Karen Esler

Karen Esler
Stellenbosch University | SUN · Department of Conservation Ecology and Entomology

PhD

About

303
Publications
108,104
Reads
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7,950
Citations
Additional affiliations
January 2006 - December 2012
Stellenbosch University, South Africa
Position
  • Stellenbosch

Publications

Publications (303)
Article
Full-text available
Wetland communities are shaped by high levels of stress, disturbance and competition. Using South African palmiet wetlands as a case study (Prionium serratum dominated valley-bottom wetlands), we explore whether autogenic or allogenic succession is the dominant process driving community dynamics in valley-bottom wetlands in drylands. Several wetlan...
Chapter
Full-text available
Chapter 6 deals with the set of methods related to ecological field data-collection methods, which can be used to understand how human activities influence ecological elements and processes, and how ecological patterns and processes influence social outcomes. The chapter discusses point counts and survey grids, transects, distance and plotless samp...
Article
Invasive alien plants negatively impact ecosystems, but recovery of native vegetation may fail following standard methods of alien species removal alone. Alternative management actions may thus be required. Cape Flats Sand Fynbos is a critically endangered vegetation type in the Cape Floristic Region of South Africa which is threatened by Acacia sa...
Article
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Community and invasion ecology have mostly grown independently. There is substantial overlap in the processes captured by different models in the two fields, and various frameworks have been developed to reduce this redundancy and synthesize information content. Despite broad recognition that community and invasion ecology are interconnected, a pro...
Article
Invasive alien plants negatively impact ecosystems, necessitating intricate management actions. In a critically endangered vegetation type within the fynbos biome of South Africa, a study was performed comparing different management interventions over plots invaded by Acacia saligna. A dynamic modelling approach was designed to analyze field data a...
Article
Palmiet, Prionium serratum, is an endemic wetland plant which dominates oligotrophic wetlands throughout the Cape Floristic Region, South Africa. Palmiet is often perceived as undesirable by landowners, in part because it is thought to have high water-use, although little is known about the water-use of this important wetland species. We estimated...
Article
The negative impact of invasive alien plants (IAPs) in protected areas (PAs) is managed through control programmes, often using area‐based management, where identified IAPs in management units are controlled simultaneously. However, this approach has shortfalls, including the methods used to prioritise management units, spatial grain dependence and...
Article
Conservation managers are required to make decisions in complex and uncertain contexts. To strengthen the robustness of conservation decisions, several approaches have been proposed to facilitate stakeholder engagement in the setting of conservation objectives and priority actions. While such processes have led to the formulation of several invasiv...
Article
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Ecological restoration is a global imperative to reverse widespread habitat loss and degradation, including by invasive alien plants. In South Africa’s Core Cape Subregion, alien tree invasions are widespread and their control continues to be a major undertaking. As funding is limited, active restoration interventions are rarely implemented and the...
Article
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Humanity is on a deeply unsustainable trajectory. We are exceeding planetary boundaries and unlikely to meet many international sustainable development goals and global environmental targets. Until recently, there was no broadly accepted framework of interventions that could ignite the transformations needed to achieve these desired targets and goa...
Article
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Private land conservation areas (PLCAs) are increasingly looked to for meeting the deficit left by state-owned protected areas in reaching global conservation targets. However, despite the increasing extent and recognition of PLCAs as a complementary conservation strategy, little research has been done to quantify their effectiveness; a critical co...
Article
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This study attempts to understand how invasive legumes such as Acacia saligna may compete with indigenous legumes such as Virgilia divaricata. The two species are trees with similar growth forms. We studied the competitive ability of invasive and indigenous seedlings under variations in soil phosphorus availability. South African fynbos vegetation...
Chapter
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Increasing resources are being allocated both to the management and research of biological invasions in South Africa. However, as with many natural resource management and conservation programmes globally, the question remains as to what extent the science provides the necessary answers for management, and whether it influences decision-making. Thi...
Chapter
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Invasive alien plant species can be a major cause of ecosystem degradation in South Africa, and ecosystem recovery may require restoration interventions beyond controlling the target alien species. Active restoration interventions are usually required if legacy effects result from the invasion. Legacy effects may induce regime shifts when threshold...
