Determining the extent of land-use change that can be tolerated by wildlife communities is crucial for effective conservation management. Recent landscape-scale studies have found increasing evidence for critical threshold levels of forest cover, after which the existing communities of plants and animals are negatively impacted. This is particularly true when plantation forests replace native vegetation. We used large datasets (Irish Bird Atlas and Forest Inventory) and a novel method, Latent Dirichlet Allocation, to model changes in bird community composition along the existing forest cover gradient in Ireland and evaluated the degree of spatial overlap between birds of conservation concern and areas of recent afforestation. We found that as we approach 35% forest cover in the landscape one community of birds replaces another as the dominant community. The highest levels of recent afforestation overlapped with areas of high numbers of birds of conservation concern. This means that habitat change is occurring in the areas with highest bird diversity. This finding has policy implications for the design of land-use policies, such as those on afforestation and forest expansion. It can be used to ensure plantation forests are planted in the right place to minimise impact on biodiversity values; that is, practitioners need to consider the level of forest already present in an area as well as the level of biodiversity in the area when selecting areas for afforestation.