M. Timm Hoffman

A national review of land degradation in South Africa: the influence of biophysical and socio-economic factors.

Studies of land degradation in South Africa have seldom addressed the issue for the whole country. As part of the first step in developing a National Action Programme to combat desertification, a national review of the soil and veld degradation problem was conducted in 1997 and 1998. The results are based on the perceptions of agricultural extension workers and resource conservation technicians from the Department of Agriculture. They indicate that it is primarily in the communal areas along the eastern and northern escarpment and in some commercial districts along the Orange River that problems of soil degradation are greatest. Veld degradation is also higher in communal areas than commercial areas, although many commercial areas are susceptible to bush encroachment and alien plant invasions. A separate multiple regression analysis indicates that both biophysical and socio-economic factors are associated with high levels of soil and veld degradation. Magisterial districts which are most degraded are characterised by steep slopes and high mean annual temperatures, and a rural population in which many people are dependent on only a few wage earners. Although the interaction is poorly understood it appears that when there are high levels of poverty in susceptible environments, land degradation is greatest.

Bush encroachment in southern Africa: changes and causes

Bush encroachment has been recognised in southern Africa since the late nineteenth century. Our review of 23 studies showed that the rate of woody cover change has ranged from −0.131 to 1.275% y−1. Encroachment was most rapid on small protected areas, intermediate under commercial tenure, and slowest under communal tenure and large, natural environments with mega-herbivores present. Several drivers of bush encroachment, which interact and change over time, have been proposed. Fires, for example, were actively suppressed during the early twentieth century. However, rainfall interacts with fire and the rate of woody increase under fire exclusion is linearly related to mean annual rainfall. A reduction in browsing herbivores from the nineteenth century would have had a positive cumulative effect on woody cover whilst an increase in grazing herbivores would have reduced the competitive effect of grasses. Encroachment was most rapid during the high rainfall, mid-1970s, which followed the 1960s drought when cattle numbers were at their peak, and the grass layer was degraded. Increasing atmospheric [CO2] and climate change have emerged as important drivers in the recent literature. Bush encroachment depends on the interplay of history, environment, management and vegetation, recognition of which is essential for containing encroachment.

A fence line in time demonstrates grazing‐induced vegetation shifts and dynamics in the semiarid Succulent Karoo

The mediterranean ecosystems of the world harbor exceptional biodiversity, and factors such as livestock grazing which may negatively affect biodiversity are of global concern. The mediterranean ecosystems of southern Africa have only sporadically been exposed to high densities of indigenous herbivores and may not be as typically resilient to livestock grazing pressure as the savannah and grassland ecosystems of semiarid Africa. We investigate this issue by assessing the impacts of two contrasting livestock grazing intensities associated with communal and commercial ranching systems on the dwarf succulent shrublands of the Succulent Karoo in Namaqualand, South Africa. We interpret the results in terms of vegetation dynamics and the implications for the current debate on nonequilibrium rangelands. The results demonstrate that the relative extent of plant community divergence between the communal and commercial rangeland has been maintained over the past 10 years, overall and within different plant growth forms. Recruitment of certain palatable shrub species occurred on the heavily grazed communal rangeland, indicating that a further decline in their populations is not inevitable. Recruitment of the unpalatable shrub Galenia africana on the communal rangeland was disproportionately greater than that of the palatable species, reenforcing the dominance of this species. Due to the longevity of woody shrubs, short-term vegetation shifts are small, limiting the potential for the recovery of overgrazed shrublands during periods of low grazing pressure. The shift on the communal rangeland toward annuals and geophytes has increased the variability of forage production and contrasts with the dominance of dwarf shrubs on the commercial rangeland. Shrub-dominated ecosystems create the potential for forage storage and inter-annual transfer of excess production, buffering livestock numbers in the face of a fluctuating environment. Despite the semiarid nature of the area and contrary to the predictions of the nonequilibrium theory, livestock and vegetation in Namaqualand interact strongly, and a close relationship between livestock numbers and primary production persists over the long-term on the communal rangeland.

A century of woody plant encroachment in the dry Kimberley savanna of South Africa

Woody plant encroachment is frequent in dry savannas. Grazing is often considered to be a major cause of encroachment in dry savannas because grasses are removed by livestock, leaving bare areas for trees to colonise in wetter years. Earlier experiments conducted in the Kimberley area of the Northern Cape showed that neither fire nor grazing was important for woody plant encroachment. We used aerial and fixed-point repeat ground photographs, including historical photographs taken at the time of the Second Anglo-Boer War of 1899–1902, to assess the scale and timing of woody plant encroachment in the dry savannas near Kimberley in South Africa (mean annual rainfall = 300–400 mm). There were large increases in woody plant encroachment in most areas. Even at the battlefield of Magersfontein, where grazing has been virtually absent since its protection in 1960, we found that encroachment by trees and shrubs has occurred. Using aerial photographs, we found that the rate of encroachment has increased substantially since 1993. However, repeated photographs at certain sites indicate that encroachment produced cohorts of trees. We show that global drivers are perhaps of greater importance than local drivers such as heavy grazing and absence of fire.

