Habitat transformation and loss is one of the greatest threats currently facing avian species. The cumulative impact of climate change on habitat loss is projected to produce disproportionate risk for endemic high-altitude species. The Southern Bald Ibis (Geronticus calvus) is an endemic high-altitude species found throughout highland grassland habitats in South Africa and Lesotho. The historical distribution has contracted notably and causal factors remain ambiguous. Furthermore, the historical population (1950–1970) was believed to be stable, but recent local surveys suggest colony declines and the current global population status remains largely unquantified. We assessed the current distribution and population status of the species through predictive modeling and trends in historical and recent colony counts across the species’ range. We examined climate and habitat change as potential causal factors contributing to the historical contraction in distribution, and projected the potential impact of future climate change predicted by global circulation models. Our study confirms that Southern Bald Ibis are of conservation concern. The loss of grasslands to expanding woody vegetation through bush encroachment was the most detrimental habitat transformation type associated with decreased colony growth and colony collapse. We recommend maintaining a minimum threshold of 50% or greater intact grassland habitat surrounding colonies to reduce colony extinction risk and promote colony persistence.
Aim: Forested regions are of global importance for a multitude of ecosystem functions and services and are critical for biodiversity. Anthropogenic climate-change compounds negative effects of land-use change on forest persistence and forestdependent biodiversity. Habitat loss and climate change have an additive effect and drive species' extinctions in similar ways, resulting in a homogenization of biodiversity. Connectivity is key in conservation planning for mitigating climate change effects and facilitating species' abilities to disperse throughout remnant habitat and track their climate niches. We used three forest-specialized and habitat-specific bird species as focal species to understand avian connectivity and conservation of each of South Africa's three threatened forest classes, as each species is range-restricted to its respective forest type.Location: South Africa.
Methods:We created ensemble models of species' distributions and combined core home-and breeding-range patches with a hybrid of least-cost pathways and ecological circuit theory linkages to assess the success of corridors in facilitating connectivity of each of the three forest types. We then predicted the likelihood of niche persistence for each species under future climate-change scenarios, and the efficacy of our connectivity modelling to facilitate range expansion or climate-niche tracking.
Results:The projected habitat loss under climate-change scenarios impacted corehabitat patch distribution, size and connectivity, exacerbated habitat fragmentation and increased resistance and the severity of pinch points and barriers along dispersal corridors. Forest systems and associated focal species projected to experience the highest levels of habitat loss/contraction occurred at mid-to high elevations.Climate-change resilience across ecosystems, and persistence of species therein, was dependent on connectivity, facilitating species' ability to track specific climate niches.
Main conclusions:Climate-change resilience of ecosystems, and persistence of biodiversity therein, is most likely to be a product of high functional biodiversity, connectedness and the ability of species to track specific climate niches. | 653 COLYN et aL.
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