Natural capital accounting (NCA) using the international System of Environmental-Economic Accounting Central Framework (SEEA CF) (UN 2014) and Ecosystem Accounting (SEEA EA) (UN et al. 2024) is increasingly being applied worldwide to track the physical quantities and monetary values of stocks of natural resources, including ecosystems and the flows of benefits they provide to economies (UN 2024).*1 Collectively, these stocks and flows of natural resources are referred to as "natural capital" (UN 2025). SEEA CF accounts are useful for quantifying land, water, forests and energy and minerals. SEEA EA accounts, on the other hand, are useful for quantifying ecosystem extent and condition, as well as physical and monetary estimates of ecosystem services and their changes over time. We summarise common types of SEEA CF and EA accounts and their contents in Table 1.

SEEA typically targets the production of national-scale environmental-economic accounts, which can be integrated with more traditional national economic accounts developed using the System of National Accounts (SNA) framework (UN 2009). There are various possible ways all these accounts can interact. Focusing on a water-related example, the SNA framework is a useful starting point for tracking how water products move through the economy between producers and consumers. SEEA CF, including SEAA CF - Water, expands the accounting by identifying where in the environment producers obtain their water supply. SEEA EA then expands the accounting even further, by tracking how ecosystem provisions affect the water supply used by producers. We show a corresponding conceptual diagram in Fig. 1. For more examples of useful conceptual diagrams that show possible interactions between the different account types, we refer interested readers to other literature (e.g. Banerjee et al. (2020), UN (2021), Global Ocean Accounts Partnership (2022), Chen and Vardon (2024)).*2

Figure 1.

An example of how different types of natural capital accounting frameworks interact to track possible interactions between the economy and water stocks and flows. Figure adapted from Vardon et al. (2019) and Vardon (2022). SNA = System of National Accounts, SEEA = System of Environmental-Economic Accounting and CPC = Central Product Classification (UN 2015).

In the United States (U.S.), a 2023 national NCA Strategy developed the vision for a comprehensive cross-government assessment of the condition and value of natural capital in a manner consistent with the Nation’s economic accounts (OSTP et al. 2023, Fenichel 2024). The U.S. National Strategy is designed to be consistent with the SEEA and, where possible and desirable, to extend it through relevant headline indicators and supplemental thematic accounts, while also developing and applying state-of-the-art approaches to valuation.*3 The strategy builds on recent experimental work in the U.S. for land, water and ecosystem accounting (Bagstad et al. 2020, Warnell et al. 2020, Wentland et al. 2020, Bagstad et al. 2021, Heris et al. 2021).

The Federal agencies responsible for managing natural resources in the U.S. are important potential users of NCA information. With almost 30% of the land area of the U.S. managed by Federal government agencies (ca. 2.6 million km²), the ability to develop and use NCA information at subnational scales is important. In a large, heterogeneous nation like the U.S., which faces highly diverse resource management challenges and tradeoffs, the ability to tailor natural capital accounts (NCAs) to support regional decision making is a critical challenge to the success of NCA.

While SEEA typically targets the production of national-scale environmental-economic accounts, which can have important macroeconomic uses (Fenichel 2024), SEEA also recognises the importance of producing accounts at multiple scales. Regional accounts can incorporate different content than national-scale accounts. For instance, regional accounts can be centered around particular resource management issues of local interest, using local information that differs from national-scale data. Examples of subnational NCA serve as both tailored accounts aiming to address relevant subnational-scale management questions (e.g. Dvarskas (2019), Farrell et al. (2021), Souliotis and Voulvoulis (2021), Barton (2022), De Nocker et al. (2022), Gacutan et al. (2022), Turpie et al. (2022), Cardona et al. (2023), De Nocker et al. (2023), Bekri et al. (2024), Smith et al. (2025)) and as experimental accounts that can later be expanded to the national scale, as has been done in the Netherlands (Remme et al. 2015, Hein et al. 2020, Schenau et al. 2022).

Regional accounts may be informative for illuminating values and tradeoffs in support of subnational-scale decision making. Given that some of the most important current limitations of NCA are its limited use in decision making and the lack of awareness of it by resource managers (Vardon et al. 2016, Bagstad et al. 2021, Clarke et al. 2023), accounts that deliver useful information for regional natural resource management may be particularly valuable. Vardon et al. (2016) provide a broad overview of where environmental accounts fit in within information systems and policy cycles, with an emphasis on identifying why there has been a mismatch between technical pushes to develop accounts and pulls from end-users, such as decision makers. Bass et al. (2017a) clarify useful policy and institutional context for NCA. They match applicable NCA-related information and analyses to various potential policy uses, including issue identification and policy response, implementation, monitoring and review. Bass et al. (2017b) provide examples of studies that have applied NCA across the aforementioned steps of the policy process, as split by major themes like water, forests and land, biodiversity and ecosystems and more.