A tenfold increase in the Orange River mean Holocene mud flux: implications for soil erosion in South Africa.

Soil erosion poses a major threat to sustainable agriculture in southern Africa but is difficult to quantify. One measure of soil erosion is the sediment flux of rivers. The Orange River is the principal source of sediment to the western margin of South Africa with an estimated mean mud flux over the last 11 500 years (the Holocene epoch) of 5.1 (3.2—7.4) million metric tons/year (Mt/yr). A total of 43 gigatons (Gt; 1015 g) representing 72% of the Holocene mud flux has accumulated on the shelf in the Orange River prodelta and mudbelt, a clayey fine-silt deposit focused on the inner to middle shelf. Only 8% (5 Gt) of the mud flux occurs in Holocene calcareous ooze on the slope. Comparison of the clay to mud ratio of offshore deposits with Orange River suspended sediment and catchment soils indicates that 20% (11 Gt) of the Holocene mud flux has been lost as clay beyond the margin. The Orange River mud flux prior to the building of large dams (1930—1969) is ten times greater than the mean Holocene mud flux and is reconciled with estimates of soil erosion within the catchment. A tenfold increase in the Orange River mud flux implies up to a hundredfold increase in total soil erosion depending on the extent of mud storage over periods of decades to centuries within the catchment. Erosion has shifted from areas of high relief and rainfall of the Drakensberg escarpment during the Holocene to intensely cultivated lands of low relief having moderate to high rainfall in the eastern catchment and to a lesser extent, grazing areas of the southern Orange River catchment.

The historical ecology of Namibian rangelands: Vegetation change since 1876 in response to local and global drivers

The influence of both local and global drivers on long-term changes in the vegetation of Namibias extensive rangelands was investigated. Fifty-two historical photographs of the Palgrave Expedition of 1876 were re-photographed and used to document changes over more than 130 years, in grass, shrub and tree cover within three major biomes along a 1200km climatic gradient in central and southern Namibia. We showed that patterns of change are correlated with mean annual precipitation (MAP) and that below a threshold of around 250mm, vegetation has remained remarkably stable regardless of land-use or tenure regime. Above this threshold, an increase in tree cover is linked to the rainfall gradient, the legacies of historical events in the late 19th century, subsequent transformations in land-use and increased atmospheric CO(2). We discuss these findings in relation to pastoral and settler societies, paleo- and historical climatic trends and predictions of vegetation change under future global warming scenarios. We argue that changes in land-use associated with colonialism (decimation of megaherbivores and wildlife browsers; fire suppression, cattle ranching), as well as the effects of CO(2) fertilisation provide the most parsimonious explanations for vegetation change. We found no evidence that aridification, as projected under future climate change scenarios, has started in the region. This study provided empirical evidence and theoretical insights into the relative importance of local and global drivers of change in the savanna environments of central and southern Namibia and global savanna ecosystems more generally.

Ecological research and conservation management in the Cape Floristic Region between 1945 and 2015: History, current understanding and future challenges

In 1945, the Royal Society of South Africa published a wide-ranging report, prepared by a committee led by Dr C.L. Wicht, dealing with the preservation of the globally unique and highly diverse vegetation of the south-western Cape. The publication of the Wicht Committee’s report signalled the initiation of a research programme aimed at understanding, and ultimately protecting, the unique and diverse ecosystems of the Cape Floristic Region. This programme has continued for over 70 years, and it constitutes the longest history of concerted scientific endeavour aimed at the conservation of an entire region and its constituent biota. This monograph has been prepared to mark the 70th anniversary of the Wicht Committee report. It provides a detailed overview of the circumstances that led up to the Wicht Committee’s report, and the historical context within which it was written. It traces the development of new and substantial scientific understanding over the past 70 years, particularly with regard to catchment hydrology, fire ecology, invasive alien plant ecology, the harvesting of plant material and conservation planning. The Wicht Committee’s report also made recommendations about ecosystem management, particularly with regard to the use of fire and the control of invasive alien plants, as well as for the establishment of protected areas. Subsequently, a combination of changing conservation philosophies and scientific conservation planning led to the creation and expansion of a network of protected areas that now covers nearly 19% of the Cape Floristic Region. We also review aspects of climate change, most of which could not have been foreseen by the Wicht Committee. We conclude that those responsible for the conservation of these ecosystems will face many challenges in the 21st century. These will include finding ways for effectively managing invasive alien plants and fires, as foreseen by the Wicht Committee. While the protected area network has expanded beyond the modest targets proposed by the Wicht Committee, funding has not kept pace with this expansion, with consequences for the ability to effectively manage protected areas. The research environment has also shifted away from long-term research conducted by scientists embedded in management agencies, to short-term studies conducted largely by academic institutions. This has removed a significant benefit that was gained from the long-term partnership between research and management that characterised the modis operandus of the Department of Forestry. Growing levels of illegal resource use and a changing global climate also pose new challenges that were not foreseen by the Wicht Committee.

