Poitevin Marshland, agricultural landscapes that have remained stable since 2010 and bird communities shaped by water levels and farming practices - DYNAMIC

For several decades, changes in agriculture across Europe – including both intensification and abandonment depending on the geographical context – have been partly responsible for a significant shift in biodiversity, with bird populations in agricultural environments being particularly affected (an overall loss of 48% of European populations over 30 years). 

Spatial scales, ranging from the farm to the landscape, are recognised as being particularly important to consider in the context of agroecological transitions and the reconciliation of agricultural production with biodiversity conservation. However, few studies have examined the joint evolution of agricultural systems and biodiversity at these scales. 

 

Approaches

Dynamic explores, within the agroecosystems of the Marais Poitevin, how bird communities have evolved over more than a decade at three sites, particularly in relation to changes in agricultural systems. These sites, each covering approximately 1,000 ha, feature varying proportions of grassland and managed crops (100% grassland, 50-50 grassland–crops, and 100% crops). They have already been monitored during two periods (2010–2012 and 2022–2023) for their bird populations and the cropping and livestock systems implemented by around thirty farmers.

The DYNAMIC project aimed to:

•    Supplement the ecological data required to analyse variations in bird communities, particularly in relation to changes in water levels;
• Update the mapping of crop rotations and semi-natural features;
•  Propose a method for analysing the joint variations in landscape, agricultural and bird community components. 

Results

Analysis of crop rotation data and the semi-natural components of the landscape reveals a high degree of stability in the agricultural landscapes across the three monitored sites between the two periods. Given the soil and climate constraints at the various sites and existing regulations, grasslands exhibit a high degree of stability (due to the waterlogged nature of the soils). Conversely, climatic constraints and soil conditions limit the scope for crop diversification within the cultivated area. Crop rotations remain dominated by durum wheat, sunflowers and maize, with a high degree of uniformity in the practices applied across the different crops.

Specific studies were carried out to model water levels in the floodplains of the three sites for the two periods under study. Using satellite imagery, a digital elevation model and direct field surveys, it was possible to identify the flooded areas and the water levels in the plots for the year 2025. Climate changes (distribution and intensity of rainfall) do not allow the DTM to be extrapolated for previous years.

For both periods analysed, bird communities show a high degree of structure across the three study sites. The ‘grassland’ site features communities dominated by waterbirds and species specialised in grassland habitats. The ‘mixed’ site hosts communities specialising in open agricultural habitats and grassland species, with a heterogeneous internal structure. The ‘crops’ site is predominantly home to species specialising in open agricultural habitats. 

Participants

INRAE units involved

• UE Saint-Laurent de la Prée - Unité expérimentale de Saint-Laurent-de-la-Prée
• UMR SADAPT - Sciences pour l'action et le développement : activités, produits, territoires 
• UMR Dynafor - Dynamiques et écologie des paysages agriforestiers

Partnerships

• UMR CESCO - Centre d’écologie et des sciences de la conservation - OFB / Muséum national d’Histoire naturelle (MNHN)
• Etablissement Public du Marais Poitevin
• Chambre d’agriculture de Vendée