCAI index) [21], and the integration of biodiversity offsetting with ES to discriminate between different land use management options such as urban development and new habitat creation [71].

Of particular interest is the integration of participatory methods with spatial modelling, an alliance of methods that is emerging as an aid to support discussions of natural resource management and collaboration between stakeholders in land use planning [11,72,73,74,75]. These methods make use of Public Participation GIS (PPGIS), which employs digital touch-tables to investigate landscape characteristics such as protected areas, landform, land use and accessibility [76], and they also identify, quantify, and list in a national register less tangible CES, such as symbolic and spiritual values [77].

VI. Importance of geography. Environmental effects often vary according to species, climate, and soil type. We found papers where the “importance of the geography” is reflected in the possibility of mapping and quantifying the new areas prone to be afforested [78,79]. Other works explored how new woodland creation can be delivered to optimise the provision of selected ES, using a recently proposed national afforestation target [80], or focusing on flood control [81]. In particular, at a small scale, flood control was found to be affected mostly by landscape configuration, while at the watershed scale, landscape configuration does not seem so important [82], reducing the importance of landscape variability for the supply of this important ES.

Landscape configuration is also important when analysing complementarity between biodiversity and a set of regulating ES relevant to lowland grasslands and croplands, in order to define a zonation for establishing conservation incentives schemes [79]. Landscape variability can also have a strong influence on the configuration of CES, informing their spatial context and providing arguments for geographic analysis at national and regional scales [83], and giving valuable information to shape land-owner networks and their attitudes to entry into ES payment schemes [84].

VII. Contributions to sustainability. Accounting for NC may contribute to assessing the ecological sustainability of forests under climate change and ecological responses [85], including under the effects of drought and wildfires [86,87]. The understanding of forests that, in old policies, were envisaged mainly as maximising the production of a single ES (timber and later carbon sequestration) is nowadays considered too limited to achieve the complexity of the problems faced by an articulated society challenged by multifaceted drivers.

Findings from the literature suggest that a clearer articulation of woodland benefits to humans is required, recognising both their variability over space and potentially detrimental impacts on other land uses [88]. The role of landowner motivations and attitudes was explored to balance out the uncertainty between tenure rights, estate priorities, woodland expansion targets and wider management issues [89], while local culture and land capabilities were explored from the perspective of individual land-owners and managers [56].

A theoretical framework to understand the contribution of social innovation to the sustainability of socio-ecological systems [90] and to evaluate social innovation in forest-dependent rural communities was developed [91]. The role of social innovation in attaining sustainability transitions pertaining to the management and use of natural capital was analysed and promoted by a number of activities and outputs, particularly those from the SIMRA (Social Innovation in Marginalised Rural Areas, 2020) project [92]. Moreover, a number of studies [93] suggested that it is important to explain and further promote the benefits (and values) of forests for local (e.g., forest dependent) communities; the importance for current and future generations of adaptive responses to challenges; and the role of social innovation for sustainable management and use of forest ecosystems [62]. A more holistic perspective on sustainability in forestry was considered necessary to improve the understanding of the complex interdependencies between economic, environmental and social conditions, which affect the organization of the use of land and its natural assets [94], especially since it is necessary to face the challenge of achieving multifunctionality [53]. A participatory and multi-level mode of governance, in a continuous process of adjustment, needs to be developed to enable forest decision-makers to consider the existing opinions and behavioural patterns of the diverse stakeholders who drive forest change and respond to it [11].

