Long-term socioecological trajectories of agro-food systems revealed by N and P flows in French regions from 1852 to 2014

Abstract

We present a quantitative description of the N and P flows characterizing the agro-food system metabolism of 33 agricultural regions in France and their time evolution since the middle of the 19th century. The data were interpreted in terms of connection between crop production, livestock breeding, human nutrition and trade of agricultural goods, and were linked to their historical background. Until the early 20th century, the integrated crop and livestock farming model dominated everywhere, and the slow increase in crop production was only possible because of an increase in livestock density. Specialized cash crop farming systems appeared in the central Paris basin only in the first half of the 20th century together with the increase in the use of industrial fertilizers. Only after WWll, under the pressure of strong interventionist policies, did specialization of French territories lead to five types of systems, favoring their openness and integration into the international market, with harmful environmental impacts. The 1980s were marked by a policy shift towards more liberalism, which reinforced specialization. However, greater environmental concern stabilized or decreased nutrient losses, while maintaining largely open biogeochemical cycles.

Modeling and empirical validation of long‐term carbon sequestration in forests (France, 1850–2015)

“…In the late 19th and early 20th centuries, the expansion of forest area was made possible by agricultural intensification, notably the development of fodder crops and abandonment of extensive grazing and other marginal land uses (Erb et al, 2008;Gingrich et al, 2019;Mather & Needle, 1998), and through the development of international agricultural trade promoted by the free trade agreements under Napoléon III (Duby & Walon, 1993). However, new regulations and rules governing the access and use of forests also impacted forest change, as did a more acute perception of forest degradation and the threat that it represents for the French economy (Mather et al, 1999) 1900 1900-1910 1910-1920 1920-1930 1930-1940 1940-1950 1950-1960 1960-1970 1970-1980 1980-1990 1990-2000 2000-2010 MtonC Biomass density Species composition Area Biomass C stocks (Le Noë, Billen, Esculier, & Garnier, 2018;Le Noë, Billen, Mary, et al, 2019). Mechanization based on fossil fuels and the increase of the average farm size promoted rural exodus and a shrink in agricultural land, which concentrated on the best soils, freeing space for forest expansion.…”

Carbon Dioxide Emission and Soil Sequestration for the French Agro-Food System: Present and Prospective Scenarios

“…These prospective scenarios for French regional agro-food systems can be represented in terms of C fluxes with the nutrientaccounting GRAFS model (Billen et al, 2014;Le Noë et al, 2018 (Figure 1). It must be made clear from this figure that only the proportion of net primary production (NPP) (above-and below-ground) that is neither exported nor respired by livestock and humans is brought to the soil as either crop residues or manure; of these only the fraction which is not mineralized can be considered as sequestered in the soil, in the end comprising a very tiny share of NPP.…”

“…Similarly, the production of permanent grassland systems is calculated from the total N input and the current Ymax value for grassland, considering the current rate of symbiotic atmospheric N fixation. The cropland and grassland productions are subsequently translated in terms of C using the coefficients gathered by Le Noë et al (2018. The NPP can be derived from the calculated harvest production applying the approach reported by Bolinder et al (2007).…”

“…Therefore, we used the estimation of SOC trajectories in agricultural soil of French regions from 1852 to 2014 already calculated by Le Noë et al (2019) to initialize the calculation of the future scenarios. Data sources to estimate C inputs to cropland and grassland include the harvested production and number of livestock reported by Agreste (2017) for the 1970-2014 period and by non-digitized official registers (available from Gallica.bnf.fr) from 1852 to 1965, the coefficient of animal excretion rates for current and past periods (Le Noë et al, 2018) for the 39 livestock categories considered, humification rates of fresh C inputs (Justes et al, 2009;Clivot et al, 2017) and the distribution of manure application between cropland and grassland, which has been documented or estimated by Le Noë et al (2018). The mineralization rate of the soil labile organic C is a function of several pedo-climatic parameters: clay content, soil pH, soil carbonate content, air temperature, humidity and the soil C:N ratio (Clivot et al, 2017).…”

“…The second one (A/R/D, for autonomy, reconnection and demitarian diet) assumes a radical change toward organic farming with diversification of crop rotations, reconnection of crop and livestock farming, and reduction of the proportion of animal proteins in the human diet. We coupled the GRAFS approach (Billen et al, 2014;Le Noë et al, 2018) and the AMG model (Saffih-Hdadi and Mary, 2008;Milesi Delaye et al, 2013) to calculate the C dynamic in agricultural soil in the two scenarios, prolonging the trajectory already described by Le Noë et al (2019). We then estimated the C emissions related to energy consumption in agriculture accounting for direct (machinery and heating) and indirect (N and P fertilizer manufacture and feed importation) emissions using the coefficients provided by Doublet (2011) (see also Garnier et al, 2019).…”