INTRODUCTION

Anthropogenic environmental change influences all ecosystems and regions, threatening species and ecosystem functions worldwide (Cowie et al., 2022;Munstermann et al., 2022). Our impacts cross broad temporal and spatial scales (Correa Ayram et al., 2020;Häder et al., 2020;Moreno-Mateos et al., 2020;Riggio et al., 2020). Furthermore, the pace of change is increasing (Holzmann et al., 2023;Urban, 2015). As our impacts begin to exceed system limits, we may be rapidly approaching critical tipping points, where regulatory mechanisms in the Earth's systems can no longer buffer against increased degradation, pollution, disturbance, and carbon output (Kéfi et al., 2022;Mooney et al., 2009;Swingedouw et al., 2020), and systems may enter novel stable states. Tipping points could result in losses of essential ecosystem services that sustain human quality of life and of functions that maintain biodiversity. However, governments and organizations have limited resources to devote to conservation or restoration, as well as limited information to steer such responses (Rappaport et al., 2015). As a result, resilience studies (Falk et al., 2022;Walker, 2020) have become increasingly important. Although resilience has been used differently in social and ecological literature (discussed further below), in general terms, resilience as we use it here refers to the ability of a system-ecological, social, or social-ecological-to return to its previous state of functionality following a disturbance or shock (Folke, 2006). Given the increasing frequency and intensity of anthropogenic disturbances, it is critical that we deepen our predictive understanding of where and when systems will return to functionality on their own from disturbance so that we can direct limited restoration resources elsewhere.

Contemporary resilience research must clarify the drivers of resilience and vulnerability that stem from natural and anthropogenic processes together. In recent decades, a conceptualization of nature as separate from humans has gradually faded, replaced by the realization that human effects permeate ecological systems and humans rely fundamentally on ecological processes, resulting in unavoidable couplings between natural and human systems (Binder et al., 2013;Collins et al., 2011;Souther et al., 2023). Research on coupled naturalhuman systems identifies critical feedbacks, nonlinearities and emergent properties, and transient dynamics, all of which influence system resilience (Arani et al., 2021;Carper et al., 2021;Turner et al., 2020;van den Berg et al., 2022). These properties make system behaviors difficult to predict and adequately track. Systems visibly dominated by human versus natural conditions (e.g., a garden or city park vs. a natural meadow or forest) require different study approaches and may be expected to respond differently to the same external disturbance. These complexities drive an ongoing search for common understandings of resilience-as disturbance recoveryand stable states-as definable conditions to which systems recover-that are able to bridge social and natural science (Adger, 2000;Aslan et al., 2018;Nikinmaa et al., 2020). Identifying model systems within which to study resilience of coupled human-natural systems may offer a pathway toward such common understanding.

Traditional ecological knowledge (TEK)-sometimes referred to as local ecological knowledge or, when pertaining specifically to Indigenous groups, Indigenous ecological knowledge-embodies coupled-human and natural systems. TEK evolves out of human interaction with local natural areas over long periods of time (Berkes et al., 1994(Berkes et al., , 2000;;Berkes & Turner, 2006). TEK may be relevant to both areas we would term "natural," with humans acting within ecosystems without leaving extensive infrastructure or removing extensive natural cover, as well as semi-natural areas within which humans live and work alongside natural spaces. This contrasts with modern agricultural systems, where resources are obtained from land following significant cover change, and resource acquisition is largely displaced from the communities utilizing extracted commodities (Monroy-Ortiz et al., 2018;Rautio et al., 2016;Rist et al., 2010;Turner et al., 2000). An ever-growing body of literature suggests that integration of TEK into conservation and management actions may improve outcomes (Souther et al., 2023). Long-term, intergenerational interactions with ecological systems often develop into a holistic understanding of ecological phenomena and human roles within ecosystems. In many but not all cases, TEK embeds "rules" for interacting in sustainable ways within natural systems, when overly extractive or otherwise irresponsible behaviors would result in negative consequences for cooccurring human communities (Berkes et al., 1994;Carpenter et al., 2009;Folke, 2015;Gadgil et al., 1993;Moller et al., 2004). Such rules may establish a baseline understanding of sustainability in modern systems. Since TEK formed over extensive time horizons, traditional knowledge systems may provide insight into how ecological conditions shift and change in contexts of contemporary global change, even when baseline conditions were not explicitly measured (Armatas et al., 2016;Bach et al., 2019;Gratani et al., 2011;Homann et al., 2008;Hopping et al., 2016;Johnson et al., 2015). Indeed, TEK has been instrumental in the identification of phenological shifts and mismatches (Armatas et al., 2016;Bardsley & Wiseman, 2012;Moura et al., 2013;Prober et al., 2011;Pyhälä et al., 2016), species decline (Coder et al., 2005;Souther, Lyndon, & Randall, 2021), and potential state changes (Vinyeta & Lynn, 2013)-making it highly relevant to efforts to understand recovery from disturbance within coupled human and natural systems (Souther et al., 2023).

