Browsing by Author "Lombard, Amanda T"

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    Accommodating dynamic oceanographic processes and pelagic biodiversity in marine conservation planning
    (Public Library of Science, 2011) Grantham, Hedley S; Game, Edward T; Lombard, Amanda T; Hobday, Alistair J; Richardson, Anthony J; Beckley, Lynnath E; Pressey, Robert L; Huggett, Jenny A; Coetzee, Janet C; Van der Lingen, Carl D
    Pelagic ecosystems support a significant and vital component of the ocean's productivity and biodiversity. They are also heavily exploited and, as a result, are the focus of numerous spatial planning initiatives. Over the past decade, there has been increasing enthusiasm for protected areas as a tool for pelagic conservation, however, few have been implemented. Here we demonstrate an approach to plan protected areas that address the physical and biological dynamics typical of the pelagic realm. Specifically, we provide an example of an approach to planning protected areas that integrates pelagic and benthic conservation in the southern Benguela and Agulhas Bank ecosystems off South Africa. Our aim was to represent species of importance to fisheries and species of conservation concern within protected areas. In addition to representation, we ensured that protected areas were designed to consider pelagic dynamics, characterized from time-series data on key oceanographic processes, together with data on the abundance of small pelagic fishes. We found that, to have the highest likelihood of reaching conservation targets, protected area selection should be based on time-specific data rather than data averaged across time. More generally, we argue that innovative methods are needed to conserve ephemeral and dynamic pelagic biodiversity.
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    Current patterns of habitat transformation and future threats to biodiversity in terrestrial ecosystems of the Cape Floristic Region, South Africa
    (2003) Rouget, Mathieu; Richardson, David M; Cowling, Richard M; Lloyd, J Wendy; Lombard, Amanda T
    The formulation of an effective strategic plan for biodiversity conservation in the Cape Floristic Region (CFR) requires an assessment of the current situation with regard to habitat transformation, and an explicit framework for predicting the likelihood of remaining habitat (i.e. that potentially available for conservation) being transformed. This paper presents the results of a detailed assessment of the current and future extent of three important factors that threaten biodiversity in the CFR: cultivation for intensive agriculture (including commercial forestry plantations), urbanisation, and stands of invasive (self-sown) alien trees and shrubs. The extent of habitat transformation was mapped at the scale of 1:250,000, using primarily satellite imagery. We compared models derived from a rule-based approach relying on expert knowledge and a regression-tree technique to identify other areas likely to be affected by these factors in future. Cultivation for agriculture has transformed 25.9% of the CFR and dense stands of woody alien plants and urban areas each cover 1.6%. Both models predict that at least 30% of the currently remaining natural vegetation could be transformed within 20 years. There was an overall accuracy of 73% between both models although significant differences were found for some habitat types. Spatial predictions of future agriculture threats derived from the rule-based approach were overestimated relative to the statistical approach, whereas future alien spread was underestimated. Threat assessment was used to derive conservation targets for subsequent stages of conservation planning for the CFR. The importance of integrating vulnerability knowledge into conservation planning is discussed. The choice of vulnerability analysis (future habitat degradation and/or impact on biological entities) and methods will depend on the complexity of the threatening processes and the availability of spatial data.
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    The thermal implications and ecological consequences of coloration in selected species : tenebrionid beetles (Onymacris bicolor and Onymacris ungui cularis), Cape gannets (Morus capensis) and Cape cormorants (Phalacrocorax capensis)
    (1989) Lombard, Amanda T; Louw, Gideon
    The thermal significance of coloration was investigated in two species of Namib Desert tenebrionid beetles and two species of marine birds. Body temperatures and heat fluxes of a black beetle (Onymacris unguicularis) and a beetle with white elytra (Onymacris bicolor) were compared in a wind tunnel in the laboratory. The effects of visible radiation, infrared radiation, conduction, convection, beetle colour and substratum colour on body temperature were analysed. Results showed that body colour has no overall effect on body temperature. Black elytra are warmed more by visible radiation, but colour is not relevant to heat loss by convection, or to heat flux between a beetle and a heated sand substratum, whether by emitted radiation or reflected visible radiation. 0. bicolor absorbs more heat by conduction and free convection from a heated substratum, but differences in shape between the two species may explain this effect. Combining the various modes of heat exchange to simulate natural conditions reveals that the extra heat absorbed by black elytra is readily dissipated by convection, and owing to the increased heating of white beetles from the substratum, heat fluxes between the two beetles balance. Body temperatures of dead and live beetles of both species were also measured in the field. Experiments were conducted on a hot sand substratum in the beetles' natural environment, under both visible (sunny) and infrared (shaded) conditions. Results supported the laboratory experiments, and showed that when temperature differences do occur between black and white beetles, these differences are generally less than 3.5 °C. These differences are small when compared with the ranges of body temperatures experienced by active beetles in the field (± 10 °C). In addition, these temperature differences occur only at low wind speeds (< 2 m s-1). Activity studies in the field showed that beetles choose to be active in high wind speeds, possibly because of the nature of their food source, which is wind-blown detritus. It is concluded that coloration does not have adaptive value in terms of the thermal biology of Namib Desert tenebrionid beetles. Physical properties of the plumages of white Cape gannets (Morus capensis) and black Cape cormorants (Phalacrocorax capensis ) were measured. Black plumages absorb more visible radiation than white plumages in still conditions. However, laboratory experiments with excised plumages showed that at wind speeds of 2 m s-1, cormorant plumages and skins were only 2-3 °C warmer than those of gannets. These differences disappeared at wind speeds of (< 2 m s-1). A biophysical heat transfer model predicted that in still, warm, sunny conditions, cormorants may gain up to 185 of their field metabolic rates, whereas gannets would gain only 42 . Field observations confirmed that nesting cormorants experience greater heat stress than gannets, even though cormorant nests occur in areas of lower micrometeorological temperatures. Cormorants begin to dissipate heat by evaporative water loss (i.e. pant) at lower environmental temperatures than gannets. The thermal consequence of coloration in these two species are that cormorants may have a lower cost of endothermy at temperatures below the thermoneutral zone, but may experience more heat stress during warm conditions; cormorants select cooler and windier nesting sites than gannets; and increased surf ace temperatures of black cormorant plumages may aid evaporative water loss from wet plumages, facilitating wing-drying. However, ptiloerection and wind may interact in the natural environment, negating the differential heating effects of coloration. It is concluded that the thermal implications of colour are negligible in both species, considering the temperate nature of their environment; Colour in both species is best explained by feeding ecology: white coloration is conspicuous to conspecifics and cryptic to prey in plunge divers (gannets), whereas black colour is cryptic to both conspecifics and prey in solitary swimmers (cormorants).