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

Juan Traba,Manuel B Morales

doi:10.1038/s41598-019-45854-0

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.

Highlights

Farmland is the most important habitat for bird conservation in Europe, harbouring more than 50% of bird species in the European Union (EU) and 55% of European bird species listed in the IUCN Red List[1,2]
The change rate of the little bustard population index during the period 2002–2017 was strongly correlated with the change rate of fallow surface over the same period
When the change rate in the Spanish CBI was considered, the association with fallow trend was even more significant. These results indicate a nation-wide relationship between the temporal trend in the amount of a particular habitat type linked to extensive agriculture, that is fallow land, and the population trends of farmland birds

Summary

Introduction

Farmland is the most important habitat for bird conservation in Europe, harbouring more than 50% of bird species in the European Union (EU) and 55% of European bird species listed in the IUCN Red List[1,2]. Yield and revenue maximization has led to an increase of inputs and agrarian operations (e.g. soil disruption though ploughing) that have severely reduced local biodiversity[7,8], including arable plants, invertebrates and birds[9] This process has led to the loss of semi natural elements of fields and their close neighbourhood (e.g. field margins), further contributing to biodiversity declines[7,8]. In spite of its relevance for wildlife and of more than two decades of EU’s agri-environmental measures aiming at preserving farmland biodiversity, the surface of fallow land has significantly decreased in Spain during the same period (Fig. 1), implying a loss of 1.1 million ha. More than 80% of steppe bird species show an unfavourable conservation status in Europe[1]

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