A map-based method for exploring responses to different levels of grazing pressure at the landscape scale

At the beginning of the last century European landscapes were a mosaic of open and forested habitats formed by centuries of human use. During the 20th century, however, this mosaic was altered. Changes in grazing pressure from domestic animals have been suggested as one of the drivers of these alterations. This paper presents a methodology developed to calculate an index of potential grazing pressure change at the landscape level. Information about location, type and number of grazing animals is used to produce detailed Geographical Information System (GIS) maps of potential grazing pressure change. Spatial information from these maps can then be geographically linked to vegetation maps such that the effect of grazing pressure changes on vegetation can be statistically analyzed. This methodology was applied to a Norwegian mountain landscape to test if decreased grazing pressure by domestic animals leads to woodland establishment in open habitats. Canonical Correspondence Analyzes (CCA) were performed and the results showed significant effects. Decreased grazing pressure increased the probability of woodland establishment in heathlands. The methodology described in this paper might be a useful tool in planning strategies both for conservation efforts and sustainable resource use.