A cautionary tale about urban trees: could ecoservice monetary estimates become economic sleights of hand?

Abstract

Estimating the monetary value of ecosystem services bridges biophysical and economic systems, facilitating dialogue and decision-making among diverse stakeholders of nature. However, the more we translate natural phenomena into monetary units to unify diverse perspectives of nature's value, the more we risk losing. The search for a single underlying unit of existence (a monad) is a long-standing philosophical concept (monism) that has aided scientific progress. In the present article, we examine major monads in natural science en route to an exploration of the risks inherent to inadvertently adopting money as a monad (monetarianism). Through a cautionary tale and case study of an urban greenspace, we highlight the hazards of monetary representations of nature and present a new view of the potential for miscalculation. A monetary monism risks obscuring the true worth of biophysical processes behind an economic sleight of hand that could lead to the loss of ecosystem services and their monetary value.

Must “all sciences pave the way for the philosopher's future task; specifically, the task is to solve the problem of value and determine the hierarchy of values”?

—Friedrich Nietzsche, Genealogy of Morals (italics in the original German)

In a bustling city, a diverse group of local decision-makers convenes to navigate the complexities of urban development. These city planners and local officials operate under a mosaic of municipal regulations and community input. Their discussions, steeped in a web of competing interests for scarce urban space, reveal the tension between advocates of economic development, environmentalists championing green and blue spaces, and community activists who emphasize equitable access to urban amenities and natural areas. These are but a few examples of the broad spectrum of interests present, whether physically, in the form of decision-makers, or mentally, through constituent pressures. This setting underscores the ongoing debate between urban development and the conservation of natural spaces, highlighting the complex challenges of planning the urban landscape.

In this thought experiment, let's assume that arguments from all sides, even those at the extremes, are nuanced and rational through the lenses of their respective value systems. The diversity of these value systems, each employing its own linguistic framework and units of value, challenge communication and collaboration. Despite the best intentions of each interest's representative, their dialogue risks metaphorically transforming “all intellectual discourse into scat singing” (Sugrue 2021), where their arguments might be lost in translation. Sugrue noted, “Only the people who don't understand what scat singing is would actually ask, Well, what do the lyrics mean?” Undeterred, participants strive to decipher the lyrics—the nuanced and reasoned arguments—behind each stance, attempting to avoid the pitfalls that emerge from misinterpreting each other's linguistic exchanges as merely “a way of making noise and gesturing at the domain of your perspective” (Sugrue 2021). As they gradually begin to comprehend the various linguistic frameworks, it becomes apparent that each argument embeds a different measure of value, expressed in different units.

Let's examine some of these units. A decision-maker concerned with climate change presents the benefits of green spaces in units of carbon sequestration, such as grams of carbon per square meter per day (Wang et al. 2021) and kilograms of carbon dioxide per resident per 50-year period (Ariluoma et al. 2021). Another decision-maker, advocating for lakes, ponds, and water features, represents urban blue spaces in units of regional cooling intensity, such as the degrees Celsius per hectare of water surface area per hectare of neighboring landscape (Ampatzidis and Kershaw 2020). These scientific metrics often intersect with those used by community health groups, who might present benefits in terms of pollution reduction (grams of particulate matter per square meter per year; Lei et al. 2021) and improvements in academic performance (in correlation coefficients; Lin and Van Stan 2020). In contrast, other measures and units are used by interests who emphasize the socioeconomic benefits of using the same spaces for expanding development (e.g., school systems and housing), such as units of building capacity (students or residents per square meter; Horsford and Sampson 2014), occupancy rates and profiles (the fraction and makeup of used capacity; Nejadshamsi et al. 2023), or revenues from property (and related) taxes (Rickman and Wang 2020) or payroll (dollars per job created; Bartik 2020).

These examples are not exhaustive. Still, one can understand and empathize if these groups (likely under pressure from their constituencies and other stakeholders) try simplifying and unifying their approaches in the pursuit of common ground. In such attempts, they are often tasked with converting diverse values into a universal metric that can be more easily communicated and understood. At this point, we can step back from our imaginative scenario to confront a real-world consensus that has indeed emerged around a universally recognized measure: money. Every unit mentioned thus far can be translated into economic value.

In this article, we explore the implications of translating diverse values into a single unit, a philosophical approach known as monism. By examining the history of similar monist frameworks in science and then considering the potential emergence of a new one (monetarianism), we highlight the rewards and the risks of reducing complex natural phenomena to monetary units. We conclude by revisiting our introductory story, steering it into a cautionary tale that illustrates the dangers of a comprehensive application of monetary monism.

