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A plant introduced with a practical purpose along the New South Wales (NSW) coast eventually became a major environmental weed. South African bitou bush was deliberately planted along the NSW coastline between 1946 and 1968 to help stabilise sand dunes, according to the NSW Environment and Heritage department. The fast-growing shrub later spread rapidly and is now found along 46% of the state's coastline, with some infestations extending up to 10 kilometres inland. What was once used to control shifting sand has since become a threat to native coastal vegetation and wildlife, prompting long-running efforts to contain and remove it.
A plant brought in to stabilise dunes
Bitou bush, scientifically known as Chrysanthemoides monilifera subsp. rotundata, is native to South Africa. NSW Environment and Heritage says it is thought to have initially reached Australia in ship ballast before later being deliberately used for dune stabilisation. Its deliberate planting along the NSW coast began in 1946 and continued through 1968. The plant was valued because it grew quickly and could help hold loose coastal sand in place. Historical government documents also record its use to stabilise and revegetate dunes affected by coastal sand mining. Planting took place at a number of coastal locations, including Ballina, Byron Bay, Crescent Head, Iluka, Lake Munmorah, Port Macquarie, Redhead, The Entrance and Tweed Heads. The same characteristics that made bitou bush useful for stabilisation, however, also helped it become difficult to control once it established beyond planted areas.
How bitou bush spread
Once established along the coastline, bitou bush spread through a combination of deliberate planting and natural expansion. The NSW government now records it along 46% of the state's coastline, with the north coast particularly heavily affected. In some locations, the shrub has moved as far as 10 kilometres inland. Bitou bush is capable of growing rapidly and forming dense stands. Rather than simply occupying empty spaces, it can move into existing coastal plant communities and create thick shrub layers. That expansion has changed the character of some dunes, headlands and other coastal habitats. Earlier government assessments described an even wider distribution at different points in time, reflecting differences in surveys, definitions and assessment periods. A NSW Scientific Committee determination in 1999, for example, reported the weed on 90% of the state's sandy coast. The current NSW Environment and Heritage data shows the figure as 46% of the state's coastline.
Native plants and animals face pressure
The main environmental concern is not simply the presence of an introduced shrub but what happens when it becomes dominant. According to NSW Environment and Heritage, bitou bush invades coastal heathlands, grasslands, woodlands and forests. It can form dense stands that replace native plants and alter habitats used by native animals. Infestations can also smother vegetation communities found on sand dunes and headlands. The NSW Bitou Threat Abatement Plan identified 157 native plant species, three plant populations and 24 ecological communities as being at risk from bitou bush and boneseed invasion. The plan also identified 24 native animal species potentially threatened by the spread of the weeds. Because of these impacts, the NSW Scientific Committee has listed the invasion of native plant communities by bitou bush and boneseed as a key threatening process affecting native plants and animals.
Efforts now focus on containment and restoration
Managing the weed is now a long-term conservation task. Bitou bush and the related South African plant boneseed were collectively listed as Weeds of National Significance in 2000. NSW has also developed a Threat Abatement Plan that directs control towards sites where removing the weed can provide the greatest benefit to threatened species and ecological communities. The approach involves more than simply removing individual plants. Control programmes involve government agencies, local authorities, community groups, Aboriginal groups, land managers and bush regenerators. The NSW plan identifies 169 priority sites, alongside northern and southern containment zones intended to limit further spread and protect important native vegetation. Under the NSW Biosecurity Act 2015, specific requirements also apply to bitou bush management. In areas north of Cape Byron and south of Point Perpendicular, eradication is required, while the central coastal distribution is managed through containment measures. The history of bitou bush shows how a species introduced to solve one environmental problem can create another when it spreads beyond its intended role. Decades after it was planted to stabilise NSW sand dunes, the shrub has become widespread enough to require coordinated control, with restoration efforts now aimed at giving native coastal ecosystems space to recover.
