INTRODUCTION

Biodiversity losses have reached an alarming state around the world putting entire ecosystems at risk (IPBES 2019). Thus, there is an urgent need for effective conservation instruments. As one solution, economic and market-based instruments have been developed that complement or even replace classical government-led regulatory conservation instruments (Sattler et al. 2013). This development finds its expression in the monetization of ecosystems and their provided services (ES; Gómez-Baggethun et al. 2010). In this context, payments for ecosystem services (PES) are particularly prominent. PES programs reward owners of ES-providing land for their conservation efforts using positive and conditional economic incentives (Wunder 2015). Since the beginning of the 21st century, the interest of scientists, national governments, and civil society organizations (CSO) in PES as well as the number of implemented PES programs increased strongly. Depending on the underlying PES definition, current estimates assume up to 550 PES programs worldwide (Salzman et al. 2018).

PES are acclaimed for their higher efficiency compared to regulatory environmental policies because of their flexibility in internalizing environmental externalities into the market sphere by a more precise spatial targeting of particularly endangered ES (Engel et al. 2008). Furthermore, PES advocates highlight the potentials of PES for improving the livelihood of local communities in Global South countries that are embedded in weak governance settings (Wunder 2007, Engel et al. 2008). In contrast, others criticize PES for paving the way for commodification processes in nature conservation by introducing terms such as ”complexity blinder” (Norgaard 2010) or ”commodity fetishism” (Kosoy and Corbera 2010). It is stated that PES conceal the complexity of ecosystems, for example, by putting a monetary exchange-value on particular ES (Kosoy and Corbera 2010). Furthermore, trading these ES as exchangeable commodities is seen critically, as it is often difficult to assign clear boundaries, values, and property rights to ES, which is particularly due to their physical characteristics and, thereby, their common- or public-good character (Bakker 2004, Farley and Costanza 2010, Kosoy and Corbera 2010, McElwee 2012). Thus, it is argued that PES run into danger of focusing on easily commodifiable ES, instead of targeting complex bundles of ES at the landscape scale (Robertson 2006, Corbera et al. 2007, Ghazoul et al. 2009, Kosoy and Corbera 2010, Scales 2015). Opponents of PES also fear potentially negative social implications of PES-related commodification trends (Kosoy and Corbera 2010, McElwee 2012, Fletcher and Büscher 2017). Some authors even reject the entire concept by highlighting PES as a form of “neoliberal conservation” (Büscher 2012, Fletcher and Büscher 2017).

Various authors highlight that commodification processes and the privatization of ES-providing land are closely related (Mansfield 2007, Gómez-Baggethun and Ruiz-Pérez 2011, McElwee et al. 2014). Secure land tenure structures are pivotal when implementing PES programs (Sattler and Matzdorf 2013, Wunder 2013, Solazzo et al. 2015, Huber-Stearns et al. 2017, Rodríguez-Robayo and Merino-Perez 2017), particularly for a stable participation of ES providers (Swallow and Meinzen-Dick 2009, Bremer et al. 2014a, Liu et al. 2018). At the same time, the empirical PES literature shows that most programs target private landholders (Porras et al. 2008, Börner et al. 2010, Vatn 2010, McElwee 2012, Ezzine-de-Blas et al. 2016, Narloch et al. 2017). Critics argue that these private-individual PES (P-PES) programs might reinforce existing social inequalities, while the social and political capital as well as the potential for collective action within local communities decreases (Kosoy and Corbera 2010, McAfee and Shapiro 2010, Büscher et al. 2012, McElwee 2012, Bremer et al. 2014b).

Land-related property rights, however, do not have to be privately held (Farley and Costanza 2010, Vatn 2010, Tacconi et al. 2013). An estimated 65% of the global land area is under customary land tenure systems, particularly held by local communities and indigenous people in countries of the Global South, although only a fraction is formally recognized by governments (Rights and Resource Initiative 2015). Therefore, it comes as no surprise that there are also PES programs in place that target groups rather than individual holders of ES-providing land. Such PES arrangements are often referred to as community-based or collective PES (C-PES; Hayes et al. 2017, 2019, Kaczan et al. 2017, Gatiso et al. 2018, Brownson et al. 2019). Various authors highlight that C-PES in some situations are promising by referring to, for example, Ostrom’s famous publication Governing the Commons from 1990 (Vatn 2010, Engel 2016, Kaczan et al. 2017).

By means of two systematic literature reviews, we aim at shedding light on the complex and controversial debate about how PES-related commodification processes and different land tenure regimes are interrelated and how they affect PES outcomes. Thereby, our overarching objective is to better distinguish analytically different degrees of commodification of PES programs to provide a basis for an easier assessment of the relations between different degrees of commodification and PES outcomes. We do so by setting a specific focus on C-PES by discussing the guiding question of this paper: Do C-PES counter commodification and privatization trends in nature conservation?

The following three research questions will guide us through this complex topic:

• How is the term “commodification” defined in PES research?
• What are the differences between P-PES and C-PES against the background of different land tenure structures?
• What are the potentials and challenges of C-PES programs and how are they related to commodification processes?

Drawing connections between commodification processes, land tenure regimes, and PES is very challenging because PES as well as ES are heterogeneously defined in the literature. For this reason, we prepend a section to the main body of this paper, in which we briefly summarize existing definitions of ES and PES. Subsequently, we introduce our methods by introducing the two systematic literature reviews we applied. The results section is divided into three subsections, each addressing one of the research questions. In the discussion we propose a new analytical framework of PES-related degrees of commodification and discuss the similarities and differences between C-PES and P-PES as well as the potential relations between different degrees of commodification and PES outcomes. We close with a brief conclusion.

ES AND CENTRAL CHARACTERISTICS OF PES

ES are heterogeneously defined (Danley and Widmark 2016). In this paper, we refer to Daily (1997:3), who defines ES as “conditions and processes through which natural ecosystems, and the species that make them up, sustain and fulfill human life.” Particularly, we highlight Farley and Costanza’s (2010) view on ES, who distinguish between ecosystem goods as physically convertible stock-flow resources that are harvestable at a particular rate, and ecosystem services that can be described as only qualitatively changeable fund-services that “are a particular type of flow, or flux, generated by a particular configuration of stock-flow resources” (Farley and Costanza 2010:2062). It follows that ES do not have the character of classical economic goods, as for example timber that can be defined as a physically delimitable and storable ecosystem good for which it is relatively easy to implement excludability and rivalry.