Crafting sturdy bridges between units

Unit conversions in biophysics can be straightforward, often requiring a simple bridge such as the division by a constant. However, when the end product is value expressed in a unit of account (e.g., money), the bridge becomes more elaborate. Bridging biophysical estimates of natural phenomena to a unit of account that adequately represents their service value to humans requires a robust framework that integrates the distinct but complementary languages of economics and ecology. Over the past few decades, several robust blueprints for such bridges have been developed to facilitate this translation (Boyd and Banzhaf 2007, Hein et al. 2020, King et al. 2024, Remme et al. 2024). A landmark effort in this regard is the Millennium Ecosystem Assessment (MEA), which offers a comprehensive system for ecosystem service characterization. The MEA has shaped global sustainability initiatives, from the United Nations’ Sustainable Development Goals to the Convention on Biological Diversity (Millennium Ecosystem Assessment 2003, 2005a, 2005b, United Nations General Assembly 2015). It also inspired models such as InVEST and ARIES, which enable spatially explicit economic quantifications of ecosystem services (Villa et al. 2014, Natural Capital Project 2024). In addition, tools offering tailored assessments (e.g., i-Tree for urban forest systems) demonstrate the adaptability required for different contexts. These efforts align with the United Nation's System of Environmental-Economic Accounting, which is steadily achieving the status of global standard (Edens et al. 2022). The increasing adoption of natural capital accounting frameworks by governments, with 92 countries, including the United States, committing to their development (Ingram et al. 2024, Malhi and Daily 2024), demonstrates growing recognition of the need to integrate the values of nature into decision-making at national and global scales. At the same time, debate persists within ecological economics over whether monetary valuation oversimplifies or distorts ecological function (Spash 2008, Victor 2020). We embrace these endeavors toward improved economic accounting of ecosystem services, aligning our perspective with a fundamental assertion of these works: “An economic definition of service units [can] lead naturally and necessarily to a bridge between economic and biophysical analysis. No ecologist should think that the economic definition of services leads away from biophysical analysis. In fact, the opposite is true” (Boyd and Banzhaf 2007).

Indeed, when economic units are meticulously crafted to mirror biophysical realities, they do more than span the divide; they forge a durable link between economic theory and ecological pragmatism, anchoring the abstract concepts of value in the tangible world of ecological processes. Such craftsmanship aims to ensure that these bridges do not just connect two disparate fields but also support the weight of decision-making that respects ecological and social intricacies, rather than merely commodifying natural phenomena (sensu Gómez-Baggethun and Ruiz-Pérez 2011). Examples, such as the Quito Water Fund in Ecuador (Kauffman 2014, González-Zeas et al. 2022), Costa Rica's national payments for ecosystem services program (Pagiola 2008, Brownson et al. 2020), and the recent San Crisanto mangrove insurance project in Mexico (Rogers et al. 2022, Pachon 2023), exemplify how monetary valuation has contributed to conservation outcomes. In each case, success hinged on the thoughtful integration of ecosystem valuation with strong governance, stakeholder alignment, and institutional frameworks that directed financial flows toward ecological stewardship. Crucially, these success stories share an implicit subsidy (space) and, therefore, hectares can be repurposed with manageable sociopolitical cost. Where land is scarce, even in ostensibly rural settings (e.g., Teufelsmoor, Germany), smallholder farmers fight to keep low-profit drained peat pastures because surrendering any plot may imperil the farm as whole (Wichmann and Nordt 2024, Hünnebeck‐Wells et al. 2025). Urban contexts further tighten the vice. With fierce competition from high (economic) yield land uses backed by powerful interests, ecosystem services must clear daunting valuation thresholds before green space can prevail (a tension explored later in this essay). Moreover, urban ecosystem services linked to aesthetic, cultural, or recreational values are shaped by a plurality of perspectives; urbanization fosters cosmopolitanism (Binnie et al. 2006), but that diversity makes such values harder to quantify and more likely to be omitted from valuation tools because of that complexity. See the “paradoxes of cosmopolitan urbanism” in Binnie and colleagues (2006). In densely populated urban settings, the cumulative effect of these under- or unvalued services is unlikely to be trivial. They may scale to obscure precisely those services most intimately tied to human well-being.

There are certainly examples of monetary representations of ecosystem services that fail to adequately bridge economic decision-making with biophysical realities (Spangenberg and Settele 2010, Silvertown 2015, Stern et al. 2021). Such failures and challenges, derived from humanity's representations of nature, have spurred over a century of scholarly work and philosophical exploration (Marsh 1864, Kenneth E. Boulding 1966, Westman 1977, Beckerman and Pasek 1997, Costanza et al. 1997, Aryal et al. 2022). As representations, unit conversions bridge disparate interpretations of nature. Early twentieth-century philosophers such as Heidegger and Deleuze warned that such conversions, by reducing nature to simplified, quantifiable units, risks distorting their immanent worth (Tissandier 2018, Weigelt 2021). From this viewpoint, complex conversions between biophysical units and value-oriented units can lead to compounded errors in valuing natural phenomena (i.e., compounded biases) and thereby amplify misapprehensions in valuation. These errors can go beyond mathematical or systematic inaccuracies, potentially propagating to the core of how we view and interact with natural phenomena, altering our engagement with the natural world. Our perspective of economic valuation of ecosystem services, although it aligns with the argument of Boyd and Banzhaf (2007), incorporates such miscalculations and misinterpretations into a concept of ecological monetarianism and a cautionary tale about urban trees that encourages us to inspect the bridges we build. Our critical view applies not only to the increasingly consequential management of trees in urban landscapes, but also to broader discourse and action toward sustainability, because sustainable development relies on the integrity of the conceptual and mathematical bridges connecting biophysical realities to human constructs, such as economic theories, cost–benefit analyses, and city ordinances.

