Energy profiles of an agricultural frontier: the American Great Plains, 1860–2000
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Agro-ecosystem energy profiles reveal energy flows into, within, and out of US Great Plains farm communities across 140 years. This study evaluates external energy inputs such as human labor, machinery, fuel, and fertilizers. It tracks the energy content of land produce, including crops, grazed pasture, and firewood, and also accounts unharvested energy that remains available for wildlife. It estimates energy redirected through livestock feed into draft power, meat, and milk, and estimates the energy content of final produce available for local consumption or market sale. The article presents energy profiles for three case studies in Kansas in 1880, 1930, 1954, and 1997. Two energy transformations occurred during that time. The first, agricultural colonization, saw farm communities remake the landscape, turning native grassland into a mosaic of cropland and pasture, a process that reduced overall landscape energy productivity. A second energy transition occurred in the mid-twentieth century, characterized by fossil fuel energy imports. That outside energy raised harvested and unharvested energy flows, reused biomass energy, and also final produce. This socio-ecological transition increased landscape energy productivity by 33 to 45% above presettlement conditions in grain-growing regions. These energy developments were not uniform across the plains. Variations in rainfall and soil quality constrained or favored energy productivity in different places. The case studies reveal the spatial variation of energy profiles in Great Plains agro-ecosystems, while the longitudinal approach tracks temporal change.
KeywordsAgro-ecosystem energy Great Plains agriculture Agricultural colonization Socio-ecological transition
For 10,000 years, agriculture has been society’s primary energy supplier (Malanima 2006, 2009; Simmons 2008). Food for subsistence, firewood for domestic heat and industrial charcoal, a transportation system based on draft animals: all originated in agro-ecosystems. Even cities imported food, livestock feed, and fuel from hinterland farms (Cronon 1991; Gingrich et al. 2012). Maintaining agro-ecosystems required a constant investment of energy, in the form of human labor, farm produce cycled through livestock, or imported energy-rich inputs. Agro-ecosystems are societal converters that supply, consume, and redirect energy through looped pathways. The American Great Plains presents a rare opportunity for analysis: an agricultural frontier well documented from its beginning 150 years ago and right through the socio-ecological transition to modern industrialized farming. Agricultural frontiers date to the beginning of agriculture, but their incidence rose during the nineteenth century due to European colonization. In places Crosby (1986) referred to as “neo-Europes,” settlers displaced Indigenous populations and carried out large-scale land conversion for agriculture. Examples occurred in the Americas, Australia, and New Zealand, but also in the Ukrainian and Russian steppes (Moon 2013). Compared to long-farmed places, frontiers present a unique agricultural context. Large labor investments converted forests and grasslands into managed agro-ecosystems. Settlers exploited rich soils to grow bumper crops with little reinvestment in fertility maintenance. Labor shortages, of both people and draft animals, made it advantageous to open new land rather than re-invest in old land (Grigg 1992; Federico 2005; Belich 2009). Between 1860 and 2000, the Great Plains underwent two energy transitions. Agricultural colonization converted a grassland biome into an agricultural landscape by the 1920s, reducing overall plant growth in the process. Then, by the 1960s, a socio-ecological transition added imported fossil fuel energy to what had been primarily a local, biomass-based energy regime (Fischer-Kowalski and Haberl 2007). Inexpensive energy washed through the system, multiplying energy outputs, but also boosting internal and unharvested biomass energy flows.
Energy flows (GJ/ha) in three Kansas counties, 1880, 1930, 1954, and 1997
More pertinent to farmers and central to agriculture’s economic goals are measures of gross and net farm productivity. Land Produce (LP) represents the energy produced by croplands, woodlands, and pastures. Livestock-Barnyard Produce (LBP) is the meat, milk, and other animal commodities produced on farms. Combined, they constitute Total Produce (TP), the gross energy production of the managed system. But, Total Produce is never entirely available to people. Farmers divert much of that production back into the farm system, as seed for next year’s crop or as livestock feed and bedding. That crucial deduction from Total Produce, denoted here as Biomass Reused (BR), is energy that people must re-invest if the farm is to continue another year. The remainder, the farm’s net energy production, is Final Produce (FP), goods available for local consumption or market sale. Agriculture’s primary goal was not always to produce more energy. Some high-energy outputs, such as firewood, had low market value, while low-energy produce like fiber crops and meat had high market value. Energy processes in agro-ecosystems are not linear, with simple inputs and outputs, but looped, with energy inputs, internal cycling, and outputs (Tello et al. 2016).