Although TEK broadly is examined for insights into sustainable management practices, traditional harvest or wild-harvest systems-defined as extraction over multiple generations of natural resources directly from ecosystems that have not been converted to croplands but instead have retained their natural structure-have been relatively neglected as a critical human-environment interaction within ecological communities (Berkes et al., 1994;Milner-Gulland, 2008;Vining et al., 2008). This may stem from the erroneous perception that traditional harvest practices do not scale beyond single-species effects to impact systems at higher ecological levels or spatial extents. Harvest for food, fuel, fiber, and other necessary materials, however, has profoundly shaped ecosystems, driving evolutionary change (Rangan et al., 2015;Sullivan et al., 2017), influencing gene flow patterns (Auffret & Cousins, 2013;Kondo et al., 2012), altering competitive regimes and trophic pathways (Crabtree et al., 2019;Dunne et al., 2016;Lepofsky & Caldwell, 2013;Smith et al., 2017;Suraci et al., 2016;Westley et al., 2021), and shaping key disturbances, such as alteration of fire regimes when fire is used for hunting (Bird et al., 2013;Bird & Nimmo, 2018;Bond & Keeley, 2005;Kimmerer & Lake, 2001;Long et al., 2021;McCune et al., 2013;Moura et al., 2019;Pellatt & Gedalof, 2014;Raish et al., 2005;Rodenburg et al., 2012). There is substantial evidence that traditional harvest has had such a significant impact on ecological systems that the fingerprint of past harvest behaviors remains evident in modern ecosystems.

In today's ecosystems, traditional harvest is often perceived as rare or small in spatial extent, particularly where regions have experienced centuries of displacement by modern agriculture, the emergence of transient and highly mobile societies that are disconnected from traditional harvest products, erosion of tradition, and transition to indoor lifestyles (Mosquera-Losada et al., 2012;Priadka et al., 2022;Turner, 2006). However, extant traditional harvest systems have persisted despite these disruptive factors, and this very persistence suggests that these systems of harvest may provide valuable insights into the resilience of ecosystems and the human communities that continue to practice harvest. Although traditional harvest systems typically involve management by humans to enhance the availability of products (Bharucha & Pretty, 2010;Rautio et al., 2016;Turner et al., 2011), wild-harvested resources by definition require natural ecosystem functions to persist over time and through changing conditions (Balmford et al., 2011;Freese, 2012), so human benefits from traditional harvest inherently rely on resilience in the face of environmental change.

In the context of social-ecological research, traditional harvest systems may represent tighter, less diffuse socio-ecological systems (SES; Folke et al., 2005) than is often the case in studies of resilience in coupled human and natural systems. In contrast to strongly humanmodified conditions, these systems entail humans working within and relying on natural ecosystem processes. Long-lasting harvest practices have been shown to shape ecosystems and are therefore critical to understanding the structure, function, and ultimately resilience of natural areas. Here, we explore (1) the scientific value of traditional harvest systems as exemplars of social-ecological feedbacks, (2) the societal relevance of these systems as anchors of cultural practices and persistence, and (3) the utility of these systems to spotlight resilience elements in coupled systems.

SCIENTIFIC VALUE: TRADITIONAL HARVEST SYSTEMS AS UNIQUE LABORATORIES FOR UNDERSTANDING THE DYNAMICS OF SOCIO-ECOLOGICAL SYSTEMS

Social-ecological systems are defined as the collection of linked components and dynamics occurring in interacting complexes of humans and nature (Anderies et al., 2004;Herrero-J auregui et al., 2018;Ostrom, 1990Ostrom, , 2009;;Walker et al., 2004). Research in this arena focuses on measuring and predicting feedbacks between complex social and natural systems, under the premise that neither can be accurately modeled without including the dynamics of the other (Folke, 2006). In practice, SES research is often more unidirectional than this would imply such that studies examine the influence of either the human or natural portion of the system and measure responses within the other. For example, studies may be performed in highly human-modified systems such as cities and agricultural areas, where quantifying the influence of natural processes is essential for sustainability projections but has historically been neglected (Herrero-J auregui et al., 2018); by invoking a SES framework in such studies, the social system is typically modeled as responding to natural drivers. On the other end of the spectrum, ecological studies of natural systems within a SES framework may apply metrics aiming to understand how social drivers influence the natural system that is the focus of study (Biggs et al., 2021). In these cases, the social system is generally employed as a treatment, and data collection is performed on responses within the natural system.

