Local management or wider context: what determines the value of farm revegetation plantings for birds?
Abstract
Small-scale revegetation plantings on farms are common to restoration efforts in agricultural regions worldwide. Such plantings provide habitat for diverse faunal groups. A key question concerns the degree to which their value for biodiversity is influenced by the features of individual plantings, which can be controlled by local land managers, or by broader-scale drivers in the wider landscape. We developed a conceptual model of factors of potential influence on birds in revegetation plantings at different spatial scales. To test this model, we surveyed native birds in 133 plantings in south-eastern Australia. Regression models were used to compare the effect of 'habitat-', 'patch-', 'farm-' and 'landscape-' scale variables on species richness (of woodland and open country birds) and the occurrence of individual species in plantings. We further tested whether the influence of variables representing local actions was swamped by larger-scale variables. Birds that occupied plantings were influenced by variables at all scales. Woodland birds were consistently richer and more likely to use older plantings (patch scale) with higher floristic richness (habitat scale), and surrounded by more wooded vegetation (at patch, farm and landscape scales). Open country species responded positively to the density of live trees (habitat scale) and the presence of large remnant tree/s (patch scale) in plantings. Variables representing local management actions generally maintained a strong influence on birds in plantings irrespective of the influence of broader drivers. Few relationships between bird species and planting attributes were contingent on features of the surrounding landscape; those that were suggested woodland birds are more responsive to local actions when broad-scale vegetation cover is greater. Synthesis and applications. Land managers can enhance the conservation value of plantings by (a) planting a greater diversity of trees and shrubs and (b) locating revegetation near other vegetation or around mature remnant tree/s. These actions will measurably increase the value of plantings for birds, irrespective of larger-scale drivers. Nonetheless, the important role of increased vegetation cover across broader agricultural landscapes emphasises that the collective efforts of individuals and larger initiatives are critical for conservation.