Human impact on the savanna woodlands

The effect of human activities on the dry savanna woodlands

In the description of the ecology of the dry savanna woodlands of Namibia, the effect of human activity should not be neglected. In view of the subdivision of the woodland vegetation into herbaceous and woody components, human impact is considered separately for each of the two.

Human impact on herbaceous vegetation

The use of fire

Although some fire occurs from natural causes, most fires today are as a result of the activities of man (Siegfried 1981). The indigenous people of Namibia have been using fire for centuries, for a variety of purposes. Vedder (1928 p. 43) describes the use of fire by the Herero as a range management tool.

Fire has also been used as an aid to hunting. The early growth of grass that is stimulated by fire in the dry season has been used to attract game animals to specific areas (Vedder 1923, Vedder 1928, p. 43, Lusepani et al 1998, Anon 1999), making them easier to find and hunt.

The removal of undergrowth results in greater long distance visibility and facilitates the detection of game animals (Tuomasjukka et al. 1998), and easier tracking (Lusepani et al 1998, Büschel 1999). In recent years the greater visibility is also said to have served poachers to detect the movement of law enforcement officers.

The greater visibility at ground level also facilitates easy detection and collection of veld foods such as the mangetti nuts (Tuomasjukka et al. 1998).

The effect of fire in the past and today should be compared in terms of the frequency and season of burning. Goldammer (1998) highlights the decline in nomadic habits of the indigenous people in this regard. This, together with the growing population of Namibia, is likely to have caused an increased incidence of fire on the woodland areas of the country.

Grazing

Grazing by domestic animals has significant effects on the development of the herbaceous vegetation. Heavy grazing pressure may reduce the competitiveness of the grasses, while light grazing may stimulate the development of the grass layer. Apart from such direct influences, grazing may significantly effect the development of the fuel load.

Harvesting of grass

The harvesting of grass for thatch has only been recently considered by the forestry authorities, although the practice seems to have been ongoing for centuries.

Human impact on woody vegetation

Timber harvesting

The Namibia Forestry Strategic Plan (NFSP 1996) describes a variety of uses for wood products in Namibia. These products range from building and fencing material to the production of utensils and farm implements. While sawn timber may not have been of significant importance in the past, the woodlands have been exploited primarily for Pterocarpus angolensis and Baikiaea plurijuga. Other important species are Terminalia sericea and Burkea africana. The carving industry is now also significantly affecting exploitation rates particularly of P. angolensis.

In order to affect some control over the harvesting and to ensure the continuity of the individual species, minimum tree sizes have been specified in the forest legislation (). However, since many of the P. angolensis stands in the woodlands seem even aged (Groome et al. 1957), this specification caused conditions similar to those of a clearfelling in some regions.

An important overview of the use of woody resources is provided by Erkkilä & Siiskonen (1992).

Fruit and seed collection

Fruit and seed are of significant socio-economic importance to many rural communities. Woody species of particular value seem to be Schinziophyton rautanenii, Berchemia discolor, Vangueria infausta, Gouibourtia colesperma the Grewia species and Strychnos species. The effect of seed collection on most species varies between regions, depending on the proximity of the plants to human settlements.

It is known that entire families of the San communities will travel long distances to S. rautanenii stands for fruit collection. Observations in the Otjozondjupa region show that in some areas almost the entire crop of is collected for food and the production of alcoholic beverages (Büschel 1999).

See also:

The effect of fire on grazing