Iterative Driver-Response Dynamics of Human-Environment Interactions in the Arizona-Sonora Borderlands 1,2, 1 CHRISTOPHER A

SPECIAL FEATURE: SUSTAINABILITY ON THE U.S./MEXICO BORDER

Iterative driver-response dynamics of human-environment interactions in the Arizona-Sonora borderlands 1,2, 1 CHRISTOPHER A. SCOTT AND STEPHANIE J. BUECHLER

1School of Geography & Development, University of Arizona, Tucson, Arizona 85721 USA 2Udall Center for Studies in Public Policy, University of Arizona, Tucson, Arizona 85721 USA

Citation: Scott, C. A., and S. J. Buechler. 2013. Iterative driver-response dynamics of human-environment interactions in the Arizona-Sonora borderlands. Ecosphere 4(1):2. http://dx.doi.org/10.1890/ES12-00273.1

Abstract. In complex social-ecological systems, human and physical processes mutually condition one another through co-adaptation at multiple scales from the local to the global. For this paper we modified a driver-response conceptual model of social-ecological interactions by considering the degree to which each binary set of processes (human or physical) is simultaneously a driver and a response to global change. Processes that we understood to be mutually conditioned offered greater potential compared to solely social or ecological communities to adapt to demographic and economic change, on the one hand, and to climate, water resources, and ecosystems dynamics, on the other. By considering case material from the United States–Mexico border region, we characterized social-ecological interactions along a continuum from those acting exclusively as drivers to others reacting to change primarily as responses. We considered water resources to integrate multiple global change processes including climate change and variability, ecosystem resilience, and human water demands for a variety of purposes. Thus, we examined in detail two watersheds in the Arizona–Sonora borderlands representing mutually conditioned social-ecological systems. First, the Rı´o Magdalena in Sonora represented an illustrative case of smallholder agriculture and rural livelihoods engaged in social-ecological interaction that exhibited both driver and response elements centered on reflexive, low-impact adaptive strategies. Second, in Ambos Nogales relying on the Santa Cruz River and its associated aquifers, urban growth, the equity of water access for human purposes, and environmental quality represented especially pressing challenges. Here, human impacts on ecosystems were the predominant drivers although there was growing concern for the medium- and longer-term implications of climate change. Adaption planning in Ambos Nogales was centered on infrastructure- based solutions including an inter-basin water transfer connection with the Rı´o Magdalena. Wastewater flows to riparian corridors posed a particular challenge for human-environment interactions. Cross-border collaboration represents an important opportunity for adaptation based on the mutually conditioned interactions presented here. We summarized the analysis of both cases by raising conceptual questions for further enquiry and for adaptation and planning that are generic for the borderlands and beyond.

Key words: adaptation; human-environment interactions; livelihoods; social-ecological systems; Special Feature: Sustainability on the U.S./Mexico Border.

Received 29 August 2012; revised 13 November 2012; accepted 14 November 2012; final version received 13 December 2012; published 10 January 2013. Corresponding Editor: D. P. C. Peters. Copyright: Ó 2013 Scott and Buechler. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits restricted use, distribution, and reproduction in any medium, provided the original author and sources are credited. E-mail: [email protected]