This is not to suggest that carefully crafted and inspected bridges will or ought never fail. Indeed, their signs of stress or failure due to inadequate understanding or flawed translations offer valuable opportunities to strengthen and refine our approaches. But what happens if a universal metric of value (such as money) starts redefining organisms or ecosystems themselves? The risk of becoming blind to the structural integrity of our conceptual frameworks is real. If monetary value becomes the foundation of biophysical research, we might end up with no substantial bridge at all, only an illusion that ecosystems are being thoroughly investigated (and economically translated). Ecologists could inadvertently settle on the economic side of this metaphorical bridge—to prioritize economic perspectives—neglecting the ecological and social nuances that may be less quantifiable or convertible, letting the bridge to less valuable organisms, ecosystems, or processes deteriorate. Although refining economic valuations of natural phenomena is important, this effort should not supplant the basic goal of understanding these phenomena on their own terms or within broader contexts (e.g., their role in the Earth system). Our pursuit of economic clarity must support, rather than replace, the core principles of natural science, the true monads of biophysical understanding.

Money as a monad

Pursuit of a universal way to understand and articulate the world has deep historical roots. The exploration of monads—singular entities posited to underpin all reality—illustrates this pursuit, revealing the underlying structures that shape existence, including human perceptions and desires. Theorizing about monads has helped refine our understanding of fundamental cause-and-effect relationships. In the eighteenth century, amid growing skepticism about whether empirical evidence alone could explain causality (Musgrave 1993), the German philosopher and mathematician Leibniz proposed The Monadology (1714) as a solution. He sought to reconcile the apparent chaos of the world with a deeper, underlying causal order, famously stating, “there is nothing fallow, nothing sterile, nothing dead in the universe, no chaos, no confusion save in appearance” (Duncan and Latta 1899). Leibniz defined monads as entities that underpin all phenomena and their interactions, operating according to consistent laws and ensuring that every event had an internal cause, even if that cause was not directly observable. These monads formed the building blocks of reality, manifesting its order and structure.

The search for monads predates Leibniz's formal definition. In Western philosophy, it traces back to the Ionians, early Greek philosophers from approximately the sixth century BCE, whose contributions significantly influenced modern science. These thinkers introduced material monads, such as atoms, and immaterial (i.e., formal) monads, such as principles of classification. By briefly examining key material (water and the atom) and immaterial monads (principles of classification; e.g., Platonic forms), we prepare the ground to explore money as a modern monad and the perspective that may be built on it: monetarianism.

For material monads, the dual dynamic of discovery and falsification is first documented with Thales of Miletus, who is also considered the first Western philosopher and protoscientist (O'Grady 2017, Van Stan and Simmons 2024). Thales’ proposition that everything is water set the stage for the exploration of fundamental elements (archai), a path that his successors expanded by suggesting other elemental monads such as air, per Anaximenes, and fire, associated with change by Heraclitus (Graham 2009). This inquiry evolved dramatically with Democritus’ atomic theory, which posited atoms as the smallest, indivisible units of matter (Laërtius 1925). However, it was not until the eighteenth century that Henry Cavendish and Antoine Lavoisier's experiments empirically challenged the water monad by isolating and purifying it (Lavoisier 1773), demonstrating its compound nature (Cavendish 1784) and enhancing the scientific understanding of water and its management practices (Kambas 2024). Similarly, the atomic monad was falsified in early twentieth century experiments when J. J. Thomson's discovery of the electron and subsequent experiments by Ernest Rutherford revealed that atoms were, in fact, divisible into smaller particles (Thomson 1905, Rutherford 1911). This falsification of the atomic monad revolutionized our understanding of atomic structure while also spurring the development of quantum mechanics.