VIII. Nature in relation with multiple capitals. The multiple modes of analysing the benefits and uses of forests raises the importance of viewing NC as an element of complexity in a system characterised by the intertwined connections between different domains: benefits from ecosystems are not produced by ecosystems independently of humans, but arise because of people’s interactions with an ecosystem [95,96], because of interactions among different components of an ecosystem, and because of the ecosystem’s interaction with other ecosystems [97]. This consideration is not confined to the provision of CES, an area where the role of people has been more explicitly recognized, but includes all types of ES [95]. Therefore, NC, considered as an input of a complex productive process of goods and services, cannot be seen as disconnected from the other capitals. This is now recognised by the role of integrated capitals [98] in shaping better investment perspectives beyond the mere economic feasibility assessed by CBA [99]; by the formulation of systemic approaches targeting multiple domains and relations between natural, human and social capitals to address productive choices in the agrifood industry [8]; and by the proposal of accounts depicting changes in provisioning services to identify ways in which capitals, material inputs and outputs are linked to land management practices and policies [100].

IX. Livable places and place-based approaches. In the context of nature regeneration, NC forms an integral part of the infrastructure that underpins successful and “livable places”, in particular enhancing relational aspects between nature and cultural aspects of wellbeing, such as living well and in tranquillity with, and in, nature [101], and supporting and feeling a sense of attachment to a place [28,102,103,104]. Exploring these relational aspects may facilitate the adoption of new solutions for conserving NC and limiting conflicts among uses [102].

5. Discussion

5.1. Emerging Approaches Relating to NC Valuation in Forest Contexts

The results presented in this paper evidence that the last 30 years of research have been characterised by the introduction of novel approaches to the valuation of forests. The analysis of economic impacts of forest management (e.g., silvicultural approaches) through welfare valuation methods and appraisal by CBA seems to have received reduced attention in the recent literature, specifically in that addressing UK case studies [51], while most analyses have moved beyond a utilitarian perspective to consider a more holistic approach [105,106].

Multifunctional forestry has received significant attention [53], including carbon smart forestry [107] and community forestry [62]. The consolidated ES approach [108] exploring anthropocentric uses of the environment and its instrumental value has been widely used [109,110,111,112,113], providing a framework of reference for policy and decision-making for decades [103]. More recently, the narrative has shifted towards an articulated facet that encompasses both ES and stocks of resources (NC). The general terminology of NC has emerged worldwide, with multitudes of initiatives promoting tools for the accounting of ecosystems as complex sets of resources. This includes approaches that track current stocks of NC and their changes over time in biophysical and monetary units [5,27,43], and a range of methods that quantify, map, and value flows of ES using quantitative and qualitative metrics [99].

Of relevant and recent interest are landscape scale studies [114] and initiatives that address the role of communities’ bonds with places, inform regional land use and landscape planning [3,59,85,115], and provide finance mechanisms for nature protection, particularly operating in woodland and peatland contexts [116]. Their goal is to inform policy and investment decisions that incorporate the values of biodiversity and ecosystems to people, with the aim of improving human wellbeing by securing Earth’s life support systems [113].

The proliferation of multiple approaches to valuing and interpreting the role of nature, ES and benefits reflects the broad range of views related to capturing nature ontologies [106,117,118]. These approaches recognise that not all benefits derived from ES are amenable to monetary valuation (e.g., environmentally related social norms; the spiritual value of the natural world as a form of relational value involving both single individuals and the human collective in connection with nature) [119], and therefore, they cannot be valued under the mainstream economic framework [120]. These values require alternative solutions to the individually centred approach adopted by economics [11,121] and alternative measures to monetary values, such as subjective metrics of wellbeing and happiness [122,123]. The valuation of CES, following a place-based approach, seems to be established well in the marine context [124], though research is emerging also in the forest landscape to propose valuation beyond the economics of marketed ES [77,83,95,103,116,125,126]. CES such as place attachment, evaluated via methods such as coding filmed stories [102] or through the integration of participatory analytical and visualisation tools using Q methodology [127], are now common in the forest and landscape contexts [11].

The proliferation of NC approaches has attracted attention to the integration of environmental science, policy and management, although there is no agreed set of definitions for the terms used and no consensus on the most appropriate framework to apply, with the result that stakeholders can be discouraged from applying such approaches [128]. Efforts have been observed at the national scale to produce national accounts [129], but they seem ineffective in positively impacting local communities. To tackle this problem, stakeholder-driven approaches and social innovation initiatives, which enable the engagement of communities in NC discussions, are becoming a tool to address local concerns in decision-making, with several experimentations proposed in the marine environment [130,131], and to promote collaborative approaches to forest governance [115].

