The consequences of agricultural specialization

One of the main pitfalls of the disconnect between crops and livestock is nitrogen management, even though nitrogen is an essential element for plant growth and development. When agriculture and livestock farming were combined, nitrogen inputs for crops were mainly provided by livestock manure (dung, slurry), which is rich in this element.

With the specialization of agriculture, farms and regions specializing in field crops suffer from a nitrogen deficit, which is generally offset by massive purchases of synthetic fertilizers. On the contrary, farms and regions specializing in livestock farming are characterized by an excess of nitrogen from livestock manure, which is present in very large quantities. This surplus is such that some of the nitrogen is lost to the environment and causes significant pollution, such as green algae in Brittany.

Furthermore, the issue of nitrogen also extends to that of protein in animal feed, as the main component of protein is nitrogen. Farms and regions specializing in livestock farming do not produce enough feed to meet the animals' needs, so they have to buy it. This is particularly the case with soybean meal, which is mainly imported from Brazil, which can lead to the phenomenon of imported deforestation.

Exchanges between farms, or how to cooperate for more sustainable agriculture

One solution that is increasingly being put forward to address this imbalance in nitrogen management is to promote links between crop and livestock farming, not within individual farms, but between farms in the same region: arable farms could sell protein-rich feed to livestock farms, which could use these crops to feed their animals.

In return, livestock farms could export manure to crop farms that lack nitrogen to fertilize their crops. This example of a circular economy seems to have only benefits on paper, but what about in reality? Our article shows that exchanges between farms are not always so virtuous, due to the emergence of rebound effects.

Rebound effect: what are we talking about?

A rebound effect occurs when efficiency gains that make it possible to obtain the same product or service at a lower cost lead to a “rebound” increase in the consumption of that good or service, which ultimately cancels out some of the environmental benefits initially achieved. In some extreme cases, the rebound effect can lead to a “backfire” effect when the increase in consumption completely offsets the initial benefits.

William Stanley Jevons (1835-1882), British economist, author of The Coal Question (1865) and theorist of the rebound effect.

The rebound effect was first described as the “Jevons paradox” during the industrial revolution and has since been observed frequently in many energy-related issues. A typical example of the rebound effect occurs when people use their cars more often because they consume less fuel, or when they heat their homes more after installing an efficient heating system.

In both examples, the energy savings, and therefore the reduction in pollution initially expected, are offset by increased consumption. In agriculture, the rebound effect has been little documented, and even less so when efficiency gains result from exchanges between farms, as is the case in our study.

Rebound effects and “backfires” in certain cooperating farms

Through our study, we wanted to understand whether the exchange of effluents or feed between farms could give rise to a rebound effect and thus limit the environmental benefits of such cooperation.

To do this, we conducted a survey of 18 farms in the Zaragoza region of Spain: half of the farms specialize in arable farming and the other half in livestock farming. Among these 18 farms, some exchange effluents or feed while others do not. We then calculated two indicators of the nitrogen rebound effect: one for arable farms to find out whether exchanges lead to lower consumption of synthetic fertilizers, and the other for livestock farms to find out whether exchanges limit the risk of nitrogen leaching into the environment.

Analysis of the results shows that only one in four arable farms uses less synthetic fertilizer thanks to effluent exchange. The other three experience not a rebound effect, but a “backfire” effect. They do use effluent, but also continue to apply synthetic fertilizers. Perhaps farmers fear that effluent alone will not provide enough nitrogen for their crops? They would then continue to use synthetic fertilizers to ensure good yields.

Among the livestock farms studied, two of the five farms that exchange manure have lower nitrogen losses than those that do not. The other three farms experience a rebound effect (one of them) or even a “backfire” effect (two of them). How can this be explained?

By exporting manure to other farms, these farms have freed themselves from a regulatory constraint that limits the number of animals per hectare in order to manage their manure properly. Without this constraint, they can raise more animals, thereby increasing their feed purchases, which increases the risk of nitrogen losses.

Through our study, we show that it is important to question the potential rebound effects in agriculture, as this is a subject that is too often overlooked when promoting new practices that are a priori beneficial to the environment. Indeed, in our study, rebound effects sometimes appeared when arable farming and livestock farming were reconnected through exchanges between farms.

In other words, cooperation between specialized farms does not necessarily lead to nitrogen savings and therefore environmental benefits. Nevertheless, this cooperation remains a promising avenue for reducing the negative impacts of agriculture while reaping the benefits of agricultural specialization, provided that rebound effects are avoided.

To this end, more ambitious measures on herd size or nitrogen management should be put in place to avoid intensifying agricultural production. Denmark has recently taken this direction by offering farmers the equivalent of $100 per ton to reduce greenhouse gas emissions from nitrogen fertilization.

Julia Jouan, Lecturer and researcher in agricultural economics, UniLaSalle; Matthieu Carof, Lecturer and researcher in agronomy, Institut Agro Rennes-Angers; Olivier Godinot, Senior lecturer in agronomy, and Thomas Nesme, Professor of agronomy at Bordeaux Sciences Agro, Inrae

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