Grant Stuart Joseph

Grant Stuart Joseph
University of Cape Town | UCT · Department of Biological Sciences

MBChB MSc PhD (Zoology)

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49
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Introduction
Conservation Biology Savanna Ecology

Publications

Publications (49)
Article
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Societal Impact Statement Debates about the impacts of human settlement on Madagascar's habitat have missed the Malagasy perspective. Using indigenous and local knowledge in the form of toponyms, we find many regions across today's treeless grasslands are named after forest/trees, suggesting they may be novel. Where observed habitat does not match...
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We provide an alternative: Figure 1 details evidence for humans extirpating tree-adapted, forest-feeding megafauna that were never pure C4-feeders, transforming (by cutting/burning) a mosaic of larger woodlands/forests/ericoids and smaller grasslands circa 1 ka, to derived treeless grassland, maintained by introduced cattle and human-lit fire, wher...
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Grasslands with little tree cover today comprise 80% of Madagascar's habitat. Determining their extent at human settlement can guide ecological restoration and enhance human well-being, so the 2021 Malagasy Grassy Biomes Workshop identified the role of extinct megafauna in determining habitat as a critical knowledge gap. Using a systematic literatu...
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Societal Impact Statement The relationship between rainfall, fire and habitat can display incongruencies. The 2021 Malagasy Grassy Biomes Workshop identified understanding fire regimes as a knowledge gap. This study pinpoints regions where anthropogenic fire has the potential to transform or has transformed habitat to treeless‐grassland, by identif...
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Societal Impact Statement The 26th United Nations Climate Change Conference emphasised the need to modify practices that negatively impact biodiversity and food security in the context of global change. Following Madagascar's drought‐induced famine, our systematic review supports the theory that grasslands of the Malagasy Central Highland that are...
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The large, iconic nests constructed by social species are engineered to create internal conditions buffered from external climatic extremes, to allow reproduction and/or food production. Nest-inhabiting eusocial Macrotermitinae (Blattodea: Isoptera) are outstanding palaeo-tropical ecosystem engineers that evolved fungus-growing to break down plant...
Article
Seventy‐five percent of Madagascar is treeless C 4 ‐grassland adapted to human‐lit fire, which likely succeeded pre‐human mosaics of forest, ericoids, grassy‐woodlands and some smaller treeless‐grasslands. In support of pre‐settlement Malagasy grasslands having evolved with many grassland specialist faunal elements, Bond et al. (2022) cite “conside...
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Woody structure, particularly that created by large trees, is crucial to savanna biodiversity pattern and process. We assessed changes in vertical and horizontal canopy over 15 years of saplings of Vachellia (Acacia) erioloba (camelthorn), a keystone species and one of the only trees to grow large in arid savanna on low rainfall areas of Kalahari s...
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Models aimed at understanding C 4 -savannah distribution for Australia, Africa and South America support transition to forest at high mean annual precipitation (MAP), and savannah grasslands of Madagascar have recently been reported to be similarly limited. Yet, when savannah/grassland presence data are plotted against MAP for the various ecosystem...
Article
Madagascar is the world's highest profile conservation priority. Yet the natural habitat of its largest biome, the 200,000 km² Malagasy Central Highlands (MCH) remains one of the most prominent and longstanding debates in conservation: are MCH grasslands natural and ancient, coevolved with endemic grazers; or new and anthropogenic, representing deg...
Article
Microhabitats may be crucial in buffering organisms from temperature extremes, particularly given increases in maximum temperature associated with global climate change. For example, thermoregulation in termite mounds is influenced by prevailing ambient conditions, and plant canopies may reduce external temperatures, in turn lowering internal tempe...
Article
Papers arguing for Malagasy central highlands (MCH) as natural grassland rely disproportionally on a single reference (Bond et al. 2008, The antiquity of Madagascar's grasslands and the rise of C4 grassy biomes. Journal of Biogeography, 35, 1743–1758). The paper argues that (1) evolution of endemic grassland specialist fauna, (2) paleoecological fi...
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High-altitude-adapted ectotherms can escape competition from dominant species by tolerating low temperatures at cooler elevations, but climate change is eroding such advantages. Studies evaluating broad-scale impacts of global change for high-altitude organisms often overlook the mitigating role of biotic factors. Yet, at fine spatial-scales, veget...
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Long considered a consequence of anthropogenic agropastoralism, the origin of Madagascar’s central highland grassland is hotly disputed. Arguments that ancient endemic grasses formed grassland maintained by extinct grazers and fire have been persuasive. Consequent calls to repeal fire-suppression legislation, burn protected areas, and accept pastor...
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Plant traits—the morphological, anatomical, physiological, biochemical and phenological characteristics of plants—determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research sp...
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Addition of nitrogen (N) to rangeland that has been degraded through overgrazing or drought can hasten vegetation recovery. Additional N may influence temporal stability of vegetation cover, however, and change species composition. Potassium (K), by contrast, may help plants survive dry periods, increasing stability. Plant longevity also influences...
Chapter
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This chapter considers the numerous small animals that often escape attention, but which may have effects on savanna functioning no less marked than that of large herbivores. It also considers the ecological importance of small animals through their interactions with woody plants in their roles as folivores, gall‐formers, frugivores, pollinators, g...
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Roads now penetrate even the most remote parts of much of the world, but the majority of research on the effects of roads on biota has been in less remote temperate environments. The impacts of roads in semi-arid and arid areas may differ from these results in a number of ways. Here, we review the research on the impacts of roads on biodiversity pa...
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As the need to better understand the ecology of hotspots of endemism intensifies, the insurance hypothesis is drawing increasing attention from policy-makers and scenario-planners. The hypothesis states that biodiversity increases ecosystem stability. When species numbers fluctuate, there is potential for further perturbation, loss of function and...