These approaches are useful for exploring how and to what extent NC has the potential to address socio-cultural values, such as cultural identities and human wellbeing. Recent examples of approaches depicting connections between natural and social values are the community voice method [132,133] and participatory mapping based on GIS analysis [131,134], which integrates stakeholders views and perceptions of ES provision with aerial and satellite images [130,131], as well as other visualization tools [135]. A number of studies in the forest sector address, locally, the analysis of preferences for landscape typologies through integrated visual approaches (GIS and 3D rendering of landscape), as explored by Nijnik and Miller [11], Miller et al. [115,136,137], and Nijnik et al. [50,138]. However, there is a lack of analysis, in the Scottish forest context, of relationships between cultural values and land management.

The implementation of Public Participation GIS (PPGIS) can help quantify symbolic and spiritual ES [76]. Accounting for the influence of landscape features in NC valuation using an interactive GIS approach [120], along with other approaches such as the Q method [114], can assist in paving the way for a more integrated participatory analysis to consider CES in land management decisions, and maximise the provisioning and regulating of ES delivery [126]. Opportunities for the integration of participatory GIS approaches reside in the importance of capturing a range of broader values that go beyond contingent aspects. We refer here to shared and transcendental values, including ethical principles and desirable end states such as “unity with nature”, that transcend specific situations [139], followed by the exploration of how these values facilitate the analysis of woodland landscapes, their conservation, and the management of conflicts under scenario analysis [140,141].

A final consideration can be made of the importance of knowledge formation for decision-making. Research shows that NC valuation can be enhanced by the incorporation of deliberation into common approaches eliciting individual preferences [25,142,143]. Deliberation through contingent valuation in the marine space, both in the Global North [130,131] and in the Global South [144], demonstrates how shared and transcendental values [145] can be elicited to assess pro-environmental behaviour, and how they might influence monetary valuations [139]. Deliberative monetary valuation for aiding decisions has not emerged in this review. Instead, innovative practices based on the integration of contingent valuation with the Q-methodology and Aggregated Ecological Indexes were used to quantify public attitudes to landscape content and understand public perceptions of land use changes to assist in decision-making [114].

5.2. Themes Emerging from the Typologies of NC Approach Proposed in the Scottish Forest Literature

The analysis of the recent global research context revealed that the use of NC approaches applied to the forest ecosystem has been the subject of a broad set of environmentally oriented research not only limited to studies addressing the implementation of NC within the sphere of environmental economics and planning. This is also demonstrated by a review of values and valuation methods made by the IPBES, focusing on more than 48,000 publications [105], wherein only 11% are statement-based valuations adopted to address economic values, while the majority are nature-based studies, and 9% propose integrated methods to explore multiple values.

These results are also confirmed by our analysis of the main themes emerging in the Scottish context, as proposed in Figure 4, which principally shows studies exploring the relations between forests and people (23%).

The theme of multifunctionality in forests is also important, as explored by 19% of the papers selected in our review. Also significant is the contribution of approaches based on solutions that may facilitate the protection of forests through the implementation of payment for ecosystem services (16%). Other themes, such as the role of stakeholder networking (7%), overcoming conflicts and trade-offs (7%), and the role of forests in reducing the effects of flooding and countering the effects of climate change, are less explored (9%). Examples addressing the economics of climate change mitigation by afforestation in the UK and the necessity of reconciling carbon sequestration forest policy initiatives with sustainable development were provided by Nijnik et al. [50]. Their results show empirical evidence that: (i) in certain cases (e.g., for certain species, management regimes, locations, etc.), afforestation projects in the UK may offer a relatively low-cost option for carbon sequestration; (ii) there is a strong case for forestry in Scotland to contribute to climate mitigation; (iii) woodland expansion is likely to be competitive with other means of removing carbon from the atmosphere, and (iv) it is important to place carbon forestry in the general context of rural land use in Scotland, where significant policy reforms are being observed.

