The precautionary principle is more and more incorporated into national law and decision-making on natural resource management and biodiversity conservation. In the coherent European network of protected areas Natura 2000, the precautionary principle finds expression in the obligation to provide favourable conditions for the long-term survival of species and habitats, especially of the priority ones listed in the annexes of the Habitats Directive and the Birds Directive. After describing principles, structure, implementation and procedures of this rather new instrument for nature conservation using the example of one of the various Natura 2000 areas in Saxony (Germany), opportunities and problems for biodiversity conservation are outlined with particular regard for the situation in an agricultural landscape. Special attention is given to the following questions: requirements of and actual threats to the target species (the butterfly