The invading flora: a regional account of the assault

Recently, State Herbarium botanist Peter Lang has compiled the numbers of vascular plants occurring in the wild in South Australia for 2013.  There are 4,940 taxa (= species, subspecies & varieties) in the state, of which 1,267 taxa (25.6%) are naturalised alien plants (weeds). A further 232 taxa (4.7%) are questionably naturalised: these are, for example, plants that are found in cultivation and have escaped, but it is not proven whether they will maintain their wild populations. Including these the total for alien taxa is 1,499 (30.3%), or almost one third of plants found in the State.

The graph below depicts the numbers of plants for each of the 13 botanical regions (as used by the State Herbarium). The lowest number of introduced taxa is found in the NW (North Western) region of the State, with only 5.9% of naturalised and questionably naturalised plants. The SL (Southern Lofty) region, which includes Adelaide, the Adelaide Hills and Fleurieu Peninsula, has the highest number of alien plants, 46.4%. As expected, more remote regions, away from large settlements, have fewer naturalised and questionably naturalised taxa.

Weeds are not only introduced through agricultural practices, but also escape from gardens. Plants listed as questionably established highlight potential weeds of the future and warrant monitoring or control, to prevent them becoming established.

Click here to see the original data.

Numbers of native (incl. questionably native), naturalised and questionably naturalised plants in South Australia (as of 11 Dec. 2013)