Groundwater use by alien invasive plants: assessing the impact of Prosopis spp invasions on water supply to groundwater dependent communities

Abstract

Invasive alien plants are estimated to have invaded at least 10 million ha of South Africa to some degree and are spreading at about 5% per annum. The deep rooted desert adapted shrub or tree, Prosopis spp, is a major invader species in the arid and semi-arid parts of the country. Near the turn of the 19 th century, six Prosopis species from Central America were intr oduced to Namibia and the arid pa rts of South Africa for fodder, fuel and shade. Here they have hybridised and spreaded rapidly. Today (2016) extensive stands of this woody weed grow in the North We st-, Northern Cape-, Free State-, Western Cape-and parts of the Eastern Cape Provinces. A study by Van den Berg (2010) showed that the average annual rate of spread of Prosopis in the Northern Cape, for example, is very high, being approximately 15% in upland areas and up to 30% in riparian areas. The species occupied only 128 000 hain 1974 in the Province. It then increased rapidly to over 1.5 million ha by 2007, roughly doubling between 2004 and 2007.

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