Traditional harvest systems emerge as intermediate to these areas of focal research because human and natural dynamics are by definition central to the system under study, and both must be directly measured in order to track, predict, and model the system (Binder et al., 2013;Thompson et al., 2020) (Figure 1). Both social and natural factors are therefore modeled as both drivers and response variables (Figure 1). This tight coupling between harvested species in natural or semi-natural environments and human populations and behaviors has the capacity to reduce noise and simplify systems in a way that may be conducive to the development of testable hypotheses surrounding such bidirectional feedbacks. That is, because traditional harvest systems are less human-dominated than agricultural systems, a higher quantity and diversity of active ecological processes can be observed by both researchers and practitioners within these contexts, much like within any natural or semi-natural ecosystem (Ens et al., 2010;Goodall, 2008;Kakinuma et al., 2008;Prober et al., 2011;Pyke et al., 2021;Rasalato et al., 2010;von der Porten et al., 2019). This suggests that ecological dynamics in these systems are responding more directly and evidently to social dynamics, and vice versa-thus allowing research to parse the relative strengths of the two influences. Feedback mechanisms can be modeled and tested by manipulating intersecting components on both sides of the relationship.

As social-ecological feedbacks influenced by traditional harvest are explored, their relevance to the current and future state of system components may become evident. Previous research has examined the influence of traditional harvest on species' traits and evolutionary pathways (e.g., Benoît & Swain, 2008;Palkovacs et al., 2018;Rangan et al., 2015;Sullivan et al., 2017) and population dynamics (Souther & McGraw, 2014;Ticktin, 2004). Beyond such within-species examination, examination of traditional harvest may lend insight to important community-scale research frameworks such as ecological range-limit theory, assembly rules, the intermediate disturbance hypothesis, and resilience science.

Under range-limit theory, for example, species' ranges, which impose strong filters on community composition, are interpreted to be dictated by a combination of abiotic factors and biotic interactions (Sexton et al., 2009); integrating traditional harvest by humans as a key biotic interaction may help explain range limits (Chardon et al., 2019;Fattebert et al., 2017;Moreno, 2001). In classic range theory, the abiotic conditions under which a species can persist are defined as the species' fundamental niche, an n-dimensional space defined by species' tolerance to climate, soils, and other abiotic factors (Grinnell, 1914;Hutchinson, 1957). The realized niche of a species, or where a species is actually found on the landscape, is often smaller than a species' fundamental niche, due to biotic interactions that displace species from areas of suitable habitat (i.e., consumerism, competition) (Elton, 1946;Grinnell, 1917;Hutchinson, 1957;MacArthur, 1958). However, beneficial species interactions, like mutualisms or facilitation, that ameliorate

In socio-ecological systems, social and natural systems are both drivers and responders, but many studies focus primarily on just one direction of such linkages. Thus, as illustrated here, studies focusing only or primarily on the response of social systems may examine the influence of climate and natural disturbance events on cities and infrastructure. Studies focusing only or primarily on the response of natural systems may examine the influence of emissions and anthropogenic disturbance on biodiversity. Traditional harvest, since it entails humans and natural resources directly influencing one another, occupies the central point where these interacting dimensions cross and both drivers and responses are examined equally. conditions beyond abiotic niche tolerances have been shown to increase the extent of the realized niche relative to the fundamental niche (Bulleri et al., 2016). Traditional harvest may reduce the realized species niche by removal during harvest or alternatively increase occupancy via intentional management or modification of habitat to increase site suitability (Chardon et al., 2019;Fattebert et al., 2017;Moreno, 2001) (Figure 2).

