Journal of Arizona History

The Columbian Exchange and Environmental History

Environmental historians, including Alfred Crosby, Donald Worster, and Richard White, who emphasize the primacy of aridity on the region, trace the environmental changes that followed the arrival of Europeans.⁴ Three bodies of environmental history scholarship inform this essay: (1) the Columbian Exchange and ecological imperialism to explain the erosive force of new biota; while (2) borderlands environmental history; and (3) large technological systems studies both emphasize how erosion was stabilized and channelized in the late nineteenth and early twentieth centuries. Together, this scholarship suggests that the Columbian Exchange was not only a force of early modern imperialism but also of nineteenth-century capitalism and twentieth-century state-sponsored modernization projects.

Alfred Crosby's The Columbian Exchange emphasizes how European and American plants and animals mixed in the centuries after contact. His Ecological Imperialism considers how this [End Page 377] mixing assisted conquest and colonization through the transport of European "portmanteau biota," the collapse of native ecology, and the creation of "Neo-Europes" in temperate regions with weather patterns most favorable to Old World plants and animals.⁵ Both works view this exchange as primarily unfolding in temperate regions: "there are wide stretches of the Americas where European flora and fauna did not and do not prosper," Crosby writes, especially those in the "hottest, coldest, driest, wettest, and, in general, the most inhospitable" regions.⁶

Within this framework, environmental historians have struggled to fit Arizona into the Columbian Exchange, despite waves of transplanted European disease, livestock, and crops that shaped its history. Many conclude, as does Crosby, that Arizona's desert environment functioned as a barrier to European colonization. Others challenge Crosby's regional determinism with case studies of instances of "success" in Old World biota penetrating non-temperate environments. This essay seeks to combine both approaches by following what I call the "sedimentation of the Columbian Exchange"—looking beyond moments of contact and impact to follow the layered consequences of biological invasion through the centuries and understand how the Columbian Exchange helped pave the way for Anglo-American capitalism in the late nineteenth and twentieth centuries.⁷ As Pekka Hämäläinen observes, history is not determined by environments, climates, or portmanteau biota but by how societies make decisions within and with them and the way those decisions structure communities and ecosystems.⁸

Environmental histories commonly frame the ecological realities of Arizona and the Southwest as incongruous with the visions of newcomers from temperate regions. As Andrew Isenberg, Katherine Morrissey, and Louis Warren have argued, imperialism remains a [End Page 378] crucial factor in the history of deserts: most people who came in from outside were imperial agents bringing systems of control and exploitation.⁹ The failure of various imperial or capitalist designs has led many environmental historians to conclude that ecological imperialism foundered in Arizona's deserts.¹⁰ Jeffrey Shepherd has outlined the components of this approach: "Many of the emigrants from the east coast tried to recreate the lands they had left until they realized that the hard soils of the Southwest borderlands could not bring forth the green pastures they desired."¹¹ Andrew Isenberg links such failure directly to the Columbian Exchange: the U.S. Army's camel experiment failed, leading Isenberg to claim the Camel Corps "stands as a counter-example to the historian Alfred Crosby's meta-narrative of European 'ecological imperialism,'" that, "while European ecological advantages helped European and Euro-Americans to dominate in temperate zones, imposing control on arid regions was another matter."¹²

The best frame for understanding the Columbian Exchange in Arizona may not be frustrated imperial designs but individual and community choices in the face of sweeping biological and geo-hydraulic change. Arizona was not the barrier for the Columbian Exchange as long supposed: natural historian William Dunmire notes that of the sixty-five crops introduced to North America between 1493 and 1848 only one—coffee—could not be grown at any place in Arizona/northern Sonora.¹³ A full understanding of the impacts of the Columbian Exchange in Arizona thus requires a shift in emphasis from "ecological imperialism" to Native decision-making, to understand, in the words of historian Natale Zappia, how "the powerful ecological, cultural, and political-economic shock-waves of the Atlantic world become absorbed" in Native communities.¹⁴ Many other historians see the region's history through the [End Page 379] prism of successive environmental changes, Indigenous autonomy, and Indigenous adaptability.¹⁵ The wheat-growing villages of the Akimel O'odham and Comanche horse bands are examples of the Columbian Exchange augmenting, not destroying, Native subsistence patterns, providing a new range of choices.¹⁶

