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Predicted ecological benchmark density for savanna elephant populations across 73 protected areas differed according to EVI and water availability given minimized poaching (A) Green fill color indicates predicted ecological benchmark density as shown in (B) the frequency distribution where densities on the x-axis represent bin centers. (C) Twenty-one countries are covered by protected areas in this assessment. See Figure E and Table F in S1 File for the 95% prediction intervals of predicted ecological benchmarks.
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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 ecologic...
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Citations
... Existing databases for other megaherbivores offer significant conservation value. For example, the AED, established in 1986, has facilitated diverse conservation research for elephants, including population trend analysis (Blanc et al., 2005;Bouché et al., 2011;Chase et al., 2016;Lindsay et al., 2017), density modelling (De Boer et al., 2013;Robson et al., 2017), and conservation planning (Litoroh et al., 2012;Stephenson and Ntiamoa-Baidu, 2010;Zacarias and Loyola, 2018). In contrast, research of similar depth is lacking for hippos, despite the detrimental impacts of high hippo population densities on vegetation and aquatic processes (Stears et al., 2018), and the direct influence of anthropogenic pressures on their population persistence (Eksteen et al., 2016;Kanga et al., 2011;Stommel et al., 2016). ...
The geographical range of common hippopotamus' (Hippopotamus amphibius) has retracted over the last century as a result of anthropogenic pressures. At present, extant common hippopotamus (hereafter, hippo) populations are fragmented and largely constrained to Protected Areas. There is an urgent need for conservation management , but data and information on the spatial ecology of hippos to base conservation strategies on are lacking. Without a centralised and collaborative database that documents their distribution and abundance, comprehensive population assessments remain a challenge. This study establishes a detailed spatial database of hippo population estimates and distribution across southern Africa, by collating recent survey data from a range of sources, facilitating population monitoring and informed conservation decision making. Drawing from a review of the primary literature, grey literature, aerial surveys, websites, and expert input, we provide a comprehensive geographic range map for hippos and evaluate hippo distribution within Protected Areas. Our review reveals several discrepancies between our data and previous hippo distribution and abundance estimates. We also highlight inconsistent methods used to survey hippo populations across southern Africa. By identifying twelve regions with large populations of hippos (>1000 individuals), our findings underscore the importance of extensive and well-connected Transfrontier Conservation Areas to support large, dense hippo populations. We encourage the IUCN SSC Hippo Specialist Group to promote standardised and coordinated surveys and progress a spatial database of hippo distribution and abundance across the rest of Africa.
... At a smaller scale, however, density-dependent changes take place close to perennial rivers (Louw, MacFadyen, Ferreira & Hui, 2021) most likely through spatial responses (MacFadyen, Hui, Verburg & van Teeffelen, 2019;Huang, van Aarde, Pimm, Chase & Leggett, 2022;Henley et al., 2023) as well as consequences of elephant density on daily movement distances of cows and resultant survival of weaned calves (Young & Van Aarde, 2010). Even so, by 2020, sample-based estimates with confidence intervals are still lower than the predicted population size at which the population would fluctuate at a park-wide scale (Robson et al., 2017). ...
... However, many protected areas are failing to halt biodiversity loss, and animal populations within them continue to decline (Lindsey et al. 2014;Bauer et al. 2015;Ogutu et al. 2016;Robson et al. 2017;Robson et al. 2022). Approximately one third of protected areas globally are unable to avert anthropogenic pressure (Jones et al. 2018), and more than 80% of Africa's protected areas are deteriorating based on conservation performance indices (Robson et al. 2022). ...
Terrestrial carnivore population declines are driven by habitat loss and fragmentation, prey-depletion, persecution, and retaliatory killings. Population strongholds now centre on protected areas, that face increasing human pressure, resulting in population isolation, declining prey populations, and livestock intrusion. I therefore aimed to investigate dispersal and connectivity, and diets of lions (Panthera leo) and leopards (P. pardus) in response to human-use and wildlife density gradients in the Greater Limpopo Transfrontier Conservation Area (GLTCA). Firstly, I investigated dispersal and connectivity for these carnivores across the GLTCA, using single nucleotide polymorphisms. I present evidence that in the prey-depleted Mozambique portion of the GLTCA, lion and leopard dispersal distances are higher compared with the prey-abundant Kruger National Park (KNP). I also provide the first evidence for long-range dispersal in female lions. Despite evidence for connectivity occurring across the GLTCA, I recorded population structuring across the region for both carnivores, likely due to habitat fragmentation by human activities in the Mozambique portion of the GLTCA. I then assessed carnivore diet responses to prey depletion and livestock availability by comparing lion and leopard diets in the prey-abundant/livestock-absent KNP (South Africa), with the prey-depleted/livestock-abundant Limpopo National Park (LNP, Mozambique), using scat analyses. Lions and leopards downshifted their prey size selection in LNP relative to KNP. Despite both carnivores expanding their dietary niche breadths in LNP relative to KNP, diet overlap did not differ between sites. This suggests that even when prey is depleted, lions and leopards can partition food resources, which likely limits competition. Despite cattle (Bos taurus) being the most abundant ungulate in LNP, lions and leopards strongly avoided cattle, supporting the notion that carnivores can perceive the risk of hunting livestock and modulate their foraging behaviour to reduce human-carnivore conflict. Should my findings reflect general patterns in carnivore dispersal and diet responses to human-use and wildlife gradients, then carnivore conservation initiates across their range should focus on prey population rehabilitation, improved livestock husbandry practices, the establishment of effective dispersal corridors and improved human-tolerance towards large carnivores.
