popular paper; [in Dutch with English summary: ] In Dutch heathlands and inland dune areas terricolous lichens constitute a large part of the botanical biodiversity. In the still existing inland dunes this diversity is largeiy intact. This also holds for smal! areas of drifting sand in heathlands. In heathlands with a continuous, thick organic layer and in flat heathlands without any terrain variation only a few common species remain. In former times such heathlands were relatively rich. The decrease of terricolous lichens Is greatest in moist, wet heathlands, where nearly all species have vanished. The decrease in diversity is caused by altered management and increased air pollution (ammonia and sulphur dioxide). There are signs of effects of global warming. For most of the habitat types, recommendations for management are given. Moist and dry heathlands may be managed by cutting the sod. Grazing, recently introduced to control the grass and shrub growth, has no positive effect and is sometimes even deleterious. Inland dunes, especially their grassy borders, and areas of drifting sand in heathlands ought to be kept untouched.