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The agriculture, forestry and other land use sector are responsible for 24% (10–12 Pg CO2e per year) of anthropogenic greenhouse gas (GHG) emissions worldwide, with concomitant opportunities for mitigation. A scientific panel used deliberative methods to identify ten technical measures comprising 26 sub-measures to reduce GHG emissions from agriculture in France. Their abatement potential and cost are compared. The proposed measures concern nitrogen (N) management, management practices that increase carbon stocks in soils and biomass, livestock diets, and energy production and consumption on farms. Results show that the total abatement potential can be divided into three parts. One third of the cumulated abatement potential corresponds to sub-measures that can be implemented at a negative technical cost. These sub-measures focus on increased efficiency in input use including N fertilisers, animal feed and energy. The second third are sub-measures with moderate cost (<€25 per metric Mg of avoided CO2e). These sub-measures require specific investments or changes to cropping systems, but additional costs or lower incomes are partially compensated for by a reduction in other costs or by the production of other marketable products. The remaining third are high-cost sub-measures (>€25 per metric Mg of avoided CO2e). These require investment with no direct financial return, the purchase of particular inputs, dedicated labour time or involve production losses. Assuming additivity, the cumulated abatement is 32.3 Tg CO2e per year in 2030, but only 10 Tg (i.e. 10% of current agricultural emissions) when calculated under current inventory rules. This study confirms that a significant abatement potential exists in the agricultural sector, with two thirds of this potential at low or even negative cost. This is likely to be an underestimated as it is based on a status quo of the current agricultural system. Results also emphasise the need to upgrade inventory rules so that efforts to reduce emissions can be accounted for

Les auteurs retracent en introduction l'évolution qui a progressivement conduit les chercheurs du département Systèmes agraires et développement de l'INRA, partis de diverses interrogations sur les conditions et les modalités du développement agricole, à s'intéresser de plus en plus aux pratiques des agriculteurs, en même temps qu'ils adoptaient une démarche systémique. La première partie de cet article fournit les repères conceptuels et méthodologiques nécessaires à l'étude analytique des pratiques agricoles, étude que les auteurs resituent dans un cadre plus large, en s'appuyant sur une modélisation simple du fonctionnement de l'exploitation agricole. Ils proposent ensuite, pour l'étude des pratiques, une démarche articulée en trois volets complémentaires, centrés respectivement sur la modalité, l'efficacité et l'opportunité des pratiques. Diverses considérations relatives à l'étude des pratiques agricoles dans le temps et dans l'espace terminent cette présentation. Dans la seconde partie, consacrée à l'étude des combinaisons de pratiques mises en œuvre par les agriculteurs, les principes exposés plus haut sont utilisés pour réinterpréter diverses démarches qui visent à évaluer l'efficacité technique de ces combinaisons, puis pour présenter le concept de système de pratiques et montrer son intérêt typologique. Les auteurs soulignent la complémentarité de ces diverses approches et leur intérêt opérationnel pour le développement, et plus spécialement pour le conseil technico-économique aux agriculteurs.

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Landscape dynamics increasingly challenge agronomists to explain how and why agricultural landscapes are designed and managed by farmers. Nevertheless, agronomy is rarely included in the wide range of disciplines involved in landscape research. In this paper, we describe how landscape agronomy can help explain the relationship between farming systems and agricultural landscape dynamics. For this, we propose a conceptual model of agricultural landscape dynamics (ALaDyn) that illustrates the specific contribution of agronomy to landscape research. This model describes the relationship between three elements: farming practices, landscape patterns and natural resources. It can stimulate agronomists to deal with research issues in agricultural landscape dynamics and enhance the interdisciplinary integration of farming systems in wider landscape research. On these premises, we discuss the main research issues that will benefit from an active involvement of agronomy, to understand, but also to assess landscape dynamics and to design relevant decision support systems.

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