south africa has a very interesting history of vegetation. obviously the country has its own indigenous vegetation. but when the white people decided to take things over the decided to do it completely - including the local flora. but as with the attempts to take over the people, the introduction of foreign flora has had less than stellar results.
when the vineyards came into effect, some bright individual decided that they might as well try to grow their own oak and build their own casks. sounds intelligent enough. the one downside to experimenting with trees in a foreign area is that you can't really do a small test plot to see how things come about. oak takes about a dozen years to mature, and i guess there was a bit of impatience with the wine people (strange considering the growing time to get a good vineyard going!). so there were whole orchards of oak trees planted in anticipation of a booming cask and wine industry. problem is that there's lots of water and lots of sun in the stellenbosch, and virtually no seasons. the oak trees grew too fast, and the wood was too porous. the casks built of the local oak just ended up draining out the wine straight through the wood! so now there are plenty of oak trees, and just nothing to be done with them. at a couple of the vineyards, the outdoor seating can be a bit dangerous since a gust of wind brings down a hailstorm of acorns.
the face of table mountain is another location where imported australian hakea trees have run rampant. beauty of these things (along with the european pine trees found all over) is that they're impervious to burning. burning actually helps to spread the seeds of pine and hakea! the problem with these plants is that they're used to getting very little water. the cape area is like heaven to them, and they suck every ounce of moisture available to them, to the detriment of the local flora. classic case of human intervention run amock.
the real problem is that these are just 2 of the several dozen instances of foreign plants that are causing all kinds of havoc on the local biosystem. and the only way to get rid of the alien plants is to hack them down (since burning doesn't work), so a *lot* of manual labor.