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INTRODUCTION rapidly, while broader contextual processes can influence coupled systems over the long term. Human societies and ecosystems are insepara- Third, the iterative functioning of human-ecosys- bly connected. Their interactions are dynamic, tem interactions can modify responses and make non-linear, and exhibit threshold behaviors. them act as drivers in sequential fashion. These Because both humans and ecosystems anticipate feedbacks can lead to unique system trajectories change and respond to drivers, coupled systems resulting from the co-adaptation of human and have memory. This does not lead to deterministic natural components of coupled systems. Fourth, outcomes but strongly shapes system behavior the combination of the first three characteristics through internal dynamics. The drivers of change (mutual conditioning, multi-scalar dynamics, can originate within coupled systems or exoge- and iterative effects) offers opportunities for nously, a result of mutual influences between adaption to global change. Based on this coupled human and ecosystem processes occurring at a system perspective, global change is understood range of spatial and temporal scales. Cross-scale to encompass climate and earth systems process- influences of human and natural processes and es as well as demographic and economic change. the variable timeframes over which they operate Our conceptual approach draws from resil- can set up sequentially evolving driver-response ience theory (Gunderson and Holling 2002, dynamics. An important goal of this paper is to Walker and Salt 2006, Gunderson et al. 2010) demonstrate, conceptually and empirically, that and social-ecological systems understandings of drivers can become responses, and vice versa. human-environment interactions (Scheffer et al. A definition is in order before we proceed. 2002, Ostrom 2007). Here we refer to social- Human-environment interactions (HEI, as re- ecological systems by the acronym SES. Global ferred to in this paper) may broadly be charac- change as described by geographers Leichenko terized along a continuum from environmental and O’Brien (2008) and Eakin (2006) must be determinism, on one extreme, to the primacy of expanded to more fully capture the iterative, co- human agency, on the other. At the first extreme, adaptive and often cyclical responses of long- physical processes are understood to occur term HEIs. Leichenko and O’Brien and Eakin independently of human influence and exert developed and applied the concept of ‘double impacts on individuals and societies. Examples exposure’ that sheds light on the complex include events such as hurricanes and earth- linkages between economic globalization and quakes, which cause serious damage globally. climatic change particularly as they act in concert The origin of these physical processes is not to shape contexts of vulnerability for populations influenced by human activity, although their such as small-scale farmers. However, the cycli- intensity and frequency may be, and the severity cal, iterative conceptualization of HEI processes of their impact clearly is—a point we will return originates in ecology. For example, Levin (1999) to. At the other extreme, human activity produc- referred to management (i.e., human) and eco- es a range of environmental impacts. For system dynamics as adaptive and, ultimately, instance, mining and extractive energy resource ‘‘self-organizing.’’ In an analogous manner, development result in habitat loss and threats to Chetkiewicz et al. (2006) described the crucial biodiversity. At both ends of the HEI continuum, explanatory value of process (i.e., dynamics) to causality and impact are seen as unidirectional. understand human-wildlife interactions inherent Here we seek to identify and describe four in more static landscape pattern. principal characteristics of coupled natural-hu- As will be seen below, by inverting the driver- man dynamics. First, human and ecosystem response relationship, we add explanatory value processes are mutually conditioned, that is, to coupled systems dynamics. Additionally, human activity is influenced by environmental when system dynamics cross thresholds—those conditions while ecosystem processes react to critical junctures of crisis, collapse, and reorgani- and internalize resources resulting from human zation as conceptualized by the adaptive cycle activity. Second, human-ecosystem interactions (Gunderson and Holling 2002)—ecosystem pro- operate at a range of spatial and temporal scales. cesses allow species to recruit resources released Localized driver-response cycles tend to occur through collapse, while analogously social and

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Fig. 1. The Arizona-Sonora Borderlands. institutional processes give rise to heightened Numerous instances of HEIs are found in the human innovation and experimentation during region. For contextual purposes, we briefly reorganization phases (McLaughlin and Dietz characterize several examples that help illustrate 2008, Young 2010). We apply our conceptual the range of conditions encountered, even approach to the United States – Mexico border, though they are not the principal focus of our specifically to the Sonoran Desert region shared analysis. Subsequently, we explore two cases by the states of Arizona in the U.S. and Sonora in from the ASB region in greater detail. In each, Mexico (Morehouse et al. 2007, Scott et al. 2008, our conceptual propositions draw from resilience Buechler 2009a, Serrat-Capdevila et al. 2009, Scott theory that we link to the evidence presented in and Pasqualetti 2010) as shown in Fig. 1. In this the particular case. paper, we refer to the Arizona-Sonora border- The first example is mining, which has lands by the acronym ASB. historically been important in the ASB region.

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Sonora witnessed increased mining between (Slack and Whiteford 2011). Many migrants stay 2007 and 2010, due in large part to high copper in the ASB region because they cannot afford to and gold prices on the international market return to their home communities in Mexico, (SGM y CG Minerı´a 2010), a process which Central or South America, or elsewhere; as a continues into 2012 when this article went to result, human population dynamics and associ- press, with manifold implications for HEIs. For ated environmental impacts are strongly influ- instance, the copper mine in Cananea, Sonora, encedbymigrationandbordersecurity owned by the conglomerate Asarco/Grupo Mex- enforcement. The human and environmental ico (Cockcroft 2010), is one of the main users of dimensions of the processes are clearly inter- groundwater in the San Pedro River watershed. linked; the coping strategy of migration (Corbett This river originates in Cananea and then flows 1988) and the institutional framework in which 25 miles north to the border with the U.S. migration is inserted in the ASB region work to (Chermak et al. 2007). Mine tailings contribute relocate and concentrate vulnerable populations to water contamination, while air quality is into an environmentally vulnerable location. significantly impacted by mining operations. Cross-border migration simultaneously oper- Beginning in 2007, Cananea miners initiated a ates as an adaptive response (to promote strike to protest employment conditions includ- livelihood stability) to changes in SES processes ing the unsafe work environment as well as the and as a driver of SES structures/functions (i.e., threats to community health from contaminated HEIs). Internal migration within the U.S., i.e., the water and air (UALE 2010). In early 2011 the Sunbelt phenomenon, is not centered on the strike was broken with the dual HEI result that border per se. As a result, for the purposes of our by mid-year wage income picked up for the analysis, the principal migration flows in the ASB migrant and local miners, while negative envi- region are those from Mexico to the U.S., return ronmental and health impacts increased. migration to Mexico, and internal migration Cross-border migration within and through within Mexico, which are frequently associated the ASB region has increasingly important HEI with the negative impacts to agricultural and effects: one of those is associated with border other livelihoods of climatic and water resource security and enforcement (Lo´pez-Hoffman et al. change (Buechler 2010) (see also case study 2009). From the mid-1990s onwards, there has example below on ranching and water scarcity). been a move away from migrants crossing at The economy of the entire U.S.–Mexico border border cities such as San Diego, California to a region is sustained by this labor migration. The new pattern in which migrants cross terrain such economic growth enabled by this labor migra- as the Sonoran desert that is mountainous and tion/exploitation affects the ecology of the region. characterized by climate extremes. Since 1993 For example, industrialization and urbanization over six thousand Mexicans have died in the processes are closely tied to labor migration southern border area of the U.S. (Cockcroft 2010). dynamics and have a deep impact on the ecology This geographical shift from urban areas to of the region. dangerous, less inhabited spaces developed as a Conventional, unidirectional driver-response result of policies such as Operation Gatekeeper models and overly structured systems thinking and Operation Hold-the-Line that focused on that take drivers, responses, and their inter- securing urban areas. This shift in the locus of relationships (including feedbacks) as static migrant crossings and closely related drug trade impede understanding of HEI dynamics. Thus, into the ASB region has greatly contributed to an it is imperative to conceptualize and empirically increase in the total number of border area examine the role of migration in the ASB (and deaths along the entire U.S.–Mexico border, with beyond) using the refined, bidirectional, and the Tucson sector representing 50% of reported iteratively dynamic HEI approach presented in deaths and 45% of all apprehensions in 2009 this paper. (Cornelius 2007, Cockcroft 2010). It has also Mining and migration are just two HEIs within meant a change in the locations most migrants the borderlands SES. HEIs in general exhibit are repatriated to, with the majority brought to different degrees of mutual conditioning, multi- border towns or cities after being apprehended scalar dynamics, iterative effects, and adaptive