The immaterial monads, particularly those conceptualized or influenced by Plato, have had an equally profound impact on Western science (Shorey 1927, Johansen 2004). Plato's famous allegory of the cave, where an immaterial monad illuminates and shapes all observable phenomena through forms, underscores the importance of abstract theory and the integration of imagination with mathematics. This influence is evident in the major theoretical advancements of nineteenth and twentieth century physics. For instance, the theoretical explorations and mathematical models that drive modern physics share strong similarities with the astronomical methods discussed in Plato's Republic (Heath 1913, Shorey 1927). In these philosophical systems, the immaterial monad central to these forms is so crucial that it is often referred to as the good (e.g., by Plato) and divine by Leibniz. What if money were to become the immaterial monad? To what extent might its integration support or perhaps inadvertently hinder the fundamental investigation of causation in natural sciences? Money is a medium of exchange, a unit of account, and a store of value. Of course, inherent in this definition is that, as a proxy for value, money can distort when market frictions, externalities, and skewed incentives lead to mispricing; that, as a medium of exchange, it is an imperfect facilitator (e.g., it is unable to capture nonmarket exchanges and subject to information asymmetries); and that, as a store of value, it is a leaky container, weathered by inflation and porous to emotional or existential worth when pressured by diminishing marginal utility.

With that in mind, consider how money shares profound similarities with monads, as they are defined by Leibniz's principles. It functions as an ostensibly immutable unit of account (i.e., $1 always equals $1 nominally). It is indivisible; although it is capable of division into smaller denominations such as cents, money cannot be fundamentally split into distinct qualitative parts. It demonstrates ontological dominance: Just as a Leibnizian monad governs its own universe, money governs physical resources (driving prices and land-use decisions) without itself intervening materially or being materially altered by the ecological phenomena it quantifies. A monetarian framework therefore positions money not just as a measure but also as a force that could reshape our understanding of value and the pursuit of knowledge. In contrast to other immaterial monads that shape reality through abstract principles, the monetary monad is derived from material phenomena and has the potential to redefine them. Although such transformations can motivate research, such as turning a region's urban forest into an asset value of $181 billion (McPherson et al. 2017), the mutable nature of monetary value (dependent on human agreement and economic conditions) introduces a perpetual redefinition of phenomena by market dynamics and fluctuations in human knowledge and values.

Therefore, the closest parallel to the monetary monad in classical philosophy might be found in Heraclitus’ concept of the universe as composed of perpetual flux, the monad of change. Interestingly, Heraclitus linked his monad (symbolized as fire) to the dynamics of monetary exchange, noting, “There is exchange of all things for fire and of fire for all things, as there is of wares for gold and of gold for wares” (fragment 90, translated in Wheelwright 1959). In this analogy, gold (then the dominant medium of account) does not possess intrinsic or stable value; rather, it is part of a system where all equivalences are fluid and contingent. The same gold coin might procure vastly different wares depending on the context, similar to the way a modern dollar's value shifts across time, space, and socioeconomic strata. And if fire consumes that which it touches, then so too might gold: transmuting the concrete into the abstract, reducing the material world into mutable units of exchangeable equivalence that, like smoke, may leave no trace of its original form. Therefore, even as a unit of account, money lacks the constancy typically required for scientific inquiry. Heraclitus’ perspective therefore presents significant challenges for empirical science: His change encompasses not just variability in observable biophysical properties but also the processes that underlie these phenomena, making it difficult to establish consistent, predictive scientific theories. Embracing a monetary monad in scientific inquiry risks importing this instability and, thereby, fundamentally prevents the discovery of efficient causal chains, by introducing a system where fundamental constants are not only intangible but also frequently redefined by markets and perception. This instability is an empirical liability that could make the bridge between scientific and economic inquiry precarious, where the monetary units that compose and orient its planks may shift or vanish under the currents of perpetual change.

A monetarian snapshot of an ecosystem in perpetual flux is still possible. One could transform, for example, empirical observations of a young, 36-hectare park in Los Angeles (California, in the United States) into a ledger of utility. Every natural element—the nutrients, the soil, the gases exchanged, and the life within it—become monetary units. The park's carbon, once a complex urban ecological asset, is now a spatiotemporal arrangement of dollar bills amounting to $2291, dispersed across what were once leaves, stems, grass, etc. (Wilson and Willette 2022; note that we do not intend to challenge the methods, figures, motivations, etc., of the study, only to use this citation for the ecoservice monetary estimates). Rainwater and captured particulates enrich this monetary landscape, adding thousands more in paper bills layered over these leaves or rolled around tree stems as if they too were currency. The capture of gases with harmful effects on human health, such as sulfur dioxide, being valued at a paltry $4 (Wilson and Willette 2022), are sprinkled like small coins across the fiscal terrain. Of course, estimating the economic value of environmental phenomena, such as this, is not in itself an issue. The problem arises when monetary representations dominate and the park's narrative shifts from ecological dynamics or inherent value to monetary value and human utility. When some stakeholders or urban land managers discuss or manage the park solely as a fiscal balance of benefits and costs, weighed against the economic metrics of alternative land uses, the park transforms into monetary units within a financial tableau, such as speculative estimates of economic utility risk obscuring the inherent functions of natural processes, starkly contrasting with previous monadic views of nature and reshaping our interaction with and valuation of natural spaces, prioritizing utility over both biophysical and economic curiosity.

