Fourteenth Australian Weeds Conference Using your cute and furries: the role of threatened species in weed awareness S.J. Vidler CRC for Australian Weed Management, PMB 1, Waite Campus, Glen Osmond, South Australia 5064, Australia Summary A brief review of available information Network also uncovered further examples, some un- has shown that weeds are a major threat to at least 41 documented but backed up by strong observational threatened plant and animal species. This information evidence from ecologists and other experts. This list is should be used as a communication tool to raise the not defi nitive. There were many more examples where level of awareness of weeds amongst the public and the ‘weeds’ were listed as a key threatening process, but media, and generate a response from policy makers. were not supported by any further information. Keywords Biodiversity, threatened species, invasive For the purposes of this review it is important to plants, weeds, communication. understand the following defi nitions. Environmental weeds Plant species that have INTRODUCTION environmental impacts outside their native range. In Australia today invasive plants and animals are Some species that are native to one part of Australia considered the biggest threat to biodiversity after are environmental weeds in other parts of Australia. land clearing. But what does this mean? Chances are Threatened species In this paper ‘threatened spe- a quick survey on the street would reveal a very poor cies’ includes all species listed with a national or state understanding of the issues and concepts represented conservation status of endangered, vulnerable, rare or in this statement. the equivalent. It also includes those species, subspe- One way to illustrate the detrimental effect of cies or populations that are considered at the same weeds on biodiversity is the large number of cases level of risk on a regional scale. In no way does this where it has been shown that specifi c weed species report intend to discount the effects of environmental are having a negative impact on threatened species or weeds on other more common species, but by con- communities. However, while it is generally accepted centrating on those species already highly vulnerable that these impacts take place there is a lack of quantita- we can highlight the urgent need for action required tive information on the matter. to reduce this ever increasing problem. In their recent review Grice et al. (2004) identifi ed Key threatening processes Any negative impact just 24 papers that quantifi ed the ecological impacts on a threatened species caused by the existence of an of invasive plant species in Australia. Many of these environmental weed in its habitat. For example, weeds did not evaluate effects on threatened species. They may out-compete a threatened plant species, cause the concluded that while more research is obviously loss of breeding sites for other species or displace a needed, many weed management decisions will have food plant for dependent fauna. In many cases land to take place in the absence of quantitative studies clearing resulting in habitat destruction, degradation on impact. and fragmentation, has been the initial cause of a In this paper, I synthesise currently available infor- reduction in species numbers and abundance. How- mation on the relationships between weeds and threat- ever, weeds can become a subsequent key threatening ened species. Much of this information is qualitative process, invading remaining habitats especially where but it provides a basis for improved communication to these are fragmented or already degraded through other the broader community about the critical impacts that factors (Groves and Willis 1999). weeds have on biodiversity in general. CASE STUDIES APPROACH TO REVIEW Ferals and competition The only mammal restricted To compile the list of 41 threatened species listed in to the alpine and sub-alpine areas of mainland Aus- Table 1, I recorded examples from published works tralia, the mountain pygmy-possum (Burramys parvus and internet searches, which provided access to the Broom), was thought to be extinct but was rediscov- extensive number of online species recovery plans, ered in 1966. It occurs on Mt. Bogong, Bogong High along with other materials. Personal contact with state Plains, Mt. Loch, Mt. Higginbotham and Mt. Buller in agency conservation staff and the Threatened Species Victoria (VIC). In New South Wales (NSW) it is found 652 Fourteenth Australian Weeds Conference only in Kosciusko National Park (Primary Industries/ Larger vertebrates can also be affected by poisons Sustainability and Environment 2003a). in some invasive plants. The Proserpine rock-wallaby The mountain pygmy-possum is a good example (Petrogale Persephone Maynes) occurs in Conway, of the fl ow-on effects of weed invasion. Its survival is Gloucester Island and Dryander National Parks, on threatened by a number of factors, but one of them is the Clarke Range near Proserpine, in areas of the Con- weeds; English broom (Cytisus scoparius (L.) Link way Range, and around the town of Airlie