The following four main themes emerged from more than 70% of the literature reviewed on Scottish cases, and we propose further discussions in relation to the NC approaches to valuation, concerning the following: (1) stakeholders’ views and the relationships between people and forests; (2) the role of woodland as a multifunctional asset; (3) the recognition of cultural services including heritage values; and (4) the promotion of financing mechanisms such as payment for ecosystem services and related tools, facilitating the blending of private and public finances for ecosystem conservation.

Stakeholders’ views and relationships between people and forests. It is emerging from the analysis of the NC approaches that the role of stakeholders is gaining more importance in research and practice. Interviews and focus groups are commonly considered a direct approach to collecting opinions and views on the roles, functions and values generated by the woodland landscape [28,64,94,95,125,146]. The emerging studies largely refer to the exploration of land use visions under Societal, Technological, Economic, Environmental, Policy (STEEP) drivers [146], an approach suitable for identifying factors that may significantly generate adverse repercussions for a business. The analysis of localised and focused individual perceptions of forest social–ecological systems [127], including in a protected area setting, is also explored [64], as are motivations for accommodating ES approaches in forest managers’ and conservation experts’ thinking [125].

We found that interactions between science, forest management, policy and climate change are commonly addressed by modelling forest growth [86,87] through the analysis of the physical and economic impacts of afforestation under climate change projections [48,51]. Beyond the modelling of climate change impacts and forest climate change alleviation capacity [147], examples of forest management supported by participatory approaches are becoming visible [107]. The role of social innovations in linking people and nature [62] and promoting the sustainable management and use of forest ecosystems is being recognised. However, its adaptation to climate change is more explored in agriculture [148] than in forestry. Data collected during workshops with forest-relevant stakeholders [149] can be used as a valuable tool to elicit changes in decisions about forestry practices (e.g., forest production, stand yield class, sequestered carbon, and potential tourism) and adaptive responses to changes under different climate projections [150] and policies [63].

The role of woodland as a multifunctional asset. This is becoming an important emerging theme in the implementation of NC approaches and valuation in relation to the role of woodland expansion to contribute to carbon emissions mitigation. However, a review carried out by Thomas et al. [88] recognised non-economic influences such as cultural perceptions and identities as multifunctional aspects of forests. External behavioural controls, such as economic compensations, expected to influence the behaviour of farmers and private investors, were not always considered important. Rather, biodiversity conservation, landscape improvement, shelter, and social or environmental outcomes were taken as primary motivations of many other groups, including communities, NGOs and hobby owners [53,56,61,86,95,151]. Having the goal of achieving multiple benefits, however, can generate conflicts among users because of the complex trade-offs between agricultural, recreational and environmental values, such as the setting of promoting hunting against biodiversity protection [60], or of encouraging windfarms against landscape protection [59].

The recognition of cultural services including heritage values. NC approaches in the context of woodland restoration and riverwood have not focused much on CES formation when dealing with climate change. A rare example is the filmed stories of West Yorkshire residents discussing a legacy of failed flood defences, although this topic is well researched in the marine context [103,124]. Of relevance is the analysis of CES carried out at different scales by different approaches, ranging from the use of systematic indicators of cultural heritage, which reflect both quantitative and qualitative aspects of human influence on land use and the built environment [70,83], to the analysis of social media pictures used to compare the spatial distribution of nature-based recreation with other ecosystem services to address synergies and trade-offs [68].

The promotion of financing mechanisms such as payment for ecosystem services. Mechanisms contributing to woodland conservation by blending private and public funds are well explored, even in specific and regionalised contexts where place-based mechanisms are proposed. The goal of new forms of finance is to move beyond mechanisms used by the Common Agricultural Policy (CAP), to which the UK no longer has any obligation, and which have had a very strong influence on land use in the UK and Europe more widely, by subsidizing agricultural production to introduce new environmental schemes, which pay farmers money for generating public goods [57,151]. Social equity in the governance of supplying ES via market approaches has been analysed [108].