Monetarianism: What might monetary monism look like?

Monism, the philosophical notion that all existence originates from a single substance or principle, manifests uniquely in the concept of the monetary monad. Before we envision how monetary monism (or monetarianism) might unfold at a systemic scale, it's important to clarify that we do not equate it with general economics. Now, imagine nature's systems recast as components of humanity's service sector, with each service composed of, quantified by, and defined in monetary units. The number of these monetary units represents not the physical amount of service provided but its estimated value. Their arrangement relative to each other reveals the structure of perceived utility: which services are prioritized, which are dismissed, and how natural phenomena are reconceived through valuation. By assigning a specific monetary value to natural phenomena on the basis of their utility to humans, money, serving as the fundamental monad, becomes the lens through which the natural world is observed, evaluated, and managed. Of course, nature can be naughty, and naughty behavior, by definition, does not serve typical human social systems. Consider the times when trees drop all their leaves into our streets, requiring costly cleanup. To account for processes that inflict costs or damages on humanity, this model requires a theoretical disservice sector (Escobedo et al. 2011, Roman et al. 2021). In this sector, we cannot, for example, detain trees or ponds (even repeat seasonal offenders); instead, disservices are quantified and subtracted from the total value of a natural phenomenon's services, ensuring that both beneficial and problematic interactions between nature and humanity are reconciled in a monetarian worldview.

The scenario just described may seem absurd to some or innocuous to others, suggesting there is little danger of monetarianism becoming adopted in any impactful way. However, there are compelling reasons to view monetarianism as potentially highly infectious and morbid. Humans routinely appraise the worth of their own services to society against monetary benchmarks—from the cost of a latte to a loft. It seems probable that a monetarian representation of nature would be intuitive and easily embraced. Viewing existence through universal monetary terms could ostensibly distill complex ecological interactions into straightforward monetary transactions, promoting what appears to be an efficient management of natural resources. If such a monetarian system were to take root, one might expect a monetary prioritization of natural elements by the public and governments and even the emergence of entire scientific programs dedicated to studying ecological and environmental systems from this perspective, akin to physicists contemplating atomic structures. Others may claim that a systemic monetarian framework has already been extensively embraced, particularly in applied sciences, such as disaster risk science, where the name itself reflects an economic bias that prioritizes human interests over ecological concerns. We believe a fairer argument, however, is that the trajectory of various current ecoservice research efforts is toward monetarianism. If or when that destination is reached, future ecologists might then resemble a hybrid of naturalist and financial analyst, adeptly navigating the stock markets of natural resources.

This transition to monetarian theorist could occur unintentionally, especially if the societal systems that motivate and support environmental research increasingly rely on monetary metrics. This reliance could inadvertently shift the focus from environmental sustainability to monetary considerations, manifesting in less subtle ways than the implicit bias seen in applied science disciplines that prioritize risks to human assets. For example, we may see meta-analyses of Earth's forests ranking their functions (as many as are known at that time) on the basis of median monetary value or its variability (e.g., Taye et al. 2021), inherently prioritizing what is most monetarily valued or variable. Similarly, in croplands, an element such as carbon may be prioritized because of its high monetary value per kilogram (e.g., tens of thousands of US dollars per hectare per year) over an element such as nitrogen with less valuable services (e.g., tens of US dollars per hectare per year; Lin et al. 2024)—even though croplands are the largest source of global nitrogen pollution (Erisman et al. 2013, Gu et al. 2023). Note that Lin and colleagues (2024) did not advocate for prioritization of elements in their paper. This monetarily driven prioritization of ecological elements also risks accelerating (or falsely legitimizing) environmental degradation when profit-seeking behavior becomes the primary lens through which nature is evaluated. In some regions, particularly Latin America, there has been resistance to monetization efforts for precisely this reason: the concern that reducing nature to financial terms may legitimize further exploitation under the guise of economic development (Purwandani and Michaud 2021).

Given the limitations of the monetary monad previously discussed, it seems improbable that monetarian strategies to understand and manage environmental systems will maximize the potential for long-term sustainability of the human–nature partnership (Boesing et al. 2020 and the references therein). Instead, these efforts may maximize nature's short-term utility for humanity. Of course, the propensity for monetary ecoservice estimates to prioritize short-term human goals over long-term environmental sustainability is a well-trodden academic path (for reviews, see Marsh 1864, Westman 1977, Aryal et al. 2022). Although the practitioners—from economists to ecologists—may not deliberately advocate for monetarianism, their methods can inadvertently foster this bias. If so, might many monetary estimates of ecosystem services actually be blazing a trail toward monetarianism?

