Negative spill-over effects of agricultural practices on plant species conservation in nature reserves

Abstract

Nature reserves are one of the most important instruments for biodiversity protection and to limit regional species extinctions. However, these functions can only be fulfilled if environmental influences from the surroundings, such as agrochemical inputs do not negatively affect the protected habitats.Here, we compare the effectiveness of conservation measures under the influence of yield-optimized cultivation in Germany using vegetation analyses of transects from the edge to the core of protected areas at 21 sites. By analysing nitrogen and phosphate deposition, herbicide number and concentration in soil and vegetation as well as Ellenberg indicator values of plant communities as a function of the distance from the field margin at each site, we aimed at assessing the impact of these stressors in different environmental settings.The results indicate strong chemical edge effects and negative influences for plant communities resulting from increased nutrient input and amounts of herbicide residues closer to the edge of the agricultural fields. Concordantly, the number of endangered plants species decreased with increasing proximity to the field edge. The strong influence of yield-optimized cultivation on the edges of nature reserves which decrease with distance show that nature protection needs effective buffer zones surrounding conservation areas, especially if nature reserves are only small and narrow. To prevent spill-over effects the application of fertilizer and herbicides on croplands adjacent to conservation areas has to be reduced. This could be achieved most effectively through organic farming and targeted agricultural subsidies.