In the context of water, Vardon et al. (2007) describe ways in which regional water accounting could be used to inform water policy in Australia. Accounting can help with broadly assessing consequences of economic growth, identifying the contributions of specific sectors to environmental problems and determining the implications of proposed environmental policy measures by sector. Information from water accounts can be used to compare water use across different industry sectors, in turn allowing for making projections about future water use by sector, including under different types of potential water restrictions. Water accounts can also provide information on water demand, including how responsive potential user groups may be to changes in water prices.

In the context of forests and land, Grover et al. (2023) review papers that have applied ecosystem accounting to forest management accounting, including at a regional level. King et al. (2024) build on that work and describe how SEEA EA can align with evidence needs for various policy responses and instruments over multiple policy cycle stages relevant to regional forest accounting. SEEA EA can provide regular and timely information on a range of policy-relevant indicators (e.g. carbon storage from forest areas, tree canopy cover and height, species-level composition, wood and non-wood forest-based economic activities etc.), which in turn helps support policy monitoring and the tracking of progress towards policy targets. As another example, the framework can link the depletion of natural forest stocks to the economic activities supported by that depletion (e.g. timber production), thereby allowing for prioritisation of activities based on policy targets. Keith et al. (2017) provide an example of how regional ecosystem accounting can be used to evaluate tradeoffs between various forest-related ecosystem services in an apples-to-apples way (i.e. in dollars of ecosystem services generated and dollars of an industry value added metric). They apply their approach to forests in the Central Highlands of Victoria, Australia, evaluating the following: water provisioning, regulating services for agriculture, carbon sequestration, cultural and recreation services, native timber provisioning and plantation timber provisioning.

In this paper, we provide a roadmap for future regional NCA efforts, describing both the preliminary steps, which make up the scoping phase, and the advanced steps, which constitute actual account development. We then provide an example of the scoping process in action from start to finish, as applied to the Colorado River Basin (hereafter, "Basin"). The Basin is a large watershed in the arid southwestern U.S. that totals about 637,000 km² (USBR 2016). With that size, the Basin is nearly as large as the U.S. State of Texas, as well as roughly equivalent to the size of France, thereby making this a large-extent regional NCA exercise. The Colorado River, which flows through the Basin, is a vital resource supporting ecosystems, economies and tens of millions of people across the southwestern U.S. and northern Mexico. However, the river faces unprecedented challenges in the 21^st century, particularly the diminishment of instream flows due to a combination of factors. The pressures of aridification are diminishing water availability, transforming ecosystems and leading to shifts in species composition and habitat loss. In addition to environmental challenges, the Basin is grappling with substantial population growth and demands for energy and minerals. Expanding demand for water further strains an already stressed system, highlighting the need for highly interdisciplinary and decision-relevant science to inform decisions in the Basin.

As part of our scoping efforts, we convened a series of discussion sessions with 41 Basin scientists and science representatives, both to introduce NCA concepts and examine the potential of NCA for the region. After describing our participant engagement process, we provide the outcomes of the discussion sessions, summarising the following: important environmental-economic linkages in the Basin, key insights and questions of interest posed by discussion session participants and scientific data resources that could fit into various NCAs for the Basin, as well as data gaps. We conclude by discussing lessons learned for future regional NCA efforts across both the scoping and development phases.

Overall, we provide a blueprint for the origination of relevant and useful regional NCAs, especially in terms of how to engage in scoping efforts. This work is relevant not just for the Basin, but for dryland ecosystems globally, particularly in the face of aridification. NCA provides a consistent framework for quantifying and valuing dryland ecosystem services, which have, in some cases, been under-emphasised in literature (Schild et al. 2018, Chaplin-Kramer et al. 2023). The provision and use of dryland ecosystem services depends greatly on the spatiotemporal distribution of water, which impacts the structure and function of ecosystems and the location of human beneficiaries within watersheds and airsheds (Bagstad et al. 2012). Drylands are common in the Global South and examples of how SEEA can better account for them will advance the state of the practice of NCA globally.