Let's walk this trail. We do not travel far before the greenery above shakes, and we witness an odd kind of currency emerging. It appears to be, in this case, US dollars representing the value of biophysical traits and processes of trees. We attempt to deposit this currency in a financial instrument but fail. Being unable to store it, we attempt to use it in financial transactions without success. Skepticism arises about this currency's claim (to represent the biophysical traits and processes of trees). What exactly does it represent? When trees are removed, the tangible biophysical effects, such as additional cubic meters of stormwater per year, grams of carbon dioxide released per year, and micrograms of pollution per cubic meter of particulate matter of 2.5 microns or less, are quantifiable in physical units. These physical units translate directly into monetary costs for the necessary work (labor, materials, oversight, etc.) associated with infrastructure adjustments for additional stormwater management, carbon release mitigation, and the decline in air quality and human health. The intact trees’ ecosystem services are physically manifest in the trees themselves. But where do we find their monetary representations? In which financial instrument are these values stored or protected? Although money exists in a diversity of recognizable forms that affirm its functionality and presence in the physical world, the monetary representations of ecosystem services often seem to lack a direct physical counterpart and have limited effective value (e.g., political, legal, or transactional). This casts serious doubts on the credibility of the currency we encountered on our walk along the trail toward monetarianism.

Although the financial valuation of an urban forest or a wetland might appear in reports and influence policy or development decisions, these numbers often do not correspond to actual money changing hands. This raises a fundamental question about their real-world functionality. The lack of direct transactability challenges the economic nature of these valuations; although monetarianism aims to equate natural capital with financial capital, its unit of account lacks the functionality to operate as true currency within the economy. Therefore, although these valuations might offer a means to highlight the tension between land development and environmental preservation, they also illustrate the practical limitations of using monetary estimates as a stand-in for real economic transactions in environmental management. Ultimately, without the ability to facilitate direct economic exchanges, these representations risk becoming impotent symbolic tools rather than functional instruments in the pursuit of optimal environmental management. A substantial literature exists seeking to address this transactability limitation, exploring avenues to enable payments for ecosystem services (Yan et al. 2022, Plantinga et al. 2024); however, as of this writing, economic valuations of ecoservices continue to struggle with this inherent transactability dilemma.

What, then, can monetarian representations of ecoservices be currently exchanged for? It can be argued that they are primarily exchanged for intangibles such as public goodwill or regulatory support. In scenarios such as tree removal in an urban park, the monetary value assigned to the trees’ ecoservices might sway public opinion or shape policy decisions. Extending this argument, if society fully embraced a monetarian viewpoint (and operated more rationally within this framework), these monetary representations might bolster public support for environmental conservation. Could widespread monetarianism, somewhat paradoxically, help us buy back our lost connection to nature? This might be possible if the values of nature that undergird this connection could be translated into monetary terms without losing vital dimensions in the process. However, if nature has any essential qualities that are undervalued or nonquantifiable, then the monetarian transformation of nature could amount to an economic sleight of hand, where one system of valuation seems to make the other disappear.

A cautionary tale: Ecoservice estimation as economic sleight of hand

Our cautionary tale begins where the introduction ended: A group of disparate stakeholders, each with unique perspectives, has come to a consensus. To advance the discussion, all values must be converted to money. Their discussion is about a public greenspace nestled among stadiums, shops, and high-end apartments, a space much like Erie Street Cemetery, in downtown Cleveland (figure 1). To ensure this conversion is done accurately, they call on a monetarian theorist to translate ecosystem services into monetary units. This theorist arrives with a robust tool commonly used for such tasks: the US Forest Service's i-Tree Eco application, which is widely used for urban forest ecosystem services. By 2020, i-Tree had over 500,000 users in approximately 150 nations, and over 1000 articles either used i-Tree or contributed to its development. For a detailed overview of i-Tree's methodologies and tool suite, see Nowak (2024).

Figure 1.

Location map showing (a) Cleveland, Ohio, in the United States, and (b) the Erie Street Cemetery, in box, nestled among stadiums and commercial areas. (c) Lidar-derived point cloud of the area, highlighting tree canopy heights and structures. Source: USGS 3D Elevation Program. (d) Detailed terrestrial lidar point cloud of a mature honeylocust tree within the cemetery.

A brief aside: We are not suggesting that using i-Tree tools, alone, is a monetarian act or detrimental to urban planning. The development and use of i-Tree has been instrumental in expanding the number and diversity of stakeholders of urban forests and inspiring actions to protect and expand urban forests. However, the cautionary tale suggests that, without substantial contextualization, widespread use of tools like this could devalue nature and lead us deeper into monetarianism.