Changing Patterns of Rural Land Use and Land Cover in South Africa and their Implications for Land Reform

Land use and land cover have changed significantly in South Africa since the 1913 Natives Land Act, in response to a wide range of political, social, cultural and environmental influences. This review examines the response of the vegetation of three biomes to these changing patterns. Vegetation change over the last 100 years is described along an aridity gradient from the arid Succulent Karoo biome in the west, across the wide expanses of the semi-arid, central Nama-Karoo biome, to the mesic Savanna biome on the east coast of South Africa. While Namaqualand has been relatively stable or has even improved in vegetation cover and composition, the Little Karoo is considered severely degraded, with a significant loss of ecological integrity. The Nama-Karoo biome has experienced a significant increase in grassiness since the 1960s in response to decreasing livestock numbers and changed rainfall seasonality. Bush encroachment has occurred over much of the Savanna biome, although this process has a long history in the region. Invasive alien plants pose an increasingly serious threat to the Savanna biome. The main implications of these findings for the land reform programme are that land use has important effects on the vegetation of South Africa, that the state has an important role to play in maintaining the proper functioning of ecosystems,and that some degree of planning for future climate and land cover change is critical within the land reform process.

How could herd mobility be used to manage resources and livestock grazing in semi-arid rangeland commons?

Pastoralists in Namaqualand, South Africa, use herd mobility to manage livestock and rangeland resources. However, their socioeconomic conditions and ecological landscapes are changing and we explore the options that are available for pastoralists to respond to these changes. This paper presents five possible scenarios for managing livestock in rangeland commons in semi-arid Namaqualand and outlines some of the major advantages and disadvantages associated with each scenario. Scenarios in response to drivers of change include (1) maintaining the status quo with an assumption that current mobility practices are adapted to local environments, (2) integrating new lands into the existing commons for use by mobile pastoralists, (3) using existing lands under existing mobile pastoralism conditions but introducing grazing reserves for use in times of drought, (4) amalgamating herds into larger units under the care of skilled herders, and (5) developing commercial-scale farms for single-occupancy owners because government might be pressured to further promote black commercial farmers to deracialise the commercial farming sector in South Africa. We consider these scenarios as starting points for discussions on future management options that pastoralists in Namaqualand may wish to consider as the managers of rangeland commons.

How Can Science Be General, Yet Specific? The Conundrum of Rangeland Science in the 21st Century

Abstract A critical challenge for range scientists is to provide input to management decisions for land units where little or no data exist. The disciplines of range science, basic ecology, and global ecology use different perspectives and approaches with different levels of detail to extrapolate information and understanding from well-studied locations to other land units. However, these traditional approaches are expected to be insufficient in the future as both human and climatic drivers change in magnitude and direction, spatial heterogeneity in land cover and its use increases, and rangelands become increasingly connected at local to global scales by flows of materials, people, and information. Here we argue that to overcome limitations of each individual discipline, and to address future rangeland problems effectively, scientists will need to integrate these disciplines successfully and in novel ways. The objectives of this article are 1) to describe the background, historical development, and limitations of current approaches employed by these disciplines; 2) to describe an integrated approach that takes advantage of the strengths and minimizes the weaknesses of these individual approaches; and 3) to discuss the challenges and implications of this integrated approach to the future of range science when climate and human drivers are nonstationary. This integration will be critical for applying range science to the management of specific land units; will contribute to and benefit from the development of general ecological principles; and will assist in addressing problems facing society at regional, continental, and global scales. Resumen Un reto muy crítico para los científicos en pastizales es proveer de información para toma decisiones de manejo de unidades de tierra donde hay pocos o nulos datos. Las disciplinas de ciencia del pastizal, ecología básica y ecología global usan diferentes perspectivas y enfoques con diferentes niveles de detalle para extrapolar la información y el conocimiento de lugares bien estudiados a otras unidades de tierra. Sin embargo, estos enfoques tradicionales se espera que sean insuficientes en el futuro porque los humanos y el clima generan cambios en magnitud y dirección, especial heterogeneidad en cubierta del suelo y sus usos se incrementa y los pastizales llegan a estar con en escala local y global por el flujo de materiales, personas e información. Aquí discutimos que para sortear las limitaciones de cada disciplina de manera efectiva y atender los problemas de los pastizales, en el futuro los científicos necesitaran integrar de manera novedosa y exitosa estas disciplinas. Los objetivos de este articulo son 1) describir los antecedentes, desarrollo histórico y limitaciones de los enfoques actuales empleados por estas disciplinas, 2) describir un enfoque integrado que resalte las fortalezas y minimice las debilidades de cada enfoque en lo particular y 3) discutir los retos e implicaciones de este enfoque integrado en el futuro de la ciencia del pastizal cuando el clima y los humanos son conductores no pasivos. Esta integración será crítica para aplicar la ciencia del pastizal para el manejo específico de unidades de tierra y contribuirá para el beneficio en el desarrollo de principios ecológicos y también direccionar los problemas que enfrenta la sociedad a escalas regional, continental y global.