ASFB and ASL 2014* Coastal floodplains, wetlands and weeds: a bigger problem than commonly envisaged. (#210)
It is often assumed that the physico-chemical environment of coastal wetlands is so severe that they are relatively immune to invasion by troublesome exotic plant species. This assumption is implicit in almost all recent published reviews of threats facing mangroves, coastal saltmarshes and other types of brackish-water coastal wetland, where a limited range of vascular plant plant taxa, often focussing on Spartina, are invoked as the major species of concern. Even though the weed flora of southern Australia is derived largely from agriculture and horticulture, neither of which includes many species tolerant of variably saline environments, a detailed State-wide assessment of threats to Victorian coastal wetlands indicated that weeds were the third most pervasive threat, after land reclamation and grazing by domestic animals. Taxa of most concern were Lophopyrum ponticum, Parapholis incurva, Hordeum marinum, and Juncus acutus. Of these, Tall Wheat Grass, L. ponticum, until recently widely promoted by government agencies as a salt-tolerant pasture grass, is the most serious invader of upper saltmarsh in Victoria because of its very broad ecological amplitude and robust life form. We assessed the effectiveness of various control measures, including slashing and various herbicides, in controlling L. ponticum infestations and their side-effects on adjacent wetland communities. A nominally grass-specific herbicide widely used for Spartina control, Fusilade®, was ineffective in controlling L. ponticum. The broad-spectrum herbicide glyphosate was more effective in controlling L. ponticum, but had severe effects on some native plant species. It seems that controlling weeds in coastal wetlands remains difficult and problematic.
