Range contractions of farmland and steppe birds over two decades in relation to agricultural management in Spain

Farmland birds have experienced severe declines across Europe and other world regions because of agricultural intensification. We assessed changes in the breeding-season distributions of farmland birds in Spain between 1998 and 2018, evaluating their responses to agricultural management at the scale of agricultural counties. Using generalized linear mixed models (GLMMs), we quantified distribution shifts and species richness changes for three bird guilds classified by their dependence on steppe-like farmland: strict steppe birds, farmland birds, and extended-farmland birds.

We found consistent declines over this 20-year period in species richness across all three guilds and widespread contractions in species' distribution ranges. Total utilized agricultural area and agricultural yields exerted generalized negative effects, indicating that the expansion of intensive farming drives pervasive habitat loss for multiple species. In contrast, herbaceous crops had positive effects on the distribution of many species, highlighting the importance of these open habitats in supporting diverse bird communities.

As expected, steppe specialists—given their strict ecological requirements—showed the most pronounced range declines. However, generalist farmland birds also exhibited substantial contractions, revealing that even less specialized species are highly vulnerable to current levels of land-use intensification. These findings underscore the urgent need to reconcile agricultural production with biodiversity conservation. Policies promoting sustainable land management—such as those outlined in the EU Regulation 2024/1991 on nature restoration (i.e. reestablishment of high diversity landscape features like fallows, rotational grazing or mowing, integrated pest management and/or organic farming leading to pesticide and fertiliser reduction)—will be critical to halting further biodiversity loss in agricultural landscapes.