Agri-environmental schemes: Conserving and improving habitat quality in Mediterranean farmland ecosystems

Abstract

[Background/Question/Methods]: Farmland ecosystems are severely threatened due to agricultural intensification which contributes to a significant loss of biodiversity. Farmland and steppe birds are particularly vulnerable species linked to these ecosystems and are the most threatened bird group, with 83% of the species subject to unfavourable status. Agri-environmental schemes (AES) are today considered the most important instruments to counteract the negative effects of intensive agriculture. However, their effectiveness seems to be highly variable between studies, localities and organism groups, making it difficult to assess their benefits. Most of these studies have been carried out at mid- or high latitudes of the northern hemisphere, and very few in the Mediterranean region. Are AES effective against agricultural intensification in central Spain? Do AES improve habitat quality? How do AES influence steppe birds? Since 2001, an AES program is being carried out in a Special Protection Area for birds (SPA 139) in central Spain. The great bustard was used as indicator species to study bird responses to AES. The great bustard Otis tarda L. is a large steppe bird which has suffered marked declines during the last decades and today is considered Globally Threatened. Males and females aggregate at leks for mating. Bustards were counted during winter and spring (2001-2010) in five experimental leks (with AES) and three control leks (without AES). We computed an index of agricultural intensification as percentage of surface engaged to cereal crop and ploughed land. Availability of plants and arthropods was estimated in 328 cereal fields, legumes, stubbles, ploughed fields, fallows, and borders between cultivated fields in areas with and without AES. [Results/Conclusions]: The abundance of bustards increased at experimental leks in winter and spring, whereas control leks did not show significant changes. Fallows, borders and legume fields had significantly more diversity, abundance and biomass of arthropod and plants. The agricultural intensification index was significantly reduced in areas with AES. These areas also showed higher food availability than areas without AES. Agri-environment schemes counteracted the negative impact of agricultural intensification. In this context, it improved habitat quality by providing increased food availability. AES may thus contribute to preserve threatened steppe-birds living in Mediterranean dryland farmland areas.