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Friday, 28 December 2012

Central-European example for AES set-aside fields, as small pieces of heaven for farmland birds


Farmland biodiversity has collapsed over the last decades in much of Europe, clearly illustrated by the decline of common farmland birds, and attributed mostly to the intensification of land use and farmland management, driven by the demand for more agricultural production. This resulted in serious overproduction in the European Union (EU) in the 1980s. To decrease overproduction, set-aside was introduced, first as voluntary (1988), then as mandatory (1992) agro-economic measure of the Common Agricultural Policy (CAP) of the old member states of the EU (EU15) taking whole fields out of production. By 1993/1994 approximately 6% of all agricultural lands, i.e. around 6.4 million ha, was set-aside in the EU15 countries. Later, a maximum of 10% of arable land was managed annually as set-aside. Several countries introduced volunteer fallowing under agri-environment schemes (AESs) as well, and also in Hungary during the EU accession in 2002.

Although mandatory set-aside fields were established to control production, they were proven to be valuable habitats for farmland birds, derived mostly from the lack of drastic disturbances during management, no arable crop production and any chemical use.

The pressure from the agricultural market and the increased demand for land for bioenergy crop plantations finally led to the abolition of compulsory set-aside in 2008 in the EU. This sudden continent-wide land-use change was predicted to result in wide scale agricultural intensification and supposed to adversely affect farmland biodiversity. Unfortunately, no EU-wide impact assessment or mitigation for set-aside loss was introduced.

However, the abolition of set-asides caused large scale land use change across the EU, the evidence to predict the consequences and develop indicators is geographically restricted, only few evidence of this exists from Central or Eastern Europe. Although these countries have large areas under agricultural management and still harbour valuable ecosystems with rich and dense farmland bird assemblages owned to the current generally more extensive agricultural management. Moreover, the relationship between population declines and agricultural change has been driven by different mechanisms in Central and Eastern Europe, therefore AESs e.g. set-aside management should not be directly extrapolated from Western Europe.

In our study we addressed the question of how could agri-environment scheme set-aside fields be used to mitigate the loss of market regulated fallows to conserve farmland birds. We aimed to assess the effectiveness of set-aside for birds by comparing set-aside and winter cereal fields, and semi-natural grasslands and to examine how bird species richness and abundance change over the course of set-aside age (1-3 years old), related to vegetation changes.

The study sites were located in the Heves Environmentally Sensitive Area (ESA), Eastern Hungary. Creation of set-aside fields is part of the arable farming action plan for the protection of great bustard (Otis tarda). Fields have to be managed by regular crop rotation with set-aside 20–25% of all the farmer’s fields. Fields can be taken out of production for 1–3 years, sown by a three component seed mixture after the last harvest, containing two grass and one leguminous plant species. Vegetation is mown once per year from 15th June.

Six replicates of one, two and three years old set-aside fields were chosen, each with an adjacent winter cereal field pair, and six additional semi-natural grasslands were also assigned. The relative abundance of birds was assessed two times during April and May in 2008.

We proved the effectiveness of set-aside management both in term of higher species richness and abundance of birds compared to the adjacent winter cereal fields. A wide range of insectivorous and granivorous species favoured set-aside fields at a comparable level to semi-natural grasslands. Two and especially three years old set-aside fields seemed to be beneficial also for SPEC (Species of European Conservation Concern) species.

Our study identified the important role of local spatial scale, i.e. vegetation heterogeneity reflects food availability. We found that abundance of several insect taxa increases significantly even in the one-year-old set-aside fields (Kovács-Hostyánszki et al., 2011), however, the high and dense vegetation made at the one-year-old set-aside fields still less suitable for birds. However, in the second and especially in the third year the considerably lower sward height and the mosaic pattern of bare ground patches with increased openness of vegetation resulted in better foraging conditions in the invertebrate rich set-aside fields, resulting in increased species richness and abundance of birds.

We argue that beneficial management of these set-aside fields is crucial for farmland birds, requiring annual mowing to maintain heterogeneous vegetation with patches of both short and taller plants. Besides, the relatively dry Hungarian summers, the high weed seed species pool in the soil and the extensive arable management might result in grasses less likely to dominate the set-aside sward after 2–3 years, which explains their preference over the first year set-asides, compared to Western European examples.

Our findings from a less studied, but diverse region of Europe provide some novel insights into the effects of set-aside management and show a promising way to counteract the negative effects on farmland birds: well-designed AESs have the potential to mitigate the loss of market regulated set-asides.

References:

Kovács-Hostyánszki, A., Báldi A. (2012) Set-aside fields in agri-environment schemes can replace the market-driven abolishment of fallows. Biol. Conserv. 152, 196–203.

Kovács-Hostyánszki, A., Kőrösi, A., Orci, K.M., Batáry, P., Báldi, A. (2011) Set-aside promotes insect and plant diversity in a central European country. Agr. Ecosyst. Environ. 141, 296–301.

Communicated by Kovács-Hostyánszki, Anikó - Centre of Ecological Research, Hungarian Academy of Sciences, Landscape and Restoration Ecology Group. E-mail: kovacsanko@yahoo.co.uk

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