Evidence of a rebound effect in agriculture: Crop-livestock reconnection beyond the farm gate does not always lead to more sustainable nitrogen management

Reconnecting crop and livestock production beyond the farm gate by exchanging raw materials (e.g., feed, manure) between farms is seen as a promising solution for improving the environmental performance of farms, since it should reduce the use of imported nitrogen (N) inputs. However, such a circular economy does not necessarily lead to a positive outcome, since cooperating farms might simultaneously intensify their production, which could cancel out the benefits of reconnecting crops and livestock: this is known as a rebound effect. The aim of our study was to identify and analyze a potential rebound effect due to reconnection of crop and livestock farms. We collected data on 18 case-study farms in a small territory in Spain. We then calculated two indicators of the N rebound effect: one based on potential savings of inorganic N fertilizer for cooperating crop farms and another based on potential savings of N losses to the environment for cooperating livestock farms. On cooperating crop farms, importing manure did not lead to replacement of inorganic N fertilizer and could lead more inorganic N fertilizer being used. Thus, their mean N rebound effect was 520 %, which constituted a backfire effect. This mean, however, covered large differences among farms. On cooperating dairy farms, exporting manure resulted in a mean negative rebound effect of −17 %, meaning that they achieved higher savings in the N balance than expected compared to non-cooperating dairy farms. Our main contribution is to show that there may be a rebound effect when reconnecting crop and livestock production beyond the farm gate due to the intensification of farms. The indicators of the N rebound effect developed can thus help identify situations that improve or degrade environmental performance. They should be used to complement existing indicators, such as N-use efficiency and the N balance, to design efficient farming systems while avoiding a rebound effect. • Reconnecting crops and livestock between farms is promising, but a rebound effect may offset the environmental gains. • The study aimed to quantify a potential nitrogen (N) rebound effect due to reconnection between crop and livestock farms. • A rebound effect appeared for three cooperating crop farms receiving manure without reducing use of inorganic fertilizers. • A rebound effect was also observed for three cooperating dairy farms that intensified their milk production. • The rebound effect indicator complements N-use efficiency and N balance for farm N performance evaluation.