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Table 1. Human-environment interactions in the Arizona-Sonora borderlands with principal characteristics of coupled natural-human dynamics.

Human- environment Mutual HEI Multi-scalar HEI Iterative HEI Adaptive potential interaction (HEI) conditioning effects dynamics of HEI Source Climate change, Low: In ASB, Medium: Globally, Low: Continual Medium/High: Wilder et al. (2010); variability, and climate is a long-term societal response Climate impacts Garfin et al. human activity unidirectional emissions to climate but are an important (2007); Sheppard (urban growth, driver of human influence climate, low climate driver of et al. (2002); agriculture) activity but with lag system response adaptive policy Liverman (1999) effect formulation Hydrologic process High: Human water High: Evidenced Medium: Very High: Serrat-Capdevila et and water use a primary by long-distance Management Adaptive al. (2007); resources driver of water water response slow or response in ASB Magan˜a and management availability, and conveyance, long- inadequate to region is centered Conde (2003); water drives term water depletion on water use, Morehouse et al. human activity groundwater and quality availability, and (2000) storage degradation; quality threshold effects evident for groundwater depletion Ecosystem change Medium: Human High: Local Medium: Ecosystem High: Iconic value Lo´pez-Hoffman et in riparian water and land riparian corridor processes driven of riparian al. (2009); Diaz- systems use primarily dynamics by human systems Caravantes and drive riparian influenced by activity but Scott (2009); system dynamics; watershed-wide, medium human Stromberg and numerous regional response Tiller (1996) riparian corridors processes at threshold of loss Agriculture, Very high: Very high: Cross- High/Low: Human High: Farmers Buechler (2009a, b); ranching and Ecosystem border migration activity affects adapt by moving Coles and Scott multiple rural dynamics, for ag and resource out of farming or (2009); Va´squez- livelihoods invasive species, ranching jobs; management; into more Leon (2009) climate/water water and climate water responds sustainable land processes stressors more than management; strongly coupled constrain labor climate to human ecosystem to human activity opportunities activity responds; rural livelihoods at viability threshold due to aging of rural population (see demographic HEI) Urbanization and High: Water linked High: Global to Medium: Slow High: Adaptive Cravey (2005); employment to urban in- local climate response to water response in ASB Varady and migration, shapes influences urban depletion, is focused on Morehouse (2004) urban water supplies expanding urban water transfers, employment and resulting job hydraulic reach, reuse, demand patterns creation delaying water management crisis Demographic High: Climate, High: High: ASB High: Fractured Slack and change, water alter ASB Environmental militarization responses to ASB Whiteford (2011); migration, and migration; stress outside compounds growth, Rosas (2011); border (in-) political, ASB drives ecosystem stress; migration, and Buechler (2010); security economic, migration within underlying insecurity in ASB; Ochoa (2008) environmental Mexico economic, lack of factors heighten political drivers comprehensive migration risk not addressed policy response capacity—the four analytical devices we apply in ics are exhibited in the ASB region. The com- this paper. Table 1 summarizes as high, medium, ments within the Table 1 matrix identify key or low the degree to which these four principal processes that we interrogate as drivers and characteristics of coupled natural-human dynam- responses. For several HEIs, we conceptually