Ecological assembly theory offers a framework to predict community composition based on three filters: (1) the dispersal filter, defined as the constraint imposed by which species in the regional pool can arrive at a site, (2) the environmental filter, which precludes colonization by species unable to tolerate the abiotic conditions at a site, and (3) the biotic filter, which describes how species interactions affect which species can colonize and persist in concert with other species at a site (Hulvey & Aigner, 2014). Assembly rules highlight interspecific competition and consumerism as key biotic filter forces that drive community dynamics as contrasted with null or neutral models (Götzenberger et al., 2012). In traditional harvest systems, humans may affect the biotic filtering process in complex ways depending on cultural practices and perceptions of human roles within ecosystems (Figure 3). Humans may act as predators or herbivores, but they also are often highly selective in their harvest choices or implement additional resource management (even if informal) in ways that may bolster the sustainability of harvestable resources into the future (see Resilience case study: traditional Emory oak acorn harvest by Apache tribes of the southwestern United States, below). Stewardship behaviors, either via harvest practices (Van der Voort & McGraw, 2006) or site management such as the removal of competing vegetation or alteration of disturbance regimes to favor particular species, may enrich communities in preferred harvest species, while unregulated harvest may cull species from local communities. As a result, traditional harvest may affect community assembly by altering interspecific interactions in highly variable and profound ways (Delcourt & Delcourt, 2004;HilleRisLambers et al., 2012;Levis et al., 2018). Indeed, the legacy of human harvest interactions in regions previously perceived as minimally impacted by anthropogenic forces, such as prehistoric Amazonia, is still apparent in current plant community composition (Roosevelt, 2013).

Disturbance is recognized as a key factor affecting and maintaining community diversity (Molino & Sabatier, 2001;Vanschoenwinkel et al., 2013;Yuan et al., 2016). The intermediate disturbance hypothesis postulates that species diversity is elevated under intermediate frequency and severity of disturbances, wherein disturbance prevents any species from achieving dominance but is not disruptive enough to prevent a high diversity of species from colonizing and completing their life cycles (Molino & Sabatier, 2001). Traditional harvest, by definition, is a form of disturbance, and when practiced sustainably, it may act as a component of an intermediate disturbance regime (Bird, 2015). Traditional methods of harvest or maintaining harvested species, such as through the use of fire to hunt or reduce pest and pathogen loads on target species, may also introduce unique disturbance into systems, helping diverse communities to persist (Bird et al., 2008).

Current disturbance regimes have been significantly altered by anthropogenic change and modern ways of life (Figure 4). The concentration of human populations in cities and towns (Turner et al., 2004) and conservation targets like the establishment of easements and preserves, which prohibit traditional human-ecological interactions like harvest (West et al., 2006), have resulted in historically low levels of certain forms of disturbance in some regions, which can paradoxically decrease ecological diversity (Kuuluvainen et al., 2021). On the other hand, climate change has intensified the severity and frequency of disturbances, such as fires, storms, and heat waves. Furthermore, over the past century, a synergy between (1) rapid growth in the global human population and

Fundamental niche Fundamental and realized niches Positive species interactions Mutualism, facilitation (+/+, +/0) Negative species interactions Competition, consumerism (-/-, -/+)

F I G U R E 2 Harvest may affect the realized niche of target species in disparate ways. If interactions ameliorate environmental conditions, the realized niche, or spatial distribution of the harvested species, may extend beyond the species' fundamental niche. Alternatively, if human harvest removes populations from suitable habitat, or if competitive regimes or consumption (predation, herbivory) is altered in ways that disfavor the harvested species, the realized niche may be reduced relative to the species fundamental niche.

(2) expansion of mechanized harvest and extraction techniques has resulted in a widespread shift from small-scale, local harvest to large-scale, highly disruptive agricultural and mining practices that require significant infrastructure to process and transport products for food, fuel, fiber, and shelter (Crist et al., 2017;Hurt, 2024;Nathaniel et al., 2021). In areas where such production is concentrated, disturbance regimes far exceed preindustrial levels (Matuoka et al., 2020). Clearly, the intensification of disturbance can have profoundly negative impacts on biodiversity; however, according to the intermediate disturbance hypothesis, the absence of disturbance in many cases may also depress diversity, and shifting disturbance regimes may drive ecological state change (Gao & Carmel, 2020). For instance, fire suppression in the western United States has resulted in overly dense forests that can suppress the regeneration of native species and also interacts with climate change to produce stand-altering fires due to overly abundant fuel loads (DellaSala et al., 2022;Fulé et al., 1997;Ott et al., 2019;Steel et al., 2015). Understanding traditional human roles in ecosystems may provide insights into effective disturbance management to retain current ecosystem structure and function.