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Linear structures include fences, roads, railways, canalised water ways and power lines, all man-made. Fencing as a way of managing livestock began in the late 1800s, and by the early twentieth century was almost fully implemented throughout the Karoo sensu lato. The advent of these fences, and now in many instances, ‘game proof’ (∼2 m high) and el...
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Predators play a disproportionately positive role in ensuring integrity of food webs, influencing ecological processes and services upon which humans rely. Predators tend to be amongst the first species to be affected by anthropogenic disturbance, however. Spiders impact invertebrate population dynamics and stabilise food webs in natural and agricu...
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ContextWith global change, microclimates become important refuges for temperature-sensitive, range-restricted organisms. In African savannas, woody vegetation on Macrotermes mounds create widely-dispersed microclimates significantly cooler than the surrounding matrix, which buffer against elevated temperatures at the finer scale of mounds, allowing...
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Africa’s savannas are undergoing rapid conversion from rangelands into villages and croplands. Despite limited research, and evidence of deleterious effects to biodiversity, international organisations have earmarked this system for cropland. Invertebrates, and ants in particular, are sensitive indicators of habitat fragmentation, and contribute to...
Article
As the Anthropocene advances, understanding the complex web of interactions between species has become a central theme in the maintenance of biodiversity, ecosystem functions, and agricultural systems. Plant-flower visitor networks yield insights into how natural vegetation supports crop pollination. Although crops themselves also support pollinato...
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Termite mounds have recently been shown to protect against drought by providing refuges for plants and foci for revegetation, but whether mounds modulate temperature remains untested. Organisms tend to experience climate at finer scales than those captured by models predicting how distributions alter with global change, so microclimates represent i...
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Questions Ungulate herbivory and formation of large termite mounds occur over different time scales, but both can affect plant community composition in savannas. Human‐managed savanna systems are increasingly dominated by domesticated grazing herbivores. These have replaced a mix of indigenous browsers and grazers, leading to changes in plant commu...
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Context Spatially heterogeneous habitats often promote woody plant species and functional diversity (FD). Ungulate herbivory can have the opposite effect. Across the globe, the type and intensity of herbivory is changing, as domestic livestock replace wild ungulates, which are increasingly confined to protected areas. Despite recognition of the imp...
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Biodiversity affects ecosystem function through species’ functional traits. Although it is possible to predict species richness (SR) patterns along environmental gradients, whether functional diversity (FD) changes in predictable ways is not known. In arid environments, SR typically increases with rainfall. Aridity may limit functional differentiat...
Article
Fine-scale spatial heterogeneity influences biodiversity and ecosystem productivity at many scales. In savanna systems, Macrotermes termites, through forming spatially explicit mounds with unique woody plant assemblages, emerge as important sources of such heterogeneity. Despite a growing consensus regarding the importance of functional diversity (...
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The influence of soil organisms on the availability of nutrients to other biota within ecosystems can be context-dependent. Fungus-culturing termites, for example, are known to concentrate nutrients by building large mounds in nutrient-poor savannas, but several factors determine the nutritional value of the mounds – whether by geophagy or consumpt...
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At finer scales, spatial heterogeneity can influence fire intensity and severity. To test whether Macrotermes termite mounds act as fire refugia for woody plants, we assessed effects of fire on individual plants, woody plant structure and composition in a miombo woodland in Zimbabwe, where elephants have decreased tree cover, leading to increased g...
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Questions We investigated whether soils of small mounds resembled large mound or matrix soils, whether changes in plant composition reflected changes in soils, and the sequence in which plants colonize and disappear from mounds of increasing size. Location Miombo woodland in northwest Z imbabwe. Methods Macrotermitinae termitaria vary in size and...
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W ith the sixth-longest bird list of any African country, Angola harbours an exceptionally rich biodiversity. Add to this one of Africa's highest bird conservation priorities—the Western Angola Endemic Bird Area (Stattersfield et al. 1998) and its biologically important scarp forests—and the biological importance of the country becomes unquestionab...
Article
Details pertaining to 22 avian holotypes, and one topotype, held in the bird collection of the Instituto Superior de Ciências da Educação, in Lubango, Angola, are presented. Not all of the taxa discussed here are currently treated as valid by at least some checklists or other keynote works.
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Landscape heterogeneity can play an important role in providing refugia and sustaining biodiversity in disturbed landscapes. Large Macrotermes (Isoptera) termite mounds in miombo woodlands form nutrient rich islands that sustain a different suite of woody plant species relative to the woodland matrix. We investigated the role of termitaria in provi...
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1. Up to 73% of the world’s rangelands are degraded, and increasing demand for meat in developing countries and a growing human population are likely to exert even greater pressures on rangelands in the next 20–50 years. Restoration of rangeland grazing potential and resilience is therefore important, particularly in the face of climate change. 2....
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The coexistence of trees and grasses in savanna ecosystems is a contentious phenomenon. Fire and herbivory disturbances are often cited as major structuring forces that create a sustainable tree–grass relationship. However, periodic flooding of savanna patches may also enable coexistence. The aim of this study was to investigate the effects of floo...
Data
Full-text available
The coexistence of trees and grasses in savanna ecosystems is a contentious phenomenon. Fire and herbivory disturbances are often cited as major structuring forces that create a sustainable tree– grass relationship. However, periodic flooding of savanna patches may also enable coexistence. The aim of this study was to investigate the effects of flo...

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