Abstract
M.Sc.
Rivers always borrow a great part of their character from the terrestrial ecosystems – the catchments – through which they flow. A multitude of natural factors determines the health of a river ecosystem, however, together with these natural factors, the combined influences of urban development, pollution, bank erosion, deforestation (and ironically many forms of afforestation), and poor agricultural practices have so degraded our rivers that they are under severe threat.
One particular group of organisms within river ecosystems that are affected by human-induced changes, are birds. Birds are rather adaptable organisms; many species are able to inhabit human environments very successfully. However, some bird species are highly specialized and adapted to specific environments, like riparian and riverine zones, and their absence or presence is a useful aid in indicating the ecological integrity of an area.
In the past, management of aquatic ecosystems was based primarily on chemical water quality monitoring. However, it is impractical to monitor each component of river make-up in detail, therefore monitoring of biological components (biomonitoring) was also incorporated; using selected ecological indices that are representative of the larger ecosystem, and that are practical to measure.
Common examples of biotic assemblages that have been incorporated into biomonitoring and used in biotic indices are aquatic macroinvertebrates, fish, plants and algae. Each assemblage is useful in its own particular way in providing us with an integrated view of the integrity of the ecological system as a whole. However, little research has been done on the potential of using birds in a suitable index to monitor changes in the environment. Because birds are so easily observed, their species so easily identified, and their distribution so widespread, it seems viable that birds could also be incorporated into an index of biotic integrity, and used for short- or long-term monitoring of river ecosystems.
The river that was selected for the purposes of this study was the Sabie River, in Mpumalanga, South Africa. The Sabie River catchment falls within the Incomati River basin, which is an international drainage basin occupied by South Africa, Swaziland and Mozambique. Land use in the catchment is characterized by forestry, rural community activities (subsistence and small scale farming of livestock and fruit), and conservation activities, in particular the Kruger National Park. In order to gain better understanding of the functioning and composition of the instream and riparian zones of the Sabie River, certain indices were applied, namely the SASS 5 aquatic invertebrate index, together with the Index of Habitat Integrity (IHI).
Dr. G.M. Pieterse