The monetarian presents this model like a magician's prized prop. “Good day, ladies and gentlemen! Esteemed stakeholders,” he begins, with a twinkle in his eye, “gather ‘round! You are about to witness a marvel of modern environmental economics. Before you stands a tool of immense power, a device capable of translating the wonders of nature into the universal language of money. Behold, the i-Tree Eco! It is no mere software; oh no. It is a portal through which the natural world may be quantified and valorized, valued in terms that even the most hardened accountant would not only understand but appreciate. But—” He paused dramatically. “—if you don't believe me, here; I will put it into your hands! Who among you would like to check it out, to look under the hood, to see the peer-reviewed publications that support it? Come now, don't be shy! Step forward, my good friends, and ensure it is sturdy, scientifically sound, reliable.”

A few audience members step forward, nervously at first, but then with more confidence as they tap on the screen, browse through the documentation, and even input a few data points of their own. “Solid, isn't it?” the monetarian asks, his smile broadening. “And now, let us not forget our trees. Tap on them, good lady and gentle sir. Give them a solid rapping of your knuckles! Firm, aren't they? Yes, these trees are very much real. And now, watch closely as we input them into our sturdy model.”

The audience leans in, captivated, as the theorist enters data into the i-Tree Eco software. Biophysical representations of the trees are converted into monetary values. The process is smooth, efficient, and seemingly precise. “Voila!” the monetarian declares, presenting the results with a grand sweep of his arm. “As per current ecosystem service valuations, these 105 trees are worth just under $1 million in replacement value and generate $3000 in annual ecosystem services. Over their lifetime, these services reach approximately $100,000” (see the estimation of this number in section S1 of the supplemental material). Of course, few in the room could articulate exactly how i-Tree's values were calculated, what assumptions were made, which valuation methods (willingness to pay or to accept or others) were chosen, or how one might compare a tree's replacement cost with its annual service yield. But this didn't seem to matter, because the tool spoke in dollars—and in monetarianism, such translation equals truth—even if no one really understood the language.

Excited, the tree advocates presented these numbers to the community and decision-makers, but developers quickly countered with figures for their new mixed-use residential–commercial project. The reality became all too clear: Despite their best efforts, the monetary values generated for the trees in their beloved green space were paltry compared with the various economic gains depicted in the developers’ plan to construct a city-center apartment building. The trees would be cut down, the land repurposed, and the park's beauty, carefully quantified, was to be sacrificed for the greatest economic progress.

In desperation, the tree advocates return to the monetarian theorist, pleading for a way to save the trees. They considered the known unknowns—the natural phenomena that models such as i-Tree currently cannot accommodate. One stakeholder, recalling a stroll through Erie St. Cemetery, remembers the lichens and bryophytes vibrantly clinging to the darkened bark on a misty Cleveland day. Remembering, too, that these organisms can store 300%–3000% of their dry weight in water (Mendieta-Leiva et al. 2020), they say, “The epiphytes—the lichens and mosses that cling to the bark—what about them? Surely, they reduce stormwater runoff even more than the bare trees. Can their worth tip the scales?” The monetarian raised an eyebrow. “Why, of course. How much rainwater can these epiphytes intercept?” Observations were gathered and input into the Lichen and Bryophyte Simulator (LiBry; Porada et al. 2013, 2014). LiBry estimated that the park's epiphytes reduce water input to the ground by 3% of the mean annual rainfall, reducing stormwater by 1118 cubic meters (m³) annually. The monetarian quickly calculates: “$2600 more in stormwater ecoservices per year.” (See section S2 of the supplemental material for further details.) But as the number was revealed, silence fell. It was still not enough. The council murmured and dispersed in dismay.

That evening, one stakeholder sat in silence at dinner. While pushing an especially dendritically shaped piece of broccoli around her plate, an idea struck. “What if there were ways to estimate a tree's worth that more closely resemble the tangible calculations used in construction?” Her family, surprised by the sudden outburst, looked up from their meals. Encouraged by their attention and seeking to clarify her thoughts, she continued: “Consider a beautiful, old honey locust in Erie St. Cemetery, for instance (figure 1). Using terrestrial lidar technology (Leica BLK360) and open-source quantitative structural modeling software (SimpleForest), we can measure the tree's woody volume. This process, requiring only approximately 4 hours of labor, yields a concrete metric—the tree's biovolume—that parallels the units used in construction. We could use this biovolume to estimate a replacement cost not on the basis of uncertain estimates of ecosystem services but estimated simply and certainly: the true replacement cost of the old locust tree as a multiple of the number of tree saplings required to replace its biovolume and the price of each sapling! It must take hundreds of saplings to equal the heft of that one locust, and there are 104 more trees, each much grander than a sapling!” Her family nodded supportively, returning to their meals. The next morning, she dedicated 4 hours to executing her plan (see the methods described in section S3 of the supplemental material).

