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Introducing rural children to real and relevant environmental issues

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Sewage effluent stream within the Wolwekraal Nature Reserve, Prince Albert

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Sewage effluent increases organic nutrient load

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Changing Succulent Karoo vegetation within Wolwekraal Nature Reserve. Vegetation directly affected by the effluent is located on the right.

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Prince Albert learners listen to a talk by Ivy Bruintjies of Renu-Karoo

By Liesel Hein, Intern, SAEON Arid Lands Node

Never has the urgency for understanding and predicting the consequences of our actions on the natural environment been as important as for this generation.

Many human developments change hydrology and soil chemistry. One such example is the release of sewage effluent into the surrounding environment, a common practice in Karoo villages.

Wolwekraal Nature Reserve, north of Prince Albert, falls within the Succulent Karoo Biome and has an average annual rainfall of 165 mm. Since 2009, the illegal drainage of sewage effluent from a municipal wastewater treatment facility onto the reserve has led to changes in the plant communities affected by the effluent.

Species composition in arid and semi-arid plant communities reflects long-term patterns in the timing and quantity of rainfall. Change in resource availability (water, nutrients, light) is likely to change the plant community composition, structure and function. Sewage effluent both saturates the soil and changes soil chemistry. Changes in these elements could alter competitive advantages from water-efficient arid plants to production-efficient plants, and could alter interactions with fauna.

Resource and community changes

Recent investigations by school learners and university students confirmed such resource and community changes associated with the effluent found within the reserve. Many species of fauna have taken advantage of the changed habitat. For example, Karoo bush rats (Otomys unisulcatus) populations have increased within the dense reed and gannabos (Salsola spp.) growth, some frog species have colonised the stream, and there is evidence that predators such as snakes, mustellids, feral cats and dogs have moved into the area to hunt the abundant prey.

These observed changes have led to a proposed investigation by SAEON and Renu-Karoo into how plant life forms from a semi-arid Karoo environment respond to increased rainfall, flooding and nutrient enrichment. The objective of the proposed study is to quantify growth, flowering, seed production and insect herbivory of three plant growth forms – the succulent Malephora lutea (springbokvygie), grass Fingerhuthia africana (vingerhoedgras), and shrub Lycium cinereum (kriedoring) – across a sewage effluent gradient.

Recent investigations by school learners and university students confirmed resource and community changes associated with sewage effluent found within the Wolwekraal Nature Reserve.

Relationships between these attributes and soil moisture, pH and conductivity will be determined. This study is an opportunity to foresee the possible consequences of increased soil moisture and nutrient availability and its application in environmental management.

Inspiring the future custodians of our natural world

Children are the future custodians of our natural world and consequently it is important to inspire them concerning its values and their associated responsibilities from an early age. As part of a SAEON training programme which aims to promote scientific education within local communities, Professor Sue Milton (co-director of Renu-Karoo and SAEON collaborator), Liesel Hein (SAEON intern), Ivy Bruintjies, Marai Isaacs and Mercia Loots (all of Renu-Karoo), guided 138 Grade 5 science learners through the local Prince Albert wastewater treatment works and the adjacent Wolwekraal Nature Reserve to learn about the water cycle and the effects of water on desert vegetation.

The learners deliberated about important problems concerning the consequences of the intrusion of sewage water on plant and animal communities, the resulting threat to the health of the nearby Dorps River running through the reserve, and how the local plant communities used their abilities to compensate for these changes in habitat.

The dynamic interactions and dependencies between the water cycle, plants and animals were demonstrated with the use of live examples within the reserve. Plant community properties and how these relate to the semi-arid environment and the effluent intrusion were also demonstrated all along the length of the sewage stream.

The young learners grasped many important ecological concepts, which is promising for the future generation to achieve breakthroughs towards a more environmentally-conscious and greater society.

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Satellite images visually illustrate change in vegetation over time owing to the intrusion of sewage effluent. In 2005, the sewage dams had not yet reached capacity and in 2012 sewage dams were working above capacity. (Image provided by SJ Milton, downloaded from Google Earth)

 

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