Other Southwest environmental histories have described how landscapes and communities became more structured by boundaries and technologies in the last two hundred years. Borderlands history, pioneered by Herbert Bolton and developed by Edward Spicer, mirrors environmental history's interest in the global resource chains of American economic power.¹⁷ The overlap between transnational history and environmental history is a function of the fact that people and ecosystems move across political boundaries. Rather than seeing Arizona as a place of exception, Katherine Morrissey, Mary Mendoza, Samuel Truett, and other environmental and borderlands historians have rooted Arizona and the West in a greater American landscape, linking places within large movements of people and capital.¹⁸ To these historians, Arizona and the larger Southwest represented a crossroads of hemispheric history, not an arid backwater resistant to ecological imperialism.¹⁹

Many Arizona environmental histories combine Thomas Hughes's large technological systems theory with non-human nature in the concept of "hybridity" developed in the work of Richard White and Sara Pritchard.²⁰ As illustrated by Marsha Weisiger and Andrew Needham, hybrid systems create landscapes of technologies, ideas, and bureaucracies as much as they structure ecological [End Page 380] communities.²¹ By the twentieth century, structured inequality within and between regions of Arizona became a primary function of both boundary-making and large technological systems.

The Columbian Exchange and Dynamic Sedimentation

Borderlands historian Samuel Truett argues that much of the history of this region unfolded as "colonial actors … took native spaces and attempted to transform them into places of their own."²² But as Natale Zappia, Jeffrey Shepherd, and David DeJong have noted, this ecological imperialism unfolded primarily within autonomous Native nations making choices based on the presence of the new arrivals. Due to the instability of new ecological arrangements and independent Native decision-making, exchanges rarely met Spanish expectations. Native resistance to incursion on their foodways consistently frustrated colonial authorities.²³

Before Spanish arrival, Native resource use in Arizona was often based on the interrelation between upland fire management and lowland agriculture. As Louis Warren has noted, however far desert peoples roamed in search of food or trade, their homes were near rivers, lakes, or marshes. Desert living required extensive knowledge, labor, movement, and cooperation. To those who lived in them, deserts were not abandoned wastelands but were lands full of food and powerful spirits.²⁴ Upland fire management was crucial for stabilizing water flows. Indigenous people often burned landscapes before the summer monsoons, when grass was driest and vulnerable tree seedlings were weakest. Burning improved vegetation growth, which encouraged game and decreased flood strength. Downstream agriculture was based on diverting low-intensity seasonal floods kept in check by upland burning. Lightweight brush and earth dams would wash away in high water, limiting erosion during floods. Many Indigenous groups throughout present-day Arizona built check dams and stone reservoirs to capture water [End Page 381] without cutting arroyos.²⁵ They flooded the fields before planting, which flushed out salts while retaining soil fertility and integrity.²⁶

Widespread trade existed among people in different regions and different social ecologies. Natale Zappia describes the "interior world" of pre-contact Arizona trade as "a braided complex of thousands of miles of primary, secondary, and tertiary trails cover[ing] the landscape" between the Gila River watershed and the Pacific Ocean, centering on the people of the Colorado River Valley. By the sixteenth century many of the most-used trails became integrated and later used by Spanish, Mexican, and Anglo settlers.²⁷

The main corridors of the Columbian Exchange into Arizona followed interior-world trade routes.²⁸ As Jeffrey Shepherd has written, the exchange involved an "alteration of the geography of Indigenous peoples."²⁹ Disease came first. The aridity and high elevations of northwestern New Spain were ideal environments for smallpox dispersal. At least a dozen epidemics between 1530 and 1632 may have struck Akimel and Tohono O'odham communities, devastating as much as 75 percent of the population of the Pimería Alta. Spanish expeditions in 1540 found many of the uplands abandoned, leaving maintenance of the fires and catchment basins at crucial places in the watershed to nature's whims.³⁰

