South Africa is ranked sixth out of the worldâ s 17 megadiverse countries , with more than 20,000 different kinds of plants , or about 10 % of all the known species of plants on Earth , making it very rich in plant biodiversity . South Africa is ranked sixth out of the worldâ s seventeen megadiverse countries , with more than 20,000 different plants , or about 10 % of all the known species of plants on Earth , making it particularly rich in plant biodiversity .