The decline of farmland birds in Sweden

Many farmland bird species have declined rapidly throughout Europe during the last 30 years and studies, mainly from the UK, suggest that these declines have been caused by agricultural intensification. However, since the conditions for farming vary considerably across Europe, the underlying causes of the population declines may also vary. The rate of agricultural intensification has been less dramatic since the mid 1970s in Sweden than in south-western Europe. Still, I show that population trends of farmland birds have declined at least as much in Sweden as in England between 1976 and 2001. Separating population trends in three Swedish landscape types with different patterns of agricultural change showed that the declines were most pronounced in the open plains characterised by intensification and in the forest farmland landscapes characterised by extensification or abandonment. Thus, the observed strong decline of farmland birds in Sweden was probably caused by the dual negative effects of intensification in productive regions and abandonment in marginal farmland. Several species displayed great temporal similarities in population trends within regions in Sweden and in comparison to England. These between population similarities may have been caused by large-scale effects of changing agricultural policies, as farmland bird population trend shifts were closely linked to agricultural policy shifts in Sweden and western Europe. However, it is also possible that reduced survival at wintering grounds may have had an additional effect because it was especially species that shared European wintering grounds that displayed the strongest between population synchrony in trends. Several farmland bird populations decreased less or even increased during the set-aside policy period (1987 to 1995) when agricultural became less intensive. However, a repeated census of farmland birds between 1994 and 2004 suggested that a general reduction of farming intensity, e.g. by increasing area of set-aside, leys and cultivated pasture, mainly benefit farmland birds in farmland-dominated landscapes where such land-use is rare, whereas a reduced farming intensity was negative for species richness in forest-dominated landscapes. In contrast, in forest-dominated landscapes farmland bird species seemed to benefit from an increased area of cereal production. My results of landscape–dependent patterns of relationships between farmland bird population changes and changes in land-use highlights the importance of developing new region-specific agri-environmental schemes. The results also suggest that an effective way of changing the present negative trends of farmland birds is a broad change in agricultural policy to reverse the geographical polarisation of farming activities