... We collated population estimates and counts of elephant populations from the African Elephant Database (75), peer-reviewed publications, and gray literature (65,69) (see the Supplementary Materials). We only used estimates that met reliability criteria A or B of Thouless et al. (1), excluded estimates from wet season surveys, and excluded populations with fewer than three surveys or only reported zero elephants. ...
The influence of protected areas on the growth of African savannah elephant populations is inadequately known. Across southern Africa, elephant numbers grew at 0.16% annually for the past quarter century. Locally, much depends on metapopulation dynamics—the size and connections of individual populations. Population numbers in large, connected, and strictly protected areas typically increased, were less variable from year to year, and suffered less from poaching. Conversely, populations in buffer areas that are less protected but still connected have more variation in growth from year to year. Buffer areas also differed more in their growth rates, likely due to more threats and dispersal opportunities in the face of such dangers. Isolated populations showed consistently high growth due to a lack of emigration. This suggests that “fortress” conservation generally maintains high growth, while anthropogenic-driven source-sink dynamics within connected conservation clusters drive stability in core areas and variability in buffers.
... The programme is now central to the country's conservation and development goals and is generally recognised as having contributed to a strong recovery in wildlife numbers (IUCN et al. 2015;Naidoo et al. 2016). In particular, Namibia's elephant population is thought to have increased from around 7,500 at CBNRM's formal inception in 1995 to over 23,000 today (MEFT & NACSO 2021), although we note that time series data from elephant surveys for Zambezi Region from 1989 to 2013 reportedly observed no trend in elephant population size (Robson et al. 2017). In Namibia's long-term development framework, CBNRM is an explicit rural development strategy, 'Vision 2030' (GRN 2004), and the Ministry of Environment, Forestry and Tourism (MEFT), previously the Ministry of Environment and Tourism (MET)), state that sustainable environmental use shall be a key driver of poverty alleviation and equitable economic growth, particularly in rural areas (GRN 2014;MEFT & NACSO 2021). ...
... 71,72 Notably, large herbivore biomass in many PAs was estimated to be much lower than is natural due to past extinctions and ongoing human pressures, e.g., poaching. 73,74 This might also challenge the actual global representativeness of our findings based on estimating collective effects of large herbivore assemblages on tree cover and heterogeneity with a modeled density-weighted total biomass of extant large herbivores 75 in strictly selected large PAs rather than all natural areas inhabited by large herbivores. Nevertheless, given that spatially explicit mammalian population density data are currently unavailable on a global scale, 38 our analysis here should still represent a reasonable global attempt. ...
... There has been a continental decline in the number of savanna elephants (Loxodonta africana) across Africa over the past two decades (Chase et al., 2016), principally due to the poaching of elephants for ivory (Schlossberg et al., 2020), as well as human-elephant conflict (HEC) (Shaffer et al., 2019) and loss of habitat (Robson et al., 2017). However, in most of the southern African states, elephant numbers and subsequent densities have either stabilised or increased in the same period (Chase et al., 2016). ...
Reduced levels of the survival of large trees (≥5 m height) in Africa's savannas are a conservation concern, particularly where large trees co-occur with African elephants (Loxodonta africana). Elephants, as ecosystem engineers, can structurally modify and lesson the savanna large tree component. Wire-netting, which involves wrapping chicken-mesh around a tree's main stem, has been used as a mitigation method to increase tree survival. We assess the trends in survival of three large tree species of conservation importance, namely Lannea schweinfurthii, Senegalia nigrescens and Sclerocarya birrea, within the Associated Private Nature Reserves (APNR) on the western boundary of the Kruger National Park, South Africa. We consider survival trends linked by both elephant impact, as well as external environmental factors. We conducted four field assessments on 2,758 trees in 2008 (baseline), 2012, 2017, and 2020, where we recorded i) elephant impact levels on each tree, ii) whether the tree had wire-netting, and iii) the tree's survival status. We then modelled tree survival status as a dependent variable against multiple environmental factors. We found that tree survival was lowest when mean annual rainfall was lowest due to the drought, particularly amongst L. schweinfurthii and S. nigrescens. Wire-netting significantly increased large tree survival in comparison to control trees over the 12-year period, however, this effect decreased after four years if the wire-netting had lost its structural integrity. We illustrate how various environmental factors, in combination with elephant impact, affect large tree survival in an African savanna with a high density of artificial water points. We also provide results on the longest known study on wire-netting as a mitigation method for elephant impact on large trees and provide evidence on how a period of drought may have accelerated large tree decline in a southern African savanna.
