Properties of land mosaics: Implications for nature conservation in agricultural environments

Agricultural landscapes are mosaics of different land uses. Their vast extent throughout the world means that they have a key role in the conservation of biodiversity. To provide a sound basis for management, it is important to recognise the emergent properties of land mosaics and understand how they influence components of biodiversity. In most studies in agricultural landscapes, inference is restricted to single sites or patches because this is the unit used for sampling and analysis. For mosaic-level inference, sampling must encompass multiple land uses and elements within a mosaic, be aggregated to represent the ‘whole’ mosaic, and be replicated across multiple mosaics. This paper reviews studies in which land mosaics are the unit of replication, to identify the influence on biota of three categories of emergent properties of mosaic structure: the extent of habitat, composition of the mosaic and spatial configuration of elements. The extent of habitat is usually a dominant influence on the occurrence of single species or the richness of assemblages defined by habitat type (e.g., forest birds). The composition of the mosaic, based on the proportions of elements present, strongly influences the species composition of faunal assemblages. Heterogeneity or diversity of elements is often positively correlated with the richness of taxonomic assemblages. In studies that separate the independent effects of emergent properties, spatial configuration generally exerts less influence on biota than extent or composition. A fourth property, the geographic position or environmental variation among land mosaics, also significantly affects the status of the fauna in many studies. Temporal persistence of species and turnover in assemblages in agricultural landscapes are also influenced by the structure of the land mosaic, but there are few long-term data sets that allow comparison of temporal changes with mosaic properties. There is great scope for further investigation of the properties of mosaics and the mechanisms by which they affect the conservation of biodiversity. This includes studies of responses from a wider range of biota (in addition to birds), investigation of spatial scale effects on faunal responses, temporal responses of the fauna to change in mosaic structure (and potential time-lags in response), and the effects of variation in mosaic structure on population demography and ecological processes.