Edge effect
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In ecology, an edge effect describes the influence of the surrounding landscape on biotope islands . It occurs at the edges in the fringing biotope of the actual biotope.
Edge effects occur in several ways: Intensive land use (agriculture) affects protected biotope islands. B. pesticides or fertilizers are blown in and washed in. Therefore the value of very small or narrow biotope islands is sometimes greatly reduced in practice.
Another type of marginal effect comes from the species inventory of the agricultural landscape, which (in contrast to the oceanic species between real islands) can also colonize the biotope islands. Nature conservation tries to counteract marginal effects by establishing buffer zones. In the biotope network, they must be taken into account in order to be able to assess the effectiveness of biotope islands and corridors.
Edge effects can be effective on a larger scale than is often intuitively assumed. Investigations in New Zealand have shown that even small bugs living on the ground still had detectable effects on fauna at a distance of one kilometer from the border of a protected area. Naturally, stronger effects are to be expected with species that regularly cross the protected area boundaries, e.g. B. Carnivores.
In addition to the negative, positive marginal effects have also actually been proven: There may be an enrichment of adjacent habitats with species. The BUND therefore demands that the field margins be preserved in our "cleared cultural landscape". Due to the edge effect, a lively exchange of species would take place here. Set field margins u. a. also represent retreat areas in which many animal species seek protection in the event of disturbances due to cultivation of fields or grassland cultivation of the adjacent areas. In rivers in Germany, attempts are being made to make use of the species exchange through the edge effect under the name "radiation effect", although reliable empirical evidence of its effectiveness is still pending.