Assessing the energy trap of industrial agriculture in North America and Europe: 82 balances from 1830 to 2012.

Early energy analyses of agriculture revealed that behind higher labor and land productivity of industrial farming, there was a decrease in energy returns on energy (EROI) invested, in comparison to more traditional organic agricultural systems. Studies on recent trends show that efficiency gains in production and use of inputs have again somewhat improved energy returns. However, most of these agricultural energy studies have focused only on external inputs at the crop level, concealing the important role of internal biomass flows that livestock and forestry recirculate within agroecosystems. Here, we synthesize the results of 82 farm systems in North America and Europe from 1830 to 2012 that for the first time show the changing energy profiles of agroecosystems, including livestock and forestry, with a multi-EROI approach that accounts for the energy returns on external inputs, on internal biomass reuses, and on all inputs invested. With this historical circular bioeconomic approach, we found a general trend towards much lower external returns, little or no increases in internal returns, and almost no improvement in total returns. This "energy trap" was driven by shifts towards a growing dependence of crop production on fossil-fueled external inputs, much more intensive livestock production based on feed grains, less forestry, and a structural disintegration of agroecosystem components by increasingly linear industrial farm managements. We conclude that overcoming the energy trap requires nature-based solutions to reduce current dependence on fossil-fueled external industrial inputs and increase the circularity and complexity of agroecosystems to provide healthier diets with less animal products. Supplementary Information: The online version contains supplementary material available at 10.1007/s13593-023-00925-5.

The Role of Wildfires in the Interplay of Forest Carbon Stocks and Wood Harvest in the Contiguous United States During the 20th Century.

Wildfires and land use play a central role in the long-term carbon (C) dynamics of forested ecosystems of the United States. Understanding their linkages with changes in biomass, resource use, and consumption in the context of climate change mitigation is crucial. We reconstruct a long-term C balance of forests in the contiguous U.S. using historical reports, satellite data, and other sources at multiple scales (national scale 1926-2017, regional level 1941-2017) to disentangle the drivers of biomass C stock change. The balance includes removals of forest biomass by fire, by extraction of woody biomass, by forest grazing, and by biomass stock change, their sum representing the net ecosystem productivity (NEP). Nationally, the total forest NEP increased for most of the 20th century, while fire, harvest and grazing reduced total forest stocks on average by 14%, 51%, and 6%, respectively, resulting in a net increase in C stock density of nearly 40%. Recovery from past land-use, plus reductions in wildfires and forest grazing coincide with consistent forest regrowth in the eastern U.S. but associated C stock increases were offset by increased wood harvest. C stock changes across the western U.S. fluctuated, with fire, harvest, and other disturbances (e.g., insects, droughts) reducing stocks on average by 14%, 81%, and 7%, respectively, resulting in a net growth in C stock density of 14%. Although wildfire activities increased in recent decades, harvest was the key driver in the forest C balance in all regions for most of the observed timeframe.

Energy Profiles of an Agricultural Frontier: The American Great Plains, 1860-2000.

Agro-ecosystem energy profiles reveal energy flows into, within, and out of U.S. 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 percent above pre-settlement 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.

A landscape ecology assessment of land-use change on the Great Plains-Denver (CO, USA) metropolitan edge.

For better or worse, in those parts of the world with a widespread farming, livestock rising, and urban expansion, the maintenance of species richness and ecosystem services cannot depend only upon protected natural sites. Can they rely on a network of cultural landscapes endowed with their own associated biodiversity? We analyze the effects of land-cover change on landscape ecological patterns and processes that sustain bird species richness associated to cropland-grassland landscapes in the Great Plains-Denver metropolitan edge. Our purpose is to assess the potential contribution to bird biodiversity maintenance of Great Plain's cropland-grassland mosaics kept as farmland green belts in the edge of metropolitan areas. We present a quantitative landscape ecology assessment of land-cover changes (1930-2010) experienced in five Great Plains counties in Colorado. Several landscape metrics assess the diversity of land-cover patterns and their impact on ecological connectivity indices. These metrics are applied to historical land-cover maps and datasets drawn from aerial photos and satellite imagery. The results show that the cropland-grassland mosaics that link the metropolitan edge with the surrounding habitats sheltered in less human-disturbed areas provide a heterogeneous land matrix were a high bird species richness exists. They also suggest that keeping multifunctional farmland-grassland green belts near the edge of metropolitan areas may provide important ecosystem services, supplementing traditional conservation policies. Our maps and indicators can be used for selecting certain types of landscape patterns and priority areas on which biodiversity conservation efforts and land-use planning can concentrate.

Agroecosystem energy transitions in the old and new worlds: trajectories and determinants at the regional scale.

Energy efficiency in biomass production is a major challenge for a future transition to sustainable food and energy provision. This study uses methodologically consistent data on agroecosystem energy flows and different metrics of energetic efficiency from seven regional case studies in North America (USA and Canada) and Europe (Spain and Austria) to investigate energy transitions in Western agroecosystems from the late nineteenth to the late twentieth centuries. We quantify indicators such as external final energy return on investment (EFEROI, i.e., final produce per unit of external energy input), internal final EROI (IFEROI, final produce per unit of biomass reused locally), and final EROI (FEROI, final produce per unit of total inputs consumed). The transition is characterized by increasing final produce accompanied by increasing external energy inputs and stable local biomass reused. External inputs did not replace internal biomass reinvestments, but added to them. The results were declining EFEROI, stable or increasing IFEROI, and diverging trends in FEROI. The factors shaping agroecosystem energy profiles changed in the course of the transition: Under advanced organic and frontier agriculture of the late nineteenth and early twentieth centuries, population density and biogeographic conditions explained both agroecosystem productivity and energy inputs. In industrialized agroecosystems, biogeographic conditions and specific socio-economic factors influenced trends towards increased agroecosystem specialization. The share of livestock products in a region's final produce was the most important factor determining energy returns on investment.

An unremembered diversity: mixed husbandry and the American grasslands.

The Green Revolution of the 1960s brought about a dramatic rise in global crop yields. But, as most observers acknowledge, this has come at a considerable cost to biodiversity. Plant breeding, synthetic fertilizers, and mechanization steadily narrowed the number of crop varieties commercially available to farmers and promoted fencerow-to-fencerow monocultures. Many historians trace the origins of this style of industrialized agriculture to the last great plow-up of the Great Plains in the 1920s. In the literature, farms in the plains are often described metaphorically as wheat factories, degrading successive landscapes. While in many ways these farms were a departure from earlier forms of husbandry in the American experience, monocultures were quite rare during the early transformation of the plains. Analysis of a large representative sample, based on manuscript agricultural censuses and involving twenty-five townships across the state of Kansas, demonstrates that diverse production reached even the most challenging of plains landscapes.