Resilience science

Here, we give special focus to resilience frameworks because, as described above, the particularly tight relationships between persistent natural and human systems in traditional harvest are both reliant on and illustrative of resilience. As anthropogenic environmental change continues and escalates, resilience science has emerged

Anthropogenic biotic filter Mutualism & facilitation (+/+, +/0) Consumerism (+/-) Competition (-,-) Key processes: Dispersal, passive, and direct planting Key processes: Consumption or extraction of natural resources Key processes: Competition with wildlife for food resources, alteration of competitive regimes to favor preferred species

Environmental filter

Dispersal filter

F I G U R E 3 Harvest may influence community assembly in variable ways. Community assembly is generally divided into a tiered process, in which a series of filters winnow the regional species pool to a local community assemblage. At any given site, species diversity of a community is first limited by the dispersal filter, or put another way, diversity is limited by which species are able to reach a particular location. Subsequently, only species with adaptations to site abiotic conditions establish and persist at that location (the environmental filter). Finally, among species that arrive and establish at a site, biotic interactions drive community assemblage. Since humans exert variable and strong influences on harvested species and co-existing non-target species, understanding human functional roles within these systems could provide insight into drivers of current ecological communities and the maintenance of diversity within these communities.

as a framework for understanding disturbance recovery, stable states, thresholds, nonlinear responses, and emergent properties (Allen et al., 2016;Folke et al., 2004;Perz et al., 2013;Suding et al., 2004;Walker et al., 2004). Under classic resilience understanding, systems have a tendency to occupy stable states that are modeled as domains of attraction such that systems are predisposed to return to these states following disturbance events that dislodge or shift them out of their historic condition (Carpenter et al., 2001). The functions, processes, and dynamics inherent in the system have a tendency to facilitate disturbance recovery (Walker et al., 2004). Disturbances of sufficient strength, however, can push the system over a threshold into a new domain of attraction, wherein the system is now lodged, its inherent processes no longer able to return it to its historic condition (Bradford et al., 2019;Gardmark et al., 2015;Gilarranz et al., 2022). Such thresholds may be difficult or impossible to predict such that systems can alter state apparently without warning (Adamson et al., 2020;Stelzer et al., 2021). Under resilience theory, systems in novel stable states remain in these states until a strong enough disturbance forces them over their new threshold-whether back to the original domain of attraction or in yet another novel direction. These basic resilience principles have been understood differently in social and ecological literature. Resilience in strict ecological parlance acquires meaning when a particular disturbance is under consideration, and different disturbances may be expected to lead to different stable states and to exhibit different thresholds (Aslan et al., 2018;Carpenter et al., 2001). Furthermore, resilience cannot be determined until system perturbation since resilience is defined as the rate of recovery or probability of recovery (Ingrisch & Bahn, 2018;Lake, 2013;Lamothe et al., 2019;van Nes & Scheffer, 2007). In social systems, resilience is often equated with health, and the capacity of individuals to absorb change without sacrificing key desirable elements (e.g., values systems, homes or wealth, physical health) is typically the metric of this resilience (Adger, 2000;Cinner & Barnes, 2019). Thus, social system resilience is often assumed based on individuals' well-being, rather than measured after a disturbance. Additionally, social system change often leads to enhanced equity or prosperity and thus meets societal goals (e.g., when development trajectories or initiatives introduce new technology, access to healthcare or education, or equity of resource distribution) (MacKinnon & Derickson, 2013). Such change may be expected to make systems more resilient or to be most easily achieved in more resilient systems (Abramson et al., 2015;Cinner & Barnes, 2019). Under a strict resilience definition, such change indicates a new domain of attraction, and systems entering this domain would be considered to be less resilient because they have undergone a state change (MacKinnon & Derickson, 2013). As a consequence of these differing perspectives, resilience research typically focuses on Disturbance No. species F I G U R E 4 Traditional harvest systems may maintain levels of disturbance that promote community diversity, falling in-between exceedingly high levels of disturbance driven by modern agricultural systems and other forms of land use change for housing, industry, and transportation. By contrast, limiting human interactions in landscapes congruent with management philosophies that conform with "pristine" ideals of nature may remove disturbances important to maintaining diversity, such as human alteration of fire regimes, bioturbation during harvest events, and influences on other disturbance agents, like herbivores, driven by human presence or hunting.

either social or ecological patterns but rarely captures both in a single assessment.

By contrast, traditional harvest systems provide an opportunity to view resilience through a truly integrated socio-ecological lens. Resilience in these systems suggests that human interaction with a natural resource will continue in spite of perturbation. This indicates that both humans and natural systems recover from that perturbation. If either player declines or disappears, the traditional harvest system erodes, and resilience falters. That is, recovery of each of the components is necessary for persistence of the whole, and this brings the resilience of the two systems into alignment so that they occupy a common scale. This in turn suggests that feedbacks can be modeled within resilience frameworks in such systems: the influence on traditional harvest stable states and thresholds of changes in the social system versus changes in the natural system can be measured and tested independently (Figure 1). Thus, via traditional harvest systems, it may be possible to operationalize and quantify resilience such that systemic changes along with their drivers can be directly measured and potential interventions applied.