Old World animals entered landscapes emptied by disease. The main goods of exchange in the interior world shifted from beads and baskets to human captives, sheep, cattle, and horses.³¹ European livestock, William Dunmire notes, "was a decidedly mixed blessing."³² Sheep, horse, and, especially, chicken added nutrition to the diets of some groups. But many, like the Quechans of the Colorado River Valley, were reluctant to integrate domesticated animals into their economy.³³ As Pekka Hämäläinen has noted, those who relied on sheep and horse raiding used them to adapt [End Page 382] to disease and environmental change.³⁴ The Apache had at least thirty thousand horses grazing Gila watershed uplands by the early nineteenth century.³⁵ Yet, horses and sheep caused more erosion. Watering holes could see thousands of horses at a time, breaking top-soil and dispersing seeds and grasses.³⁶ The Diné on the Colorado Plateau, having learned equestrian close-herd shepherding from the Spanish, channeled rainwater over increasingly compacted soil. There and elsewhere in present-day Arizona, trailing and gullying grew as livestock husbandry expanded in the eighteenth and nineteenth centuries.³⁷ As Natale Zappia argues, "by the end of the eighteenth century, an irreversible shift toward equestrian culture transfixed Native identities."³⁸ Sheep and horses began playing a role in social status among the Diné.³⁹ Erosion and fodder loss led some horse cultures to expand. The Apache, Comanche, and Diné increased raiding as Spanish and Mexican troops retreated south. Some raids pushed into the heart of Mexico itself.⁴⁰

Hoping to prevent this expansive raiding, Spanish and later Mexican authorities sought new alliances with other Native groups through gifts of horses and wheat. The resulting alliances illustrate the overlap of Spanish ambition and Native autonomy.⁴¹ In the Gila watershed and elsewhere, some Native communities looked to expanding mission chains as refuge from expansive raiding.⁴² The Akimel O'odham allied with the Spanish to forestall Apache incursions. Spanish authorities, in turn, encouraged Akimel to leave ranchería settlements and concentrate along the middle Gila River. There, they began growing wheat, placing them in a regional commercial network. The Akimel O'odham, who had rarely traded food before, began to store and trade wheat to other groups whose dietary resilience was strained by livestock erosion and weed growth. To [End Page 383] support this expanding trade, the Akimel O'odham expanded irrigation canals to the south bank of the Gila, building larger log and brush dams to raise water onto new fields. "Strict social controls" evolved to manage their water infrastructure, featuring regular days of work under a village captain, David DeJong argues. By the late eighteenth century, densely settled villages around irrigated wheat fields little resembled the dispersed villages of a century prior.⁴³

Changes in living patterns emerged because of new environmental realities and contributed to increased erosion. Before the nineteenth century, many peoples of the region lived in smaller bands. By the first half of the nineteenth century, many had gathered into larger bands to defend against slavers and, later, violent Americans.⁴⁴ These Americans built forts, mines, and wagon roads, which led to a stable flow of new people and goods. Growing inequality became channelized along the paths of commerce.

In the first half of the nineteenth century, the Akimel O'odham became a food-rich community amid strife, using winter-planted wheat to become a major food supplier of the region.⁴⁵ Commercial grain agriculture expanded quickly: the Akimel O'odham sold more than 110,000 pounds of wheat in 1858 and 350,000 pounds in 1860.⁴⁶ Akimel O'odham farmers, who had already transitioned to using wooden ploughs, were increasingly desirous of iron farm tools and equipment after the 1840s.⁴⁷ Ploughs further exposed topsoil to wind erosion, especially during dry periods.⁴⁸ They also brought the Akimel O'odham into commercial trade with Americans to obtain materials unavailable from Tucson or the Tohono O'odham.⁴⁹ Their main trading partners were the growing number of half-starved Anglo migrants in the 1840s, whose wagons were themselves a source of erosion. Wagon ruts became channels for erosion, often along creeks and rivers. Roads leading to and from oases along the Gila watershed "created essentially ideal conditions for flood-water erosion to cut a channel along the wagon roadway, and to destroy the oasis characteristics of the valleys."⁵⁰ [End Page 384]

