Loss of biological diversity mostly results direct and indirectly from habitat destruction and fragmentation. Habitat fragmentation implies that the remaining habitat is increasingly scattered over small and isolated habitat patches. Consequences of habitat fragmentation are (i) reduction of suitable habitat and subsequent decrease in population size; (ii) decrease in gene-flow between spatially or functionally isolated populations; and (iii) deterioration of habitat quality and increased impact of edge effects due to changes in patch size and shape. These processes may lead to a reduction in fitness and loss of genetic diversity and - if such effects act synergistically - may cause species extinction at local, regional, or even global level. Population ecological and genetic characteristics of arthropod populations in habitat patches are studied in relation to their potential use as bio-indicator and early warning system in conservation biology. Additionally, variation in assemblage composition and structure can be used as a tool to assess the natural value of particular habitat types and to evaluate the impact of different types of management techniques such as mowing, grazing or hydrological management. Research is mainly conducted in Flanders (beaches, salt marshes, coastal and inland dunes, wetlands) and in mountain rainforests from the Taita Hills (South-East Kenia).