Expanding grasslands? Structural biome shifts in the dryland rangelands of the eastern Karoo revealed through long-term observation of climate, vegetation and land use change
type: CreativeWork
description: Biome shifts caused by climate and land use change threaten global dryland ecosystems and the provision of services needed to sustain human livelihoods. The overarching drivers of early 20th century dryland degradation in South Africa have been attributed to high stocking rates and overgrazing by domestic livestock. Predictions of an eastward encroachment of shrublands into the semiarid grasslands, and resultant declines in productivity, emerged in the 1950s based on concerns that livestock overgrazing would persist. In response to these concerns, appropriate research and government interventions were implemented to address rangeland and livestock mismanagement. However, the role of long-term climate as a driver of semiarid vegetation change was poorly understood, particularly for changes occurring at the interface of the NamaKaroo and Grassland biomes where shrubland encroachment could be detected along a gradient of increasing annual rainfall. It is this gradient that controls the natural biome transition from shrub-dominance to grass-dominance. However, the prediction of shrubland encroachment was refuted when research in the early 1990s revealed that the vegetation of this region (known as the ‘eastern Karoo') had undergone an increase in grass cover; a trend that persisted into the early 2000s. Questions around the influence of changing rainfall patterns on driving this increase in grassiness have since been investigated at a single location in the eastern Karoo. Findings indicated that an increase in annual rainfall drove the increase in grass cover, but the generality of this relationship across the broader rainfall gradient of the biome transition has not been examined. In addition to rainfall, grazing by domestic livestock has had a significant influence on the relative proportion of grasses and shrubs in the eastern Karoo. While other studies have alluded to changes in land use, few data have been presented and the relative influence of land use change has…
abstract: Biome shifts caused by climate and land use change threaten global dryland ecosystems and the provision of services needed to sustain human livelihoods. The overarching drivers of early 20th century dryland degradation in South Africa have been attributed to high stocking rates and overgrazing by domestic livestock. Predictions of an eastward encroachment of shrublands into the semiarid grasslands, and resultant declines in productivity, emerged in the 1950s based on concerns that livestock overgrazing would persist. In response to these concerns, appropriate research and government interventions were implemented to address rangeland and livestock mismanagement. However, the role of long-term climate as a driver of semiarid vegetation change was poorly understood, particularly for changes occurring at the interface of the NamaKaroo and Grassland biomes where shrubland encroachment could be detected along a gradient of increasing annual rainfall. It is this gradient that controls the natural biome transition from shrub-dominance to grass-dominance. However, the prediction of shrubland encroachment was refuted when research in the early 1990s revealed that the vegetation of this region (known as the ‘eastern Karoo') had undergone an increase in grass cover; a trend that persisted into the early 2000s. Questions around the influence of changing rainfall patterns on driving this increase in grassiness have since been investigated at a single location in the eastern Karoo. Findings indicated that an increase in annual rainfall drove the increase in grass cover, but the generality of this relationship across the broader rainfall gradient of the biome transition has not been examined. In addition to rainfall, grazing by domestic livestock has had a significant influence on the relative proportion of grasses and shrubs in the eastern Karoo. While other studies have alluded to changes in land use, few data have been presented and the relative influence of land use change has…
author: Arena, Gina
keywords: Biological Sciences
date published: 2021
date modified: 2026-07-22T22:22:41Z
provider: University of Cape Town
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Department of Biological Sciences

PropertyValue
property ID: Handle
value: http://hdl.handle.net/11427/35666