Benjamin Mapani

Impacts of mine dump pollution on plant species diversity, composition and structure of a semiarid savanna in Namibia

Effects of mine dump pollution on semiarid savanna vegetation were investigated in Kombat, Namibia. Vegetation structure, species richness, composition and diversity were compared between polluted and control sites. Concentrations of arsenic, chromium, copper, lead and zinc in soils were significantly higher closer to a 99-year-old mine dump than in a control site and exceeded internationally recommended guidelines by as high as 11 times. Mine dump pollution has significantly reduced woody plant densities, species richness and diversity in the affected area due to disappearance of pollution-sensitive species and preponderance of tolerant ones. Species composition and structure of vegetation close to the mine dump significantly changed, possibly due to negative impacts of heavy metals on recruitment as pollution-sensitive species died off, whereas tolerant species invaded the vacated ecological niches. Ordination analyses confirmed a strong pollution gradient, with measured heavy metals accounting for 57.3% of the observed variation in species data, suggesting that other factors are also important determinants in the area. It is recommended that the mine dump and its surrounds should be rehabilitated and regular monitoring should be carried out to remedy the situation and arrest further pollution of the surrounding environment.

Should We Be Concerned with Long-Term Health Problems Associated with Pesticides in Namibian Groundwater?

In the modern world there are several sources of pesticides and other phenyl type organic compounds. Why do we use pesticides? Simply that the world’s agricultural practices have commercialized to feed an overgrowing world population. Agriculture has also become a very lucrative business, where various players try to find niches to market their products. At the same time, societies have continued to become more aware about their natural environment and how to sustain it. As far back as 500 A.D., the city of Athens passed a law requiring all refuse to be disposed in a designated landfill outside the city walls (Zakrzewski, 1997); this was followed by many such laws in Europe. However direct linking of disease and health to environmental occupation was done by Dr. Percival Pott, in 1775 (quoted in Zakrzewski, 1997), who correctly linked the “chimney workers” with the unusual high rate of scrotal cancer, which he associated with exposure to soot in their work environment (Zakrzewski, 1997). In a city like Windhoek, pesticides may arise from the control of grasses on road pavements (Mapani, 2005); or from small scale urban agricultural gardens behind homes. However the major source of pesticides is by far from the farming industry. It is estimated that in the United States alone, close to 98% of the sprayed insecticides and 95% of the herbicides finally reach an unintended sink (destination) (Miller, 2004). The effect of this is obvious when it comes to infiltration of water into the ground that has been used in the irrigation of crops. Pesticides are one type of compounds that undergo “biomagnification” in the food chain (US EPA, 2003). This aspect is especially dangerous as it ensures that the threat from the pesticide is not decreased with time, but rather increased. The United States Environmental Protection Agency (US EPA, 2003) has classified pesticides into four categories; namely; (i) organophospates; (ii) N-methyl carbomates; (iii) triazines and (iv) chloroacetanilides. Some specific pesticide compounds have common mechanisms of toxicity, and require cumulative risk assessment over a relative long period, in order to define the potential risks. However the danger to aquatic life as described below in section 2 is well known, but the danger to human health is ill defined in comparison; with only a few