Abstract
AbstractAgriculture is one of the primary threats to biodiversity but agricultural land can also provide key resources for many species and, in some parts of the world, agricultural land supports important populations of species of conservation concern. In these cases, it is important to understand species’ use of agricultural land before further expansion or intensification of agricultural activities occurs. Agriculture in Iceland is still relatively low in intensity and extent, and internationally important populations of several breeding bird species are abundant in farmed regions. In these high latitude landscapes, agricultural land could provide resources that help to support these species, and the consequences of future agricultural expansion will depend on the nature of these relationships. To address these issues, we conducted surveys of bird abundance at 64 farms in areas of Iceland that vary in underlying soil productivity, and quantified (a) levels of breeding bird use of farmed land managed at three differing intensities, ranging from cultivated fields to semi‐natural land and (b) changes in patterns of use throughout the breeding season, for an assemblage of species. Breeding birds use all three land management types in large numbers but, overall, bird abundance is lower in more intensively managed farmland. However, more intensively managed agricultural land supports higher densities of birds than semi‐natural habitats in areas with lower underlying productivity. This suggests that in landscapes in which agricultural land does not yet dominate, conservation and commercial production can co‐exist, especially in areas of low productivity. Areas like Iceland, in which agricultural land still supports large populations of internationally important species, are rare and this study highlights the need to protect these systems from the agricultural development that has led to widespread biodiversity loss throughout most of the world.
Highlights
The development and expansion of agriculture throughout the world has been a major driver of biodiversity loss (Foley et al, 2005; Green et al, 2005; Millennium Ecosystem Assessment, 2005), primarily because the resulting landscapes do not provide the resources needed by many species at the appropriate spatial and temporal scales (Robinson & Sutherland, 2002; Tscharntke et al, 2005)
The aim of this study was to quantify (a) levels of breeding bird habitat use along a gradient from heavily managed agricultural land to semi-natural land; (b) seasonal changes in patterns of habitat use during the breeding season; and to explore the consistency of these patterns between (c) regions with varying underlying productivity and (d) species, to understand the influence of current levels and structure of agricultural management in Iceland on the important ground-nesting bird populations that breed in these areas, and the implications for declining wader populations in intensively managed agricultural regions elsewhere
Densities did not vary significantly between regions but there was a significant interaction with management type, with lower densities occurring in intensive management in the south and north, whereas the highest densities (~300 waders/km2) were recorded in the intensive management category in the west (Table 2, Fig. 3)
Summary
The development and expansion of agriculture throughout the world has been a major driver of biodiversity loss (Foley et al, 2005; Green et al, 2005; Millennium Ecosystem Assessment, 2005), primarily because the resulting landscapes do not provide the resources needed by many species at the appropriate spatial and temporal scales (Robinson & Sutherland, 2002; Tscharntke et al, 2005). Agricultural management often results in the creation of open areas, drainage of wetlands and associated creation of ditches, all of which can potentially provide habitat that might be suitable for nesting birds, when at suitable spatial scales, and cultivated fields can provide abundant and accessible invertebrate prey resources. Such positive effects of low-intensity agriculture can be compromised by expansion and/or intensification of land management. When agricultural management intensity increases and expands over large areas, the loss of landscape heterogeneity is typically associated with severe reductions in biodiversity
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