v www.esajournals.org 5 January 2013 v Volume 4(1) v Article 2 SPECIAL FEATURE: SUSTAINABILITY ON THE BORDER SCOTT AND BUECHLER identify thresholds. The final column in the table a population of 159,787 inhabitants in 2000 to a provides citations to research, case examples, and population of 220,292 in 2010. The city of conceptual approaches that, we consider, illus- Nogales, Sonora, grew in area from 3,028 ha in trate the HEI types and analytical aspects listed 2000 to 3,950 ha in 2010. The population of in the preceding columns. Further elucidation is Nogales city has indeed experienced substantial provided in the discussion and the cases that growth from 159,103 inhabitants in the year 2000 follow. to 212,533 inhabitants by 2010 (INEGI 2000, 2005, 2010, Barnett 2010). Although reliable estimates HUMAN-ENVIRONMENT INTERACTIONS: are unavailable, since the start of the U.S. AGRICULTURE,URBANIZATION, AND economic crisis there has been return migration HYDROLOGIC PROCESSES to Mexico due mainly to the unemployment crisis in the U.S., to tightened employment- The state of Sonora, the second largest in related controls and to proposed legislation such Mexico, shares a 365 mile border with the U.S. as SB1070 in Arizona (Buechler 2010). One state of Arizona (Fig. 1). Border cities and states indication of this return migration is the report become conflated in the public’sperception by Sonora’s department of education that the (Gorenflo 2011). This conflation clouds percep- population of migrant school children from the tions of HEIs in border areas. The characteriza- U.S. rose by almost 25% from the beginning of tion that has permeated border studies is that the 2010 to the same period in 2011 (NPR 2011). border cities and states have similar demograph- These demographic characteristics help shape the ics: large and growing populations with high context within which human-environment inter- population densities. While this may be true for actions take place and intersect with climate and some urban corridors such as San Diego-Tijuana water processes. Due to demography, climate, or El Paso-Ciudad Juarez, the statistics do not and water, agricultural production and urban bear this out for ASB as a whole. The city of activities are in sensitive interaction with one Nogales, Arizona had a population of 20,837 in another in this border state. 2010; this represented a slight decline from the 2000 Census, which recorded 20,878 people. Rıó Magdalena NogalesislocatedinSantaCruzCounty, The intricate HEI relationships described have Arizona; this county experienced a 23.6% in- been examined in multiple locations along the crease in population between 2000 and 2010 with Rıó Magdalena, Sonora, in an ongoing study 47,420 inhabitants recorded in the 2010 Census initiated by Buechler in 2007. The municipality of (United States Census Bureau 2011). This part of Magdalena experienced some population growth the U.S. border therefore is a high growth area between 2000 and 2010, growing from 24,447 to but the growth is occurring outside of the main 29,707 inhabitants (CONEVAL 2005, INEGI border city here. 2010a). San Ignacio, a village with approximately Arizona’s southern neighbor Sonora has not 720 people (INEGI 2010b), is located less than 10 escaped from the characterization of high- km from Magdalena and 75 km from Nogales, growth, high urban density, with most of the Sonora, and Nogales, Arizona. The municipality focus placed on the city of Nogales. In reality, the of Imuris, located approximately 15 km to the state of Sonora continues to have one of the north of San Ignacio and 50 km to the south of lowest population densities in Mexico. From a Nogales, has had a rapid growth rate with a density of 12 people per square km in 2000 it rose population of 12,316 people in 2010, compared to to 15 per square km in 2010 (INEGI 2010a). The 9,988 people in 2000 (INAFED 2005, INEGI number of cities in Sonora with a population of 2010c). The capital city of the state of Sonora, 15,000 and above (the category used by the Hermosillo, is located about 200 kilometers to the national statistics agency INEGI for the largest south. ‘‘localities’’) remained approximately the same One tributary of the Rıó Magdalena is the between 2000 and 2010, with 72 such cities in Alisos, which flows south from the watershed existence in 2000 and 75 in 2010 (INEGI 2010b). just outside of Nogales, Sonora. This has partic- The municipality of Nogales, Sonora, grew from ular multi-scalar implications for HEIs in the