Accompanying emergent markets for ES to stabilise revenue is fundamental for attracting land manager support and thus further develop forestry on estates. Many estates depend on diversification for survival, which supports the delivery of a wider range of public values such as regulating ES. This includes non-timber-orientated productive forestry aims, such as domestic energy, carbon sequestration, and recreation. The capacity of the land-based sectors in Northeast Scotland to mitigate climate change, with particular reference to the role of forests, has been analysed by Slee et al. [152]. Accessing carbon markets can be seen as a way to support the planting of new woodlands and encourage silviculture treatments to estate forests [58]. However, carbon markets, especially regulatory and international ones, still face numerous challenges [138,153].

Encouraging and enabling context-specific Payment for Ecosystem Services (PES) schemes, in which service-providers and beneficiaries are more closely related such that systems-level relationships are internalised and governed at the catchment scale, is discussed by Slee et al. [152], who suggest PES should work around ensuring the provision of a bundle of services, including flood alleviation, water supply, local food and energy to nearby settlements. PES schemes, based on the implementation of regional place-based approaches that incorporate multi-level governance, were proposed to bundle ES, including those provided by forest across multiple scales [3,11,23,122], working also on the notion of shared values [24,25,116,143].

5.3. Emerging Gaps and Suggestions for Future Research: Towards the Integration of Valuation Methods

This review has highlighted the recurrent approaches to the valuation of forest-based NC and emerging themes that would help facilitate a more integrated strategy for sustainable development. Approaches to NC valuation that fall into the category of multiple and integrated capitals analysis were shown to be of limited interest. However, specific thematic analyses of networking strategies, such as social innovation [154], have increased in many countries, including Scotland, Spain [62], and Ukraine [155]. These approaches of multiple and/or integrated capital analysis can be particularly interesting from a research standpoint, as they may lead to the understanding of potential trade-offs or synergies between natural, human, and social capitals that are still overlooked by policymakers and development agencies, as well as to the recognition of potential conflict situations that may arise. This has been recently recognised by Dasgupta [9], and was proposed in the last Scottish Land Use Strategy [18].

Gaining a deeper understanding of multi-target interactions between capitals will be useful for developing integrated approaches to achieving the valorization of forest stakeholders and local communities without jeopardising the environment. Consider Sarkki et al. [108], who demonstrated how pragmatism in environmental science and policy can undermine sustainability transformations, where people use existing policy agendas and scientific narratives to promote their own goals instead of being open to change. Thus, from a methodological perspective, mixed-method approaches can offer a winning strategy to achieve the multiple goals that the integrated views of capitals require. However, this integration is still in its infancy.

Recent research tackling the broad field of NC approaches has attempted to integrate mixed methods of valuing contingent and relational human–nature aspects in the marine environment [124] and in the context of wooded landscapes [115]. However, limited studies have addressed these aspects in a comprehensive framework through a combination of methodologies and tools (e.g., of participatory, analytical, and visual/digital, c.f. Nijnik et al. [156]) in the context of aiding management decisions. In addition, although some papers have addressed the use of participatory tools, such as those based on ES mapping and GIS analysis to explore stakeholders’ preferences, they were not designed to investigate at depth the intrinsic values upon which contextual preferences may find support. Indeed, Kenter et al. [157] warned there is a danger of a methodological divide, in which conventional economic valuation techniques deal with utilitarian and productive services, whilst more deliberative and participatory methods deal with shared social and cultural ones, in isolation from each other. The analysis in this paper adds support to this, and emphasises the important need for the greater integration of valuation approaches.