PES understandings are far from being homogenous too (Sattler and Matzdorf 2013, Wunder 2015, Kaiser et al. 2021). The existing definitions reach from Coasean conceptualizations describing PES as conditional and voluntary private negotiations between ES providers and ES beneficiaries to much broader Pigouvian conceptualizations also counting government-funded and (partly) involuntary schemes to the PES approach. This variety of existing definitions makes it difficult to investigate the outcome of PES programs in an analytic-empirical manner (Martin-Ortega and Waylen 2018). We characterize PES by referring to three key design elements (Kaiser et al. 2021). First, PES create positive incentives, monetary or in-kind, to reward ES providers for their ES protection efforts and thus to change undesirable behaviors that are harmful to the environment (Wunder 2005). Second, conditionality is a central PES characteristic and includes regular monitoring practices that are related to the state of ES. Thus, ES providers only receive payments from ES buyers, if the ES provision can be verified, or to keep it short: “you only pay for what you get” (Wunder et al. 2018:145). Referring to the ES definition of Daily (1997) implies that ES are very complex and hard to quantify. For this reason, particular ES proxies are used that provide information about the quality of an ES, respectively, the current state of an ecosystem process in order to create a certain degree of rivalry and excludability on ES with public or common good characteristics. There are two ways that conditionality can be applied: by monitoring the ES proxies directly (e.g., tonnes of CO₂ sequestered or measuring the water quality) and, less direct, by monitoring specific management practices for which an ES securing effect can be assumed based on scientific research (Muradian et al. 2010). These management practices are monitored by focusing on specific land use indicators. We define management indicators as indirect ES proxies. Still, ES proxies are usually not discrete and physically transformable economic goods. Instead, these proxies can be described as follows: “Because most PES schemes often rely on external assessments of the value of these environmental services to birth the commodities that can be traded and sold, such constructions are similar to what Polanyi deemed ‘fictitious commodities’ in that they do not exist in-toto, but must be created, resulting in commodification that is always incomplete and contested (Polanyi, 1957, p. 76)” (McElwee 2012:414). Third, ES providers can decide voluntarily whether they join the PES contract. Applying the voluntariness criterion only on the ES providers’ side means in reverse that also the public sector can act as ES buyer. We do not consider compensations for environmental legal restrictions as PES because these programs do not fulfil the ES providers’ voluntariness criterion.

METHODS

The results of this study are based on a systematic literature review using the search engine Scopus because it provides a high coverage of peer-reviewed literature (Mongeon and Paul-Hus 2016). For identifying relevant literature, we applied two separate systematic literature searches (see Fig. 1). We used the first literature search to focus on the understandings of the term “commodification” in the context of PES (first research question). The second review focused on the issue of property and land tenure structures in the context of PES in order to analytically compare C-PES and P-PES programs (second research question). We used both literature reviews to have a closer look at potentials and challenges of C-PES against the background of commodification processes (third research question). Each terminology included both “payments for ecosystem services” and “payments for environmental services.” Although some authors use both terms interchangeably, others see them as two distinct categories; for details see, for example, Derissen and Latacz-Lohmann (2013). This review uses the term “payments for ecosystem services” for reasons of consistency.

After applying the two search terminologies in Scopus, relevant scientific publications in the period of 2000 to 2019 were reviewed following the PRISMA guideline (Moher et al. 2009). We start with the year 2000 because of the remarkable increase of PES literature starting after this year (Schomers and Matzdorf 2013). First, we screened abstracts for relevance. Second, the publications identified as eligible were analyzed in detail. Based on the relevant content of these publications a coding structure was developed using the text analysis software MAXQDA. The developed coding structure enabled a clustering of relevant topics addressing the research questions, which led to the guiding structure of the following results section. When other relevant publications addressing the research questions were referenced within the identified literature, we integrated these publications into the literature review as well (snowball system). Of course, if statements from other authors relevant to our research interest were cited within the literature, we traced them back to the primary publications. A detailed overview of the scientific publications identified as eligible can be found in Appendices 1 and 2, indicating also publications detected based on the snowball system.

RESULTS

Understandings of commodification in the PES literature

We identified 27 eligible and accessible publications based on the abstract reviews out of which 10 publications include a more detailed analytically description of the term ”commodification.” Further publications were included based on the snowball system (see Appendix 1).

Ambiguous understandings of commodification

Many of the analyzed publications use the term commodification without defining it in detail. Instead, commodification is often mentioned in combination with terms such as “market-based.” Our review suggests that this sometimes leads to misunderstandings about the critique because in these cases commodification is often directly associated with classical markets including a market-based price determination. As a consequence, several authors have already pointed out that PES build only seldomly on ES markets, in which ES commodities are competitively and fully voluntarily traded (Corbera et al. 2007, Tacconi 2012, Muradian 2013, Wunder 2013, Hahn et al. 2015). Does this imply that the relationships between PES and commodification processes are not as strong as some scholars suggest? Our review shows that this depends on the particular understanding of commodification as well as on the PES program in focus. Publications dealing with the term commodification, also outside the PES research, show a high heterogeneity of understandings (Castree 2003). Introductory definitions suggest that markets for clearly defined ES are a necessary part of the commodification of ES (Bakker 2005, Kosoy and Corbera 2010, Gómez-Baggethun and Ruiz-Pérez 2011, Corbera 2012, Kallis et al. 2013, Namirembe et al. 2014, Leimona et al. 2015). Commodification is, for example, defined as “the creation of an economic good through the application of mechanisms intended to appropriate and standardize a class of goods or services, enabling these goods or services to be sold at a price determined through market exchange” (Bakker 2005:544) or as “the conceptual and operational treatment of goods and services as objects meant for trading. It describes a modification of relationships, formerly unaffected by commerce, into commercial relationships. Commodification of ecosystem services thus refers to the inclusion and internalization of ecosystem functions into pricing systems and market relations” (Gómez-Baggethun and Ruiz-Pérez 2011:619).

Understanding commodification as a process

Various authors, and often the same ones, also emphasize that commodification should not be understood as a fixed state, but rather as a process, which does not have to be unidirectional and irreversible (Kosoy and Corbera 2010, Muradian et al. 2010, Hahn et al. 2015, Osborne and Shapiro-Garza 2018, Martin-Ortega et al. 2019). Thereby, several of the identified publications refer to Gómez-Baggethun and Ruiz-Pérez (2011), who propose four stages of commodification in the context of ES: “economic framing, monetization, appropriation, and commercialization” (Gómez-Baggethun and Ruiz-Pérez 2011:620). Kosoy and Corbera (2010) highlight three stages of commodification that include the separation of ES from the entire ecosystem, the assignment of single exchange-values to ES, and the linking between ES providers and beneficiaries through a market or market-like exchange. Hahn et al. (2015) come up with a classification of economic instruments for biodiversity and ecosystem services divided into seven degrees of commodification. These are mainly determined by the institutional design of the program, for example the type of price signal or ES buyer. Furthermore, Muradian et al. (2010) emphasize various PES-related degrees of commodification that depend on the definability of ES as tradable commodity, which is particularly determined by the conditionality-related monitoring type. Whereas, for example, schemes based on the direct measurement of ES proxies show a higher degree of commodification, programs building on the monitoring of management practices for which a positive influence on the provision of ES can be assumed are commodified to a lower degree.