v www.esajournals.org 6 January 2013 v Volume 4(1) v Article 2 SPECIAL FEATURE: SUSTAINABILITY ON THE BORDER SCOTT AND BUECHLER study area (Table 1), given that Nogales extracts only permitted when they replace old wells water from the Alisos, pumps it over the (Martıńez Peralta 2007), in practice there appears watershed divide, and is planning to release to be an expansion of groundwater irrigated wastewater back to the Alisos after treating it at a areas in the region. Increasing volumes of water plant under construction along the Alisos (Pri- are being transferred from rural areas north of chard and Scott, in press). We will return to this San Ignacio to supply the growing urban area of below in the section on Ambos Nogales. Nogales, where a municipal water board sup- Mutual HEI conditioning is seen in the multi- plies water with permission from CONAGUA. directional relationship (Table 1) between climate, Water resources used for agriculture in San water, and human activities like farming in this Ignacio include water from springs, from wells region. San Ignacio is experiencing population and from the Magdalena River (Buechler 2012). growth due to its location near the international Water resource management in this area exhibits highway, its proximity to urban employment mutual HEI conditioning in the way that humans centers in Magdalena to the south, and Imuris influence where the water is used through and Nogales to the north. Other attractions are various channeling mechanisms but the location cheaper housing and land options available in San of groundwater and springs also condition where Ignacio and the perceived safety for families in agriculture can be practiced. relation to the surrounding urban areas. San The state of Sonora, which occupies 9.4% of the Ignacio is located at the edge of the Sonoran land in Mexico, is among the top five agricultural desert, which has been experiencing winter and producers and ranks second after Sinaloa in the spring warming trends, with fewer occurrences of share of Mexico’s total irrigated area in Mexico. freezing temperatures, longer periods without Sonora has 658,509 hectares under irrigation, freezes, and increased minimum temperatures in which is 11% of Mexico’s total (FAO 2004, FAO the winter (Weiss and Overpeck 2005). The pace 2008, SGM y CG Minerıá 2010). As seen in Fig. 2, of these trends is expected to accelerate, altering drought conditions in which annual precipitation vegetation in the Sonoran desert, which is also has been below the 1985–2010 average of 414 mm expected to expand in extent. Some estimate that (16.3 inches) endured over the past decade Mexico in general may see lower summer (Va´squez-Leon and Buechler, in press) and are precipitation but greater winter precipitation likely continue with La Ninã conditions expected (Maganã and Conde 2003). This would translate for 2012–13. into less water for irrigation late during the In relation to the agricultural, ranching, and growing season (summer and fall) when fruit sets livelihoods HEI (Table 1), this area of Sonora has leading to effects such as smaller fruit (Buechler, agricultural production mainly including fruit fieldwork 2007–2011). Combined with higher orchards and vegetables, sorghum, corn, beans, temperatures, the impacts on vegetation and and forage crops, in addition to dairy production crops are expected to be negative (Maganãand and calf production for sale to U.S. feedlots Conde 2000). Additionally, multi-year droughts (Va´squez-Leon and Buechler, in press). Men tend have had very negative impacts on farming-based to work in ranching activities related to meat livelihoods in the region (CLIMAS 2011). production and women are concentrated in Iterative HEI dynamics are also evident in the cheese and milk production. Male migrants also slow response to water depletion and an ex- find work in ranches on the Arizona side of the panding urban hydraulic reach, which is delay- border. Women, and to a much lesser extent men, ing the imminent water crisis (Table 1). A are engaged in processing fruits into canned Mexican National Water Commission (CONA- peaches and pears, canned and candied quince, GUA) report in 2002 revealed that the Magdalena candied lemons and fig and quince jams. These River basin is in deficit; more surface and products generate income from sales to roadside groundwater are extracted from this basin than stands, bakeries and supermarkets (Buechler are recharged through rainfall. The Magdalena 2009a, b). Mesquite wood gathered from the aquifer is one of 19 aquifers in the Magdalena surrounding hills continues to be relied on for River basin, which has been under an official heating in the winter, when fuel for cooking is drilling ban since 1978. Although new wells are also switched from gas to wood, and for

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Fig. 2. Annual precipitation (mm), Nogales, Sonora, Mexico, 1985–2010 (Source: CONAGUA). preparation of candied quince (Buechler 2009a, is, land that was abandoned due to migration or b). to flooding along riverbanks several years ago is In addition to farming, men and women in San being put back into agricultural production Ignacio engage in other livelihood activities such largely by return migrants. Mexican migration as work in the copper, gold and other mines in to the U.S. for employment in agriculture and Sonora; in maquiladoras in the largely U.S.-owned ranching is common; however, people engaged assembly plants in Magdalena, Imuris and in these activities are increasingly being laid off. Nogales; in greenhouses near San Ignacio and This is due to environment-related problems near Imuris; in small and medium-size business- such as increasing water scarcity that leads to es in Magdalena, Imuris and Nogales; and work higher water prices that constrain agricultural in public institutions in Magdalena. Many and ranching activities on the U.S. side; this is households also rely on remittance income from precipitating return migration to agricultural migrants to the U.S. (Buechler, fieldwork 2007– areas in Sonora (Buechler 2010). The availability 2011). of trees for fuel wood (kindling, heating, and The Rı´o Magdalena case reveals complex cooking) will influence certain economic and interactions between risk, crisis, adaptation, and daily sustenance activities in this region in resilience for several HEIs. With water resources addition to water. Economic and environmental for agriculture becoming constrained, alternative conditions within and outside the ASB are crops are being selected (vegetables versus fruit, influencing labor options, thus revealing multi- for example), agricultural land is being aban- scalar and cyclical (migration and return migra- doned, and alternative rural and urban non-farm tion, for example) HEI effects as shown in Fig. 3. employment is being sought. However, the Withbothsidesoftheborderexperiencing converse is also true but to a lesser extent; that shortages of water for agriculture and ranching

