Working Within Constraints: Managing African Savannas for Animal Production and Biodiversity

The mean density of livestock biomass on African rangelands now greatly exceeds that of indigenous large herbivores, although livestock cannot fully substitute for wildlife with respect to co-evolved ecosystem processes involving herbivory. The dominance of livestock in semi-arid rangelands is largely due to water provision, which uncouples livestock population dynamics from the rainfall-driven trajectories followed by indigenous ungulate species in wildlife areas. Ecological sustainability cannot be achieved with a few exotic species maintained at unprecedented biomass densities in savanna ecosystems, which are evolutionarily adapted for species-rich communities of ungulates of a wise range of sizes. Integrating wildlife and livestock in multi-species animal production systems offers a partial solution. Community-based ecotourism can effectively augment pastoralism in semi-arid rangelands but, as rainfall increases, the opportunity costs become too high. Direct payment approaches show promise for offsetting opportunity costs, although major obstacles remain in the form of political corruption and obstructive practices by national governments

\u3cem\u3eThe Director\u27s Desk\u3c/em\u3e Standardizing the Data on Wildlife-Vehicle Collisions

There are few more dramatic manifestations of human– wildlife conflict than squealing brakes, a sickening crunch, flying gravel, and then silence except for the weakly spasmodic scrabbling of a semipulverized deer as it lies dying on the side of a highway. The scientific analysis of wildlife–vehicle collisions is an applied science of increasing importance throughout the industrialized world, but it is yet woefully deficient in theoretical underpinnings and standardized methodology. The overarching discipline of road ecology has only recently gained formal recognition through the publication of the first definitive book on this topic by Forman et al. (2003). And until now, there has not been a target journal in which research on the problem of wildlife– vehicle collisions can be highlighted and developed within a focused readership

The Differences Between Rewilding and Restoring an Ecologically Degraded Landscape

Rewilding is a developing concept in ecosystem stewardship that involves reorganizing and regenerating wildness in an ecologically degraded landscape, with present and future ecosystem function being of higher consideration than historical benchmark conditions. This approach differs from ecosystem restoration but the two concepts are often conflated because (a) they both rely on similar management actions (at least initially) and (b) it can be erroneously assumed that they both aim for similar states of wildness. Rewilding and restoring both influence biodiversity, and common management actions such as species reintroductions (e.g. beavers or wolves) can be integral to a rewilding project. However, in contrast with restoration, rewilding has lower fidelity to taxonomic precedent and promotes taxonomic substitutions for extinct native species that once underpinned the delivery of key ecological functions. We suggest the adaptive cycle as the appropriate conceptual framework in which to distinguish rewilding from ecosystem restoration. The focus of restoration ecology is to return an ecosystem to as close to its former state as is possible after a major disturbance, by directly reinstating it on the ‘foreloop’ of the adaptive cycle. In contrast, rewilding draws from the ‘backloop’ by promoting reorganization and redevelopment of the ecosystem under changing environmental conditions. If environmental conditions have changed so significantly that a regime shift is inevitable, then rewilding can facilitate the development of a novel ecosystem to sustain the provision of ecosystem services. Synthesis and applications. Rewilding and restoring both have their places in biodiversity conservation. In each case, their respective merits should be weighed in relation to stakeholder priorities, prevailing and predicted environmental conditions, the level of biological organization targeted for management, and existing and future management capacity. We provide simple schematic decision‐pathways to assist in exploring whether an ecologically degraded landscape might be a candidate for restoration, active rewilding, or passive rewilding

Browsing lawns? Responses of Acacia nigrescens to ungulate browsing in an African savanna

