The decline of farmland birds in Spain is strongly associated to the loss of fallowland

Abstract

Farmland bird populations have strongly declined across Europe over the last decades due to agriculture intensification, despite successive reforms of EU’s Common Agricultural Policy (CAP). In parallel, CAP has led to a reduction of fallow land, a critical habitat for biodiversity in agroecosystems. Fallow land in Spain, a country harboring the largest European populations of many endangered farmland birds, has decreased by 1.1 million ha in 15 years. The significant positive relationship between yearly change rates of the Spanish Farmland and Cereal Bird Indices (FBI and CBI) and fallow surface change highlights the adequacy of fallow land cover as an indicator of the state of farmland bird communities at country level. Moreover, the strong and positive association between the reduction in abundance of the fallow specialist little bustard and fallow surface suggests a potential causal link between these two factors. These results highlight the need for a new CAP that guarantees the maintenance of fallow land in European agroecosystems if farmland bird populations are to be conserved.

Drivers of population change in common farmland birds in Germany

“…Negative effects of increasing maize cultivation on farmland bird diversity in Germany are also identified by Sauerbrei et al (2014). The loss of fallow land is likely to affect farmland bird species via the loss of habitat for breeding birds, as well as the loss of valuable food sources for granivorous sedentary birds and partial migrants during winter (Henderson and Evans 2000, Sudfeldt et al 2009, Traba and Morales 2019. Moreover, insect abundance is likely to be much higher on fallow land than on cultivated field blocks (Traba and Morales 2019), e.g.…”

“…because it is not treated with insecticides and accordingly the loss of fallow land may also reduce food availability for insectivorous species. Studies from other European countries also identified fallow land as one of the most important habitats in agricultural landscapes, particularly for farmland birds (Traba and Morales 2019).…”

“…Also, ground-breeding farmland birds nesting on arable fields show the strongest declines among the species group in several studies (Heldbjerg et al 2018, Jerrentrup et al 2017 and generally species associated with arable land seem to suffer stronger declines than species associated with grassland and pasture (Reif andHanzelka 2016, Heldbjerg et al 2018). Additionally, changes in the availability of fallow land, largely determined by EU subsidised set-aside, have been identified to have strong effects on farmland bird populations Evans 2000, Traba andMorales 2019). A comprehensive assessment of factors influencing farmland bird populations in Germany at the national scale is however currently missing.…”

Changing the fallow paradigm: A win–win strategy for the post‐2020 Common Agricultural Policy to halt farmland bird declines

“…It would be necessary to define suitable ecological indicators reflecting the improvement in biodiversity or ecosystem services arising from the environmental practices put in place. The effects of managements should be evaluated on particular species of conservation concern and using global measures, such as the farmland bird index, able to effectively document the health state and trends of bird communities (Traba & Morales, ). It would be equally necessary to set efficient control measures to ensure compliance on conditionality, as these are basic statutory requirements.…”

“…Results from the Pan‐European Common Bird Monitoring Scheme for 39 common farmland birds monitored between 1980 and 2015 show that this bird group is undergoing the steepest population declines, with a regressive trend of −55% (PECBM: http://www.ebcc.info/european-wild-bird-indicators-2017-update/). The loss of landscape heterogeneity and the disappearance of semi‐natural vegetation types, such as field margins and fallow land, are key drivers of farmland bird decline (Benton, Vickery, & Wilson, ; Traba & Morales, ).…”