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Fig. 3. Driver-response dynamics of Rı´o Magdalena human-environment interactions. and with rising maximum temperatures that 1). Return migrants from the U.S. to Mexico are make heavy work more onerous, particularly attempting to find employment in an economy for the aging population, income-generating unable to produce sufficient numbers and quality opportunities in these activities are being con- of jobs to match the skill base of jobseekers strained. Some farmers are switching between (ECLAC/ILO 2009). The economic crisis has also activities (such as a switch from ranching to affected migrant remittances. The amount of each vegetable production) and some are attempting remittance on average declined since the start of to obtain jobs outside of agriculture such as in the economic crisis in late 2006 and the increase assembly plants, although this is usually a in the amount remitted in the first quarter of 2011 generational strategy as sons and daughters of was largely being offset by the stronger value of farmers become more educated than their par- the peso against the dollar and rising inflation in ents and seek non-agricultural employment. If Mexico (Ordaz-Dı´az 2011). This has meant that fruit production declines substantially due to many have to seek remunerative work in more higher sapling die-off and more prolonged pest dangerous activities, e.g., mining and a range of attacks resulting from lower water availability cross-border trafficking activities in the broader and higher temperatures, then the traditional ASB region. Diversification of livelihood activi- canned and candied fruit production will not be ties is an example of the adaptive potential of viable anymore. This may harm important social HEI; however, some activities are riskier than networks around the gifting and exchange of others with those most risky exhibiting merely these homemade products, which are particular- temporary adaptive potential. ly important for women, which in turn can act to To synthesize the case evidence presented and increase their vulnerability in the face of eco- relate this to the bidirectional driver-response nomic and environmental change (Buechler model we posited above, it is illustrative to 2012). diagrammatically represent HEI dynamics as The border region’s economic crisis has multi- shown in Figs. 3 and 4. scalar human-environment effects (Walsh 2011) that are linked to the demographic change, Ambos Nogales migration, and border (in-) security HEI (Table The twin border cities of Ambos Nogales,

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Fig. 4. Driver-response dynamics of Ambos Nogales human-environment interactions.

Arizona and Sonora (see Fig. 1) rely on relatively border have populations typically ten times scarce water from three principal aquifers: the greater than on the U.S. side (Varady and Santa Cruz, the Nogales Wash (Arroyo Nogales), Morehouse 2004). Santa Cruz County, Arizona, and the Alisos. Surface water flows in these is currently growing at 1.3% per year and is watersheds are intermittent due to extended projected to continue growing into the next drought and related hydroclimatic processes. century (ADC 2006). In the municipalities of Water demand for urban supply competes with Nogales and Santa Cruz, Sonora (spanned by the water for riparian corridors in a clear example of city of Nogales), the population is larger and is mutual conditioning, the first HEI aspect of growing more rapidly at 1.6% per year (INEGI interest in our conceptual approach. This raises 2005) than in the Arizona portion. As seen in Fig. important questions of scale and definition of the 5, the Nogales, Sonora population is projected to HEI system. In order to relate empirical evidence stabilize by about 2060, earlier than in Arizona presented below to the conceptual propositions (Scott et al. 2012). on iterative driver-response dynamics (Fig. 4), Water for ‘‘human consumption’’ (consumo we emphasize two water-resource delineations, humano) has priority over other uses in Mexican namely aquifers and riparian corridors. Human federal legislation, and as a result installed interactions at this scale are evident in ground- pumping capacity for urban water supply is water levels, riparian water quality and ecosys- expected to continue to grow in tandem with tem dynamics. In accordance with resilience population. Per capita water supply in Nogales, theory, there are also important cross-scale Sonora, is low (180 liters, or 48 gallons, per capita dynamics manifest as water demand resulting per day), and is expected to rise. This figure from demographic changes, specifically, the includes both residents who receive piped water increasing feminization of agriculture and the supply and a large and growing population aging of the rural population, that are essentially living in informal settlements (colonias marginales) exogenous drivers, i.e., they respond to global without access to household-level water supply and national economic forces beyond the imme- (Wilder et al. 2010), where water consumption is diate scale of the HEI under consideration. a fraction of the 180-liter daily average. In general, Mexican urban centers on the Water in Nogales, Sonora is supplied by the

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Fig. 5. Population growth in Ambos Nogales, Sonora and Arizona (Sources: data for Nogales City and Santa Cruz County, Arizona from Arizona Department of Commerce 2006; and for Nogales and Santa Cruz Municipios from Instituto Nacional de Estadı´stica y Geografı´a 2005).

