• Energy Research
• natural sciences close

This paper documents the origin and conceptual ambiguity of the terms Sustainable, Ecological and Agroecological Intensification. It defines the concept of Ecological Intensification from an agroecological perspective, and examines in energy terms whether it may be sustainable. To illustrate the theory, we apply Land Cost of Sustainable Agriculture (LACAS) methodology to Spanish agriculture, which is representative of Mediterranean agroclimatic conditions. As a result, we demonstrate the impossibility of generalizing an extensive Organic Farming (OF) scenario under the techniques currently used by organic farmers. This is due to the fact that it would bring about a reduction of 13% in agricultural production. Which necessarily means that OF has to be intensified under agroecological criteria. This option is also explored in two scenarios. As a result, we show that it is possible to compensate the yield gap between OF and conventional agriculture by implementing low-entropy internal loop strategies which reduce the land cost of generating the necessary nitrogen flows. However, these cannot exceed the limits established by the structure of Spanish territory. That is, agroecological intensification cannot be prolonged indefinitely over time since it is limited by the land available.

Along the last century there has been an unprecedented growth in both global food production and related socioecological impacts. The objective of this paper is to analyse the effects of long-term metabolic patterns of agrarian systems on land use and cover changes (LUCC) (...)

For a large extent of historiography, the history of Spanish agriculture during the twentieth century is a story of success. However, this narrative has been built on monetary analysis, and it does not usually take into account the effects on rural society and agroecosystems. The aim of this paper is to analyze what has happened from a biophysical perspective to ascertain whether transformations linked with industrialization of agriculture have also been positive. For this, we have integrated the results—some unpublished and others already published—of a broader research project about different aspects of food production from a biophysical perspective in Spain, applying methodologies pertaining to the Social Metabolism. Our research seeks to provide a new narrative, emerging through the consideration of environmental aspects of the process, providing a more complex vision of the process of industrialization in European agriculture. The results show that the industrialization of Spanish agriculture has brought about profound changes in land uses and in the functionality of the biomass produced, increasing pressure on croplands and, paradoxically, facilitating the abandonment of an important proportion of pasture and croplands. This has led to the subordination of a very significant portion of Spanish agroecosystems to the feed demands of intensive livestock farming. This process has been based on the injection of large quantities of external energy. Agricultural production has undergone significant growth since the 1960s, but this has been insufficient to deal with the growing demand created by the change in the Spanish diet and the increasing trend to focus on livestock farming. The process of globalization has allowed both roles to be reconciled, although in recent decades Spain has accentuated its role as a net importer of biomass from a biophysical perspective, with very significant impacts on third party countries, particularly in Latin America. From a biophysical perspective, the industrialization of Spanish agriculture has entailed negative consequences that threaten the sustainability of Spanish agroecosystems and also negatively affect the sustainability of other territories.

Abstract This paper analyses the use of energy in the Spanish Agri-Food System (ASF) between 1960 and 2010. It distinguishes between several different forms of energy (renewable, non-renewable, final and primary), six sectors and up to a hundred activities. The use of energy in the AFS increased 10.2 fold during the period analysed, from 181 TJ to 1855 TJ, between 1960 and 2015. In the first stage, up to 1985, agriculture accounted for the majority of new consumption. However, from that date onwards, consumption in other sectors such as transport, packaging and homes grew at a faster rate. A decomposition analysis reveals that the increase in activity in the sector, in other words managed biomass, explains 46% of the increase in the use of energy, whereas the rest is explained by losses in efficiency, chiefly losses in efficiency within a sector that requires a greater amount of resources per biomass produced. The final energy consumption of the AFS over the total consumption of the economy represents 19.6%, suggesting a significant potential of agri-food policies as means of reducing the use of energy.

The high grain yield of modern varieties (MV) respond to the increase in fossil-based inputs, and the widespread belief that they are more productive than old varieties (OV) is biased. This belief focuses only on marketable biomass, without considering the consequences on agroecosystem sustainability of the reductions in other portions of NPP. Additionally, field comparisons of OV and MV were normally conducted under industrialized farming conditions, which is detrimental for OV performance. Both trials carried out in this study comparing wheat OV and MV show that, under Mediterranean rainfed conditions and traditional organic management, aerial and belowground biomass production of OV is higher than that of MV, without significantly decreasing yield and enabling a better competition against weeds. From the data of our trials, bibliographic review and information from historical sources, we have reconstructed the NPP and destinations of biomass of Spanish wheat fields (1900–2000). Varietal replacement entailed the reduction in residues and unharvested biomass (UhB), which involved soil degradation in rainfed cereal fields and undermining heterotrophic trophic webs. Our results suggest that OV can increase the sustainability of rainfed Mediterranean agroecosystems at present through the improvement of soil quality, the reduction of herbicides use, and the recovery of biodiversity.

Abstract Synthetic nitrogen (N) fertilization has helped boost agricultural yields, but it is also responsible for direct and indirect greenhouse gas (GHG) emissions. Fertilizer-related emissions are also promoted by irrigation and manure application, which has increased with livestock industrialization. Spanish agriculture provides a paradigmatic example of high industrialization under two different climates (temperate and Mediterranean) and two contrasting water management regimes (rainfed and irrigated). In this study, we estimated the historical evolution of the C footprint of N fertilization (including all the life cycle GHG emissions related to N fertilization) in Spanish agriculture from 1860 to 2018 at the province level (50 provinces) for 122 crops, using climate-specific N2O emission factors (EFs) adjusted to the type of water management and the N source (synthetic fertilizer, animal manure, crop residues and soil N mineralization) and considering changes in the industrial efficiency of N fertilizer production. Overall, N-related GHG emissions increased ∼12-fold, up to 10–14 Tg CO2e yr−1 in the 2010s, with much higher growth in Mediterranean than in temperate areas. Direct N2O EFs of N fertilizers doubled due to the expansion of irrigation, synthetic fertilizers and liquid manure, associated with livestock industrialization. Synthetic N production dominated the emissions balance (55%–60% of GHGe in the 21st century). Large energy efficiency gains of industrial fertilizer production were largely offset by the changes in the fertilizer mix. Downstream N2O emissions associated with NH3 volatilization and NO3 − leaching increased tenfold. The yield-scaled carbon footprint of N use in Spanish agriculture increased fourfold, from 4 and 5 Mg CO2e Mg N−1 to 16–18 Mg CO2e Mg N−1. Therefore, the results reported herein indicate that increased productivity could not offset the growth in manufacture and soil emissions related to N use, suggesting that mitigation efforts should not only aim to increase N use efficiency but also consider water management, fertilizer type and fertilizer manufacture as key drivers of emissions.