In Fig. 2, we show a roadmap with steps in the development of regional NCAs. Steps can be split into two phases: preliminary steps that fall under a scoping phase and later steps that fall under actual account development. We propose this roadmap as a potential way to bridge the gap between technical pushes to develop accounts and policy pulls from end-users (Vardon et al. 2016), regardless of whether the regional NCA exercise of interest follows a broad-based approach (a general accounting exercise using all existing data sources) or a tailored approach (an exercise geared towards a specific policy question of interest). For either type, we argue that participant engagement should play a major role, especially in terms of increasing the odds that accounts become policy relevant.

Figure 2.

Roadmap for regional natural capital accounting (NCA), with steps split across scoping and development phases. The focus of this paper is the scoping of natural capital accounts in the Colorado River Basin ("Basin"), as summarised in the right-hand side box. USGS ASIST = U.S. Geological Survey Actionable and Strategic Integrated Science and Technology.

Development of regional NCAs begins with the establishment of a geographic area of interest (step #1). Step #2 entails determining all relevant management units within the area. In the U.S., this could include private, municipal, county, regional, State, Tribal and Federal entities. Step #3 entails identifying contacts from those management units, as well as additional contacts from across the administrative, scientific and political spheres (Kervinio et al. 2023). Step #4 encompasses the participant engagement process, which helps determine important environmental-economic linkages across relevant topics in the geographic area, key participant insights and questions and relevant existing data sources and gaps. Step #5 consists of evaluating the data sources in terms of their suitability for NCA. Together, these five steps make up the scoping phase of regional NCA efforts. In this paper, our main focus is on detailing all scoping steps for an application to the Basin (refer to right half of Fig. 2).

We additionally describe the steps in the NCA development phase. Step #6 entails using what was learned from the participant engagement process to establish a final boundary of the geographic area, define ecosystem accounting areas of interest and select the most appropriate type(s) of NCAs to develop. Step #7 consists of adjusting applicable data sources such that they can be made compatible across the relevant spatial and temporal scales. This could include condensing a national-level dataset down such that it only includes data for the region of interest. Step #8 covers the actual generation of NCAs, for example, in spreadsheet form. Spreadsheets generally consist of both supply and use tables that track ecosystem services of interest across the established ecosystem accounting areas. The participant engagement process helps dictate the units across which to track supply and use. One candidate is tracking by economic unit, such as households, industries and government. Other candidates are possible too, such as tracking ecosystem services over different ecosystem types. Step #9 covers the refinement of the accounts, including efforts to make them public and accessible. Finally, step #10 consists of communicating the accounts to relevant contacts in management units and the administrative, scientific and political spheres, as well as the public.

In the remainder of this paper, we describe all scoping steps in detail as applied to the Basin, starting with a description of the study system, moving to an accounting of the participant engagement process and then summarising takeaways.

The Colorado River headwaters begin at an elevation of about 3,105 m as snowmelt-dominated streams in the alpine tundra of the Rocky Mountains. The river flows over 2,300 km through coniferous forests, semi-arid plateaus and canyons and arid to hyper-arid desert landscapes, ending in a parched delta in Mexico’s Sea of Cortez (Blinn and Poff 2005, Metcalfe et al. 2023). The Basin (Fig. 3) holds some of the driest and hottest areas of the U.S. and the majority of it is arid. The river crosses through Tribal lands, seven U.S. States (Arizona, California, Colorado, Nevada, New Mexico, Utah and Wyoming) and two Mexican States (Sonora and Baja California).

Figure 3.

Map of the Colorado River Basin, including land ownership. The watershed boundary shown is the 2-digit Hydrologic Unit Code (HUC-2) boundary, which includes subwatersheds not hydrologically connected to the Colorado River, but which fully cover southern Arizona and southwest New Mexico (including watersheds flowing south into Mexico).

Management of the Colorado River is dictated by a combination of compacts, contracts, court decisions and decrees, federal laws and regulatory guidelines that are collectively referred to as the "Law of the River" (USBR 2015, Colorado River Science 2025). Together, these various documents dictate the apportioning and regulation of water use and management both across the U.S. and Mexican States.*4 Distribution of surface water within the Basin is largely conducted by the U.S. Bureau of Reclamation, through management of large Federal water projects like Glen Canyon Dam (Lake Powell) and Hoover Dam (Lake Mead).

