Invasion of native plant communities by bitou bush and boneseed - key threatening process listing

The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to list the Invasion of Native Plant Communities by Chrysanthemoides monilifera as a KEY THREATENING PROCESS on Schedule 3 of the Act. Listing of Key Threatening Processes is provided for by Part 2 of the Act.

NSW Scientific Committee - final determination

The Scientific Committee has found that:

1. Chrysanthemoides monilifera is a South African species of which two subspecies occur in Australia - ssp. monilifera - boneseed, and ssp. rotundata - bitou bush. Both subspecies invade and displace native plant communities.

2. Chrysanthemoides monilifera ssp. rotundata was first recorded in New South Wales from near Newcastle in 1908, and was extensively planted for dune stabilisation between 1946 and 1968. It has spread rapidly and is now found on 90% of the sandy coast of New South Wales, covering an area in excess of 70,000 ha.

3. Vigorous growth, prolific seed production and effective seed dispersal of both subspecies enable them to compete strongly with, or in some places eliminate, native vegetation.

4. Chrysanthemoides monilifera is currently declared a noxious weed in coastal Local Government Areas where it occurs in New South Wales.

5. The dense monoculture of Chrysanthemoides monilifera which develops after invasion threatens local vegetation at all sites which are affected. This may result in local and regional declines of many plant species and communities, possibly to the extent that they become endangered. The changed structure of the habitat may adversely impact on both native vertebrate and invertebrate fauna and may favour the prolification of non-indigenous species.

6. Invasion by Chrysanthemoides monilifera is an identified threat to a number of species and communities listed on Schedule 1 of the Threatened Species Conservation Act, including Zieria prostrata, Chamaesyce psammogeton, Acacia terminalis subsp. terminalis and Eastern Suburbs Banksia Scrub. The ability of Chrysanthemoides to become the overwhelming dominant in invaded ecological communities threatens all communities within the area of potential distribution of both subspecies of Chrysanthemoides monilifera. In the case of ssp. rotundata, communities at risk include dune grasslands and heathland, heathlands on headlands, scrub sclerophyll woodland and forest, and, littoral rainforest. Subspecies monilifera is a threat to a range of woodlands and forest. Many species in the threatened communities would themselves be threatened in consequence. This may include the following threatened taxa; Eastern Bristlebird, Dasyornis brachypterus; Little Tern, Sterna albifrons and Beach Stone-curlew, Esacus neglectus.

In view of 2, 3, 4, 5 and 6 above the Scientific Committee is of the opinion that the Invasion of Native Plant Communities by Chrysanthemoides monilifera adversely affects two or more threatened species or ecological communities and it could cause species that are not threatened to become threatened.

Proposed Gazettal date: 12/3/99
Exhibition period: 12/3/99 - 16/4/99