Therefore, it is important to take the respective underlying understanding of commodification in PES research into account. Describing PES as a purely market-based nature conservation instrument certainly falls short against the background of the currently implemented PES programs and their diverse designs. For this reason, Hahn et al. (2015) propose the term “economic instruments” that better covers the diversity of programs, whereby they use the term “market-based” as a subcategory. Wunder (2015) acknowledges this debate, too, by changing his seminal definition from the ES buyer-seller to the ES provider-user. Understanding commodification as a process with different degrees mirrors this debate by allowing for a better differentiation to which degree commodification becomes apparent in different PES designs and how these different degrees are potentially linked to the social and ecological outcome of PES programs. Furthermore, it allows for investigating whether the degree of commodification of a PES program changes over time. Fletcher and Büscher (2017), for example, describe commodification, and more generally neoliberalization, as gradual processes over time and argue that PES programs potentially pave the way for an increasing thinking in terms of commodities and markets in nature conservation in the long run. Thereby, symbolic meanings such as the monetary valuation of ES aimed at gaining attention for ES protection are potential forerunners of a subsequent commodification and marketization of ES because monetary incentives, whether based on true markets or not, introduce a neoliberal thinking in terms of commodities and exchange values (Gómez-Baggethun and Ruiz-Pérez 2011, Fletcher and Büscher 2017, Kolinjivadi et al. 2017).

The relations between commodification and privatization processes

Several publications draw relations between the terms “commodification” and “privatization” (McAfee and Shapiro 2010, Kallis et al. 2013, Osborne and Shapiro-Garza 2018, Martin-Ortega et al. 2019). Often, privatization is seen as one component of commodification processes. Osborne and Shapiro-Garza (2018:101), for example, highlight privatization as a step to commodification that includes the transfer of “exclusive rights of a resource to an individual, group, or institution in the form of legal title” by referring to the principal elements of the commodification of nature identified by Castree (2003). Some of the identified papers refer to Gómez-Baggethun und Ruiz-Pérez (2011:620), who emphasize that the ES appropriation, which constitutes one step toward an increase of commodification, “operates through the formalization of property rights on specific ecosystem services, or on the lands producing such services. This stage has often involved privatization, through which ecosystems that were previously in openly accessible regimes, or in communal or public property regimes, have been turned into private property.” However, the definition of the term “privatization” and the relations to commodification processes remain often vague. Therefore, Bakker (2005) calls for an analysis of commodification and privatization as distinct processes.

Differences between P-PES and C-PES against the background of land tenure structures

In the following subsection we give an overview of how land-related property, respectively, land tenure structures are defined and what the differences between PES targeting private-individual landowners (P-PES) and those building on common property regimes (C-PES) are. In our literature review we identified 69 eligible and accessible publications that deal with the issue of land tenure structures out of which 15 publications give detailed information about the understanding and conceptualization of land-related property structures in the context of PES programs and the differences between P-PES and C-PES.

Characterizing land tenure structures using the property rights bundle approach

Property can be understood as (social) relationships between members of society and objects/valuables (Bromley 1992, von Benda-Beckmann et al. 2006, Mansfield 2007). One way of looking at these property relations is through the lens of bundles of property rights as it was famously introduced for natural resource systems by Schlager and Ostrom (1992). The framework can also help to characterize the diversity of land tenure structures in the context of PES programs (e.g., Kitamura and Clapp 2013, Sikor et al. 2017). According to Schlager and Ostrom (1992:250) bundles of property rights are the product of rules that are defined as “generally agreed-upon and enforced prescriptions that require, forbid, or permit specific actions for more than a single individual.” Schlager and Ostrom highlight five important property rights: access, withdrawal, exclusion, management, and alienation rights. Whereas access and withdrawal rights are classified as first-order operational-level rights, exclusion, management, and alienation rights are classified as second-order collective-choice rights. The latter group of rights gives right holders the opportunity to participate in the definition of first-order rights. Whereas withdrawal rights, for example, give the right holder the permission to use ecosystem goods (stock-flow resources) at a given extraction rate, holders of management rights can change these operational-level withdrawal rights, which leads to the change of internal resource use patterns. The right of alienation is of particular interest when it comes to a change of ownership of land, as this right enables collective-choice rights holders to sell or lease management and/or exclusion rights. Sikor et al. (2017) revise this framework and add under the umbrella of use rights (first-order operational-level rights following Schlager and Ostrom) the right of obtaining indirect benefits via, for example, PES and other result-based payments. Understanding property as a bundle of rights makes the complexity and heterogeneity of property structures visible, even more so when taking into account the complex distribution of rights among different actors, for example, in the case of complex tenant-landowner property structures (Nsoh and Reid 2013). Furthermore, the concept clarifies that property rights owners can possess a bundle of rights of various extent reaching from authorized users holding only access and withdrawal rights to full owners holding all five property rights (Schlager and Ostrom 1992).

Characterization of P-PES programs

Most PES programs target privately owned land (Porras et al. 2008, Börner et al. 2010, Vatn 2010, McElwee 2012, Ezzine-de-Blas et al. 2016, Narloch et al. 2017). We did not find any detailed P-PES definitions. However, when referring to the property rights bundle described by Schlager and Ostrom, land targeted by P-PES is usually owned by individual landowners or firms that possess an extensive bundle of land-related property rights, including management, exclusion, and alienation rights too (Mansfield 2007, Ostrom and Hess 2007). However, private property is never all-encompassing and thus, for example, management rights are limited to some extent (Mansfield 2007, Ostrom and Hess 2007, Vatn 2010). Sikor et al. (2017) clarify this point by introducing authoritative rights as a further type of rights that limit the extent of second-order rights. This is the case, when, for example, landowners are legally bound to specific land-use types or by setting minimum environmental standards such as the non-use of pesticides. Taking our understanding of PES into account, landowners possess relatively extensive management rights regarding the land-use practices affecting the provision of ES targeted in the PES program. Otherwise, the voluntariness criterion on the ES-providers’ side cannot be fulfilled.

Characterization of C-PES programs

Common or community-based property “includes all situations where rights to own or manage terrestrial natural resources are held at the community level under statutory law” (Rights and Resource Initiative 2015:3). Common property regimes should not be confused with open access regimes that are open to all. In contrast, the members of common property regimes are able to define and “exclude nonmembers of that group from using a resource” (Ostrom and Hess 2010:6). At the same time, the bundles of rights approach emphasizes the complexity and diversity of land-related property structures in terms of the design and distribution of property rights. Therefore, such systems of collective natural resource management can often be understood as forms of hybrid governance, as individuals keep some property rights while transferring particularly management rights to the community level in order to cooperate for a successful and sustainable management of natural resources (Ménard 2011, Muradian 2013). Thus, the complex distribution of property rights among different actors makes it often difficult to clearly distinguish different property categories such as state, common, or private (Wiber 2005, von Benda-Beckmann et al. 2006, Sikor et al. 2017). This blurring becomes illustrated in the case of PES programs where land is formally recognized as common property while each community member enters the PES contracts individually (e.g., Osborne and Shapiro-Garza 2018). Land-related property structures become even more complex when taking the diverse organizational and decision-making structures into account, which are, for example, influenced by legal forms and the organization’s purpose, e.g., for-profit versus non-profit. Furthermore, it can be assumed that social and cultural norms and values of individuals, collectives, and the surrounding society as well as the capabilities (for example, in terms of wealth) of groups or individuals play an important role for the choice of land-use practices too (von Benda-Beckmann et al. 2006). Hence, C-PES can be assumed to be diverse in terms of their land tenure structures and the related social-ecological outcomes as well.

