The dunes of Schiermonnikoog are highly varied. The long, wet areas in particular are a true treasure trove of plants. During recent years, these dune valleys have become increasingly overgrown with birch and creeping willow. This process is primarily caused by enrichment of the soil by fertilizers and reduction of the rabbit population by a variety of diseases. To preserve rare plants, the Nature Conservation Society takes active measures, such as sod cutting, mowing and grazing.