Total water use covers both withdrawals and consumption, with the latter given by the difference between withdrawals and discharges (Averyt et al. 2013a). In the Basin, over half (52%) of overall water consumption can be attributed to irrigated agriculture; this is driven in large part by cattle-feed crops like alfalfa and other types of hay, which account for 62% of all the agricultural water consumption. Other important consumptive uses of Colorado River water include evapotranspiration (19% of overall consumption), municipal, commercial and industrial (MCI) uses (18% of overall consumption) and reservoir evaporation (11% of overall consumption). These consumption estimates are provided by Richter et al. (2024), who budgeted all water consumption in the Basin from 2000-2019. Keying in on MCI uses, the river provides municipal water supply for 35 to 40 million people (USBR 2016). The Colorado River serves hydropower facilities and thermoelectric power plants that have contributed over 19,200 megawatts of power per year (American Rivers and Western Resource Advocates 2014). With respect to withdrawals, water use by the electricity sector makes up a significant part of the water budget across the entire U.S., especially on account of water cooling requirements (Averyt et al. 2013a). At the watershed scale, even just a single power plant can stress water supply through demand for cooling water (Averyt et al. 2013b). Instream benefits from the Basin include various recreation opportunities and critical fish and wildlife habitat, amongst others (USBR 2016).

Cascading impacts of drought across the Basin arise in part because agricultural, mineral, municipal and environmental water uses all depend on the same finite water sources. The ongoing challenge of addressing such impacts has made the search for tools to inform resource decisions ever more urgent. Potential interconnections between water needs can be approached through multi-resource analysis, an approach that uses various sources of information about a region's natural resources to inform the modelling of resource interrelationships across scenarios of change and their impacts on people (Jenni et al. 2018).

As the Basin becomes more susceptible to drier conditions and megadroughts (Williams et al. 2020, Gillett et al. 2021, Wahl et al. 2022, King et al. 2024), the resulting increase in hazards is pushing resource managers and scientists to consider the Basin from a system-wide perspective that recognises the interaction of multiple human- and natural-system drivers (Lisonbee et al. 2022, Elias et al. 2023). Warmer temperatures have reduced snowpack (Heldmyer et al. 2023), increased evaporation and enhanced drying of soil and vegetation (Williams et al. 2022), leading to increased wildfire risk and declines in surface runoff and groundwater recharge. Decreased precipitation and surface water availability can increase reliance on groundwater, which if overused, depletes aquifers (Jasechko et al. 2024, Zipper et al. 2024). Post-fire erosion increases sedimentation of streams, which can negatively affect aquatic biota (Belongia et al. 2023). Increased aridification also leads to drier soils and reduced air quality from dust storms (Duniway et al. 2019).

NCA is well suited to provide consistent structure for broad-scale science integration and multi-resource assessments (Dahm et al. 2023). Despite the early overall stage of NCA in the U.S., three examples of such accounts already exist for the Basin. First, the Lower Colorado River is the subject of the longest-running and most-detailed water accounting exercise in the U.S. Since 1964, in response to the U.S. Supreme Court case Arizona v. California, the U.S. Bureau of Reclamation has completed annual water accounting reports detailing many aspects of water availability and use in the Lower Colorado River, in a manner largely compatible with SEEA Water physical supply and use tables (USBR 2023). Second, Richter et al. (2024) recently developed a water accounting exercise for the Basin, which quantifies 2000-2019 average water use with a particular emphasis on crop-specific water use, as well as estimates of reservoir evaporation and evapotranspiration by riparian vegetation. While neither of these examples were developed using the SEEA Water framework, both illustrate the value of accounting and have the potential to be connected to other types of accounts (e.g. for riparian and upland ecosystems). Finally, Warziniack et al. (2024) built a pilot forest account for the Upper Basin, focused on the extent of forest types and monetary values for timber, carbon storage and water purification. Their study used a computable general equilibrium model to account for changes in monetary values of forests in the Upper Basin through 2100. Although these accounts are partial from the perspective of SEEA, they provide a starting point for more extensive NCA efforts in the Basin.

Outside of the context of NCA, Kaval (2011) provides a review of the total economic value of the Colorado River Basin, with a discussion of various ecosystem service categories and their corresponding economic values.

Meeting the science needs of communities and resource managers impacted by multidecadal drought is a “grand challenge” requiring integration of existing technologies, data, knowledge and models across related and disparate disciplines, facilitated by new science and technology (Jenni et al. 2017). At the geographic scale of the Basin, the challenge is most effectively accomplished by engaging in science co-design and co-production with parties who represent, protect, use and manage natural resources.

