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.

The genetic consequences of habitat specificity for fig trees in southern African fragmented forests

“…The responses of species to forest fragmentation are highly variable (Henle et al, 2004), and may result in no discernable effects (Berens et al, 2014), a loss of genetic diversity and increased population differentiation (Matolweni et al, 2000;McManus et al, 2015) or even extinction of forest specialists (Lawes, 2004;Olivier et al, 2013;Cooper et al, 2017;). The effects of fragmentation, although unlikely ever to be beneficial, are therefore unpredictable and remain poorly understood.…”

“…It nonetheless remains unclear whether wasp-assisted pollen flow can be sufficient to connect forest specialist fig trees into a single large genetic unit across sub-continental scales, especially given that the dispersal of Ficus seeds often extends for only short-distances, despite the services of strong flyers such as frugivorous birds (Zhou and Chen, 2010). Seed dispersal distances in South Africa may have been reduced further by the loss of forest specialist birds and mammals after their own populations responded to fragmentation (Lawes, 2004;Olivier et al, 2013;Cooper et al, 2017).…”

Influence of historical and contemporary habitat changes on the population genetics of the endemic South African parrotPoicephalus robustus

“…Habitat loss is one of the main extinction drivers in wild parrots globally (Collar 2000, Pain et al 2006. Despite the Cape Parrot experiencing a range decline of 59% in the past quarter century alone (Cooper et al 2017), recent census data suggests that the population is not in decline (Downs et al 2014).…”

Biological Invasions as a Component of South Africa’s Global Change Research Effort

“…Some of the impacts of invasive species can be seen as positive, even if the overall net impact is negative. For example, Cooper et al (2017) noted that the invasion of treeless landscapes by alien trees can provide nesting sites for native raptors and other birds, expanding their ranges; and Coleman and Hockey (2008) found that the invasion of bare rocky seashores by alien mussels has boosted populations of African Black Oystercatchers, Haematopus moquini). These types of effects can complicate management, and lead to conflict.…”