Beach in ssp. scoparius) and blackberry (Rubus fruticosus L. Queensland (Nolan and Johnson 2001). The Glouces- agg.). Not only do these weeds harbour foxes, which ter Island population is threatened by two weeds, pink prey on the possum, but they also out-compete its food periwinkle (Catharanthus roseus (L.) G.Don) and rub- plants (PI/SandE 2003a). Thus there is a two-fold im- bervine (Cryptostegia grandifl ora Roxb. ex R.Br.), but pact on the possum; an introduced predator to contend particularly the pink periwinkle. Pink periwinkle is with, and less food to survive on. closely related to the wallaby’s natural food plants, but The Bathurst copper butterfl y (Paralucia spinifera unlike the native plants, it is toxic when eaten. There Edwards and Common) is believed to be the rarest are similar concerns about other potentially toxic gar- butterfl y in Australia. It is currently known from 29 den plants, as wallabies have been observed grazing in locations all within two council areas in western NSW household gardens, particularly in drier times (Nolan (NSW National Parks and Wildlife Service – NPWS and Johnson 2001). 1999a). The Bathurst copper is an excellent example of the complex associations that can occur between Habitat degradation Weeds can also lead to habitat species. It shares a symbiotic relationship with a na- degradation by reducing access to breeding, resting tive blackthorn (Bursaria spinosa spp. lasiophylla or feeding sites. The cotton-pygmy goose (Nettapus E.M.Benn.) and a small black ant (Anonychomyrma coromandelianus Gmelin), a very small duck with a itinerans Lowne). Caterpillars of the Bathurst copper goose-like bill, is relatively common on lagoons, dams feed on the native blackthorn while in a mutualistic and ponds in Queensland. However, it is now consid- arrangement the small black ant tends to the butterfl y’s ered an endangered species in NSW where aquatic larvae (NSW NPWS 1999a). weeds are infesting the lakes and swamps it prefers, Noxious weeds threaten most sites where this and where it feeds off native hydrilla and pondweed rare butterfl y is still recorded. Blackberries form (Garnett 1993, NSW NPWS 1999b). ‘Aquatic weeds, impenetrable thickets around the blackthorn plants, especially water hyacinth Eichhornia crassipes – are completely smothering them at some sites. In other believed to have contributed to the species’ decline areas these food plants are overgrown with Scotch by choking the surface of some coastal wetlands and broom (Cytisus scoparius), and now St. John’s wort rendering them unsuitable’ (Ayers et al. 1996). (Hypericum perforatum L.) invasions are also consid- Other recent threats include exotic grasses such ered a key threat (Ayers et al. 1996). as aleman grass (Echinochloa polystachya (Kunth) A.S.Hitchc.) and olive hymenachne (Hymenachne Toxic mix In another butterfl y example we see the amplexicaulis (Rudge) Nees), which can also choke out effect of poisonous plants. In 1870 the Richmond waterways used by the pygmy-geese (Garnett 1993). birdwing butterfl y (Ornithoptera richmondia Gray) On the fl oodplain of the Northern Territory (NT), was reportedly very common in the streets of Bris- and slowly spreading into QLD, a thorny shrub up to bane (Queensland (QLD) Museum). Today, no natu- 6 m high forms a dense monoculture that replaces all ral breeding sites are known between Caboolture to native vegetation. Mimosa (Mimosa pigra L.), a native the north and Nerang in the Gold Coast hinterland. to South and Central America, infests some 80,000 ha Richmond birdwings normally lay eggs only on two of the NT (Martin 2003). This invasion has displaced species of native Pararistolochia vines; P. praevenosa vast areas of native sedgeland which once provided (F.Muell.) M.J.Parsons (itself a rare species) and P. nesting sites and food for many bird species includ- deltantha (F.Muell.) M.J.Parsons (University of QLD ing the endangered yellow chat (Epthianura crocea 2003). Most of these vines have disappeared with the tunneyi Matthews) (Groves and Willis 1999). Just clearing of coastal rainforests. Remaining butterfl ies 500 remaining individuals of this western Arnhem mistake the ornamental Dutchman’s pipe vine (Aris- Land race of yellow chats inhabit the coastal and sub tolochia elegans Mast.) for the native Pararistolochia coastal fl oodplains of the NT, from the Mary River to vines on which they lay their eggs. Toxins in this in- the East Alligator River. The recovery plan is clear: troduced plant kill the young caterpillars when they ‘The major current threat is the invasion by the weed begin feeding. The impact of this environmental weed Mimosa pigra, which is thought to render the habitat is thus very direct and immediate. unsuitable’ (Garnett and Crowley 2000). 653 Fourteenth Australian Weeds Conference Competition The Cumberland Plain Woodland, itself Fire The desert sand skipper (Croitana aestiva Ed- a federally endangered vegetation community, is also wards) is a small brown and yellow butterfl y known home to the rare shrub pink pimelea (Pimelea spicata only from a small number of specimens collected in R.Br.).