Abstract
Landscape modification and habitat fragmentation are one of the major current threats to biodiversity. The main source of habitat fragmentation is the loss of focal habitat area, but changes in the composition of the surrounding landscape also have a direct effect on biodiversity. These changes may lead to the loss of some species but also may favor species replacement. Farmland birds in Europe are affected by landscape changes due to farmland intensification, such as the spread of irrigation, which may occur at different spatial scales. As irrigation is expected to increase in the coming years, which may affect protected areas, it is necessary to evaluate its potential consequences over focal biodiversity. In this study we assess the relationship between the increase of irrigated land at different spatial scales and changes in a dry cereal farmland bird community, bird abundance and species richness, using generalized linear models. We used a dry cereal farmland affinity index to describe the level of community specificity for dry cereal farmland. The increase in irrigated tree orchards produced an increase in species richness up to 500 m away from the irrigated area, which had a negative effect on the dry cereal farmland bird community, by triggering a replacement of specialist by generalist species. Our results show the importance of landscape-scale effects of irrigation occurring outside protected areas on the farmland bird community inside Natura 2000 sites, as well as how these effects are detected even at long distances from the disturbance source.
Highlights
Local species diversity and abundance often depend on spatial scales larger than the focal habitat patch (Fahrig, 2003; Villard and Metzger, 2014; De Camargo et al, 2018)
Mean Dryland affinity index (DAI), total bird abundance and species richness across transects (n = 178) was −0.53 ± 0.93, 2.55 ± 1.18 birds/ha. Both total bird abundance and species richness were lower in the 10 transects with highest DAI value (Table 2)
Our results show the effects of changes in landscape composition for dry cereal farmland bird communities, and how the amount of irrigated areas located at up to 500 m can alter species richness and community composition inside protected areas of the Natura 2000 network
Summary
Local species diversity and abundance often depend on spatial scales larger than the focal habitat patch (Fahrig, 2003; Villard and Metzger, 2014; De Camargo et al, 2018). Irrigation represents a drastic, quick, and large-scale change of dry cereal farmland landscapes, with predicted and demonstrated negative effects on biodiversity, and on farmland and steppe birds (Brotons et al, 2004; González-Estébanez et al, 2011; Traba et al, 2013; Cardador et al, 2015; De Frutos et al, 2015). Because irrigated land is expected to continue increasing in the years and given that landscape changes may affect protected areas or biodiversity hotspots, even if changes occur outside their borders, it becomes necessary to evaluate its potential consequences over high nature value areas (e.g., Natura 2000 sites) that have been designed to preserve dry cereal bird communities
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