South African National Parks

Abstract Background Reductions in United States (US) funding for tuberculosis (TB) and HIV programmes have raised concerns and challenges for TB care and management in South Africa and globally. We used mathematical modelling to illustrate the potential impact of unmitigated funding disruptions, estimating long-term effects on TB incidence and mortality over 2025–2035. Methods Stakeholder-informed scenarios were modelled, assuming both minimal and maximal disruptions to key TB and HIV services, including preventive therapy for people living with HIV (PLHIV), TB testing, TB treatment initiation, and antiretroviral therapy (ART) coverage. Results and discussion Between 2025 and 2035, reduced ART coverage was projected to result in 235,000–1,000,000 additional HIV infections; and a 12–41% increase in TB episodes, and 21–72% rise in TB deaths among people living with HIV. Overall, 220,000–730,000 additional TB episodes and 67,000–225,000 TB deaths are anticipated, potentially reversing years of progress. Although mitigation efforts were not included in the model, early responses in South Africa have involved increased diagnostic testing and additional domestic funding. To maintain progress in TB and HIV control, rapid and sustained programmatic responses and funding are essential to prevent substantial setbacks and avert avoidable illness and death.

Killer whales (Orcinus orca) are cosmopolitan apex predators that interact with numerous species, including sharks, skates, and rays (subclass Elasmobranchii). Interactions between killer whales and elasmobranchs have garnered attention from the scientific community, but the dynamics of these events are poorly understood, as interactions are often challenging to observe. In this study, we collated imagery of interactions between killer whales and elasmobranchs to create the first image-based repository of interspecific interactions between marine predators. A total of 320 photos and videos from 82 unique interactions were collected from 12 countries. A minimum of 18 elasmobranch species across 16 genera were identified from the imagery. Furthermore, 10 different interaction types were documented, encompassing both predatory and non-predatory behavior. This dataset can provide insight into various research topics, including killer whale predation techniques, elasmobranch behavior, and the identification of individual killer whales that specialize in elasmobranch prey. As a new and openly accessible resource, this dataset provides the foundation to support future ecological and behavioral research on killer whale and elasmobranch interactions.

Abstract Background Wildfires in mountainous regions pose significant ecological and socio-economic threats, with their frequency and severity expected to increase due to climate change. Therefore, accurately and promptly characterizing wildfires is crucial for understanding their behaviour and potential damage. Remote sensing and geostatistical methods have become increasingly relevant for providing this timely and precise characterization. This study analyzed the wildfire event that occurred in November 2022 in the Golden Gate Highlands National Park (GGHNP), South Africa, using the spectral-rich imagery from Sentinel-2. The fire severity in the region was quantified using the difference Normalized Burn Ratio (dNBR). This study employs a Generalized Linear Model (GLM) and Random Forests (RF) to identify and quantify the relationships between fire severity and key environmental factors. These environmental factors include topographical variables, climatic factors, and the Normalized Difference Vegetation Index (NDVI), along with various vegetation communities. Results The results revealed that over 50% of the GGHNP was affected by wildfires, with 0.4% of the area experiencing severe burns and less than half of the area remaining unburned. The GLM explained 52.1% of the variation in fire severity (R 2 = 0.521) and identified NDVI, aspect, solar radiation, terrain ruggedness, evaporation, and temperature as the most influential factors. RF identified NDVI, aspect, and solar radiation as the most influential factors based on variable importance (%IncMSE and IncNodePurity) values. Conclusions Overall, these findings enhance wildfire prediction, management, and mitigation strategies in the ecosystem. Future research should focus on investigating long-term fire trends and the effects of climate change to inform conservation efforts in fire-prone mountainous regions. This study demonstrates the novelty of using GLM and RF to integrate Sentinel-2 dNBR, vegetation communities, climate and topography interaction in the South African grassland ecosystem. Additionally, the study analyzes fire severity by management compartments and validates severity maps with SANPark control points, providing insight for fire management.

Savannas are fire-prone ecosystems that contribute substantially to global fire emissions, but these emissions may be partly offset by deposition of fire-derived, persistent pyrogenic carbon (PyC) in soils. Although estimates of PyC contributions to soil organic carbon (SOC) storage in savanna exist, factors driving its accumulation remain unclear due to limited measurements with consistent methods. To address this, we sampled 253 sites across tropical savannas in Kruger National Park, South Africa, spanning broad gradients in fire regimes, grass biomass, rainfall, and soil texture. Here we show, PyC measured with H2O2/HNO3 digestion contributed, on average, 14.08% (se = 0.36%, n = 253) of SOC in surface soils, with values up to 40%. While fire frequency and grass biomass influenced soil PyC stocks, savannas with higher clay content and lower rainfall – conditions favoring PyC preservation – tended to accumulate more. These results demonstrate PyC’s significant contribution to SOC storage and highlight environmental factors driving its accumulation in tropical savannas, providing an empirical basis for understanding fire’s role in the savanna carbon cycle.

Abstract In Earth history, our understanding of how large‐bodied herbivores shape a variety of ecosystem processes is limited by the quality of paleoecological proxies for herbivore composition and abundance. Fecal stanols are lipids that can be produced by microbes within animal digestive systems and that could remedy this dearth of proxies. We used two multi‐decadal herbivore exclosures in Kruger National Park, South Africa, to constrain whether and how biomarker signatures preserve signals of herbivore abundance. Soil samples and dung counts were collected along transects across crests, mid‐slopes, and sodic sites inside and outside exclosures. Soils were analyzed for steroid (sterols and stanols) concentrations and distributions. We found that stanol concentrations were significantly greater in sodic soils outside exclosures, where herbivore dung densities were greatest. In contrast, sterol concentrations did not differ between treatments. Ratios of stanol isomers to sterols, which account for both compound degradation and source, increased strongly with herbivore dung counts. Finally, while herbivore species compositions influenced steroid distributions, total herbivore abundance was their strongest predictor. Further calibration is needed, but this work provides strong preliminary evidence that wild herbivore populations are quantitatively recorded by fecal biomarker distributions.

Abstract Lightning is an important agent of tropical tree mortality, but we know little about lightning-caused disturbances beyond one lowland tropical forest in Panama. Here we quantified variation in the frequency and severity of visually-detectable lightning-caused disturbances across topography in the montane forests of Nyungwe National Park, Rwanda. This was the first systematic assessment of lightning-caused disturbance in Africa and a preliminary test of the hypothesis that forest tolerance to lightning is higher where lightning disturbances are more common. Lightning-caused disturbances were observed six-times more frequently on ridges than in valleys, but lightning-caused disturbances in valleys tended to cause more tree-level damage than those on ridges. Overall, lightning disturbances tended to kill a lower proportion of trees in this Afromontane forest than in previously documented lightning disturbances in tropical America. We also observed less tree-level damage toSyzygiumspp.(Myrtaceae) compared to the community-wide average, providing support for taxonomic differences in lightning tolerance. Our results indicate that lightning disturbance severity differs within and among sites, mediated in part by differences in lightning tolerance among tree species, and provide some support for the hypothesis that disturbance severity declines with disturbance frequency.