Organismo Operador Municipal de Agua Pota- riparian corridor along the Santa Cruz River in ble, Alcantarillado y Saneamiento (OOMAPAS), Arizona. Due to both water scarcity and the costs from the Santa Cruz River (30%), the Nogales it pays for wastewater treatment at the NIWTP, Wash (23%), and the Alisos watershed (47%) Mexico has commenced construction of a waste- located to the south of the city and part of the Rı´o water treatment facility located to the south of Magdalena basin. The water supply situation in Nogales in the Alisos watershed, which supplies Nogales, Sonora is more challenging than in half the water of Nogales, Sonora. The release of Nogales, Arizona because of the absolute growth urban wastewater into riparian corridors, cur- in projected demand and because almost half the rently in Arizona and in the future in Sonora, is a demand is supplied by inter-basin transfer marked example of the hydrologic process and involving pumping water from the Alisos water- water management HEI (Table 1) resulting from shed. This raises sustainability concerns centered coupled SES dynamics. Natural limits to water on the water and energy nexus, an example of the availability condition the supply available to multi-scalar (and multi-sectoral) concerns form- human populations, and both drive institutional ing the second analytical component of interest in and infrastructural options and also give rise to a our conceptual approach. set of response options that must iteratively Currently, wastewater generated on both sides adapt to these limits, e.g., growth management, of the border flows by gravity to the Nogales water-use efficiency with savings used for deficit International Wastewater Treatment Plant management not solely supply expansion. This is (NIWTP) nine miles north of the border, where an example of our third analytical category, it is treated and subsequently released to a iterative HEI dynamics.

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Additionally, local watershed and aquifer the large pool of expelled migrants (many from conditions as well as ecosystem processes are southern Mexico or even Central American influenced by dynamics and decision-making at countries) who are left on the Mexican side of broader scales. The institutions for the manage- the border by U.S. interdiction, is clearly more ment of water, human population and economic pronounced in Ambos Nogales on the border. growth, and environmental quality similarly This also gives rise to heightened management exhibit varying degrees of adaptive capacity, and control of water and its attendant ecosystem with water managers in Sonora forced to dynamics, which is manifest through infrastruc- consider options, like transfer of water and ture, e.g., the Los Alisos inter-basin transfer and wastewater to and from the Alisos, in response the Nogales International Wastewater Treatment to growth in demand and heightened variability Plant. However, because the intensity of human in supply. occupation of the landscape (higher population levels, greater commercial and industrial activity, CONCLUSIONS and the physical border barrier), this system exhibits HEI dynamics that are closer to thresh- In reflecting on the theoretical propositions we old conditions as indicated in Table 1 and the have raised in this paper, we summarize that discussion above. This in turn has already environmental and human drivers of change are resulted in irreversible ecosystem change, deple- also responses to earlier or very nearly simulta- tion of aquifers, and pollution of surface and neous processes of change. More specifically, groundwater bodies (Prichard and Scott, in physical processes (climate change and variabil- press). With a legacy of environmental impact, ity, stream and aquifer hydrology, and species increased institutional learning including composition and dynamics in riparian ecosys- through cross-border scientific and resource- tems) are mutually conditioned along a contin- management exchanges, and the sensitivity in uum by human activity (water and energy both countries of environmental conditions at the production and consumption, land use including border, various stakeholders in Ambos Nogales urbanization, and decision-making). In this pa- (including the water utilities on both sides and per we considered a range of human-environ- the Universities of Arizona and Sonora) have ment interactions (HEIs), and examined two initiated steps towards adaptive management of cases from the U.S.–Mexico border in greater ecosystems and water resources, for example, the detail. The Rı´o Magdalena and Ambos Nogales Santa Cruz component of the U.S.–Mexico Trans- in the Arizona-Sonora borderlands region illus- boundary Aquifer Assessment Program. But the trate four types of HEI dynamics that we heightened managerial and planning capacity is proposed as conceptual devices that offer ex- perhaps outstripped by the urgency and magni- planatory value of specific interactions. These tude of HEI impacts. are: mutual conditioning, multi-scalar dynamics, By contrast, the Magdalena system still retains iterative effects, and adaptive capacity. Each flexibility and capacity in ecosystems and water- occurs within the cases considered although with resources terms. It is less precipitously inclined a set of dynamics that is uniquely conditioned by toward the imminent crossing thresholds and location, the endogenous and exogenous pro- does not exhibit the irreversibility challenges so cesses at play, and to a significant extent, by the evident in Ambos Nogales. But economic and goals of human agents. As a result, management institutional conditions are precarious such that efforts to adapt to global change can seize and capacity to address and manage HEI challenges harness opportunities presented by the bi-direc- in Magdalena may similarly be outpaced by HEI tional driver-response approach we have pre- drivers, particularly water scarcity. And this sented. points toward the physical resource thread that Empirical evidence from the Arizona-Sonora directly ties the two cases: water extraction by supports our conceptual claims. The effect of the Nogales from the Alisos watershed and planned border itself, i.e., economic development and wastewater return flows, both of which have urban wage income in maquiladoras, other urban- hydrologic, ecosystem, and human (health and based employment, cross-border trafficking, and economic) consequences in the larger Rı´o Mag-