SOCIETAL VALUE: TRADITIONAL HARVEST SYSTEMS AS CONDUITS TO MARGINALIZED COMMUNITIES AND MEANINGFUL CULTURAL-ECOLOGICAL CONSERVATION

Traditional harvest systems have been relatively neglected in studies of TEK in many parts of the world, in part, because they are assumed to be largely extinct due to extensive changes in both ecosystems and human behaviors, distributions, and populations in modern decades (Arjona-García et al., 2021;Hoole & Berkes, 2010;Wehi & Wehi, 2010, but see Dobson et al., 2019;Milner et al., 2006;Nielsen et al., 2018). Neglect or ignorance of cultural diversity is well documented and has led in many cases to exclusion of traditional practices from planning, management, and conservation decision making (Bulkan, 2017;Domínguez & Luoma, 2020;Negi & Nautiya, 2003). Local and indigenous peoples have been too often omitted from decision making regarding the creation and enforcement of protected areas (e.g., Dawson et al., 2023), the permitting and management of natural resources extraction (Posey & Dutfield, 1996), designation of land ownership and governance (Godden & Cowell, 2016), and even implementation of well-meaning programs such as education and public health systems (Battiste, 2017;King et al., 2009). As a result of their exclusion, many local and Indigenous communities have been treated as effectively invisible, setting up indefinite neglect of their rights and responsibilities.

At the same time, for precisely those reasons that traditional harvest systems have become rare or overlooked, they are often important conduits to marginalized communities. Traditional harvest remains associated with rural communities, economically disadvantaged groups, oral traditions, and historical resource governance (Frey et al., 2023). Those who practice traditional harvest include communities that depend on traditional resources for sustenance or income, as well as individuals aiming to reconnect to historical legacies (Garibaldi & Turner, 2004;Levers et al., 2021). As societies develop, however, urbanization becomes common (Wehi & Wehi, 2010), rural communities shrink in comparison, and foraging from natural habitats becomes rare (Chaves et al., 2021;Gandolfo & Hanazaki, 2014). Furthermore, increased globalization and digitization have resulted in losses of traditional languages and practices (Meighan, 2022), and technological advancements have supplanted outdoor activities and professions (Soga & Gaston, 2016).

Scientific research that elucidates traditional harvest systems and the factors associated with their resilience holds the potential to support decision making that can reduce both ecological harm and cultural erosion. Where humans are connected to landscapes, it may be possible to implement conservation actions that serve to bolster both ecological and human community diversity and function (Pretty et al., 2009). Sustaining traditional harvest systems, for example, may require supporting plant and animal reproduction and gene flow, historic disturbance regimes and forest structure, traditional access and tools, and cultural knowledge regarding temporal and spatial distributions of resources (Souther et al., 2023). Management that maintains each of these elements has the potential to support the long-term resilience of these systems via holistic understanding.

RESILIENCE CASE STUDY: TRADITIONAL EMORY OAK ACORN HARVEST BY APACHE TRIBES OF THE SOUTHWESTERN UNITED STATES

Traditional harvest systems are structured through interrelated human and ecological functional roles. Both the social and natural components of these systems exhibit resilience dynamics and elements, and these operate both separately and in response to one another. Thus, both ecosystems and human societies occupy domains of attraction, from which they may be disturbed via perturbations of sufficient strength. Communities with sufficient resilience may return to their former states through natural recovery, but this is unlikely when disturbances have pushed communities into new domains of attraction. As social-ecological systems, traditional harvest systems furthermore occupy shared domains of attraction incorporating both the social and ecological characteristics of a given state. Resilience of these systems requires recovery of both social and ecological factors following disturbance.

To bring real-world context to this conceptual model, we examine the case study of traditional Emory oak acorn harvest by the Apache tribes of the southwestern United States. Emory oak acorns are central to Apache traditions, diet, and calendar (Coder et al., 2005;Souther, Lyndon, & Randall, 2021). Prior to displacement by the US government, the homeland of the Apache people was defined by the distribution of the oak, and tribes moved through Arizona and New Mexico as acorns became ready to harvest (Coder et al., 2005;Souther, Lyndon, & Randall, 2021). Families would camp in oak groves during acorn season, following the ripening of acorn for harvest (Coder et al., 2005). The relationship between the trees and the people was self-sustaining, both dependent upon and influenced by each other; however, much knowledge of Apache interactions with oak systems outside of harvest is unrecorded and may be lost. As Coder et al. (2005) documented, "Without a hunt, hunting songs could not be sung," to describe how separation from ancestral lands led to significant erosion of cultural knowledge. This system was dislodged from its domain of attraction when the Apache tribes were removed to reservations, separating them physically from many Emory oaks. Though no formal assessment of oak abundance on tribal lands has been completed, ca. 70% of Emory oak stands occur on lands managed by the USDA Forest Service alone, suggesting that less than 30% of Emory oak stands occur on land managed by Western Apache tribes (Souther, Lyndon, & Randall, 2021).

