Atlas data indicate forest dependent bird species declines in South Africa

Abstract

SummaryForest ecosystems in South Africa are at risk from a variety of anthropogenic threats impacting the faunal species dependent on them. These impacts often differ depending on species-specific characteristics. Range data on forest dependent bird species from the South African Bird Atlas Project (SABAP1 and SABAP2) were analysed to determine links between deforestation, species characteristics and range declines. Half of the species studied were found to have declining ranges. Range change data for these species were correlated with data on changes in land cover from 1990 to 2014. To determine which land cover changes affect extinction, occupancy was modelled for 30 sites across South Africa which experienced a loss of more than 10 species. Most species lost were birds of prey or insectivores. Indigenous forest decreased in 17% (n = 5) sites, while plantations/woodlots decreased in 60% (n = 18) sites. Occupancy modelling showed extinction to be mitigated by plantations in 6/28 species, and forest expansion mitigated extinction in 7/28 species. Responses to deforestation did not appear to be related to particular species characteristics. Half of South Africa’s forest-dependent bird species have declining ranges, with the loss of these species most prominent in the Eastern Cape province. Four responses to changes in forest and plantation cover are discussed: direct effects, with forest loss causing species loss; matrix effects, where plantation loss resulted in species loss; degradation of indigenous forest; and the advent of new forest arising from woody thickening caused by carbon fertilisation, which may not result in optimal habitat for forest-dependent birds.