School of Earth & Environmental Sciences
Kelly, Liam J M, PATTERNS OF SEA SPURGE (EUPHORBIA PARALIAS) INVASION IN NEW SOUTH WALES, AUSTRALIA, BEnvSci Hons, School of Earth & Environmental Sciences, University of Wollongong, 2015.
Environmental weeds pose an ongoing problem for biodiversity values around the world. To deal with widespread weed invasions in the face of limitations on resources, practical and achievable management strategies must be developed. Where prevention and total eradication is not feasible, many weed management strategies are based around establishing containment zones to arrest further spread. To be effective, containment zones must consider the dispersal distance of the invader, to ensure that an adequate proportion of the population’s recruitment in new area is removed before becoming established. Optimisation of surveillance strategies is desirable to achieve this, and is typically done through modelling the distribution of the species or its pathways of dispersal to locate and target areas most at risk of invasion. For coastal dune weeds such as sea spurge (Euphorbia paralias) efforts to model dispersal distances and pathways can be complicated by long-distance marine dispersal of propagules. The aim of this study was to establish the distribution of sea spurge along the coast of New South Wales, Australia, where invasion has progressed from the south over the past few decades. Over the invasion front, an attempt was made to determine any factors making beaches more susceptible to invasion so that surveillance actions might be optimised. Considering the role of propagule pressure in driving invasion, beach attributes were selected pertaining to likelihood of propagule stranding at a beach, such as orientation and wave energy, as well as latitude and an index of anthropogenic disturbance. Additionally, sea spurge management actions undertaken by the Far South Coast National Parks and Wildlife Services at the bottom of coastal NSW were used as a case study to assess the effect of ongoing management of sea spurge populations on undisturbed NSW beaches. Presence/absence data for sea spurge was obtained for a total of 481 beaches on the NSW coast through information gathered from land managers, management documents and field surveys, with sea spurge having invaded 309 (64.2%). The likely northern extent of the invasion was determined. Latitude was found to have an influence on sea spurge invasion, with invasions becoming more infrequent moving north. This relationship can be used to prioritize surveillance for emergent populations which otherwise appeared uninfluenced by beach characteristics. The FSC NPWS management programme showed that with sustained effort, sea spurge populations can be reduced substantially to the effect of minimising propagule output, but total eradication was not possible. These findings can be used to inform a state-wide management strategy for responding to sea spurge invasion by helping establish containment zone parameters, and setting effective regional management goals with the outcome of stopping or slowing the invasion.