Mesquite (Prosopis spp.), a group of about 40 small leguminous trees are native to the south-western USA and Mexico. Several species, especially Honey Mesquite (Prosopis glandulosa), were introduced into South Africa in the late 19th and early 20th centuries as both a shade tree and as a source of fodder for domestic livestock. It was cultivated and planted out in many arid areas of central, northern and western parts of South Africa. It forms dense thickets that even goats cannot penetrate and its spread is now largely unchecked. In parts of the Northern Cape there are stands that extend over thousands of hectares and as such become useless to livestock husbandry. 

What we find most alarming is that many farmers are allowing Mesquite to spread on their properties. In the early stages of invasion physical control would be relatively easy but once established along water courses it spreads rapidly away from them. 

The worst affected areas lie in the Karoo, Kalahari, Namaqualand and Bushmanland. The danger lies in that these small trees are highly adapted to surviving even the most severe droughts. Once established they completely out compete the endemic flora. The highly palatable pods are eaten by game and stock but many seeds are dispersed in their droppings. Complicating things further the hardy seeds can remain dormant in the soil for up to 10 years. 

Cutting the trees is also problematic as they will regrow from dormant buds below the ground surface, necessitating regular follow ups. Many farmers say that they cannot afford chemical control, nor the labour for physical removal. But by 'ignoring' the problem they are losing many thousands of hectares that would have sustained their livestock. 

Drive around Van Wyks Vlei, Kenhardt, Upington, Poffadder and Carnarvon, amongst others, and the dense stands of bushes that you see, with intertwined branches, are of no use to man nor beast.