Contrasting contributions of diversified low-input cropping systems and hedgerows to ecosystem services in mixed crop-livestock systems - C-DIVERS

A transition toward sustainable and resilient agricultural systems, which combine biodiversity conservation with enhanced ecosystem services, is necessary. Diversified, low-input cropping systems (i.e., systems designed with a high level of crop diversity in rotation and reduced use of pesticides and nitrogen fertilizers) and hedgerows are identified as potential means of making this transition. However, significant knowledge gaps persist regarding their respective contributions to promoting agroecosystem multifunctionality. The spatial scales—field or landscape—at which the effects of diversified, low-input cropping systems and hedgerows operate, as well as the factors that hinder or facilitate their adoption by farmers, are also insufficiently understood to date.

 In the context of mixed farming systems in Brittany, the objective of the C-DIVERS project was twofold: 

• first, to explore the effects of crop diversity, the use of inputs (pesticides and nitrogen fertilizers) and hedgerows at the field and landscape scales on the agroecosystem multifunctionality; 
• second, to explore the barriers and drivers to the implementation of diversified, low-input cropping systems and hedgerows within farms.

Approaches 

The initial hypotheses of the C-DIVERS project were as follows: 

• Cropping systems with high level of crop diversity in rotation and low levels of chemical inputs, with hedgerows bordering fields, as well as a heterogeneous landscape context (high crop diversity and hedgerow density) combined with low pesticide use (large areas of organic farming) promote high agroecosystem multifunctionality; 
• The barriers and drivers of plant diversification (i.e., the implementation of diversified rotations, the establishment or maintenance of hedgerows) differ depending on the time scale considered and on the socioeconomic and technical determinants behind these barriers and drivers; 
•  The opportunity cost (i.e., a way of assessing the economic barriers and drivers of plant diversification) is, in the long term, unfavorable to hedgerows due to their high maintenance costs.

In order to test these three hypotheses, the following approaches were used: 

• An assessment was conducted of the environmental (seven functions), agronomic (one function), and socioeconomic (two functions) performances underlying the agroecosystem multifunctionality of winter cereal fields with varying levels of crop diversity in rotation and contrasting landscape contexts; 
• A comprehensive survey was carried out based on the results of a prospective external study prior to the C-DIVERS project; the aim of the survey was to identify the socioeconomic and technical determinants acting as barriers and drivers for the adoption of diversified cropping systems and the establishment or maintenance of hedgerows in the short and long term; 
•  An economic assessment  was made of the long-term opportunity costs of establishing or maintaining hedgerows on a farm, according to different valorisation scenarios (it was not possible to make this assessment for the implementation of diversified cropping systems).

Results

The results showed that the levels of crop diversity and the presence of hedgerows, whether at the local or landscape scale, do not promote all the performances expected for the development of multifunctional agroecosystems. However, they highlight that the presence of a hedgerow at the field border promotes specific ecological (pollination) and agronomic (agricultural production) outcomes. Furthermore, the reduction of pesticide use at the local scale could be beneficial for biodiversity conservation. However, the spatial diversity of crops within landscape mosaics appeared to reduce the regulation of crop pests in crops, possibly due to dilution effects.

With regard to socioeconomic and technical determinants, the results of this project showed that, in the short term, farm characteristics (e.g., perceived risks and personal norms expressed by farmers) are decisive for plant diversification, along with market-related costs and benefits and agronomic management considerations. Factors external to the farm, including public policies and the configuration of supply chains, have been demonstrated to exert influence. Conversely, access to technologies and consumer behaviour, often mentioned in the literature, have not been pointed as significant determinants during our survey. Over the long term (15 years), the results showed that factors related to agronomic management outweigh perceived risks and market-related considerations: plant diversification emerges as a strategy that facilitates pest management, reduced dependency on chemical inputs, and enhances livestock feed autonomy. However, the calculation of opportunity costs over a 25-year period for hedgerows showed that no valorisation scenario can fully offset the loss of productive area converted into hedgerows compared to specialized dairy farming. Among the options considered, enrolment in the CAP second pillar agri-environmental scheme (MAEC “Biodiversity”) appeared to be the most profitable in terms of return on investment and opportunity cost..

Participants

INRAE units involved

• UMR BAGAP - Biodiversité, agroécologie et aménagement du paysage
• UMR SAS - Sol, agro et hydrosystème, spatialisation
• UMR SMART - Structures et marchés agricoles, ressources et territoire

Partner

• Institut Agro Rennes-Angers, campus de Rennes