Agricultural intensification impacts native, but not non-native, plant richness and species-area relationships across south-eastern Australia

Agriculture has led to global biodiversity declines, necessitating conservation within working farms to retain native species and ecological function. Designing effective on-farm conservation strategies requires understanding how native and non-native plant species respond to agricultural intensification. Management efforts can then be directed towards habitats on farms that offer higher biodiversity returns. Here, we assessed native and non-native plant responses to agricultural intensification using species richness and species-area relationships (SARs) across farms in three regions of south-eastern Australia. We used quantitative vegetation attributes to class habitats on farms into 16 condition states along an agricultural intensification gradient within three ecosystem types (woodlands, derived grasslands, native grasslands). We then recorded plant species richness in nested quadrats (0.5 m 2 –500 m 2 ) at 811 sites across 48 farms. Native plant richness and native SAR parameters (slope: species accumulation rate; intercept: richness at 1 m 2 ) declined with increasing agricultural intensification. By contrast, richness and SAR parameters of non-native species showed little change across the intensification gradient. There were minimal regional differences in the trends between SARs and intensification for either native or non-native plants. Our findings suggest that reductions in habitat size (e.g., by converting an area to crops) are likely to result in larger losses of native plant diversity in less intensively managed farmland, independent of ecosystem or location. These outcomes can be used to inform mitigation practices to protect biodiversity on farmland.