Assessment of determinants of high nature value (HNV) farmland at plot scale in Western Pyrenees

The concept of High Nature Value (HNV) farming hinges on the causality between agroecosystems with low intensity of management and the corresponding environmental outcomes, including high levels of biodiversity and the presence of semi-natural habitats. Although European strategies for rural development and biodiversity conservation have long recognized the importance of HNV farmlands, many of those areas are currently threatened by intensification and land abandonment. A variety of approaches have been developed for identifying HNV areas and measuring changes in their distribution and extent at landscape scales. In contrast, quantitative approaches for evaluating differences in HNV among the most basic units of management (farms and farm plots) are scarce and almost exclusively based on biodiversity indicators. This gap limits our ability to derive existing gradients of HNV at fine scale and the underlying cause conducive to HNV. Hence, we implemented an index to capture multiple facets of HNV based on expert knowledge criteria and field surveys performed at the finest scale of management (plot). First, we computed this index for hundreds of grasslands located across the Western Pyrenees. Then, we analysed the relationship between the nature value of plots and environmental, management and socio-economic variables. Our results evidence a gradient between low diversity and intensively used agricultural plots and HNV grasslands in the Western Pyrenees. Highest nature values were significantly related to the occurrence of plots in meadows located in steep areas within the Natura 2000 network, whereas lowest values were related to recently opened areas and the number of treatments per year. Importantly, this index, which could be adapted to other farming areas, provides quantitative information to support the implementation of result-based schemes, including eco-schemes and agri-environment-climate interventions of the new CAP (2023-2027).