We measured browsing-induced responses of Acacia trees to investigate browsing lawns as an analogy to grazing lawns in a semiarid eutrophic African savanna. During the two-year field study, we measured plant tolerance, resistance, and phenological traits, while comparing variation in leaf nitrogen and specific leaf area (SLA) across stands of Acacia nigrescens, Miller, that had experienced markedly different histories of attack from large herbivores. Trees in heavily browsed stands developed (1) tolerance traits such as high regrowth abilities in shoots and leaves, high annual branch growth rates, extensive tree branching and evidence of internal N translocation, and (2) resistance traits such as close thorn spacing. However, phenological escape responses were weak even in heavily browsed stands. Overall, browsing strongly affected plant morpho-functional traits and decreased both the number of trees carrying pods and the number of pods per tree in heavily browsed stands. Hence, there is experimental evidence that tolerance and resistance traits may occur simultaneously at heavily browsed sites, but this comes at the expense of reproductive success. Such tolerance and resistance traits may coexist if browsers trigger and maintain a positive feedback loop in which trees are continually investing in regrowth (tolerance), and if the plant\u27s physical defenses (resistance) are not nutritionally costly and are long-lived. Our results confirm that chronic browsing by ungulates can maintain A. nigrescens trees in a hedged state that is analogous to a grazing lawn. Further research is needed to fully understand the long-term effects of chronic browsing on reproduction within such tree populations, as well as the overall effects on nutrient cycling at the ecosystem level

Ripple compensation for a class-D amplifier

This paper presents the first detailed mathematical analysis of the ripple compensation technique for reducing audio distortion in a class-D amplifier with negative feedback. The amplifier converts a relatively low-frequency audio signal to a high-frequency train of rectangular pulses whose widths are slowly modulated according to the audio signal (pulse-width modulation, PWM). Distortion manifests itself through unwanted audio-frequency harmonics that arise in the output due to nonlinearities inherent in the design. In this paper, we first develop a small-signal model, which describes the fate of small-amplitude perturbations to a constant input, and demonstrate how this traditional engineering tool may be extended to allow one to infer the most significant contributions to the full output in response to a general audio input. We then compute the audio output of the amplifier through a perturbation expansion based on the ratio between audio and switching frequencies. Our results explicitly demonstrate how the ripple compensation technique significantly linearizes the output, thereby reducing the distortion

Orthopaedic referrals using a smartphone app: Uptake, response times and outcome

Background. It is well established that South Africa (SA) suffers an immense burden of violence and injuries. The responsibility of providing care for these injuries falls mainly on public health services, resulting in overloading of the health system. Prior to a recent intervention, the large burden had been exacerbated by limitations in the traditional referral system that highlighted the need for a better referral system. Vula’s smartphone app was introduced at Tygerberg Hospital in August 2016. This study evaluated the uptake, response times and outcomes using this app.Objectives. The main objectives of the study were to describe: (i) the number of referrals; (ii) referral response times; (iii) referring facilities; and (iv) referral outcomes. Secondary objectives were to: (i) evaluate whether the referral outcome pathway was appropriate; and (ii) assess professional conduct and evidence of upskilling.Methods. This retrospective, descriptive study investigated Vula app referrals to the Division of Orthopaedic Surgery at Tygerberg Hospital between 1 August 2016 and 31 March 2017. Vula was advertised to key facilities in the hospital’s referral network. All referrals to the division during the study period were systematically included in the analysis of operational outcomes, although some were excluded from the subsequent referral outcome analysis. Operational outcomes included the number of referrals, referring facilities and referral response times. Referral outcome analysis included the clinical diagnosis, referral pathway, whether the referral was used for upskilling and whether it was conducted in a professional manner.Results. A total of 2 275 referrals from 39 different facilities were received during the study period from 238 individual users; 50% of referrals received a response within 11 minutes, while a small percentage received no response. Clinical and demographic characteristics of 1 985 patients included in the referral outcome analysis indicated that the majority of trauma and emergency referrals involved males, with closed fractures being the most frequent clinical presentation. Although the most common referral outcome was immediate transfer, one-third of the patients were treated at the referring hospital with advice only.Conclusions. The large volume of orthopaedic referrals received through the Vula app suggests that Vula represents a successful alternative to traditional referral methods. Referrals managed by advice only could suggest that Vula facilitates some relief for the overburdened trauma services. Future research could further explore Vula’s role in strengthening the public health system, including interventions for high-volume referral areas and upskilling of referring health workers.