Energy inputs (TIC) take two forms. Biomass Reused (BR) is energy derived from within the agro-ecosystem itself and was always the largest input (9–27 GJ/ha). External Inputs (EI) include Labor (L) invested by the farm community plus energy carriers imported from outside the agro-ecosystem, such as machinery, fuel, synthetic chemicals, and imported livestock feed. Labor, which never exceeded 0.04 GJ/ha, was by far the smallest of these External Inputs. Imported energy derived from fossil fuels, on the other hand, rose in importance over time, from negligible in the nineteenth century to 4–12 GJ/ha at the end of the twentieth century. The defining feature of the socio-ecological transition to industrial agriculture was increased inputs of fossil fuel energy embodied in imported tractors and trucks powered by internal combustion engines, plus their fuel. After the 1950s, chemical fertilizers, replete with embodied fossil fuel energy, constituted the largest imports on farms, while pesticides, electricity, and imported livestock feed contributed additional amounts. Irrigation was minimal in the counties evaluated here, but EI also includes the energy cost of lifting and distributing irrigation water. By the end of the twentieth century, External Inputs of fossil fuels, chemical fertilizers, pesticides, and electricity delivered 15–30% of Total Inputs Consumed, but Biomass Reused still contributed over 70%. Tracing these energy flows across 140 years reveals the energy story of the Great Plains as it moved from a raw frontier to become a modern, industrial breadbasket to the world.
Variations of Great Plains agriculture
Nemaha County, Kansas, is on the wet eastern edge of the plains. Tallgrass and mixed-grass prairie covered most of the county, with low woodlands only along rivers. Nemaha averages 875 mm of precipitation annually, enough to support a variety of crops. Rich soils are deep and gently sloping with clay loam or silty clay loam textures (Kutnink et al. 1982). It was the first part of the interior grassland settled by Euro-Americans, beginning in the 1850s. Nemaha represents the prosperous, mixed-farming communities created during the mid-nineteenth century agricultural colonization of the Great Plains (Cunfer and Krausmann 2016). Only 200 km to the southwest, Chase County, Kansas, strikes a marked contrast. Rainfall averages 815 mm, supporting a vigorous native vegetation of tallgrass and mixed-grass prairie (Neill 1974). The soils, however, are only a few centimeters thick and poor for agriculture. The thin-skinned limestone hills are unsuitable for the plow. Only in bottomland along rivers did settlers find soils deep enough for cropland. Instead, they exploited generous native grasses for cattle grazing. Since the 1850s Chase County has been ranching country, with land devoted to fattening beef cattle and only a small amount planted in feed crops and hay to see cattle through winter (Malin 1984). Farther west, settlement had barely begun in Decatur County, Kansas, in 1880. Semi-arid climate averaged 525 mm of annual precipitation and supported short-grasses on 98% of the land. Soils are deep and level, with a silt loam texture (Hamilton et al. 1989; Cunfer and Krausmann 2009). Farmers eventually grew dryland wheat and drought-tolerant sorghum on half of the area and dedicated the other half to extensive, low-density cattle grazing. These three case studies represent characteristic types of Great Plains non-irrigated agriculture. Nemaha County’s rich soils and adequate rainfall supported prosperous mixed farming. Chase County’s adequate rainfall but poor soils allowed only extensive cattle ranching, while Decatur County’s good soils but low rainfall supported cereal farming and extensive cattle grazing.
Mixed farming in Nemaha County, Kansas
Nemaha County’s tallgrass prairie generated 90 GJ/ha of aboveground biomass energy in its presettlement condition (NPPpot). As Euro-Americans transformed that grassland into an agricultural mosaic, they reduced plant productivity (NPPact) significantly. By 1880, 25 years after initial settlement, energy productivity from the land was down 24% to 68 GJ/ha. Half a century later, it had fallen to 56 GJ, just over half of its presettlement value. Then, in the mid-twentieth century, a technological revolution—the socio-ecological transition—drove productivity higher. NPPact rose to 71 GJ/ha in 1954, then to 120 by 1997. At the end of the twentieth century, total plant energy production was 33% higher than under presettlement conditions. This progression, in two phases, reveals agriculture’s basic environmental impact on natural systems.
