Abstract
Conserving biodiversity on farmland is an essential element of worldwide efforts for reversing the global biodiversity decline. Common approaches involve improving the natural component of the landscape by increasing the amount of natural and seminatural habitats (e.g., hedgerows, woodlots, and ponds) or improving the production component of the landscape by increasing the amount of biodiversity‐friendly crops. Because these approaches may negatively impact on economic output, it was suggested that an alternative might be to enhance the diversity (compositional heterogeneity) or the spatial complexity (configurational heterogeneity) of land cover types, without necessarily changing composition. Here, we develop a case study to evaluate these ideas, examining whether managing landscape composition or heterogeneity, or both, would be required to achieve conservation benefits on avian diversity in open Mediterranean farmland. We surveyed birds in farmland landscapes of southern Portugal, before (1995–1997) and after (2010–2012) the European Union's Common Agricultural Policy (CAP) reform of 2003, and related spatial and temporal variation in bird species richness to variables describing the composition, and the compositional and configurational heterogeneity, of the natural and production components of the landscape. We found that the composition of the production component had the strongest effects on avian diversity, with a particularly marked effect on the richness of farmland and steppe bird species. Composition of the natural component was also influential, mainly affecting the richness of woodland/shrubland species. Although there were some effects of compositional and configurational heterogeneity, these were much weaker and inconsistent than those of landscape composition. Overall, we suggest that conservation efforts in our area should focus primarily on the composition of the production component, by striving to maximize the prevalence of biodiversity‐friendly crops. This recommendation probably applies to other areas such as ours, where a range of species of conservation concern is strongly associated with crop habitats.
Highlights
Conserving biodiversity on farmland is essential for reversing the global biodiversity decline, but achieving this goal has been hindered by the pervasive intensification of agricultural land uses (Donald, Sanderson, Burfield, & Van Bommel, 2006; Krebs, Wilson, Bradbury, & Siriwardena, 1999; Sutcliffe et al, 2015)
Our study examined the relative role of landscape composition and heterogeneity on spatial and temporal variations in avian diversity in Mediterranean farmland, showing that the composition of the natural and the production components had far stronger effects than those of their compositional or configurational heterogeneity
Our study supported the expectation that the natural component should have a strong effect on species richness, in particular that of woodland and shrubland birds, while the effects of the production component should be strong, on farmland and steppe bird species
Summary
Conserving biodiversity on farmland is essential for reversing the global biodiversity decline, but achieving this goal has been hindered by the pervasive intensification of agricultural land uses (Donald, Sanderson, Burfield, & Van Bommel, 2006; Krebs, Wilson, Bradbury, & Siriwardena, 1999; Sutcliffe et al, 2015). The production on former arable land of permanent crops such as olive orchards or energy crops such as willow short rotation coppice may increase biodiversity, by attracting shrubland and woodland species to farmland (Rey, 2011; Sage, Cunningham, & Boatman, 2006) Despite these potential benefits, changing crop types on private land may be difficult, because this is conditional on complex farmers’ decisions driven by a combination of agricultural policies, biophysical and socioeconomic constraints, and market demands (Ribeiro et al, 2014). Results of our study were used to discuss the importance of considering landscape composition and heterogeneity of both the production and natural components when managing farmland landscapes for conservation, and how this importance may vary widely in relation to conservation objectives
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