Wagon roads also structured human movement in new ways. As Jeffrey Shepherd notes, Beale's wagon road followed trails long used by Pais and Mojaves. But higher traffic in the mid-nineteenth century forced the Pais into a series of defensive wars to protect their villages and crops. The Hardy toll road connecting the Colorado River to Prescott split northern and southern bands in half, limiting the Pais' ability to resist colonization through cooperation.⁵¹ This "signified a new division of space … reflected the penetration of capitalism … as well as a new legal regime that segregated Indians from lands they had inhabited for centuries." Many Pai bands came close to annihilation and retreated to larger settlements at locations least impacted by Anglo colonization.⁵²

As Native peoples responded to environmental change by altering their settlement patterns, the Arizona landscape came to be dotted by pockets of Anglo settlement, many at water sources vital for Native hunting and farming. Anglo towns, railroad depots, and mines disrupted underground water flows and left many springs dry. As Diana Davis has written, Anglos brought new ways of channeling water: "Irrigation boosters also often promoted deserts and desert settlement with unrealistic descriptions of the deserts' riches."⁵³ Mormon colonies in the Little Colorado and San Pedro valleys, part of a colonization effort designed by church leadership, created full-time settlements seeking to transform arid landscapes into a veritable Garden of Eden, a Zion in the desert.⁵⁴ As William Abruzzi has detailed, settlers had little understanding of regional ecology or hydrology. They often sited towns in flood-prone areas lower in watersheds with little understanding of how upland erosion left them vulnerable.⁵⁵ These new arrivals frequently exacerbated erosion by building semi-permanent dams with timber pilings and forcing streams to cut new erosive paths during floods.⁵⁶ [End Page 385]

Pockets of new arrivals, whether collected in mission settlements, forts, or mines, brought added layers of sedimentation to Arizona. Boundaries between Native and settler societies hardened, including around Indian reservations. Hoping to protect a major source of food for hungry Anglo settlers, the U.S. government drew reservation boundaries to protect Akimel O'odham villages—but not the upstream sources of water that proved so vital to their wheat production. In 1872, Mormon settlers arrived in the upper Gila River Valley and founded Safford. Settlements in Thatcher, Pima, and Duncan followed in rapid succession. Each wave of settlement further strained water supplies and brought new sources of erosion. Within two decades, the once food-and-water-rich Akimel O'odham hungered while tending smaller patches of dusty fields.⁵⁷

Channelization and Inequality

The dynamic sedimentation of nineteenth-century Arizona, unleashed by the ripples of the Columbian Exchange, began to collect around new boundaries and new technological systems. New arrangements of people, vegetation, water, and soil stabilized around hardened borders, resource-hungry mines, and lined irrigation canals. Each brought increased channelization of people, goods, and water as larger numbers of people, sheep, horses, and crops competed for dwindling water resources.⁵⁸ Rivers and gullies flooded with increased severity. New channels of water and commerce often severed Native people from food and water sources. Hungry people frequently moved to local mines and ranches, laboring for new capitalist enterprises. By the end of the nineteenth century, the increased power of the federal government reified these unequal relationships into fixed settlement patterns.⁵⁹

Historical geographer Gray Brechin helps explain how once-fluid regions develop rigid social structures. Brechin describes a "pyramid of mining" in gold-rush California and Nevada in which city and countryside alike were organized around resource extraction.⁶⁰ Borderlands historians notice a similar process in Arizona, [End Page 386] emanating from the dual expansion of Anglo-American capital and the federal state.⁶¹ What were once seasonal patterns of migration or flows of goods became a scheduled flow of goods toward semipermanent mining settlements. Commodities increasingly moved on regularly scheduled railroad trains rather than via mule trains or along Native trails.⁶²