Farm families could not consume or sell all of the farm system’s Total Produce, however. First, they had to re-invest a portion to secure farm continuity into the next year. Biomass Reused (BR) diverted some Land Produce into feed and forage for livestock, bedding straw, and seed for next spring’s crop. In 1880, Biomass Reused consumed 18 GJ/ha, nearly 80% of Total Produce, climbing to 23 GJ in 1930. What remained, Final Produce (FP), was available for consumption or export to market. This energy flow, the primary objective of family labor and enterprise, was 5 GJ/ha in 1880 and 8 GJ/ha 50 years later in 1930. In those two years, from a gross farm productivity of 23–31 GJ/ha, farmers re-invested about 20 GJ as Biomass Reused, leaving net productivity (FP) of 5–8 GJ. External Inputs were modest at 4 GJ/ha in 1880 and 3 GJ/ha in 1930. They included farm machinery and fuel (plus the embodied energy of manufacture and transport) and a small amount of imported livestock feed. Labor (L), as demanding as it was for farm families, was less important in energetic terms, constituting only 0.04 GJ/ha. That low number demonstrates how effectively agriculture amplifies human work. In Nemaha County in 1930, a farmer returned 7.7 GJ/ha of Final Produce from a Labor investment of 0.04 GJ/ha, a ratio of 193:1. Pioneer farmers, through their sweat and ingenuity (and aided by generous liberal land policies), converted a tallgrass prairie into a prosperous farming community, one that required large energy reinvestments but sustained a comfortable lifestyle.
Not all energy flows changed in unison, however. While EI rose by 120% between 1930 and 1954, Final Produce increased by only 70% and Biomass Reused was flat. Unharvested Phytomass jumped from 26 to 35 GJ/ha. Then, all energy flows rose sharply in the next 40 years. In 1997, EI was 12 GJ/ha and NPPact jumped to 120 GJ/ha. Much of that, 57 GJ, was biomass harvested from farmland as LP, but UPH also rose, to 63 GJ/ha, nearly double 1954 levels. Unmanaged wildlife around Nemaha farms now had access to more energy than they had in over a century. Of the 58 GJ/ha of Total Produce, nearly half (27 GJ/ha) went into a much-increased Biomass Reused and the remainder to Final Produce (31 GJ/ha), which had increased by 240%. By pouring fossil fuel energy into their enterprises, farmers raised marketable production dramatically: FP quadrupled between 1930 and 1997.
Figure 3 reveals an interesting progression in the socio-ecological transition. Between 1930 and 1954, EI rose by 4 GJ/ha and FP kept pace, rising by 5 GJ. Then, between 1954 and 1997, EI climbed another 5 GJ, but this time, FP went up by a remarkable 18 GJ/ha. As farmers mechanized in the early part of the socio-ecological transition, abandoning horses and mules for tractors, energy inputs rose and so did energy outputs. Then, in a second phase of transition, driven now by fertilizer, productivity exploded. Energy inputs climbed throughout the twentieth century, but the great gains in crop production happened only in its last several decades. Historians of agriculture have focussed on machinery as the defining technology of industrialized farming (Williams 1987; Fitzgerald 1991; Cunfer 2005). Most link agricultural modernization to the adoption of tractors, but synthetic fertilizers, with their high embedded energy content, were the most important driver of increased crop production, and that occurred a few decades later. Mechanization improved labor productivity, whereas synthetic fertilizers improved land productivity.