Article
Full-text available
The ecological niche of a species describes the variation in population growth rates along environmental gradients that drives geographic range dynamics. Niches are thus central for understanding and forecasting species’ geographic distributions. However, theory predicts that migration limitation, source–sink dynamics, and time-lagged local extinct...
Article
The Cape south coast of South Africa has attracted significant archaeological research because it hosts the earliest evidence of human cultural and material complexity. Furthermore, the now-submerged Palaeo-Agulhas Plain provided habitat and resources for humans during the emergence of modern behavioural traits. Using a human behavioural ecology ap...
Article
Tree bark is widely used in traditional medicine in southern Africa. The growing demand for medicinal bark requires scientifically sound harvest systems for sustainable use. A conceptual framework and decision matrix are presented to aid forest managers in selecting the most appropriate system for the sustainable harvesting of particular species. T...
Chapter
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Urban areas are considered hotspots for invasions by alien plant communities. Anthropogenic activity within these areas often facilitates the introduction and spread of invasive alien plants, with urban gardens acting as a significant source of propagules. This makes natural areas within and surrounding urban areas particularly vulnerable to invasi...
Article
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Although conceptual frameworks describing biodiversity and cultural keystone species have been widely accepted over the past 15 years, there remains a need for an overarching framework that covers the various components of biocultural diversity. We present a conceptual framework to enable the better understanding, monitoring, and maintenance of bio...
Article
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The Hutchinsonian niche is a foundational concept in ecology and evolutionary biology that describes fundamental characteristics of any species: the global maximum population growth rate (rmax); the niche optimum (the environment for which rmax is reached); and the niche width (the environmental range for which intrinsic population growth rates are...
Article
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The identification of research questions with high relevance for biodiversity conservation is an important step towards designing more effective policies and management actions, and to better allocate funding among alternative conservation options. However, the identification of priority questions may be influenced by regional differences in biodiv...
Article
A horizon scan was conducted to identify emerging and intensifying issues for biodiversity conservation in South Africa over the next 5–10 years. South African biodiversity experts submitted 63 issues of which ten were identified as priorities using the Delphi method. These priority issues were then plotted along axes of social agreement and scient...
Article
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We conducted a survey among people working in the nature conservation community in an implementation, research or policy capacity to identify research questions that they felt were important for ensuring the conservation of the Cape Floristic Region. Following an inductive process, 361 submitted questions were narrowed to 34 questions in seven them...
Article
It is often assumed that clearing invasive alien species will lead to the dissipation of their negative impacts and recovery of native plant diversity. However, this is often not the case because clearing of primary invasive alien species can lead to secondary invasion by non-target species. We investigated the effects of vegetation type and applic...
Article
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Aim Species distribution models (SDMs) provide valuable insights into species–environment relationships and potential climate change impacts on diversity. Most SDMs do not account for the role of natural disturbance regimes such as fire in determining current and future species distributions, or how species traits mediate their response to these st...
Article
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Protected areas and adjacent landscapes are increasingly being viewed as integrated. A more general awareness is emerging of the relevance of collectively managed landscapes for conservation and human well-being. In Namibia, areas dedicated to conservation are increasing because of the proliferation of conservancies and game reserves. Management to...
Article
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Insect predator densities and plant nutritional status can affect insect herbivore densities, but these effects have not yet been assessed in the context of an invasive species management. This study investigated the influence of (i) altered predatory arthropod abundance and community composition (top-down-effects); and (ii) altered leaf nitrogen a...
Article
Wetlands globally are highly threatened by agriculture, and damage associated with it, such as invasion by alien species and the impacts of fertilizers and pesticides. South African palmiet wetlands make an interesting case study to investigate this, as they are valuable valley-bottom, peat-forming systems, highly threatened by agricultural develop...
Article
In many protected areas in South Africa, invasive Australian Acacia species pose on-going management challenges, perpetuating high long-term management costs. Due to limited availability of resources, conservation actions need to be prioritised within and across Protected Areas (PA). We draw on comprehensive datasets spanning over 20 years from the...
Article
An improved understanding of indigenous plant use by humans over time may assist in our understanding of how the Greater Cape Floristic Region's flora (GCFR) contributed to the survival of modern humans. To address this issue, two databases were created documenting all archaeological (all plant species found in archaeological sites dating 0–80,000...