Our literature review shows that various studies focus on PES programs targeting communities instead of individual landowners, particularly in the Global South. In most publications these PES programs are labeled as ”community-based” or ”collective” PES (Hayes et al. 2017, 2019, Kaczan et al. 2017, Gatiso et al. 2018, Brownson et al. 2019). In Table 1 we provide an overview of the definitions identified. Both terms show great similarities. However, the collective PES definitions are more explicit compared to some community-based PES definitions because all collective PES definitions highlight that the incentives are given to groups (Kerr et al. 2014, Kaczan et al. 2017, Hayes et al. 2019). Particularly, Kaczan et al. (2017) highlight common property of land as a characteristic of collective PES. At the same time, they also mention the opportunity that neighboring landowners join a PES contract together. However, also in such cases, ES-relevant withdrawal rights are collectively adapted at the community level to fulfil the requirements of the PES contract. Thus, landowners agree that former individual management rights are assigned to the community level.

In contrast, community-based PES definitions are fuzzier because a coupling with common property regimes is often not explicitly mentioned. The definition by Brownson et al. (2019), for example, states that local communities have influence on “program design, implementation or monitoring” (Brownson et al. 2019). This definition does not exclude the implementation of P-PES. The definitions by Brownson et al. (2019), Gatiso et al. (2018), and Dougill et al. (2012) also keep the door open for hybrid PES designs, which means, for example, that a share of the total incentives is given to communities and another share directly to individual landowners, who are members of the community (Brownson et al. 2019). Thus, it is not clear whether ES-relevant management rights are assigned to the individual or to the community level. Only the definition by Sommerville et al. (2010a) points more directly at the existence of common property rights. We assume that the broader conceptualization of community-based PES is due to the existence of linkages to the broader approach of community-based conservation (CBC), which links development and conservation objectives by engaging local community actors at various levels. Brownson and colleagues, for example, highlight that “CB-PES can also be conceived as a subset of CBC which provides direct payments to communities or individuals to increase ES provisioning rather than investing in development projects” (Brownson et al. 2019). From here on, we refer to collective PES using the abbreviation “C-PES” because we are interested in PES contracts that directly target communities or groups.

Potentials and challenges of C-PES and the relations to commodification processes

In the following we briefly summarize the findings about the potentials and challenges of C-PES programs. In total, we identified 22 eligible publications. Most of these publications are case studies, but we also refer to the literature reviews about collective and community-based PES by Hayes et al. (2019) and Brownson et al. (2019). We identified only three studies that more explicitly examine relations between commodification processes and C-PES outcomes.

The potentials of C-PES and the important role of social capital for their success

Generally, studies examining the outcome of C-PES—for example, regarding the provided ecological additionality as well as potential co-benefits and trade-offs with other ES not directly covered in a program, or regarding effects on the social justice—show mixed results. However, different authors emphasize the pre-existence of social capital as an important factor for the outcome of C-PES. The term social capital is used frequently in various disciplines and attracted particular attention in the social sciences by referring to theories by Pierre Bourdieu (Bourdieu 1986). Understandings and uses of this term depend on the disciplinary context (Jacobs 1961, Putnam et al. 1994). Ostrom’s use of the term social capital refers to shared norms and trust within communities, which enable them to manage common pool resources collectively at low monitoring and enforcement costs (Ostrom 1990, Ostrom and Ahn 2009). Especially the literature about C-PES often follows this broad understanding of social capital, while some authors add further components that constitute social capital. McGrath et al. (2018), for example, emphasize five important components of community-related social capital by referring to Campos et al. (2015): “1. groups and networks, 2. trust and solidarity, 3. collective action and cooperation, 4. information and cooperation, and 5. empowerment and political action.” Brownson et al. (2019) use a more general definition and describe social capital as “relationships and [the] technical and institutional capacity within communities or community-based organizations” (Brownson et al. 2019:7).

Research about C-PES suggests that a high level of pre-existing social capital in the form of well-functioning and local institutions perceived as fair, strong social networks, trust between community members, and well-established common property regimes coincides with a higher participation rate as well as with increased ecological and social effectiveness (Corbera et al. 2007, Brouwer et al. 2011, Bremer et al. 2014a, Engel 2016, Nieratkaa et al. 2015, Narloch et al. 2017, Hayes et al. 2019, Moros et al. 2019), though systematic empirical research supporting this hypothesis is still lacking (Bremer et al. 2014b). Following this argument, C-PES might outperform P-PES in the case of a pre-existing stable self-governance. Different studies show that C-PES reach a higher legitimacy in such cases because local community needs can be easier taken into account and high levels of procedural and distributional justice can be better guaranteed when it comes to distributing the received benefits (Nieratkaa et al. 2015, Brownson et al. 2019). This might minimize conflict risk at the local level (Bremer et al. 2014b). Furthermore, C-PES can create important incentives for an additional strengthening of the local cooperation, collective action, and contract compliance (Nieratkaa et al. 2015). Furthermore, some studies suggest that C-PES can also lead to a strengthening of previously low levels of social capital by increasing local cooperation, collective action, contract compliance, and land tenure security (Bremer et al. 2014b, Neitzel et al. 2014, Nieratkaa et al. 2015, Alix-Garcia et al. 2018, Brownson et al. 2019, Hayes et al. 2019). Thus, although the reported level of social effectiveness and ecological additionality is rather low in the short run, the strengthening of the communities’ social capital might support the successful management of natural resources in the long run (Clements et al. 2010, Bremer et al. 2014b). Various studies also emphasize the advantageous low transaction costs of C-PES, which is the result of the often significantly lower number of necessary contracts compared to P-PES leading to lower costs of identifying participants, negotiating contracts, and securing monitoring and enforcement of rules (Ghazoul et al. 2009, Vatn 2010, Muradian 2013, Kerr et al. 2014, Midler et al. 2015, Nieratkaa et al. 2015, Narloch et al. 2017). Therefore, parts of the transaction costs are covered by the targeted communities when deciding internally over the distribution of the provided incentives by building on the pre-existing social capital and the available local knowledge about existing costs and benefits (Engel 2016, Narloch et al. 2017). Additionally, smallholders, who particularly in the Global South are often embedded in common property regimes, get supported instead of wealthy and large private landowners because the smallholders’ bargaining power is strengthened (Swallow and Meinzen-Dick 2009). Some studies reveal that C-PES programs lead to an increase of the intrinsic motivation to protect ES, thereby leading to so-called “crowding in” effects (Bremer et al. 2014b, Agrawal et al. 2015, Moros et al. 2019), while other studies show opposite results (Narloch et al. 2012).