Extensive cattle ranching in Chase County, Kansas
With each move westward on the Great Plains farmers faced greater environmental challenges. Although Chase County is not far from Nemaha, its energy profile looks quite different. Only slightly drier, but with poorer soils, all managed energy flows in Chase County were smaller. Rich grasslands supported extensive cattle grazing beginning in the 1850s, when Euro-Americans appropriated Native American land and replaced wild bison with livestock (Malin 1984; Courtwright 2011). Presettlement energy productivity was the same in both places (89–90 GJ/ha). In Chase County, agricultural management reduced total productivity (NPPact) over time, but only by 15%, to fluctuate between 74 and 79 GJ/ha between 1880 and 1954. In the late twentieth century, ranchers pushed NPPact back up to 91 GJ/ha, matching presettlement amounts. They accomplished this recovery through productivity gains on the 12% of land plowed for crops, mainly through fertilizer application. Chase County ranching had a smaller basic environmental impact than did Nemaha County farming.
That finally changed in the second half of the twentieth century, but only modestly in energy terms. EI rose to 4 GJ/ha in 1997 and Land Produce jumped by 80%. Unharvested Phytomass was still flat at 69 GJ/ha. Ranchers drove livestock density from 18 animals/km2 in 1954 up to 28 in 1997 by creating concentrated feed lots within extensive pastures. They also fed more produce to those cattle, raising Biomass Reused from 11 GJ/ha in 1954 to 19 in 1997. NPPact rose by 15% to 91 GJ/ha in 1997, identical to its presettlement value. Final Produce doubled to reach 4 GJ/ha. This was a notable increase, but hardly the spectacular results created in the grain-growing regions. In Chase County, EI tripled over 120 years but only reached 4 GJ/ha in 1997, a level matched in Nemaha already in 1880. Final Produce dipped in the mid-twentieth century then doubled by 1997, but in that year it generated only an eighth of Nemaha’s output. UPH remained stable through more than 150 years, above 70% of presettlement NPP. Biomass Reused rose after 1954, reaching a level five times that of FP. Natural conditions put strict limits on agro-ecosystem productivity in Chase County, and farm communities adapted by limiting cropland while fully exploiting pasture for cattle grazing (Cunfer and Krausmann 2016).
Dryland cereal production in Decatur County, Kansas
Great Plains agro-ecosystems underwent two energy transformations. Agricultural colonization began in the eastern plains in the 1850s, in the western plains in the 1880s, and concluded everywhere by the 1920s. Through the first 75 years, nearly all land in the region became either cropland or grazed pasture (Cunfer 2005). In the process, farmers reduced plant productivity compared to presettlement conditions. Then, over the next 75 years, a second energy transformation, the socio-ecological transition, multiplied plant productivity again. Today, the two grain-growing counties produce 33 to 45% more energy than they did prior to settlement; plant production in the ranching county is virtually identical to that in c.1850. The socio-ecological transition depended on fossil fuel energy in a variety of forms, but most prominently in synthetic fertilizers. Tractors and trucks transformed farm family lifestyles and required energy imports, but they only modestly raised land productivity. In the mid-twentieth century, biomass energy outputs lagged behind climbing fossil fuel energy inputs. Then, when fertilizer took off in the 1950s, productivity rose much faster. Climbing NPPact came from Land Produce, which rose by multiples, and also from Unharvested Phytomass. The latter rose modestly in grazing regions where it had always been high and dramatically in grain-growing areas. Landscape conversion into agro-ecosystems during agricultural colonization increased harvested portions of NPPact and decreased unharvested portions. The socio-ecological transition boosted all energy pathways.
Higher rainfall in the eastern plains allowed farmers to benefit more and earlier from external energy investments. In 1930, Nemaha farmers applied 1 kg of fertilizer per hectare of cropland, compared to 1/3 kg in Chase County and none in Decatur (US Census Bureau 1930). In 1954, farmers in wetter Nemaha and Chase Counties applied 45 and 39 kg/ha, respectively, while those in dry Decatur County had not yet reached 1 kg (US Census Bureau 1954). By 1997, fertilizer applications had leveled off in Chase County (43 kg/ha), risen substantially in Decatur County (59 kg), and tripled in Nemaha County (139 kg). By the late twentieth century, all Kansas farmers employed energy-rich fertilizer to boost crop yields, but more so in eastern Kansas, where rainfall was sufficient for nutrient-hungry corn. In the dry western part of the state, farmers grew wheat and sorghum, which need less water and fewer soil nutrients. Nemaha County farmers began the socio-ecological transition decades earlier and reaped greater productivity increases than did grain farmers in Decatur County.
