Restoration promotes recovery of woodland birds in agricultural environments: a comparison of 'revegetation' and 'remnant' landscapes.
Abstract
Ecological restoration in rural environments is a global challenge for the 21st century. Restoration measures - such as agri-environment activities, woodlots, natural regeneration and conservation plantings - collectively alter landscape structure with the aim of restoring conservation values that are characteristic of natural ecosystems. We tested the landscape-scale benefits of restoration for woodland birds, species of conservation concern in southern Australia, by assessing the richness and composition of avian communities in rural landscapes along a gradient in habitat restoration, benchmarked against landscapes with comparable extent of native vegetation. We selected 43 landscapes (each 8 km2) in Victoria, Australia, representing: (a) a trajectory of decline in the extent of remnant native wooded vegetation ('remnant' landscapes), (b) a trajectory of gain in planted vegetation ('revegetation' landscapes) and (c) a similar gradient comprising a mix of remnants and planted vegetation ('mixed' landscapes). In each landscape, repeat surveys of birds were undertaken at 12 sites, stratified in relation to land cover. Species richness of all terrestrial and woodland birds showed similar positive responses to total wooded cover in each landscape type, but woodland birds had reduced richness in 'revegetation' relative to 'remnant' and 'mixed' landscapes. Across all landscapes, key factors influencing richness were the extent of wooded cover and proportion comprised of plantings, scattered trees in farmland and mean annual rainfall. The composition of woodland bird assemblages differed between 'remnant' and 'revegetation' landscapes with predictable differences associated with foraging traits. Synthesis and applications. Restoration plantings stimulate recolonisation of otherwise-depleted landscapes, effectively reversing a decline in woodland birds. Key insights include: (a) benchmarking 'revegetation' against 'remnant' landscapes provides a valuable means to quantify restoration outcomes at the landscape scale; (b) time-lags in vegetation maturation contribute to a trajectory of recovery that differs from a trajectory of decline, in both richness and composition of the avifauna; (c) scattered trees have a critical role for avifaunal conservation in farm landscapes; (d) restoration plantings are most effective in 'mixed' landscapes, where complementary resources from remnant and planted vegetation are juxtaposed; and (e) restoration plantings on individual farms contribute to landscape-scale biodiversity gains while also having socio-ecological and production benefits.