Article
Humans that inhabited the glacial refugia in the Cape Floristic Region are assumed to have harvested and consumed plant underground storage organs (USOs) as an important carbohydrate source during the Middle Pleistocene. Botha et al. (this issue), Singels et al. (this issue) and others have demonstrated the rich resource that such plants might offe...
Article
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Studies of invasive Australian Acacia have shown that many seeds are still produced and accumulate in soil stored seed banks regardless of the presence of seed-targeting biological control agents. This is despite claims of biological control success, although there is generally a lack of data on the seed production of invasive Australian Acacia bef...
Article
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Addressing complex challenges facing social-ecological systems (SES) requires the integration of knowledge from a diversity of disciplines and stakeholders. This requirement has resulted in the establishment of many integrative research programmes, both globally and locally, aimed at coproducing knowledge relevant to solving SES challenges. However...
Article
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The legume Acacia mearnsii invades South Africa’s fynbos riparian zones and may alter the nitrogen (N) dynamics and supply in these areas that typically support few native N fixers. Nitrogen uptake by A. mearnsii may also be influenced by water availability, potentially affecting riparian-specific performance and impact estimations. We expected to...
Preprint
Full-text available
The ecological niche of a species describes the variation in population growth rates along environmental gradients that drives geographic range dynamics. Niches are thus central for understanding species geographic distributions and forecasting biodiversity responses to environmental change. However, theory predicts that migration limitation, sourc...
Article
Moving towards more integrative approaches within the invasion sciences has been recognized as a means of improving linkages between science, policy, and practice. Yet despite the recognition that biological invasions pose complex social-ecological challenges, the invasion literature poorly covers social-ecological or distinctly integrative researc...
Article
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The concept of “connectedness with nature” is increasingly used in environmental and sustainability discourse. However, this construct has also been critiqued and proponents charged with harboring an ambivalence that paradoxically reinforces a sense of separation from “nature”. We respond to one critique by demonstrating that whilst problematizing...
Article
The success of different rehabilitation treatments following surface mining on the arid west coast of South Africa was assessed. Treatments consisting of one or a combination of topsoil addition, plant translocation and seeding were applied to experimental rehabilitation sites in 2001, while the treatment of another site in 2008 combined all three...
Article
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There are many different anthropogenic causes of wetland degradation, such as disturbances which affect the physical structure of wetlands, resulting in erosion (altered fire regimes, road and railway building through wetlands, channelization of wetlands), pollution, land-cover change, and climate change. These different types of degradation have v...
Article
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Successful long-term invasive alien plant control programmes rely on alien plant distribution and abundance data to assess, prioritise, implement and monitor the efficacy of the programme. Here we assess the impact of data accuracy using the alien plant programme in Table Mountain National Park, South Africa. A systematic plot-based survey method w...
Article
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Introduced rainbow trout Oncorhynchus mykiss have invaded many headwater streams in South Africa’s Cape Fold Ecoregion (CFE) and pose arguably the greatest threat to several species of threatened native fishes. Trout impacts in these systems appear to be density-dependent; we hypothesized that temperature is a key factor determining trout density a...
Article
We evaluated the impact of non-native rainbow trout Oncorhynchus mykiss on a population of endemic Cedarberg ghost frog Heleophryne depressa in the upper Krom River (Olifants-Doring River Catchment, Cape Fold Ecoregion). We compared H. depressa abundance (using kick-sampling and underwater video analysis) and environmental conditions between sites...
Article
Despite the importance of water purification to society, it is one of the more difficult wetland ecosystem services to quantify. It remains an issue in ecosystem service assessments where rapid estimates are needed, and poor-quality indicators are overused. We attempted to quantify the water purification service of South African palmiet wetlands (v...
Article
Effective ecological restoration requires detailed monitoring to determine the success achieved through different interventions in achieving objectives. In 2017, we resurveyed riparian sites along the Berg River in the Western Cape, South Africa, that have been cleared of invasive stands of Eucalyptus camaldulensis in 2010 using two clearing method...