v www.esajournals.org 12 January 2013 v Volume 4(1) v Article 2 SPECIAL FEATURE: SUSTAINABILITY ON THE BORDER SCOTT AND BUECHLER dalena basin. Inter-American Institute for Global Change Research More generally, targeting adaptation and (Grant SGP-CRA #005, which is supported by NSF strategies to respond to conditions that them- Grant GEO-1138881), the National Oceanic and Atmo- ’ selves emerge from prior HEI iterations, then, is a spheric Administration s Climate-Society Interactions Program, and the Morris K. and Stewart L. Udall question of scale. Opportunities for adaptation Foundation. This project was supported in part by NSF are seized, or missed, by households, communi- grant number EAR-1039127. ties, states, and nations. The challenges and drivers that generate their impacts similarly LITERATURE CITED occur at scales from the local, e.g., ecosystems (threatened habitat or loss of connectivity corri- Arizona Department of Commerce [ADC]. 2006. Re- dors) and water (groundwater cones of depres- search Administration, Population Statistics Unit. sion by highly localized intensive pumping) to http://www.azcommerce.com/econinfo/ the regional and global (including climate demographics/ change). Barnett, A. S. 2010. Nogales, Sonora, Me´xico: creci- miento superficial de Nogales. http://www. The dynamics and interactions identified here municipiodenogales.org/castellano/sociedad/ have permitted reflection on future outcomes, superficie.htm less in any predictive sense than with the intent Buechler, S. 2012. Gendered fruit and vegetable home to uncover broader processes of change and their processing near the U.S.-Mexico border: climate implications. What remains particularly chal- change, water scarcity and non-capitalist visions of lenging is identifying and suitably responding the future. In M. L. Cruz Torres and P. McElwee, to drivers of global change that operate at scales editors. Gender, natural resources and sustainabil- beyond the immediate domain of action. This ity: critical case studies from the Americas and will require connectivity, networking, and above Asia. University of Arizona Press, Tucson, Arizona, USA. all, a heightened sense of working toward Buechler, S. 2010. Migration in a Mexican border common goals. The appropriate scale for such community in the context of economic and initiatives may well lie between the local area of environmental dislocations. Paper presented and measurable and identifiable impacts, on the one panel moderated ‘‘Migration, communities, and hand, and the broadest global scale of climate economic crises,’’ International Sociological Asso- and macro-economic change, on the other. This ciation Meetings, July 2010, Gothenburg, Sweden. points toward regional (U.S.–Mexico border- Buechler, S. 2009a. Gender, water and climate change wide) scales of integration, formation of commu- in Sonora, Mexico: implications for policies and programmes on agricultural income generation. nitiesofpractice,aswellasidentification, Gender and Development 17(1):51–66. monitoring, and planning for HEI impacts. Buechler, S. 2009b. Gender dynamics of fruit and vegetable production and processing in peri-urban ACKNOWLEDGMENTS Magdalena, Mexico. Pages 181–198 in A. Hovorka, H. de Zeeuw, and G. Prain, editors. Women feeding This paper was prepared for the workshop ‘‘Sus- cities. RUAF Foundation, Leusden, The Nether- tainability on the Border: Water, Climate, and Social lands, and International Development Research Change in a Fragile Landscape,’’ held May 16-18, 2011, Centre, Ottawa, Canada. at The University of Texas at El Paso. The authors Chermak, J., J. Talberth, and J. Hansen. 2007. Fort would like to thank William Hargrove and other Huachuca and the San Pedro River: improving workshop organizers for the invitation to participate water deficit liability calculations through econom- and present the earlier version of our analysis that, ic modeling. Center for Sustainable Economy, Santa with very helpful comments from the anonymous Fe, New Mexico, USA. review process, resulted in this paper. Thanks also to Chetkiewicz, C. L. B., C. C. St. Clair, and M. S. Boyce. Gary Christopherson of the Center for Applied Spatial 2006. Corridors for conservation: integrating pat- Analysis at the University of Arizona for preparing the tern and process. Annual Review of Ecology, maps. The material presented draws from research Evolution, and Systematics 37:317–342. Stephanie Buechler completed on a Fulbright grant, Climate Assessment for the Southwest [CLIMAS]. and from ongoing work Christopher Scott is conduct- 2011. La Nin˜a drought tracker. http://www.climas. ing with support from the National Science Founda- arizona.edu/drought-tracker/jan2011 tion(NSF,GrantDEB-1010495),theU.S.-Mexico Cockcroft, J. D. 2010. Mexico: ‘‘failed states,’’ new Transboundary Aquifer Assessment Program, the wars, resistance. Monthly Review 62(6).

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