That afternoon, she hurried back to the council, where they were continuing their efforts, working with the monetarian. She stepped forward. “A single tree like the honey locust has a biovolume of 10.27 m³. In contrast, a typical 2-inch caliper sapling, available for around $280 from a local nursery, contains just 0.007 m³ of woody volume. To replace the honey locust's biovolume, we would need 1450 saplings, costing around $406,000. If we build our bridge between the biophysical and economic worlds in this way, the total value of the 105 trees in Erie St. Cemetery exceeds $42 million! That is 42 times the estimate from your i-Tree model!”

Hope flickers in the room, but the monetarian, after a pause, shares a sobering truth. “Even with these improved methods, the value of your precious trees, those green, mixed-use apartment buildings of birds and bees and beetles, still pales in comparison to their human-made and occupied counterparts. Although the cemetery's trees may now be valued at approximately $42 million, this figure is still far less than the economic worth of a building of the type conjured by the developers and their partners at City Hall, such as the approximately $85 million Skyline 776 Apartment next door (also called The City Club Apartments; Prendergast 2020).” Someone said, reflexively and almost under their breath, “What will happen to the trees?” The atmosphere thickened as the question settled. “There are no trees now,” the monetarian said flatly. His words hung in the air like a death knell.

Panic set in. “Then give us the money!” they cried. “We'll buy new trees, new blue spaces, new phenomena of nature, procure the services that were previously performed by these trees for our constituents—anything to restore what we've lost!” But the monetarian only laughed, a dark, knowing chuckle that echoed through the room. “Money? What money? There is none,” he replies, his eyes gleaming. Cleveland, like most cities across the world, has no regulatory mechanism to monetarily compensate the public for its lost trees, no way to collect the replacement value of the lost trees, be it $1 or $42 million.

As the stakeholders of nature and their communities departed, dejected and defeated, one woman paused at the door. Her mind drifted to the unmonetized squirrels, soil meiofauna, gaseous exchanges, etc., and a Gestaltian doubt crept in (sensu Schroeder 2007). Could converting additional natural phenomena to monetary value ever accurately represent the worth of any place to its inhabitants? Her gaze unfocused in thought then sharpened just as the monetarian turned to leave. She caught a glimpse of his foot shuffling beneath his cloak and gasped. Though she only saw it for a moment, she swears to this day that it was cloven. A realization struck: In their quest to quantify and control, to value the invaluable, they had not just lost their trees; they had sold the natural foundation on which their very souls were nourished, the very essence of their connection to nature, to a force they scarcely understood.

And so, the cautionary tale reaches its chilling conclusion. The process of converting nature's multifaceted contributions into monetary units has reduced it to something intangible, untradeable, and ultimately, irreplaceable. The i-Tree Eco model and others like it, though valuable, cannot monetarily capture the deeper significance of natural phenomena—their cultural, psychological significance, or other intrinsic or unknown values that evade monetarian calculus, especially in dense urban areas. This economic sleight of hand has made these vital components disappear, leaving behind only the stark reality of lost greenspace and frustration that a tree's economic value seems only qualitative and mythical. Therefore, despite our best efforts to quantify nature's worth in monetary terms, the scales of monetarianism remain tipped in favor of human development.

Author Biography

John T. Van Stan II (j.vanstan@csuohio.edu), Kevin E. Mueller, and Benjamin J. Noren are affiliated with the Department of Biological, Geological, and Environmental Sciences at Cleveland State University, in Cleveland, Ohio, in the United States. Michael O. Wiitala is affiliated with the Department of Philosophy and Religious Studies at Cleveland State University, in Cleveland, Ohio, in the United States. Jack Simmons is affiliated with the Department of Philosophy and Religious Studies at Georgia Southern University, in Savannah, Georgia, in the United States. Meimei Lin is affiliated with the Department of Earth, Environment, and Sustainability at Georgia Southern University, in Savannah, Georgia, in the United States. Qiping Huang is affiliated with the Department of Finance at Georgia Southern University, in Statesboro, Georgia, in the United States. Philipp Porada is affiliated with the Institute of Plant Science and Microbiology at the University of Hamburg, in Hamburg, Germany. Theodore A. Endreny is affiliated with the Department of Environmental Resources Engineering in the College of Environmental Science and Forestry, at the State University of New York, in Syracuse, New York, in the United States.

Funding

JTVS and BJN acknowledge support from US National Science Foundation (grant no. DEB-2206358). This work was also supported in part by the United States Forest Service National Urban and Community Forestry Advisory Council (USFS NUCFAC), grant 21-DG-11094200-242.

Author contributions

John Toland Van Stan (Conceptualization, Data curation, Formal Analysis, Funding acquisition, Investigation, Methodology, Project administration, Supervision, Writing - original draft, Writing - review & editing), Michael O Wiitala (Conceptualization, Writing - original draft, Writing - review & editing), Philipp Porada (Formal Analysis, Software, Visualization, Writing - original draft, Writing - review & editing), Theodore A Endreny (Formal Analysis, Writing - original draft, Writing - review & editing).