Both social and natural systems entered new domains of attraction following this disruption. Most Emory oak groves no longer experience the regular management that was once applied by Apache harvesters, and as a result, the system is now subject to new regimes of fire frequency and severity, acorn removal and dispersal, understory composition, and disease dynamics (Coder et al., 2005). The Apache people, as well, are now in many cases physically removed from the trees, with the result that their diets and seasonal activities have changed (Coder et al., 2005). These changes work in concert with generational shifts, common among many Indigenous cultures of the United States, toward sedentary and indoor lifestyles, increased use of technology, and reduced connection to traditions and language (Long & Lake, 2018).

Several key components of resilience can be measured and described in this coupled system. We propose a social-ecological resilience model wherein both social and ecological resilience rely on connectivity, refugia, and diversity, all of which contribute to the persistence and recovery of functions following perturbation, and all of which lend themselves to potential metrics in traditional harvest systems (Table 1). This model applies to the Western Apache and Emery oak system but could be adopted more widely to explore these components in different systems. Connectivity in the ecological system entails population distribution that permits gene flow via pollen and seed dispersal between Emory oak groves T A B L E 1 The Emory oak harvest system as a case study provides insights into social-ecological resilience, which may be enhanced by connectivity, refugia, and diversity within both the social and ecological systems.

Resilience components

Social system Ecological system Indicators Possible metrics Indicators Possible metrics Connectivity Generational exchange Harvest by multiple generations Gene flow Genetic diversity Collaboratives Frequency of information exchange Corridors Landscape connectivity Refugia Elders Human population demographics Multi-age stands Oak population demographics Traditional ecological knowledge Frequency of knowledge transfer Heterogeneous disturbance Incidence of wildfire, disease, drought Diversity Youth Harvest by multiple generations Genetic Genetic diversity Academia Frequency of information exchange Functional Functional richness Industry Frequency of information exchange Species Species richness

Note: Connectivity allows the flow of information, resources, and genetic material, as well as the movement of people and organisms in response to change. Refugia hold knowledge breadth and adaptive capacity and remain intact through disturbance events. Diversity on both sides provides wide-ranging functions and traits that can allow a system to change and adapt in response to changing conditions. Possible metrics of these elements in this system and other similar cases may be examined for quantification and prediction of resilience. (Christie & Knowles, 2015). Connectivity can be disrupted by habitat fragmentation as a result of land use change, high severity fire, and climate change (Fischer & Lindenmayer, 2007;Laurance & Williamson, 2001;Opdam & Wascher, 2004). Connectivity can be maintained or restored via habitat conservation or restoration, construction of corridors, or assisted migration of seeds and seedlings to ensure gene flow (Loss et al., 2011). In the social system, connectivity entails linkages among people within the community (e.g., transgenerational, cross-sectoral), and as such can facilitate the maintenance and transmission of traditional practices, as well as collaborative support in carrying out key activities (e.g., harvesting acorns vs. preparing acorn-based foods vs. maintaining grove access and health). Meanwhile, connectivity within the coupled system itself implies that humans are able to travel to groves, can access the trees within them, and have the legal right to perform their harvest and management activities (Table 1). Barriers such as private property, poorly maintained roads, or dense vegetation can decrease connectivity in terms of access to Emory oak stands. Loss of human-ecological connectivity is a key barrier to resilience in this case study and can occur gradually or, as in this case, rapidly (as a result of forced migration to reservations). Tribal communities and ecosystems are both sensitive to this type of rapid disturbance where ecological and social connections are suddenly lost.