Our participant engagement process was greatly aided by the ongoing Basin-wide U.S. Geological Survey (USGS) Actionable Strategic Integrated Science and Technology (ASIST) Initiative, which aims to meet current and future science needs in the Basin and streamline the delivery of integrated drought science. ASIST's overall science strategy entails iteratively co-producing science and science delivery tools (Dahm et al. 2023). Since 2020, the ASIST team has engaged with Federal, Tribal, State and local agencies, non-governmental organisations and others to identify needs, leverage the knowledge base across USGS and support the multidisciplinary integration of data and models to enhance decision making in the Basin. The ASIST team engages with over 1,200 individuals in diverse roles; prior to this project, about 300 scientists, decision makers and resource managers had already participated in various ASIST-related workshops and events.

A key step in the engagement process involves using literature assessments to develop focused engagement topics (Tillery et al. 2022). Prior ASIST efforts identified a set of seven decision-maker needs for the Basin through literature and internal and external discussions with partners:

1. drought prediction, integrated predictive modeling and early warning indicators;
2. integrated science to address future drought impacts;
3. groundwater dependent streams, ecosystems and research;
4. wildfire risk and post-fire impacts;
5. impacts of drought on high-elevation landscapes, including consequences for landcover, forest health and snowpack;
6. integrating ecosystem responses to drought and climate change;
7. impacts of drought on the human system and development (Dahm et al. 2023).

To conduct our scoping steps in a structured and tractable way, we drew from past Basin science planning documents (USGS 2024b) to narrow down to four distinct, but interrelated, natural resource management topics facing the Basin:

1. water availability and use, including both water quantity and quality;
2. aquatic and riparian ecosystem management;
3. upland ecosystem management;
4. energy and minerals development, including both new development and the effects of legacy mining.

We then planned a series of virtual discussion sessions with experts from across these four topics in the Basin. We planned two sessions per topic: a first with USGS scientists (henceforth "scientists") and a second with subject-matter experts and science representatives from Federal agencies, States, Tribes, non-governmental organisations, research institutions and others (henceforth "science representatives”). Following classifications from Kervinio et al. (2023), a bulk of the participants from the latter group work in the scientific sphere, but with a specific emphasis on informing the political sphere (e.g. informing environmental targets).

We used ASIST’s lists of prior contacts (e.g. workshop participants) as a starting point for an overall participant pool. We identified eligible participants through one of three mechanisms:

1. participants who had signalled interest or provided feedback relevant to one of the four topics in prior ASIST-led one-on-one or group discussions;
2. participants who had recently engaged in ASIST workshops on similar topics and expressed interest in further participation in science co-production with USGS;
3. participants who had expressed interest in one of the four identified topics during prior decision-maker needs literature assessments.

Using these mechanisms, we narrowed down to about 50 potential participants per topic. We were particularly interested in Federal partners, given their expertise in developing and applying national-scale science tools, which have high potential relevance to NCA. The Federal focus helped us narrow the remaining participant pool further and, ultimately, we targeted about five participants per session.

Between 3 October and 9 November 2023, we hosted eight virtual 90-minute discussion sessions, with a total of 41 experts in attendance.*5 Participants spanned a wide range of careers, subject-matter expertise and Federal government agency representation (Table 2). Four to five individuals attended the riparian and riverine ecosystem management, upland ecosystem management and energy and minerals development sessions, for a total of 27 attendees. The water availability and use sessions had greater participation, with six attendees in the scientist session and eight in the science representative session. We conjecture that the number of participants for the water-related sessions was higher for at least two reasons. First, the outreach and the development of the contact lists was initiated from internal and external relationships that were heavily skewed towards people from the USGS Water Resources Mission Area and the Colorado Water Science Center. Second, water availability and reservoir depletion are extremely high-profile issues in the Basin and the pool of ASIST participants focused on those topics is larger. After the sessions, a total of five participants provided further email comments or suggestions.

We used the below five-step format for the sessions:

1. We introduced ourselves and explained the project’s connection to prior ASIST efforts;
2. We asked participants to introduce themselves, with a focus on the relevance of their work to science or resource management in the Basin;
3. We presented an overview of NCA, describing, for example, what it is, its origins (e.g. background on SNA, SEEA and the U.S. NCA Strategy) and previous applications. For each topic, we introduced possible sub-topics to stimulate discussion and introduce the various types of SEEA CF and SEEA EA accounts. We also noted some NCA-relevant economic linkages for each topic (e.g. water consumption, recreation) and asked participants to provide any additional examples. We always followed the introductory presentation with a question and answer session, during which respondents could ask questions to improve their understanding of NCA;
4. We led a group exercise. For the scientist sessions, the goal of the exercise was determining how existing scientific projects and products could support future production of NCAs. For the science representative sessions, the goal of the exercise was to encourage discussion around key policy drivers, actors and decisions in the Basin, with an emphasis on discussing the potential ability of NCA to address management questions;
5. We concluded the sessions by describing our planned next steps, including synthesising the information and requesting feedback.

