1 Department of Policy Analysis, National Environmental Research Institute, Aarhus University, Aarhus University2 Department of Environmental Science - Emission modeling & enviromental geography, Department of Environmental Science, Science and Technology, Aarhus University3 Department of Environmental Science - Emission modeling & enviromental geography, Department of Environmental Science, Science and Technology, Aarhus University
In Denmark, agriculture occupies 28,000 km² or 65% of the land. As a consequence, habitats for wild species are mainly characterized by small patches, surrounded by intensive agriculture. Due to extensive agricultural management, set-aside land can spatially connect habitats and thus positively affect habitat connectivity, which is of importance to the survival of wild species. In 2008 set-aside schemes were abolished, leading to a considerable re-cultivation of former set-aside land and consequently to a decline in the area of set-aside land from 6% of all agricultural land in 2007 to 3% in 2008. The main argument against regulations of the re-cultivation of set-aside land with the aim to minimize declines in habitat-connectivity was that re-cultivation would primarily occur on highly productive land at a long distance from habitats, while set-aside land located on marginal land, close to natural habitats, would typically not be re-cultivated. I developed an indicator aiming to measure the effect of the reduced area of set-aside land on habitat-connectivity. For a raster-map with a resolution of 25x25 meters, the indicator combines the distance to habitats with the area percentage of set-aside land. The indicator is scaled from 0-100, where 100 indicates the largest positive effect on habitat connectivity, while 0 indicates no effect. Analyses show that the halving of the area of set-aside land has led to 50% reduction of the effect of set-aside land on habitat connectivity. This indicates that re-cultivation was not linked to distances to natural habitats. Analyses also show that if re-cultivation had been regulated with respect to distance to habitats, the reduction of the effect of a halving of the area of set-aside land on habitat-connectivity could have been reduced to only 10%.