Another key element fundamental to resilience is the presence of refugia (Table 1). Disturbances are inevitable in both social and ecological systems. Refugia may be defined as areas that maintain their composition and function through such disturbances, and then, it may serve as sources of recolonization as the broader landscape recovers (Ashcroft, 2010;Krawchuk et al., 2009). In the Emory oak system, ecological refugia are habitats that maintain genetically diverse and reproductive groves, even through disruptions such as climate change, fire, and habitat destruction, and could thus be utilized to restore connectivity following disturbance. Social refugia, meanwhile, may include elders who maintain traditional ecological knowledge and practices and are able to pass on their knowledge and traditions to younger generations (Singh et al., 2013). These refugia diminish with increased mortality among tribal elders and loss of knowledge that is not passed on to others. In this case study, the loss of elder knowledge, along with low exposure to or interest in traditional acorn harvesting by younger generations, has emerged as a key challenge to the restoration of traditional social-ecological interactions (Coder et al., 2005;personal observation). Without concerted efforts to transfer knowledge and increase motivation and participation in acorn harvesting, many tribal members see this loss of refugia as the primary barrier to restoring social-ecological relationships.

Finally, resilience in this system relies on maximizing diversity within both social and ecological systems (Table 1). Ecological diversity at the genetic level can bolster adaptive capacity within Emory oak systems by elevating the probability that genotypes able to withstand climate change and other disturbances are present. Furthermore, Emory oak trees act as keystone resources supporting biodiversity more broadly. Acorns are critical forage for a wide range of vertebrates and invertebrates (McPherson, 1992;Souther, Lyndon, & Randall, 2021). Some of those vertebrates, in turn, act as acorn dispersers, maintaining connectivity and gene flow across subpopulations. The trees themselves additionally provide shade and structure that offer cover and nesting sites to wildlife (Rivera, 2024). A diverse Emory oak ecosystem is foundational to ecosystem services writ broadly. Resilience of the social system is also dependent upon diversity, with participation by diverse parties in Emory oak harvest, conservation, and restoration essential for long-term persistence. As described above, engagement of multiple generations in harvest and management is essential for retaining these practices into the future. Beyond this, however, most Emory oak groves today occur on lands managed by federal agencies, municipal or county lands, and private ranchers. This makes a diverse collaborative effort that includes these various governing bodies critical for retaining access and effectively sharing management resources so that traditional harvest may continue indefinitely. Finally, climate change and its effects represent no-analogue conditions, and connecting with researchers who can predict and evaluate the response of the ecosystem to such changes may be critical for adapting management as needed.

The social-ecological system examined here provides valuable insight into social-ecological system resilience and is both guiding current restoration activities and stimulating multi-party collaborations, which may be critical to support the continued function of the system under emergent effects of climate change. Furthermore, ongoing efforts to restore and support traditional harvest practices include outreach to elders and youth and are facilitating social justice engagement (Souther, Randall, & Lyndon, 2021). In these ways, this case study exemplifies the value of traditional harvest system research to both scientific and societal advancement. Continued investigation of this and similar systems and measurement of their connectivity, refugia, and diversity may provide critical insights into areas of vulnerability and potential resilience support (Table 1). Indeed, as recovery from disturbance, indicative of resilience, is measured within this or any system, it may become possible to integrate variables that are linked to hypothesized ecological and social components of resilience into quantitative models in order to estimate their relative and interacting roles within the system (Figures 5 and 6). Such quantitative studies of traditional harvest species, though they require a challenging depth and extent of data collection, are likely to elevate our collective ability to measure and predict social-ecological resilience.

CONCLUSION

We posit that traditional harvest systems, although they have largely been dismissed in importance and assumed to be reduced in both extent and number compared with historical conditions, represent a unique opportunity to quantify feedbacks within SES that may help to expand our understanding of the effects of natural system dynamics on human communities and vice versa. Research on traditional harvest systems may enable quantification of dynamics that often remain abstract. Such advances may in turn enable areas of resilience and vulnerability to be highlighted. Surfacing these systems brings marginalized communities and practices to light and helps us to refine our understanding of human roles in ecosystems.

Resilience research seeks to understand conditions under which systems return to their former states after disturbance versus transitioning to new stable states. In traditional harvest systems, novel disturbances alter both natural processes responsible for the maintenance of harvestable populations and drivers of human harvest behaviors. Disruption of the interaction between people and traditionally harvested food sources could result in fundamental changes within the social-ecological system. In light of broadscale environmental change, understanding how human-environment interactions interact with systemic resilience-both by representing points of vulnerability and by restoring important functions after disruption-is of particular interest in social-ecological research. Although they have been relatively neglected by researchers, traditional harvest systems are tightly coupled and structured by feedbacks and may thus contribute both scientific and societal value as windows into social-ecological dynamics.

AUTHOR CONTRIBUTIONS

SS led the development of concepts and ideas and directed the writing. CA wrote the first draft and coordinated manuscript revisions. DS contributed to conceptual models and supplied language at each draft stage.