Higher Plant Diversity in Organic Ecological Focus Areas

Organic farming has a positive effect on plant diversity in Swiss grassland, but ecological focus areas are needed support plant diversity more broadly.

Agri-environmental schemes such as ecological focus areas and organic farming aim to reduce the impacts of intensive agriculture on the environment and help facilitate biodiversity. To examine the effectiveness of such schemes, Agroscope researchers analysed 1170 grassland areas from the ALL-EMA ‘Agricultural Species and Habitats’ monitoring programme. They assessed the effects of two agri-environmental schemes on plant diversity and indicators for forage production. They compared extensively managed ecological focus areas and organic grassland with conventional and intensively managed grassland, focussing on plant species richness, weed abundance, forage value and nutrient availability. The latter two act as indicators of forage production. The analysis also considered slope and elevation of each grassland site and whether these were managed as meadow or pasture, i.e. used mainly for mowing or grazing.

Organic ecological focus areas have the highest plant diversity

The two agri-environmental schemes had significant positive effects on plant; however, on average, species richness was considerably higher in ecological focus areas (+ 6.6 species10 m²) than in organic grassland (+1.8). The effects of both schemes were additive, with organic ecological focus areas having the highest plant diversity. The positive effects were similarly found in meadows and pastures. However, pastures generally had slightly higher species richness than meadows. As expected, forage value and nutrient indicators were lower in ecological focus areas than in intensively managed, fertilised grassland. Yet, there were fewer weeds in the ecological focus areas than in intensive grasslands. Organic farming had only a marginal impact on the indicators for forage production.

The steeper and higher the plot, the greater the plant diversity.

Some of the positive effects of the two agri-environmental schemes were linked to topography. More elevated and steeper grasslands had greater plant species richness and were more often managed as ecological focus areas and/or in compliance with Swiss organic farming regulations. This covariation between topography and grassland management must be taken into account in future assessments of agri-environmental schemes. The positive additive effect of the two agri-environmental schemes shows that they can contribute to biodiversity conservation in Swiss agricultural landscapes, though to a varying degree. As such, the conservation of biodiversity and associated ecosystem services is a fundamental requirement for ensuring the long-term sustainability of Swiss agriculture.