The challenges of C-PES

Other studies come to opposite conclusions regarding the outcomes of C-PES (Narloch et al. 2012, Gatiso et al. 2018). This can often be explained by a pre-existing low level of self-organization, collective action, and social capital within the targeted communities (Hayes et al. 2017). In this context, many authors highlight the pre-existence of power imbalances, information asymmetries, and the unequal internal distribution of social capital and property rights within the groups as counterproductive for the implementation of C-PES, which leads, for example, to the problem of elite capture by powerful local group members (Agrawal and Gibson 1999, Sommerville et al. 2010a, Kariuki et al. 2018, McGrath et al. 2018). In such cases, C-PES are often perceived as less fair, which potentially fuels conflicts within communities (Muradian et al. 2010, Midler et al. 2015, Nieratkaa et al. 2015, VonHedemann 2019). Generally, the communities’ internal payment distribution and the related ability to act collectively is a key factor for the success of C-PES (Zabel et al. 2014, Nieratkaa et al. 2015, Engel 2016). Here, C-PES often “face[s] a commons dilemma: every group member benefits from the payment, but incurs a private cost on contributing to performance, implying incentives to free ride (Vatn 2010, Zabel et al. 2014)” (Engel 2016:153). This dilemma is also known as “second-order collective action dilemma”: when groups establish a new set of rules, all group members can benefit, while potentially not all group members contribute to the costs of establishing this new set of rules, which, in turn, hinders the motivation to establish those rules in the first place (Ostrom 1990, Hayes et al. 2019). Furthermore, Sikor et al. (2017) emphasize that the implementation of C-PES is challenging because the embeddedness of local communities in complex constellations of external social actors increased strongly in the last decades. Therefore, the establishment of land-related rules and property rights for the successful implementation of C-PES depends not only on the community and its ability for collective action, but also on additional external actors, such as private, governmental, or CSO actors (Sikor et al. 2017). Additionally, the variety and complexity of ES play an important role for the success of C-PES (Swallow and Meinzen-Dick 2009, Fisher et al. 2010, Kinzig et al. 2011). As C-PES programs target different ES with varying characteristics, e.g., regarding the excludability and rivalry of benefits or the scale at which land management changes are required to generate high quality ES, each program design must be examined carefully, taking the specific local circumstances into account.

Scarce empirical knowledge about the relations between commodification processes and C-PES outcomes

Most of the publications dealing with PES-related commodification processes remain rather at a theoretical or conceptual level, while case studies analyzing the relation between PES-related commodification processes and PES outcomes are rare. This is not surprising given the diversity of understandings of commodification and the challenge to evaluate the social and ecological PES outcomes holistically. Focusing particularly on C-PES, we identified only very few publications that explicitly evaluate commodification-outcome relationships. Osborne and Shapiro-Garza (2018), for example, gather findings about two forest-based carbon offsetting initiatives targeting communities in Mexico. While one project targets individual smallholders, the other project represents a C-PES with communally held carbon offset rights. The first project is rather negatively evaluated because easy monitoring of carbon services, the embedding into a carbon market, and commercial timber production was prioritized over local ecological and social co-benefits. Thereby, decision making was shifted away from local smallholders to the project managers leading to a weakening of traditional governance structures and practices, to the disadvantage of women, and to the decrease of the ecological quality of the forest ecosystems (Osborne 2011, 2015). Furthermore, carbon prices did not reach expected levels in the long run and producers were exposed to price fluctuations. There have also been attempts to privatize land that was previously under common property (Osborne 2015). In contrast, the C-PES project is more positively evaluated: project participants felt much more engaged. Particularly, the transfer to the authorities of the communities instead of individual smallholders turned out to be advantageous. Furthermore, the project started with non-market funding in the first eight years leading to a more stable funding and more space to integrate local values and desires. The authors also emphasize that the state of Oaxaca, where the participating communities are located, is well known for its strong and stable local community institutions, implying that context and history matter. Therefore, the results of the study correspond very well with the other findings concerning potentials and challenges of C-PES, while suggesting that commodification, expressed, for example, by the type of price determination or local land tenure structures, plays an important role for the program outcome. Another study by Leimona et al. (2015) gathers findings for several cases in Asia, both P-PES and C-PES programs, and discusses commodification under the view point of strict conditionality. Thereby, the authors show that the monitoring of direct water ES proxies can be very challenging and potentially fuels conflicts. Namirembe et al. (2014) gather different tree-based reward mechanisms targeting both individuals and communities in African countries. They identify various carbon PES programs with high degrees of commodification because of their strict focus on emission reduction and carbon sequestration services and their embeddedness in global carbon markets. Thereby, they emphasize risks of crowding out conservation motivations and the challenges associated with low carbon prices for the fairness of the program.

DISCUSSION

Reframing commodification in the context of PES

Our review reveals that commodification is diversely understood. This diversity of understandings makes it challenging to investigate PES-related commodification processes and how they affect ecological and social outcomes of C-PES and P-PES. For this reason, we reframe commodification by analytically differentiating between degrees of commodification. Generally, we understand commodification as a process toward the creation of well-defined entities that become tradable through a market(-like) exchange. Thereby, commodification processes pass various degrees that become manifested through the institutional design of an environmental policy instrument (Hahn et al. 2015). This process does not need to be unidirectional; it can also stop at some point or even reverse (Gómez-Baggethun and Ruiz-Pérez 2011). We argue that PES-related commodification processes can be discussed and operationalized using two closely interrelated but distinct spheres (Fig. 2). The first sphere is related to the degree of commodification of ES-providing land and can be investigated taking the bundle of land-related property rights by Schlager and Ostrom (1992) into account. The second sphere refers to the commodification of the ecosystems’ fund-services and, thus, addresses the commodification of ES through the creation of a new type of property rights that is added to the pre-existing bundle of property rights. Most publications we reviewed deal with the second sphere of commodification.

The commodification of ES-providing land

The first sphere addresses the commodification of ES-providing land. Land-related commodification processes can be studied by taking the bundle of property rights approach proposed by Schlager and Ostrom (1992) into account. The degrees are determined by the existence of alienation rights, the design of management rights, and the complexity of decision-making processes concerning the use of the given property rights.

First, the right of alienation is central for transferring land into a commodity-like status by allowing landowners to sell or lease the land-related property rights bundle, including management and exclusion rights, on national and/or international land markets. Private landownership mostly includes alienation rights, while these are rarely in place in the case of common property regimes (Bremner and Lu 2006, Ostrom and Hess 2007). Therefore, we understand land privatizations as the commodification of the land-related property rights bundle to make land marketable on national or international land markets. Already Karl Polanyi (1957) stressed the increasing marketability of land accompanied by the rise of capitalism when he shaped the term “fictitious commodity.” Alienation rights economically mobilize land and can in some cases be a door-opener for international companies to acquire land titles, which can facilitate land and “green grabbing” (Fairhead et al. 2012, Scales 2015) when these alienation rights are strongly deregulated, as also discussed in the context of PES in countries of the Global South (Vatn 2010). However, it cannot be concluded that common/collective or state property would necessarily lead to a more sustainable use of resources, as our review about the complexity and diversity of property regimes shows. Furthermore, it is also important to note that state property is often subject to land deals too, happening between the land-owning state and a foreign state (Vatn 2018).

