To assess the biodiversity consequences of contemporary land-use trends in Northern Europe, where agriculture is being replaced by forestry, we need a better knowledge of the contributions of constituting habitats to biodiversity. Here, we use purposefully collected data from 87 sites to model how agricultural habitats, including semi-natural pastures, sown temporary grassland (leys), cereal crops, and forest habitats comprising both mature production forests and clear-cuts, contribute to landscape-scale diversity of plants, bumblebees and butterflies in boreonemoral Sweden. At the local scale, species richness was highest in semi-natural pastures, intermediate in cereal crops and leys and lowest in forest. In clear-cuts, species richness was similarly high to that in semi-natural pastures. Countryside species-area models show that at a landscape scale, the high local richness in clear-cuts was more than offset by the low species richness encountered in forest. At landscape scale, semi-natural pastures, and in the case of plants also cereal crops, were major contributors of unique species. Leys and semi-natural pastures were both important contributors to bumblebee diversity. The effect of the surrounding landscape composition on local diversity was weak, suggesting that area-based approximations of landscape-scale species richness were reasonable. We conclude that clear-cuts constitute habitats for open-land species but cannot maintain landscape-scale diversity in the face of agricultural abandonment when open land is replaced by even-aged production forests. Maintaining farmland, in particular semi-natural pastures but also cereals and leys, is therefore critical to maintaining the landscape-scale species richness of plants and insects in forestry-dominated areas.