Loss in grassland plant diversity linked to landscape-wide land-use intensity rather than landscape structure

Abstract

Grazed semi-natural pastures provide keystone habitats for biodiversity in agricultural landscapes dominated by intensively managed land. However, such pastures are frequently isolated and embedded in intensively managed landscapes, and therefore the species composition of grassland plant communities depend on the structure of the surrounding landscape. In particular, both pollinator abundance and the share of insect-pollinated grassland plants decrease with increasing proportions of arable land in the surrounding landscape [1]. Whereas parallel declines in pollinators and insect-pollinated plants in pastures can be attributed to landscape effects, it is generally not known whether intensive agricultural practices or landscape simplification drives these declines. The main reason for this knowledge gap is the fact that estimating agricultural intensity across entire landscapes has hitherto been much more laborious compared to quantifying landscape structure. Capitalising on recent developments in remote sensing, we are now able to disentangle the effects of land-use intensity and landscape heterogeneity with higher accuracy than before. In 2017, we selected 29 grazed semi-natural pastures embedded in landscapes dominated by arable agriculture in southern Sweden to quantify the relative effects of land-use intensity and landscape structure on grassland plant communities. In total, we recorded 141 species of herbs and grasses. Using arable productivity as a proxy for agricultural land-use intensity, we found that plant species richness in pastures declined significantly with increasing land-use intensity in the surrounding agricultural landscapes. In addition, we found significant changes in plant community composition along our land-use intensity gradient. In contrast, we did not find any effects of increasing structural simplification of the agricultural landscapes surrounding our focal pastures. Our results suggest that grassland plant communities in pastures are primarily affected by increasing land-use intensity in the surrounding agricultural landscapes, rather than by increasing structural simplification of the landscapes.

Reference [1] Clough Y, Ekroos J, Báldi A et al. (2014). Density of insect-pollinated grassland plants decreases with increasing surrounding land-use intensity. Ecology Letters 17, 1168-1177.