Second, the design of management rights affects the degree of commodification of ES-providing land. The extent of management rights in combination with withdrawal rights decisively determines whether or not land-related stock-flow resources (Farley and Costanza 2010), like timber or agricultural goods, can be appropriated and transformed into monetarily valuable goods and treated as commodities that are sold on markets (cf. Richter and Furubotn 2010). Management rights are limited by, for example, regulatory environmental policies (cf. Mansfield 2007). We argue that extensive management rights, which go hand in hand with a retreat of regulatory policies, contribute to a higher degree of commodification because it is easier to use the land and the related stock-flow resources for different economically productive purposes, which in turn increases the economic value of land (Kaimowitz 2002, Vatn 2010). Both, P-PES and C-PES, require extensive management rights, at least regarding management practices that affect the provision of those ES targeted in the PES program, because ES providers sign PES contracts on a voluntary basis and are not obliged to ES-protecting management practices due to regulatory policies. Thus, landowners possess a great individual freedom to use their land as they wish (Mansfield 2007, Vatn 2010). The extent of management rights also affects the opportunity costs of the owners of ES-providing land, besides key influencing factors such as the quality of the land-related resource base, the proximity to markets, the given infrastructure or discount rates (West et al. 2018, Wunder et al. 2018). Opportunity costs describe the loss of economic value due to the renunciation of more commercial forms of land use for reasons of ES conservation and stay in a close relation to the willingness to accept (WTA) of the ES provider (Pagiola et al. 2004). It can be assumed that more extensive management rights increase the opportunity costs in most cases, making it even harder to collect enough funding. However, in practice PES often do not cover the opportunity costs (Kosoy et al. 2007). This can be explained by the fact that ES providers do not only decide to enter a contract by taking solely economic aspects into account (Lima et al. 2019), as the theory of a homo economicus would suggest. Instead, ES providers can also have an intrinsic motivation to provide ES, which in turn lowers the WTA, even though the opportunity costs remain stable. Therefore, not only the design, distribution, and extent of land-related property rights determines the choice of land management practices, but also prevailing cultural norms and values as well as the economic power of actors possessing these rights (von Benda-Beckmann et al. 2006).

Third, we argue that land under private property is related with a higher degree of commodification of ES-providing land because decisions about the land use are made more individualized and, thus, more direct. In contrast, C-PES often build on complex, aggregated decision-making processes (Hayes et al. 2019). It seems reasonable to assume that individualized decision making eases the adaptation of production processes, which are based on land-related resources and/or ecosystem goods, to changing market prices. Additionally, it can be assumed that private property is more often embedded in a profit-oriented legal form, which might increase the profit-seeking behavior leading potentially to a higher WTA of ES-providers, making it even harder to collect enough funding for PES programs. In contrast, in the case of C-PES, management rights are in place too, but tied to a more complex community level (Ménard 2011, Muradian 2013). We assume that decision-making processes are often not as fast and much more complex in these cases. In our view, this lowers the degree of commodification of ES-providing land because the compatibility with international markets with fast-changing price signals is arguably lower. Furthermore, some studies indicate that communities show a higher intrinsic motivation for nature protection (Bremer et al. 2014b, Agrawal et al. 2015, Moros et al. 2019), which might lead to a lower WTA because joining a PES contract is then not only rooted in pure economic considerations. However, whether these assumptions hold true in practice needs to be investigated. Particularly, it can be assumed that such relationships between property regimes and land use diverge between different geographical regions because of different political, legal, cultural, and ecological circumstances.

Overall, we assume that the land targeted by C-PES programs shows lower degrees of commodification against the background of often missing alienation rights and the more complex decision making about the land uses. However, because the demarcations between private and common property are not sharp, the degree of commodification should be carefully examined.

The commodification of ES

With the second sphere of commodification we refer to the commodification of ES, defined as fund-services which “are a particular type of flow, or flux, generated by a particular configuration of stock-flow resources” (Farley and Costanza 2010:2062). Making these fund-services monetarily valuable requires new types of property rights, which can be considered as an add-on to the property rights described in Schlager and Ostrom’s (1992) framework. In this sense, the commodification of ES can also be interpreted as a subset of land-related commodification processes. These new types of property rights are temporary use rights for using the benefits that fund-services provide and that are sold from ES providers to ES buyers. Thus, the ES providers gain the right of receiving payments (monetary or in-kind) that result from the disposal of temporary use rights; Sikor et al. (2017) call this type of right “indirect use right.” The degree of ES-commodification is determined by different PES design components. We argue that three design components are of particular importance for the determination of the degree: the conditionality type, the type of ES buyer(s), and the price determination. In the upper half of Figure 2, we summarize the ES-related commodification sphere by focusing on these three design components. We joined the type of ES buyer(s) and the price determination on the y-axis by using the term “market-based character.”

First, the degree of ES-commodification is affected by the conditionality type and, thereby, by the definition and monitoring of ES proxies. Castree (2003) emphasized the important role of proxies for the commodification of nature. If the conditionality is related to the regular measurement of direct ES proxies (e.g., water quality or CO₂ sequestration per hectare and year), the degree of commodification is rather high. One example of a C-PES program building on direct ES proxies is a conditional payment program for ecotourism and wildlife friendly agriculture in Cambodia, which couples payments by tourists with the watching of rare bird species (Ingram et al. 2014). In contrast, PES programs that couple the conditionality with the monitoring of management-related indirect ES proxies (e.g., pesticide reduction goals on agricultural land or specific logging methods) contribute to a lower degree of commodification. With this categorization we return to Muradian et al. (2010), who state: “While in some PES schemes the tradable service is relatively clearly commodified, based on outputs from environmental functions — such as tons of carbon sequestered by forests in a given period of time — in many cases the characterization of the commodity is fuzzy, based on inputs and assumptions (shared beliefs) about the relationship between land use and the provision of ecosystem services” (Muradian et al. 2010:1206).

Second, the type of ES buyers influences the degree of ES-commodification. Private individuals or companies acting as ES buyers contribute to a higher degree of ES-commodification because such PES programs follow rather a Coasean PES conceptualization based on private, voluntary market transactions. Vice versa, PES programs where governments act as ES buyers show a lower degree of commodification because private market transactions are non-existent and classical voluntariness is seldomly given. A well-known government-led PES is the program “Socio Bosque” in Ecuador (Hayes et al. 2015). CSOs stay in between, as they often act as intermediary.

Third, the price determination differs remarkably between PES programs and affects the degree of ES-commodification. Usually, classical commodities are sold on a market based on a price shaped by supply and demand and/or by negotiation. PES programs based on these classical price determinations contribute to higher degrees of ES-commodification. One example is carbon schemes that couple carbon sequestration services with markets for tradable CO₂ certificates (offsetting), as established by the CSO Plan Vivo (Dougill et al. 2012). Such programs differ in how often negotiations about prices for ES proxies are carried out. In contrast, payments can also be determined without any negotiation processes at the start of a PES program. This is often observable in the case of government-financed programs with pre-defined and usually uniform prices set by the state (Wunder 2008). The mainly government-financed program “Pago por Servicios Ambientales” in Costa Rica is one example of a PES program using state-determined but differentiated prices (Pagiola 2008). This form of price determination contributes to a low degree of ES-commodification.