These results add nuance to previous studies of NPPact in the Great Plains (Lauenroth 1979; Bradford et al. 2005) and reveal an agro-ecological context rarely addressed in HANPP studies. Assessing the entirety of the U.S. Great Plains, Bradford et al. (2005) estimated that cultivation raised aboveground NPP by 26%, somewhat lower than the 33 to 45% increase estimated here. Most of that gain came from corn cultivation, and a smaller part from wheat and sorghum, with irrigation and fertilizer applications as the primary drivers of increasing NPP. Without contradicting those region-wide results, the case studies explored here highlight internal energy loops and expose the energy constraints imposed by climate and soil. Human Appropriation of Net Primary Production studies have addressed global scales (Imhoff et al. 2004; Haberl et al. 2007, 2009; Krausmann et al. 2009, 2013; Erb et al. 2009a, 2009b) or European nations (Haberl et al. 2005; Musel 2009; Schwarzlmuller 2009; Kohlheb and Krausmann 2009; Vackar and Orlitova 2011; Gingrich et al. 2015) but not the New World. Long-term HANPP studies in those regions begin centuries after agricultural colonization and focus on the twentieth century’s socio-ecological transition. Other HANPP studies address the Philippines (Kastner 2009), South Africa (Niedertscheider et al. 2012), New Zealand (Fetzel et al. 2014), and Canada’s Nova Scotia (O’Neill et al. 2007). Thus far, scholars have neglected the Americas, which were characterized by Euro-American colonization, low population densities, and export-focussed agro-ecosystems. There are no HANPP studies of agricultural frontiers (except for New Zealand, where settlers converted forest to sheep pasture but grew few crops). Most HANPP research assumes that native vegetation was forest, rather than grassland, with important implications for NPPpot. The energy consequences of clearing forest for farmland are different from those in native grassland. For example, Gingrich et al. (2015) found that the socio-ecological transition led to less cropland, forest regrowth, and NPPact values around 10% higher than NPPpot. The present study shows that NPP gains from the socio-ecological transition may be even higher in grasslands.
Comparative internal energy flows also reveal interesting patterns. All farms and ranches in the Great Plains required reinvestment of Biomass Reused. That was true during the late nineteenth and early twentieth centuries, but even more so after the socio-ecological transition. In both ranching and grain-growing regions, rising EI did not substitute for Biomass Reused, but rather drove it higher alongside Final Produce; likewise with Unharvested Phytomass. Increasing flows of BR fed more livestock for meat production, but LBP remained small compared to other energy flows, never climbing higher than 1 GJ/ha. The conversion from livestock feed (BR) to meat (LBP) is inefficient, with large energy losses via waste heat. Converting fossil fuels (EI) into feed crops (BR) and then into meat (LBP) is even less efficient. Increased EI did not diminish BR or UPH on their way to boosting FP. Instead, EI raised all three energy flows. The flush of new energy through agro-ecosystems affected all aspects of farms, including domesticated livestock, market exports, and some wildlife.
While the socio-ecological transition brought changes everywhere in the Great Plains, there were regional variations. Wetter, eastern areas began importing fossil fuel energy earlier than drier areas, and they saw larger returns. Regions with poor soils also increased energy imports, but at lower levels and later than places with abundant cropland. In the eastern plains, farmers invested in tractors in the 1910s and applied synthetic fertilizer in the 1920s (Kansas State Board of Agriculture 1915; U.S. Census Bureau 1930). By the 1930s farmers in the dry western regions transitioned to tractors, but they adopted fertilizer only after the 1950s, and even then applied it at a third the rate of those to the east. In Kansas’s bluestem pastures, where soils were thin, ranchers used fossil fuel energy to increase feed crops, but energy imports and exports remained low. Rainfall and soils were limiting factors, even in an era of cheap, abundant fossil fuel energy.
This research was supported by the Social Science and Humanities Research Council of Canada’s Partnership Grant 895-2011-1020 and the Eunice Kennedy Shriver National Institute of Child Health and Human Development, U.S. National Institutes of Health grants R01 HD033554 and R01 HD044889. Thanks to Simone Gingrich, Fridolin Krausmann, members of the Sustainable Farm Systems project and two anonymous reviewers for their constructive comments.
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