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St Lucia, South Africa

Pfab M.F.,South African National Biodiversity Institute | Victor J.E.,South African National Biodiversity Institute | Armstrong A.J.,Ezemvelo KZN Wildlife
Biodiversity and Conservation | Year: 2011

Biodiversity targets, or estimates of the quantities of biodiversity features that should be conserved in a region, are fundamental to systematic conservation planning. We propose that targets for species should be based on the quantitative thresholds developed for the Vulnerable category of the IUCN Red List system, thereby avoiding future listings of species in an IUCN Red List threat category or an increase in the extinction risk, or ultimate extinction, of species already listed as threatened. Examples of this approach are presented for case studies from South Africa, including threatened taxa listed under the IUCN Red List criteria of A to D, a species listed as Near Threatened, a species of conservation concern due to its rarity, and one species in need of recovery. The method gives rise to multiple representation targets, an improvement on the often used single representation targets that are inadequate for long term maintenance of biodiversity or the arbitrary multiple representation and percentage targets that are sometimes adopted. Through the implementation of the resulting conservation plan, these targets will ensure that the conservation status of threatened species do not worsen over time by qualifying for higher categories of threat and may actually improve their conservation status by eliminating the threat of habitat loss and stabilizing population declines. The positive attributes ascribed to the IUCN Red List system, and therefore to the species targets arising from this approach, are important when justifying decisions that limit land uses known to be detrimental to biodiversity. © 2011 Springer Science+Business Media B.V.

Nash K.L.,James Cook University | Allen C.R.,U.S. Geological Survey | Barichievy C.,Ezemvelo KZN Wildlife | Barichievy C.,University of Witwatersrand | And 3 more authors.
Oikos | Year: 2014

Habitat structure across multiple spatial and temporal scales has been proposed as a key driver of body size distributions for associated communities. Thus, understanding the relationship between habitat and body size is fundamental to developing predictions regarding the influence of habitat change on animal communities. Much of the work assessing the relationship between habitat structure and body size distributions has focused on terrestrial taxa with determinate growth, and has primarily analysed discontinuities (gaps) in the distribution of species mean sizes (species size relationships or SSRs). The suitability of this approach for taxa with indeterminate growth has yet to be determined. We provide a cross-ecosystem comparison of bird (determinate growth) and fish (indeterminate growth) body mass distributions using four independent data sets. We evaluate three size distribution indices: SSRs, species size-density relationships (SSDRs) and individual size-density relationships (ISDRs), and two types of analysis: looking for either discontinuities or abundance patterns and multi-modality in the distributions. To assess the respective suitability of these three indices and two analytical approaches for understanding habitat-size relationships in different ecosystems, we compare their ability to differentiate bird or fish communities found within contrasting habitat conditions. All three indices of body size distribution are useful for examining the relationship between cross-scale patterns of habitat structure and size for species with determinate growth, such as birds. In contrast, for species with indeterminate growth such as fish, the relationship between habitat structure and body size may be masked when using mean summary metrics, and thus individual-level data (ISDRs) are more useful. Furthermore, ISDRs, which have traditionally been used to study aquatic systems, present a potentially useful common currency for comparing body size distributions across terrestrial and aquatic ecosystems. © 2014 The Authors.

This study investigated the relationship between grazing veld condition and herbaceous plant species richness in the moist Midlands Mistbelt Grassland in KwaZulu-Natal. The observed herbaceous plant species richness and composition of 12 sample plots (50 m × 50 m) was determined in three study sites using quadrat samples (50 cm × 50 cm in size) and the estimated species richness was determined using the jacknife estimate of species richness. Grazing veld condition was established using the spike-point sampling technique and the benchmark method for data analysis. The relationship between the herbaceous plant species richness and the veld condition scores was determined using the linear and curvilinear correlation analysis. Veld condition scores for the 12 plots ranged from 2.43% to 120.65%, whereas the species richness ranged from 46 to 107 (observed) and 60 to 136 (estimated) species per plot. There was no relationship between herbaceous plant species richness and grazing veld condition scores (r = -0.2723, P = 0.392, df = 10, n = 12). Therefore, veld condition scores cannot be used as a surrogate for species diversity and vice versa. There was a positive curvilinear relationship between observed grass and forb species richness (r = 0.5478, P = 0.0652, df = 10, n = 12). © 2012 Copyright NISC Pty Ltd.

Karssing R.J.,Ezemvelo KZN Wildlife | Rivers-Moore N.A.,Consulting Freshwater Ecologist | Slater K.,Applied Behavioural Ecology and Ecosystem Research Unit
African Journal of Aquatic Science | Year: 2012

Current literature suggests that little, if any, research has been conducted in South Africa to determine the impact of alien trout on indigenous amphibian biodiversity. The aim of this study was to establish whether waterfalls in the uKhahlamba Drakensberg Park, South Africa, are seasonally important in conserving indigenous Natal cascade frog Hadromophryne natalensis tadpole populations from the threat of predation by alien rainbow trout Oncorhynchus mykiss and brown trout Salmo trutta at Injesuthi and Monk's Cowl Nature Reserves, respectively. Relative abundances of trout and tadpoles of Natal cascade frogs were assessed after sampling using electrofishing. Habitat templates were compared for above- versus below-waterfall sites. Trout predation is the most likely causative agent for an observed abrupt decline in H. natalensis tadpole abundance occurring below waterfalls. Tadpole abundance in the study was reduced by a factor of 4.69 and 15.71 below the selected waterfalls at Injesuthi and Monk's Cowl in association with O. mykiss and S. trutta populations, respectively. © 2012 Copyright NISC (Pty) Ltd.

Nash K.L.,James Cook University | Allen C.R.,U.S. Geological Survey | Angeler D.G.,Swedish University of Agricultural Sciences | Barichievy C.,Ezemvelo KZN Wildlife | And 10 more authors.
Ecology | Year: 2014

Ecological structures and processes occur at specific spatiotemporal scales, and interactions that occur across multiple scales mediate scale-specific (e.g., individual, community, local, or regional) responses to disturbance. Despite the importance of scale, explicitly incorporating a multi-scale perspective into research and management actions remains a challenge. The discontinuity hypothesis provides a fertile avenue for addressing this problem by linking measureable proxies to inherent scales of structure within ecosystems. Here we outline the conceptual framework underlying discontinuities and review the evidence supporting the discontinuity hypothesis in ecological systems. Next we explore the utility of this approach for understanding cross-scale patterns and the organization of ecosystems by describing recent advances for examining nonlinear responses to disturbance and phenomena such as extinctions, invasions, and resilience. To stimulate new research, we present methods for performing discontinuity analysis, detail outstanding knowledge gaps, and discuss potential approaches for addressing these gaps. © 2014 by the Ecological Society of America.

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