Karst in southern Africa

[spa] En el presente trabajo se revisa la distribución de las rocas karstificables en África meridional, distinguiendo entre dos clases predominantes: las calizas dolomíticas proterozoicas de textura esparítica, propias de las mesetas interiores, y las calizas arenosas terciarias de la costa, cuya textura es micritica. La densidad de formas kársticas superficiales es variable y comparativamente baja en relación con otras regiones. Las cuevas corresponden a un origen freático-somero y pueden contener abundantes espeleotemas. Se han podido detectar dos fases principales de crecimiento, aunque la precipitación moderna es menos intensa. El más importante periodo de karstificación puede ser atribuido a tiempos considerablemente remotos. Los impactos ambientales sobre el karst de África meridional abarcan desde cambios en la hidrogeología debido a la extracción de agua con fines económicos, pasando por el drenaje de minas y las modificaciones en la cubierta superficial, hasta efectos directos resultantes de actividades mineras, en especial para la obtención de oro, de guano de murciélago y primitivamente de espeleotemas. Algunas rocas madres son empleadas en minería para su aprovechamiento en la fabricación de acero. Hasta ahora los problemas causados por la contaminación son de escasa importancia. Las cuevas situadas cerca de los principales centros de población sufren impactos de utilización que a menudo pasan inadvertidos. Las consecuencias de nuevas instalaciones militares, junto a Bredasdorp están siendo objeto de seguimiento. En África meridional se cuenta con las bases necesarias para la realización de programas efectivos de gestión ambiental.[eng] The paper reviews the distribution of karst rocks in southern Africa and distinguishes between two dominant types: the sparitic Proterozoic dolomitic limestones of the interior plateaux and the Tertiary micritic sandy limestones of the coast. The density of surface karst forms is variable and low by comparison with overseas regions. Caves are shallow phreatic in origin and may contain massive speleothem development. Two major phases of growth are recognised. Modern precipitation is minor. The major karst forming period is believed to be of considerable antiquity. The impacts on southern African karst range from changes to the geohydrology due to economic extraction, mine dewatering and changes to the surface cover, to direct effects of mining particularly for gold, for bat guano and formerly for speleothems. Some host rock is directly mined for use in steel making. Pollution is so far of minor importance. Caves near major population centres suffer user impact which is often inadvertent. The consequences of a new military installation near Bredasdorp are being monitored. In southern Africa the basis exists for effective management programmes

Spatial patterns of large African cats : a large-scale study on density, home range size, and home range overlap of lions Panthera leo and leopards Panthera pardus

SUPPORTING INFORMATION : APPENDIX S1. Site information. APPENDIX S2. Intuitive explanation of the autocorrelated kernel density estimator. APPENDIX S3. Sources of density data. APPENDIX S4. Mathematical modifications of Jetz et al.’s (2014) overlap equation. APPENDIX S5. Lion pride size data.1. Spatial patterns of and competition for resources by territorial carnivores are typically explained by two hypotheses: 1) the territorial defence hypothesis and 2) the searching efficiency hypothesis. 2. According to the territorial defence hypothesis, when food resources are abundant, carnivore densities will be high and home ranges small. In addition, carnivores can maximise their necessary energy intake with minimal territorial defence. At medium resource levels, larger ranges will be needed, and it will become more economically beneficial to defend resources against a lower density of competitors. At low resource levels, carnivore densities will be low and home ranges large, but resources will be too scarce to make it beneficial to defend such large territories. Thus, home range overlap will be minimal at intermediate carnivore densities. 3. According to the searching efficiency hypothesis, there is a cost to knowing a home range. Larger areas are harder to learn and easier to forget, so carnivores constantly need to keep their cognitive map updated by regularly revisiting parts of their home ranges. Consequently, when resources are scarce, carnivores require larger home ranges to acquire sufficient food. These larger home ranges lead to more overlap among individuals’ ranges, so that overlap in home ranges is largest when food availability is the lowest. Since conspecific density is low when food availability is low, this hypothesis predicts that overlap is largest when densities are the lowest. 4. We measured home range overlap and used a novel method to compare intraspecific home range overlaps for lions Panthera leo (n = 149) and leopards Panthera pardus (n = 111) in Africa. We estimated home range sizes from telemetry location data and gathered carnivore density data from the literature. 5. Our results did not support the territorial defence hypothesis for either species. Lion prides increased their home range overlap at conspecific lower densities whereas leopards did not. Lion pride changes in overlap were primarily due to increases in group size at lower densities. By contrast, the unique dispersal strategies of leopards led to reduced overlap at lower densities. However, when human-caused mortality was higher, leopards increased their home range overlap. Although lions and leopards are territorial, their territorial behaviour was less important than the acquisition of food in determining their space use. Such information is crucial for the future conservation of these two iconic African carnivores.The Natural Sciences and Engineering Research Council of Canada and a Hugh Kelly Fellowship from Rhodes University, Grahamstown, SA.https://onlinelibrary.wiley.com/journal/13652907am2024Centre for Wildlife ManagementMammal Research InstituteZoology and EntomologySDG-15:Life on lan

An ethic for geography: The role of the affective domain in developing environmental awareness

Geography is a subject with integral ethical and moral components. However, because of the subject's traditionally close association with scientific rationality this factor has not always been recognised. The significance .of the affective dimension of geographical learning is explored for tts value in creating and developing both environmental awareness and environmental responsibility

Spatial patterns of large African cats : a large-scale study on density, home range size, and home range overlap of lions Panthera leo and leopards Panthera pardus

Spatial patterns of and competition for resources by territorial carnivores are typically explained by two hypotheses: 1) the territorial defence hypothesis and 2) the searching efficiency hypothesis. According to the territorial defence hypothesis, when food resources are abundant, carnivore densities will be high and home ranges small. In addition, carnivores can maximise their necessary energy intake with minimal territorial defence. At medium resource levels, larger ranges will be needed, and it will become more economically beneficial to defend resources against a lower density of competitors. At low resource levels, carnivore densities will be low and home ranges large, but resources will be too scarce to make it beneficial to defend such large territories. Thus, home range overlap will be minimal at intermediate carnivore densities. According to the searching efficiency hypothesis, there is a cost to knowing a home range. Larger areas are harder to learn and easier to forget, so carnivores constantly need to keep their cognitive map updated by regularly revisiting parts of their home ranges. Consequently, when resources are scarce, carnivores require larger home ranges to acquire sufficient food. These larger home ranges lead to more overlap among individuals' ranges, so that overlap in home ranges is largest when food availability is the lowest. Since conspecific density is low when food availability is low, this hypothesis predicts that overlap is largest when densities are the lowest. We measured home range overlap and used a novel method to compare intraspecific home range overlaps for lions Panthera leo (n = 149) and leopards Panthera pardus (n = 111) in Africa. We estimated home range sizes from telemetry location data and gathered carnivore density data from the literature. Our results did not support the territorial defence hypothesis for either species. Lion prides increased their home range overlap at conspecific lower densities whereas leopards did not. Lion pride changes in overlap were primarily due to increases in group size at lower densities. By contrast, the unique dispersal strategies of leopards led to reduced overlap at lower densities. However, when human-caused mortality was higher, leopards increased their home range overlap. Although lions and leopards are territorial, their territorial behaviour was less important than the acquisition of food in determining their space use. Such information is crucial for the future conservation of these two iconic African carnivores