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Savannas once constituted the range of many species that human encroachment has now reduced to a fraction of their former distribution. Many survive only in protected areas. Poaching reduces the savanna elephant, even where protected, likely to the detriment of savanna ecosystems. While resources go into estimating elephant populations, an ecological benchmark by which to assess counts is lacking. Knowing how many elephants there are and how many poachers kill is important, but on their own, such data lack context. We collated savanna elephant count data from 73 protected areas across the continent estimated to hold ~50% of Africa’s elephants and extracted densities from 18 broadly stable population time series. We modeled these densities using primary productivity, water availability, and an index of poaching as predictors. We then used the model to predict stable densities given current conditions and poaching for all 73 populations. Next, to generate ecological benchmarks, we predicted such densities for a scenario of zero poaching. Where historical data are available, they corroborate or exceed benchmarks. According to recent counts, collectively, the 73 savanna elephant populations are at 75% of the size predicted based on current conditions and poaching levels. However, populations are at <25% of ecological benchmarks given a scenario of zero poaching (~967,000)—a total deficit of ~730,000 elephants. Populations in 30% of the 73 protected areas were <5% of their benchmarks, and the median current density as a percentage of ecological benchmark across protected areas was just 13%. The ecological context provided by these benchmark values, in conjunction with ongoing census projects, allow efficient targeting of conservation efforts.

The SARS-CoV-2 virus and COVID-19 illness are driving a global crisis. Governments have responded by restricting human movement, which has reduced economic activity. These changes may benefit biodiversity conservation in some ways, but in Africa, we contend that the net conservation impacts of COVID-19 will be strongly negative. Here, we describe how the crisis creates a perfect storm of reduced funding, restrictions on the operations of conservation agencies, and elevated human threats to nature. We identify the immediate steps necessary to address these challenges and support ongoing conservation efforts. We then highlight systemic flaws in contemporary conservation and identify opportunities to restructure for greater resilience. Finally, we emphasize the critical importance of conserving habitat and regulating unsafe wildlife trade practices to reduce the risk of future pandemics. In Africa, COVID-19 has created a perfect storm of reduced funding, restrictions on the operations of conservation agencies, and elevated human threats to nature. This Perspective discusses solutions to move beyond this immediate crisis.

Calls to increase the global area under protection for conservation assume existing conservation areas are effective but, without adequate investment, they may not be. We collected survey data from expert respondents on perceived budgets, management, and threats for 516 protected areas and community conservation areas in savannah Africa to create a ConservationArea Performance Index. Combining this index with an indicative biodiversity outcome—population status of African lion, Panthera leo—we found that 82% of the sampled area was in a state of failure or deterioration, with only 10% in a state of success or recovery. A large proportion of succeeding or recovering conservation areas received external support through collaborative management partnerships. That Africa’s current conservation area network—the foundation of conservation efforts—is crumbling complicates proposed strategies to protect additional land. We contend that investing in the effective management of existing conservation areas— potentially through well-structured collaborative management partnerships— should be prioritized urgently.

Through the Subtropical Thicket Restoration Program, about 21.5 million cuttings of spekboom (Portulacaria afra) were planted over the period 2004-2016 in the Addo Elephant National Park, Great Fish River Nature Reserve and the Baviaanskloof Nature Reserve. This planting includes a large experiment of 330 quarter-hectare plots in which 14 different planting treatments were used. These experimental plots, known as the thicket-wide plots, comprised 200,000 cuttings, with the remaining 21.3 million cuttings planted out in what were called the large-scale plantings. Some of the large-scale plantings were replanted with cuttings -- a procedure referred to as blanking. The data show that survivorship in the large-scale plantings is extremely variable, ranging from 0% to 93%, with a mean of 28% across all 64 plots sampled. Geographical reasons for this variation were not evident in their data set. A generalized linear model showed, for example, that geology, aspect, elevation and slope were not related to survivorship.

Conservation management approaches for elephants in southern Africa, and particularly in the Kruger National Park, have changed. Recently, Kruger’s managers adapted their approach from artificially manipulating elephant numbers to reinstating and embracing densitydependent processes that could limit or regulate the elephant population. However, few studies have evaluated whether changes in Kruger’s elephant management approach were effective in achieving the desired outcomes. This is a common shortcoming in conservation endeavours and has the potential to undermine future initiatives. In my thesis, I address this shortcoming, and assess whether recent changes in conservation management in Kruger induced demographic responses from the elephant population that ecological theory predicted and managers desired.My assessment into how calf recruitment and population growth rates responded to ecological limitations (i.e. climate, primary productivity and density) during two contrasting management eras suggests that changes in management induced predicted and desired demographic responses. During the culling era (i.e. density suppression, water supplementation and fencing), population growth rates were primarily driven by the density-independent, climate-mediated, reproductive patterns of the population. In the post-culling era (i.e. natural variation in density, artificial waterhole and fence removals), density-dependence was reinstated and took over as the primary driver of population growth. Although not empirically tested, density-dependent weaned calf survival and dispersal likely contributed to densitydependent population growth during the latter era and should be the focus of future work.I then determined that the changes in management promoted density-dependent habitat selection, a fundamental driver of population regulation. I found that as densities increased following the cessation of culling, selection for woody cover, an important resource for elephants, generalized (i.e. decreased selection of areas with high woody cover and increased selection of areas with lower woody cover). Furthermore, selection for areas close to or far from rivers was mediated by rainfall. While not directly related to changes in density, varied selection for rivers may moderate density-dependent feedbacks to demographic parameters by alleviating foraging restrictions and clustering around key resources. The question remains however, whether density-dependent and rainfall-mediated changes to habitat selection have fitness consequences for elephants that could ultimately regulate the population.Elephants in Kruger responded, at least demographically and partly, to changes in conservation management as theory predicted and managers desired. Although the population has not yet entered the sought after state of long-term stability, my assessment suggests that some of the density-dependent processes necessary to regulate the population are present. I suggest avenues of further study and advocate that ecological principles provide an effective framework for the scientific evaluation and conservation management of elephants within and beyond the Kruger National Park.

THE CHILDREN from Jewells have set a fine example by holding an Outback Day to support drought-stricken farmers in NSW.

CD8 + T cells are critical for elimination of cancer cells. Factors within the tumor microenvironment (TME) can drive these cells to a hypofunctional state known as exhaustion. The most terminally exhausted T (tT ex ) cells are resistant to checkpoint blockade immunotherapy and might instead limit immunotherapeutic efficacy. Here we show that intratumoral CD8 + tT ex cells possess transcriptional features of CD4 + Foxp3 + regulatory T cells and are similarly capable of directly suppressing T cell proliferation ex vivo. tT ex cell suppression requires CD39, which generates immunosuppressive adenosine. Restricted deletion of CD39 in endogenous CD8 + T cells resulted in slowed tumor progression, improved immunotherapy responsiveness and enhanced infiltration of transferred tumor-specific T cells. CD39 is induced on tT ex cells by tumor hypoxia, thus mitigation of hypoxia limits tT ex suppression. Together, these data suggest tT ex cells are an important regulatory population in cancer and strategies to limit their generation, reprogram their immunosuppressive state or remove them from the TME might potentiate immunotherapy. Exhausted CD8 + T cells with diminished effector functions accumulate in tumors. Here, the authors show that hypoxia induces a suppressive phenotype in exhausted T cells and that interfering with hypoxia-mediated CD39 expression limits immunosuppression in the tumor and augments immunotherapy, resulting in arrest of tumor growth.