Does the conservation of threatened species limit crop production? On farm cultivation of Marsilea quadrifolia in rice fields

The maintenance of a favorable conservation status of species listed in the Habitat Directive 92/43/EEC, the main European legal conservation framework, is mandatory. However, it is constrained in agroecosystems, where the needs of stakeholders and adequate agricultural management are necessary to guarantee the coexistence between nature conservation and agricultural production. Marsilea quadrifolia L. is an aquatic pteridophyte of wetlands, growing both in natural habitats and in seminatural habitats such as agroecosystems. In the past, it was considered a weed of rice fields but is currently threatened due to changes in agrotechniques. Reintroduction attempts of M. quadrifolia in its natural growing site were only partially successful, but the species can grow in organic rice farms and low-input systems where herbicide application is null or reduced. An on farm cultivation of M. quadrifolia was conducted in an organic rice field for three years (2021–2023) to assess whether the species can be maintained in rice fields through sustainable practices without reducing crop yield. The results are promising but highlighted some constraints such as the need to motivate farmers with training and participatory approach to land sharing for contributing to a more sustainable and biodiversity-friendly farming. Agro-environmental compensations from the EU Rural Development Plan must be further developed to promote species conservation in agroecosystems.