Future research should propose new avenues to achieve integration in NC valuations of local stakeholders’ perspectives by considering a broader range of values, such as the value typologies proposed by the IBPES [105,106,158] that comprehend guiding principles and life goals, along with more specific and contextual values, the latter explored by the MEA [109] and the UK NEA [111]. This broad set of ontologies, also referring to the overarching Frame of Life [158], could be used to explore utilitarian, eco-centric and biocentric values by eliciting stakeholders’ perspectives to facilitate the emergence of forest management proposals and scenarios. Future research should show how to facilitate practical approaches to the use in decision-making of this broad range of values. In addition, research addressing how to implement approaches to forest management should further explore qualitative and quantitative analyses, focusing on three elements: (1) participatory mapping through innovative digital and visualisation tools that can help facilitate the definition of stakeholder roles, forest governance, and the qualitative analysis of NC stock and ES preferences, under different policies and management scenarios; (2) stakeholder interviews, focus groups, and/or community and participatory video voice analysis for the in-depth characterisation of cultural aspects; and (3) the valuation of NC and ES through preference methods and approaches, including multi-criteria analysis, Q methodology, and other approaches facilitating data and analysis integration, or (where possible) by using accounting rules already implemented by the office of national statistics. Finally, the broad set of information collected by the above methods can be discussed again by stakeholders, through the use of deliberative tools to find a consensus on the measures necessary to maximise win–win solutions.

6. Conclusions

This paper has explored a range of approaches to the valuation of Scottish forests and woodlands, and emerging themes discussed under these approaches, which focus on relations between forests and people (23% of papers selected) and the multifunctional role of forests (19% of papers selected), beyond the more traditional economic utilitarian values. In carrying out this review, we have focused our search on general key strings. This has likely reduced the range of economic studies using stated and revealed preference approaches for eliciting the utilitarian monetary values of nature. Although this category may be understated in our analysis, a more detailed literature review performed by the IPBES found that economic valuations form only a limited fraction of the ample range of values proposed by the research [159]. What our research confirms is that this range of new values is not part of practice yet [160]. Other limitations of our approach can be seen in the scope of the research. While the overview on the use of NC is based on a range of academic papers over all geographic and time scales published in the catalogue ISI Web of Science and the Google Scholar web engine, our considerations apply mainly to the UK, and more specifically to the Scottish context. In addition, we have not included grey literature. Although usually less considered by researchers, this type of writing can be more efficacious when used in understanding the context and the practice around which the implementation of NC can be addressed.

From our review, it emerged that early attempts at the valuation of natural capital were mainly proposed within the purely economic domain, while more recent attempts have used mixed methods to address non-monetary values, with special reference to the inclusion of CES. Integration between several domains or capitals, where the total wealth is perceived as a holistic entity addressing economic, natural, human, and social aspects, is slowly emerging. Conversely, attempts at investigating multiple benefits, characterised by the direct use of forests (e.g., timber) and regulating ES (such as carbon sequestration), can be individuated in the literature. Recent advancements can be observed in the analysis of information shared in social media addressing recreational aspects, in conjunction with the investigation of landscape variations and composition, and by facilitating the participation of stakeholders in the selection of preferred patterns of landscapes, providing high levels of ecosystem services, by using GIS, visualization tools and remote sensing technology.

Different valuation methods tend to be applied to different types of value. The stated and revealed preferences and CBA tend to be applied to utilitarian aspects of NC and ES, whilst qualitative and participatory approaches tend to be applied to the less tangible aspects of NC, such as the cultural, spiritual, community, and wellbeing aspects. From the review, it has clearly emerged that a holistic approach that integrates these practices with the traditional economic valuation of flows and stocks of NC is still missing, and a complete approach to the analysis of transcendental, shared and contextual values has not been achieved in the valuation of Scottish forest assets. Future avenues of research should provide a broad range of approaches and tools to address multiple values, consider their policy implications, and explore their use to achieve better decision-making using local knowledge from stakeholders and citizens, as an essential complementary element to the political and academic knowledge that is usually the only source of information considered in guiding the decision-making process.