... We used long-term mean Enhanced Vegetation Index (EVI) from Robson et al. (2017), which is an index of primary productivity across our study range ( Figure 2D). We use EVI rather than Normalized Difference Vegetation Index (NDVI) because EVI overcomes some of the contamination problems present in NDVI data (e.g., contamination associated with canopy background and residual aerosol influences), and EVI is less likely to become saturated in areas that have high green biomass (Pettorelli et al., 2005). ...
Across Africa, space for conservation is sometimes limited to formally protected areas that have become progressively more isolated. There is a need for targeted conservation initiatives such as the demarcation of landscape connections, defined as areas that encompass environmental variables that promote the natural movement of individuals between populations, which can facilitate gene flow. Landscape connections can mitigate genetic isolation, genetic drift, and inbreeding, which can occur in isolated populations in protected areas. Promoting gene flow can reduce the risk of extirpation often associated with isolated populations. Here we develop and test models for identifying landscape connections among African savannah elephant ( Loxodonta africana ) populations by combining habitat suitability modeling with gene flow estimates across a large region including seven countries. We find a pronounced non-linear response to unsuitable habitat, consistent with previous studies showing that non-transformed habitat models are poor predictors of gene flow. We generated a landscape connections map that considers both suitable habitats based on telemetry occurrence data and gene flow estimated as the inverse of individual genetic distance, delineating areas that are important for maintaining elephant population connectivity. Our approach represents a novel framework for developing spatially and genetically informed conservation strategies for elephants and many other taxa distributed across heterogeneous and fragmented landscapes.
GRAPHICAL ABSTRACT
... 30%) since 2006 [6,38], correlating with high rates of illegal killing [51,30] and large seizures of trafficked ivory [42,47]. This threat to a charismatic species results in lost tourism revenues for African states [22], dilutes the important ecosystem function of elephants [28] and results in both hunters and rangers losing their lives [5,1]. Conservation responses have involved a diversity of local and international interventions, from law enforcement and community engagement at the local level, to demand reduction and global ivory trade bans. ...
Ivory poaching continues to threaten African elephants. We (1) used criminology theory and literature evidence to generate hypotheses about factors that may drive, facilitate or motivate poaching, (2) identified datasets representing these factors, and (3) tested those factors with strong hypotheses and sufficient data quality for empirical associations with poaching. We advance on previous analyses of correlates of elephant poaching by using additional poaching data and leveraging new datasets for previously untested explanatory variables. Using data on 10 286 illegally killed elephants detected at 64 sites in 30 African countries (2002-2020), we found strong evidence to support the hypotheses that the illegal killing of elephants is associated with poor national governance, low law enforcement capacity, low household wealth and health, and global elephant ivory prices. Forest elephant populations suffered higher rates of illegal killing than savannah elephants. We found only weak evidence that armed conflicts may increase the illegal killing of elephants, and no evidence for effects of site accessibility, vegetation density, elephant population density, precipitation or site area. Results suggest that addressing wider systemic challenges of human development, corruption and consumer demand would help reduce poaching, corroborating broader work highlighting these more ultimate drivers of the global illegal wildlife trade.
... In addition, as competition for land grows, tensions around the historical displacement of people from PAs (75) may grow, increasing the risk of land conflicts and adverse outcomes for conservation. Hence, terrestrial, freshwater, and marine ecosystems in SSA are becoming increasingly degraded, reducing the abundance and diversity of species (86,88,(92)(93)(94)(95). Worryingly, some of the countries with the highest projected population growth rates are notable for their biodiversity, endemism, populations of charismatic wildlife, and vast PA estates, such as DRC, Ethiopia, and Tanzania (Figure 3). ...
Sub-Saharan Africa's (SSA's) iconic biodiversity is of immense potential global value but is jeopardized by increasing anthropogenic pressures. Elevated consumption in wealthier countries and the demands of international corporations manifest in significant resource extraction from SSA. Biodiversity in SSA also faces increasing domestic pressures, including rapidly growing human populations. The demographic transition to lower fertility rates is occurring later and slower in SSA than elsewhere, and the continent's human population may quadruple by 2100. SSA's biodiversity will therefore pass through a bottleneck of growing anthropogenic pressures, while also experiencing intensifying effects of climate change. SSA's biodiversity could be severely diminished over the coming decades and numerous species pushed to extinction. However, the prospects for nature conservation in SSA should improve in the long term, and we predict that the region will eventually enter a Green Anthropocene. Here, we outline critical steps needed to shepherd SSA's biodiversity into the Green Anthropocene epoch.