Farmland bird populations in Europe declined significantly during the last quarter of the 20th century, posing a serious threat to biodiversity. This study assesses whether these declines are linked to differences in agricultural intensity, influenced by political history. Population and range changes were modeled using indices of agricultural intensity. Countries with more intensive agriculture experienced greater population declines and range contractions, especially in the European Union (EU) compared to former communist countries. Cereal yield explained over 30% of the variation in population trends. The results suggest that recent agricultural trends have had measurable negative effects on bird populations across Europe. The introduction of EU agricultural policies into former communist countries aiming to join the EU is predicted to cause significant declines in bird populations. The study found that agricultural intensity, influenced by political systems, is a key factor in bird population declines. EU countries, with higher agricultural intensity due to policies like the Common Agricultural Policy, showed more severe declines than former communist countries. Cereal yield was the most significant predictor of population trends, explaining 31% of the variation. The study also found that geographic distribution changes were strongly related to cereal yield. The results indicate that agricultural intensification has had measurable and widespread negative effects on farmland bird populations, comparable to major threats like deforestation and climate change. The study emphasizes the need for EU agricultural policies to support biodiversity alongside farming. Without such changes, farmland bird populations and other species are expected to continue declining, especially in countries joining the EU in the near future.Farmland bird populations in Europe declined significantly during the last quarter of the 20th century, posing a serious threat to biodiversity. This study assesses whether these declines are linked to differences in agricultural intensity, influenced by political history. Population and range changes were modeled using indices of agricultural intensity. Countries with more intensive agriculture experienced greater population declines and range contractions, especially in the European Union (EU) compared to former communist countries. Cereal yield explained over 30% of the variation in population trends. The results suggest that recent agricultural trends have had measurable negative effects on bird populations across Europe. The introduction of EU agricultural policies into former communist countries aiming to join the EU is predicted to cause significant declines in bird populations. The study found that agricultural intensity, influenced by political systems, is a key factor in bird population declines. EU countries, with higher agricultural intensity due to policies like the Common Agricultural Policy, showed more severe declines than former communist countries. Cereal yield was the most significant predictor of population trends, explaining 31% of the variation. The study also found that geographic distribution changes were strongly related to cereal yield. The results indicate that agricultural intensification has had measurable and widespread negative effects on farmland bird populations, comparable to major threats like deforestation and climate change. The study emphasizes the need for EU agricultural policies to support biodiversity alongside farming. Without such changes, farmland bird populations and other species are expected to continue declining, especially in countries joining the EU in the near future.