Article
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We provide reflectance spectra for 22 South African palmiet wetland species collected in spring 2015 from three wetlands throughout the Cape Floristic Region. In addition, we provide summarized plant functional trait data, as well as supporting and meta-data. Reflectance spectra were collected with a portable ASD Fieldspec Pro using standard method...
Article
For pasture-based dairy farming to become more sustainable, the negative environmental impacts associated with milk production must be minimized. These negative impacts include eutrophication, ammonia emissions and greenhouse gas (GHG) emissions. Two tools, a nutrient budget and a carbon footprint calculator, allow farmlevel assessments of these ne...
Article
Full-text available
African savannas are increasingly affected by woody encroachment, an increase in the density of woody plants. Woody encroachment often occurs unexpectedly, is difficult to reverse, and has significant economic, cultural and ecological implications. The process of woody encroachment represents a so-called regime shift that results from feedback loop...
Book
The world’s mediterranean-type climate regions (including areas within the Mediterranean, South Africa, Australia, California, and Chile) have long been of interest to biologists by virtue of their extraordinary biodiversity and the appearance of evolutionary convergence between these disparate regions. Comparisons between mediterranean-type climat...
Article
Lantana camara L. (sensu lato), one of the world’s worst invaders has disseminated rapidly and continues to expand in its invaded range. Invasiveness of a species can broadly be gauged by determining trait values, considered as manifestation of performance ability. In spite of vast range expansion, performance of Lantana in its different invaded ra...
Article
Full-text available
Tree euphorbias share many traits with arborescent cacti in having tall and multi-branched forms of growth which have selective value for maximizing photosynthetic surface area and water storage. The candelabra growth form of Euphorbia cooperi, and likely other Euphorbia species with similar canopy architecture in southern Africa, allows these plan...
Article
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The degree to which invasive Acacia species affect South Africa’s livestock production has received little attention. We investigated the ecological impacts of Acacia mearnsii invasion on forage quality and quantity and on soil resources, along A. mearnsii invasion gradients, on South African rangelands and the subsequent conditions following clear...
Article
To become more sustainable, dairy farms should aim to maximise productivity at a minimum cost to the environment. Standard environmental impact measures were combined with non-parametric total factor productivity analysis to investigate if this is possible in a pasture-based production system. Stocking density and energy-corrected milk production p...
Article
Native freshwater fish populations throughout South Africa's Cape Fold Ecoregion (CFE) are in decline as a result of human impacts on aquatic habitats, including the introduction of non-native freshwater fishes. Climate change may be further accelerating declines of many species, although this has not yet been studied in the CFE. This situation pre...
Article
Scenarios are important tools to facilitate the communication among scientists, practitioners, and decision-makers, and, thus to support policy and management decisions. The use of scenarios has an enormous potential to reduce ecosystem restoration costs and to optimize benefits, but this potential remains poorly explored. Here, we recommend and il...
Article
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According to recent national energy plans and policy documents, the number of renewable energy developments is expected to increase in South Africa, thus contributing to the diversification of the country’s energy system. Consequently, numerous solar power developments are being deployed in the sunny arid interior – areas generally represented by t...
Article
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The canopies of many tree species sustain a large diversity of folivorous arthropods and phytopathogenic fungi. These organisms are thought to influence overall tree and stand productivity. Leaf diseases caused by Phyllosticta owaniana and Periconiella velutina, phytopathogenic fungi commonly found on the native riparian tree Brabejum stellatifoliu...
Article
Scenarios are important tools to facilitate the communication among scientists, practitioners, and decision-makers, and, thus to support policy and management decisions. The use of scenarios has an enormous potential to reduce ecosystem restoration costs and to optimize benefits, but this potential remains poorly explored. Here, we recommend and il...
Article
Pine plantations and pine invasions have numerous impacts on native ecosystems in the Fynbos biome of South Africa. The severity of these impacts greatly determines the extent of potential ecosystem recovery after the pines are felled. The recovery potential of fynbos after felling of pine plantations of varying longevity and the subsequent applica...
Article
The degree to which renosterveld shrublands are fire-dependent is currently unclear. To address this issue, the following questions were asked: Does smoke stimulate germination of soil-stored seeds in renosterveld? Does recently-burned renosterveld display changed composition and higher diversity than unburned vegetation? How do the species composi...