We recorded the sessions and reviewed the recordings to distill participants’ comments into a consistent list of important topics and economic linkages, key insights and questions and data sources and gaps. After compiling preliminary results, we contacted all session participants via email and gave them an opportunity to provide feedback. We asked them to ensure that we correctly interpreted the information from their discussion sessions and we also provided them with an opportunity to help identify any remaining data sources. We gave participants three weeks to provide feedback and we sent a follow-up email reminder one week before the deadline.

Important economic linkages

Key insights and questions

Data sources and gaps

In this section, we first summarise important lessons learned from the scoping phase, as grouped by the steps from Fig. 2 to which they correspond. We then discuss lessons that could apply to steps in the development phase of future regional Basin NCA efforts.

Scoping

Development

NCA discussions during this project revolved around how it might be possible to quantify various natural resources in the Basin, including the ecosystem services they provide (e.g. water filtration, habitat provision, recreational opportunities). NCA facilitates interdisciplinary collaboration by bringing together economists, ecologists, hydrologists, urban planners and others. Meanwhile, science co-production, as has been conducted by the USGS ASIST Initiative, can help uncover how economic values influence the decisions natural resource managers make in complex systems. A key component of co-production is to engage various science users, including resource managers, decision makers and local communities. Together, NCA and science co-production provide a platform to facilitate broad discussions around the value of natural resources. By establishing a common language and framework, NCA can foster dialogue and cooperation amongst diverse groups, leading to more integrated and effective management strategies. This is especially important in the Basin, which spans arid to hyper-arid regions and crosses multiple jurisdictions, including Tribal lands and multiple U.S. and Mexican States. Synergy is crucial for developing adaptive management practices that respond to the dynamic challenges posed by aridification and other resource demands, and a collaborative approach is essential for addressing the complexities of the Basin, where various groups have competing interests.

NCA could improve our understanding and management of complex ecological and hydrological dynamics of the Basin, which cross diverse landscapes and ecosystems. NCA can provide metrics on the quantity, condition and value of natural resources, including ecosystems, helping to illustrate the interconnectedness of natural systems and human activities. By integrating physical data on natural resources with economic assessments, NCA can systematically assess the value of the Basin's natural resources, including ecosystem services. More consistent and comprehensive resource inventories can, in turn, help policy makers make choices that better balance tradeoffs across urban and economic development, resource extraction, environmental sustainability and conservation. For example, understanding the connections between rangeland and forest health and water resources can encourage investments in conservation and restoration projects that yield multiple benefits. Insights gained from NCA could help better inform the management of large Federal water projects, such as Glen Canyon Dam and Hoover Dam, by highlighting the ecological trade-offs associated with water distribution and usage. A holistic approach can help encourage the wise management of water resources, while mitigating the long-term impacts of aridification.

In this paper, we laid the groundwork for a future Basin NCA effort by detailing the scoping of accounts. Ultimately, the application of NCA in the Basin would provide a proactive tool for sustainable resource management. NCA supports decision making aimed at attaining more resilient natural and economic systems in the Basin, which would help ensure that both ecological integrity and human livelihoods are preserved in the face of ongoing challenges. By recognising and consistently quantifying the value of multiple natural resources, including ecosystems, stakeholders can prioritise actions that protect and enhance these resources. As the region navigates the challenges of the 21^st century, including water scarcity and ecosystem change, NCA offers a scientific approach that can both inform policy and engage communities in the stewardship of their natural heritage. Through careful, science-informed management, the Colorado River can continue to thrive as a lifeline for both people and nature, with its health and sustainability ensured for future generations.

In Table 7, we provide definitions of common acronyms used throughout the manuscript.

We greatly appreciate the contributions of the scientists and science representatives who participated in discussion sessions and provided input. We are grateful to Sharon L. Qi (U.S. Geological Survey) for providing the map of the Colorado River Basin. We would like to thank William Andrews and Joe Casola (U.S. Geological Survey), as well as the journal reviewers, for providing valuable feedback on a draft manuscript. Support for this work was provided by the U.S. Geological Survey. Support for Enriquez's and Bagstad's time was provided by the U.S. Geological Survey's Land Management Research Program and Land Change Science Program, respectively. Any use of trade, firm or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.