Finally, there are two additional design components that influence the degree of commodification and thereby the market-closeness of PES programs:

• Incentive type: PES programs that use monetary incentives show a higher compatibility to classical markets and therefore show higher ES-commodification tendencies than schemes that build on in-kind incentives
• Number of ES buyers and sellers: the higher the number of ES buyers and sellers the easier the creation of competitive ES markets, which, in turn, increases the degree of ES-commodification

C-PES as a counterpart of commodification and privatization trends in nature conservation?

At the beginning of this paper, we asked whether C-PES counter commodification and privatization trends in nature conservation. In the following, we discuss how our proposed framework can help to (1) analytically compare degrees of commodification of C-PES and P-PES and (2) investigate how different degrees of commodification of PES programs are related to social and ecological outcomes. Our understanding of C-PES is summarized in Textbox 1.

Analytical differences between C-PES and P-PES regarding their degrees of commodification

Our two-sphere commodification framework shows that the degree of commodification of ES-providing land is usually lower in the case of C-PES compared to P-PES because of the often missing alienation rights and the more complex decision making. However, the degree of commodification of ES is not necessarily low as well. Thus, there is not necessarily a functional relationship between the two spheres of commodification. This can be illustrated by two C-PES programs: a local PES project in Madagascar and a voluntary carbon scheme in Indonesia. Both programs share a low degree of commodification of the ES-providing land because land under common property is targeted. At the same time, the ES proxies sold reach very different degrees of ES-commodification. The PES project in Menabe targets ES-providing land owned by local communities that collectively possess local forest management rights (Sommerville et al. 2010a, 2010b), which results in a low degree of commodification of the ES-providing land. The degree of ES-commodification is low, too, because the project is CSO-financed while targeting biodiverse forests by providing in-kind incentives in return for the provision of indirect ES proxies such as the prohibitions of hunting lemurs and cutting timber. Furthermore, the price is determined each year by CSO Durrell, which acts as ES buyer (Sommerville et al. 2010b). The voluntary carbon scheme at Lake Singkarak in West Sumatra targets collectively managed land too (Neilson and Leimona 2013, Burgers and Farida 2017). At the same time, the ES-commodification reaches a high degree. ES funding is generated through the selling of carbon certificates by the intermediary organization “CO² Operate” to private buyers. The price determination is flexible because of the selling of the carbon certificates on carbon markets. The project targets direct and indirect ES proxies. On one hand, the payments are directly coupled to CO₂ sequestered by planted trees. On the other hand, the communities are obligated to fulfil management plans. It remains an open question whether C-PES show a lower degree of ES-commodification compared to P-PES on average. Milne and Chervier (2014), for example, emphasize that community-based PES programs in Cambodia show lower degrees of commodification because of the use of in-kind incentives. However, more empirical research is necessary to examine potential differences in other regions and globally.

A clear empirical finding, however, is that most PES program designs follow rather a Pigouvian approach resulting in low degrees of ES-commodification anyhow (Sattler and Matzdorf 2013). In our view, this comes as no surprise given the physical characteristics of ES that make their commodification in many cases very challenging (cf. Bakker 2004). The commodification of ES follows the aim of creating an artificial scarcity of previously not monetarily valued and often freely accessible as well as non-rival services in order to collect funding for nature protection (Mansfield 2007, Farley and Costanza 2010). In market-based PES approaches the creation of artificial scarcity is related to the aim of increasing the willingness to pay (WTP) of private ES buyers. However, creating this scarcity for ES is not as easy as for classical ecosystem goods (e.g., timber or agricultural products). Ecosystem goods are extractable at a chosen rate, physically transformable and storable, which makes it easier to treat them as market commodities because excludability and rivalry can be easily enforced. In contrast, ES are the result of a specific composition of ecosystem components and therefore only directly consumable and not storable. Direct or indirect ES proxies and their expression in monetary values are used to illustrate the importance, and thus the scarcity, of an ecosystem function for ES beneficiaries (Gómez-Baggethun and Ruiz-Pérez 2011). Thereby, temporary use rights are sold that are tied to ES proxies. The PES mechanism follows the principle of renting a car for a day to enjoy the service of mobility or of renting an apartment for a year to enjoy the service of habitation. However, ES and classical services differ strongly. For most conventional services the exclusion of potential free riders is relatively easy. Furthermore, the rate at which conventional services are provided is usually controllable, which means that the supply (for example of rentable cars or flats) can be flexibly adjusted to the demand. As a result, there is a scarcity for conventional services because of the easier introduction of excludability and the existing rivalry, which together are important prerequisites for the successful market-based price determination. In contrast, the ES-commodification is more difficult because of the spatial and temporal distribution of ES. First, there is often a spatial distance between the ES-providing stock and the location where the benefits occur (Farley et al. 2010, den Uyl and Driessen 2015, Kaiser et al. 2021). The spatial distribution of ES and their related benefits becomes further complicated through leakage effects, when the environmental additionality gained at one place becomes defeated by environmental destruction occurring elsewhere instead (Engel and Muller 2016). Additionally, rivalry for ES is in many cases rather low because the demand is not as easily adjustable as for many conventional services. Therefore, many ES have public service characteristics, which is why creating scarcity for ES and the benefits derived by humans is so complicated (Farley and Costanza 2010). Second, the scarcity of ES often only becomes visible in the future. Anticipating this future scarcity is challenging for economic agents as short-term profits tend to be valued higher in the economic system, leading to the discounting of prospective costs and benefits (Voinov and Farley 2007, Adhikari and Baral 2018, Dasgupta 2021). These discounting effects become further reinforced by uncertainties because it is often not exactly predictable how land use changes on ES-providing land will affect the provisioning of ES (Lima et al. 2017). For example, the concept of ecosystem multifunctionality stresses this complexity of ecosystems and the intertwined relations between multiple ecosystem functions (Hector and Bagchi 2007, Manning et al. 2018). Furthermore, tipping points, where the resilience of ecosystems becomes disrupted (Thellmann et al. 2018, Dakos et al. 2019), increase these uncertainties. Thus, ES are much more complex than conventional services. Often we only find out which of the ecosystem functions are valuable to humans after destroying ecosystem components that are key for those ecosystem functions (Farley and Costanza 2010). We assume that this temporal and spatial masking of the benefits of ES often leads to a low WTP of ES beneficiaries. Hence, government-paid PES programs are so common. They often include pre-determined payment levels by referring, e.g., to land use-related opportunity costs or to other valuation methods instead of using a market-based price determination. This results in often low degrees of ES-commodification. In the end, the choice of the funding source and the price determination depends strongly on the ES type and, thereby, on the question whether potential ES buyers can be made to pay for ES on a voluntary basis in order to collect funding for the protection of endangered ecosystems and their provided ES.