The expansion of Arizona's mining economy stabilized the movement of people and resources, and increased erosion. Mines consumed local resources, especially water and wood. Nearby forests were thinned, and erosion-preventing upland vegetation was lost. Loose alluvium from mines, often piled alongside streams, was carried away during rains.⁶³ Food for miners stimulated more agricultural settlement. Cattle grazing and lowland ploughing consumed remaining native grasses and exposed soil to further erosion. By 1890, the Salt and Gila River valleys had nearly fifty thousand acres under irrigation upriver from Akimel O'odham holdings.⁶⁴ Upstream agriculture contributed to native vegetation loss at the same time irrigation canals and wagon tracks channeled water in new ways. Arizona's waterways oscillated between silted, dried beds, and violent floods.⁶⁵ As an example of the erosive force of these new flows, studies reveal that by 1912, the Santa Cruz River channel near the San Xavier Reservation had expanded to ten to twelve feet deep and from two hundred to six hundred feet wide.⁶⁶ Flood water no longer expanded gently over bottomlands, but raged in cut arroyos.

As watercourses widened, displaced sediment moved downstream, choking irrigation ditches. DeJong writes, "by 1905, the geomorphology of the river forced the Pima [Akimel O'odham] to abandon most of their traditional irrigation system. To irrigate Pima fields now required a costly conveyance system."⁶⁷ By the mid-1890s, conditions were so severe that the reservation's agent requested permission from the Bureau of Indian Affairs to purchase an additional 225,000 pounds of wheat to prevent starvation.⁶⁸ Thousands left the reservation. [End Page 387]

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Water flowed in the Santa Cruz River near Tucson in the early twentieth century (c. 1910). Buehman-Subjects-Missions-San Agustin, Buehman photo file, #B200271, Arizona Historical Society, Tucson.

Wrestling with flooding, erosion, and a region inscribed by boundaries, Akimel O'odham farm production went from food surplus to deficit. Jeffrey Shepherd notes a similar development in the Pai homeland. Upon returning from their internment in La Paz in the 1870s, the Pai found their homeland dotted with towns, ranches, and mines. Near starvation, many sought work in the mines and ranches that had imposed food insecurity.⁶⁹ By the 1880s, argues Louis Warren, much of the western "working class" were Native peoples in similar circumstances, working as guides, servants, and wage laborers outside their starving communities.⁷⁰ Cities and towns replaced springs or winter hunting grounds as migration destinations.⁷¹ [End Page 388]

The bounding of Native foodways were not only material but also bureaucratic impositions of the federal government. As Katherine Morrissey has argued, "the physical process of boundary making … link[s] the material with the abstract."⁷² During the second half of the nineteenth century, according to Samuel Truett, the U.S.–Mexico borderlands was a world of movement also "deeply inscribed with boundaries."⁷³ National borders transformed from figurative "lines in the sand" to fences curtailing the movement of cattle and people.⁷⁴ These new boundaries, whether between nations or around reservations, became increasingly racialized.⁷⁵ Human culture soon came to fit into the structured logic of control. Beyond Native reservations, mining towns and even larger settlements like Tucson soon organized into racialized neighborhoods.⁷⁶ Across Arizona, social mobility became more difficult as physical movement became easier. New property lines restricted transhumance. Housing and work patterns coalesced around race and gender rather than kinship or patronage.⁷⁷

Large, federally sponsored water and erosion-fighting projects reinforced this inequality. As Louis Warren and Jeffrey Shepherd have noted, the perceived failure of white settlement in the 1880s and 1890s in arid regions of the West drove demands for federal intervention.⁷⁸ A key proponent of this movement, the National Irrigation Association, called for federal projects to help suddenly troubled tribes like the Akimel O'odham. By the 1920s, the Gila River Reservation was integrated within the Salt River Project (SRP) but a series of imposed rules denied the tribe surface-water access and forced it to purchase SRP hydroelectric energy. The tribe [End Page 389]

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Dairy cattle at the feed trough, Casa Grande Valley Farms, Pinal County, Arizona, April 1940. Photograph by Russell Lee, courtesy of Library of Congress, https://www.loc.gov/item/2017742174.