Furthermore, our commodification framework raises the question whether PES-related degrees of commodification change over time. Fletcher and Breitling (2012), for example, emphasize that government-paid PES are sometimes described as an intermediary step toward the creation of ES markets, suggesting an increase of the degree of ES-commodification over time. At the same time these ambitions often seem to fail, which is likely due to the above-mentioned commodification-resisting character of ES. Furthermore, the question remains open whether PES lead to changes of the degree of commodification of ES-providing land. Gómez-Baggethun and Ruiz-Pérez (2011:620) state that the appropriation of ES “has often involved privatization, through which ecosystems that were previously in openly accessible regimes, or in communal or public property regimes, have been turned into private property.” However, the fact that most PES target private land tenure regimes does not imply that the PES programs actively transformed land tenure toward private property regimes. Instead, it can be assumed that ES-providing land is private already before the program is introduced. In this case a PES program is rather a follower than driver of land privatizations. However, there are also examples, like the study about a carbon PES in Mexico by Osborne and Shapiro-Garza (2018), that confirm that the implementation of PES programs can trigger land privatizations by introducing PES programs targeting individual community members. However, there is a lack of evidence how often PES play a key role for land privatizations (McElwee 2012) and how negotiations about the adaption and introduction of property rights take place at the local level (Kosoy and Corbera 2010). It remains also an open question whether C-PES programs safeguard and strengthen common land tenure regimes, or if C-PES, too, lead in some cases to a privatization of land in the long run. Therefore, more empirical research covering longer time periods is important to better understand how PES programs and land tenure transformations interact, while also taking the local circumstances and the history of land tenure regimes as well as their diverse structures into account.

Exploring the relations between degrees of commodification and social-ecological PES outcomes

Our framework of different PES-related degrees of commodification allows for a more nuanced analysis of the potential relations between the degree of commodification of a PES program and the ecological and social outcomes. Generally, there is a research gap regarding the investigation of commodification-outcome relationships (Kosoy and Corbera 2010, Osborne and Shapiro-Garza 2018). This also applies to C-PES, as our review shows. However, the results and our proposed commodification framework also reveal first insights of how degrees of commodification might affect C-PES outcomes.

According to our PES-related commodification framework C-PES programs show lower degrees of commodification of the ES-providing land. The results of the literature review show that this can be an advantage, particularly if the participating communities have a high level of social capital, because of better outcomes in terms of social justice, minimized conflicts, strengthened local cooperation, and lower transaction costs. Furthermore, it is worthwhile to have a closer look at the relations between degrees of commodification of ES-providing land and the contract length because studies indicate that PES success is positively correlated with contract length (Nsoh and Reid 2013, Sattler et al. 2013, Börner et al. 2017). We assume that a low degree of commodification of ES-providing land potentially supports a higher contract compliance in the long run because land under collective property is possibly less prone to changes in ownership due to the collectively possessed management rights and the often non-existent alienation rights. Additionally, some studies indicate that communities targeted by C-PES show a higher level of intrinsic motivation for protecting ecosystems (Bremer et al. 2014b, Agrawal et al. 2015, Moros et al. 2019), which could imply that the contract compliance at the ES providers’ side is less affected by changing economic conditions (e.g., market price fluctuations of ecosystem goods). In other words, the supply elasticity of products for which the land input is necessary might be comparably low because the decisions about the land use are less driven by opportunity costs and profit-seeking behavior. However, the composition of different values, such as use and non-use values, is highly context dependent as well as influenced by the local community governance and the political and social context (Sachedina and Nelson 2012). This again underlines the need to systematically categorize the underlying types of collective property that C-PES depend on to test our assumptions. In contrast to C-PES, the private land that P-PES build on is potentially prone to land ownership changes because of the often-existent alienation rights. Especially if the land is valuable due to its location and/or resources configuration in combination with the existence of extensive management rights, it is very lucrative for private individuals or profit-seeking private companies to buy such land. These global capitalistic dynamics are also controversially discussed under the “accumulation by dispossession” concept developed by Harvey (2004). Thereby, the profit-seeking behavior of landowners, which potentially increases in the case of ownership changes, might lead to unilateral terminations of PES contracts. This risk could only be prevented if the contract compliance is binding over a longer period, even if ownership changes. Moreover, various authors stress associated risks when PES target private land, for example, that the private enclosure of land could bring benefits for the middle class and rich people or for large private companies at the expense of poor people (Kosoy and Corbera 2010, McAfee and Shapiro 2010, Büscher et al. 2012, McElwee 2012, Bremer et al. 2014b), which, in the worst case, can lead to the displacement of local people by people with enough money and power to acquire land titles (Cavanagh and Benjaminsen 2014, Scales 2015). Again, it is important to investigate more in-depth when and to which extent these negative consequences appear.

Furthermore, our framework provides a basis for investigating the relations between different degrees of ES-commodification and the outcome of both P-PES and C-PES. Various authors emphasize risks of commodification processes that can be related to our proposed design components determining the degree of ES-commodification. It is, for example, stressed that cash payments could crowd out conservation motivations of the ES providers (Kosoy and Corbera 2010) or that the use of easy-to-measure direct ES proxies could blind the state or importance of other ecosystem functions (Norgaard 2010). Our review of the C-PES literature also reveals that high degrees of ES-commodification can result in negative outcomes, for example when a market-based price determination leads to fluctuations or low prices undermining the acceptance and the social effectiveness of a program (e.g., Namirembe et al. 2014, Osborne and Shapiro-Garza 2018). However, the scarce knowledge on commodification-outcome relationships of PES programs calls for more systematic research that could provide a broader empirical basis. At the same time, such comparative evaluations are challenging given the diverse institutional PES settings as well as the varying political, cultural, and ecological circumstances PES programs are embedded in. A further challenge remains in defining and measuring program outcomes. One program outcome often considered refers to the evaluation of the pre-defined program aims, e.g. by assessing the ecological additionality a PES program might produce (Engel 2016). However, to uncover a potential complexity blinding of PES programs outcomes needs to be assessed from various perspectives, for example by examining how the targeted ES interact with other ecosystem functions in terms of co-benefits and trade-offs or by focusing on the social outcomes of a program, covering also longer periods of time. Frameworks like, for example, the “Social-ecological Systems Framework” (Ostrom 2009, Bennett and Gosnell 2015), the “Institutional Analysis and Development Framework” (Ostrom 2005, Hayes et al. 2017), or the ecosystem multifunctionality approach (Manning et al. 2018) can provide guidance. Otherwise, an overly narrow view on PES outcomes entails the risk that PES research itself might contribute to complexity blinding.

CONCLUSION

In this study we explored how commodification and different forms of land tenure are understood and discussed in PES research. We put a particular focus on C-PES programs and how they differ from P-PES programs. Furthermore, we reviewed the potentials and challenges of C-PES and how relations between commodification processes and the outcome of the program are drawn. The results indicate that C-PES show promising outcomes, particularly in the case of a high level of pre-existing social capital of the communities participating. At the same time, research examining the impacts of commodification processes on program outcomes is rare. This is partly due to a blurred understanding of what commodification means. For this reason, we proposed a two-sphere commodification framework distinguishing between the degrees of commodification of land-related property rights bundles and ES-related degrees of commodification. This framework allows for a better analytical comparison of the degrees of commodification of C-PES and P-PES programs as well as their potential relations to program outcomes. In this context, it would also be interesting to investigate how degrees of commodification change over time and how the two spheres of commodification might interact. Last, it is important to consider the great diversity of common land tenure regimes, but also of land tenure regimes generally, by also taking the specific local institutional, cultural, historical, and ecological characteristics into account.

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