was also denied membership in the Salt River Valley Water Users Association.⁷⁹

Native marginalization in large projects such as SRP knitted together Colorado River, Colorado Plateau, and Gila watershed communities into lasting dynamics of unequal exchange. Trails of the interior world transformed, in two short generations, into wagon lines, railroad lines, then power lines. In the early twentieth century, Phoenix grew dramatically, fed by dams, canals, and power plants. Simultaneously, the Navajo Nation became a place of extraction. During this period, state and federal officials came to view the Navajo Nation as vital for infrastructure growth in the Southwest. However, Diné confined to their reservation found growing sheep herds had fewer good range tracts to forage. Bureau of Indian Affairs (BIA) officials struggling to manage ever-moving herds and bands of people encouraged stationary settlement and saw rangeland erosion as a threat to this stability.⁸⁰ BIA custodians [End Page 390]

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Sacaton Indian Reservation. O'odham man plowing his land as part of the Salt River Project. Photograph courtesy of Library of Congress, https://www.loc.gov/item/93502778/

used erosion, blamed on Diné overgrazing rather than drought, to justify increased federal management of tribe and rangeland during the late nineteenth and twentieth centuries.⁸¹

As Andrew Needham has noted, conflict between Diné sheep-herders and BIA officials decisively tilted in the government's favor when massive Southwest hydroelectric dam projects gained favor. Dam-builders worried erosion on the Navajo reservation would compromise their water systems with silt. Further pressure on the BIA and Diné officials ultimately led to the destruction of millions of sheep in the 1930s.⁸² Thus, arresting erosive regimes became essential to federal management of the Diné, their lands, and to the electrification of Phoenix. The arrival of the U.S. government in the form of the Roosevelt Dam and BIA sheep management represented the dawning of a new era in Arizona's history, one in which the power of the federal government and eastern capital arrested erosion and channeled human communities in [End Page 391] new ways.⁸³ This system came in stages, waves along right of ways and irrigation ditches, built upon a shifting foundation of environmental change stretching back to the trails of the interior world in the 1500s.

Stabilizing the Sun Belt

Though this narrative ends with the erosion of Native communities, their resiliency is one of the remarkable post-scripts of this story. For example, the Akimel O'odham used their national status to advocate for surface water rights in the Salt River and San Carlos Irrigation projects.⁸⁴ The Hualapai nation responded to the concentration of their dispersed bands by advocating for united nationhood through their active participation in the Indian Rights Association, eventually fending off a Santa Fe Railroad claim to a portion of their home-land.⁸⁵ The Colorado River Indian Reservation now controls one-third of Arizona's Colorado River water adjudication.⁸⁶

As Samuel Truett has argued and these histories suggest, Arizona and the Southwest are a "palimpsest of spaces."⁸⁷ Native and settler communities became unmoored, collected, eroded, and sedimented into a multitude of places across the Arizona landscape. The Columbian Exchange of the early modern period accelerated through the nineteenth century in Arizona, in successive layers of biological change, erosion, and waves of imperialism and capitalism that continue to this day.

Twentieth-century relationships between regions structured around power lines and irrigation canals were written into communities responding to intergenerational layers of disease, livestock, and crop arrivals. This network of systems and boundaries was not an inevitable result of aridity or the mixed nature of borderland societies but the result of human decisions within the long Columbian Exchange, unfolding episodically in specific places through the forces of human culture.

Environmental history helps us see how the Columbian Exchange worked its way through the landscape primarily through idiosyncratic human decisions, leading to successive layers of [End Page 392] erosion. Arizona's environmental history since 1500 consists of erosion and sedimentation amidst colonization, with channelization becoming the order of the day. Anglo settlers sought to remake Arizona into a collection of commercial sites during the second half of the nineteenth century. In doing so, they created new artificial rivers carrying silt and sediment to new places, forming stable—and unequal—community dynamics in the process. In this way, the Sunbelt grew from the Columbian Exchange. [End Page 393]