Edited by Charles Perrings, Mark Williamson and Silvana Dalmazzone
Chapter 6: Weed invasions of Australian farming systems: from ecology to economics
Andrew R. Watkinson, Robert P. Freckleton and Peter M. Dowling* 1 INTRODUCTION Many of the world’s worst pest infestations result from the introduction of alien species. In the case of weeds of farming systems, examples include the invasion of Bromus tectorum into western North America (Mack, 1981), Amarathus retroﬂexus in Eastern Europe (Thomas and Annal, 1995) and the introduction of Avena fatua into Western Europe during the Iron Age. In Australia such invaders form a prominent component of the biota with approximately 11 per cent (1952 species) of the Australian ﬂora being made up of alien species. In some states the proportion of the biota that is alien is considerably higher, with 21, 25 and 23 per cent of species in New South Wales, South Australia and Victoria, respectively, being introduced (Groves, 1997). These species can pose a considerable threat to both natural and managed ecosystems. In farming systems, in particular, introduced weeds are a major economic burden. In crops, the weeds Chondrilla juncea, Heliotropium europaeum and Avena fatua are estimated to cost A$10m, A$40m and A$42m, respectively; in pastures Echium plantagineum, Onopordum spp. and Vulpia spp. are estimated to cost A$30m, A$20m and A$30m, respectively (CSIRO, 1997). Where the economic state of farming may be somewhat precarious, particularly during droughts, proﬁts are marginal and these losses are signiﬁcant. In order to better manage such problems, a modelling approach has increasingly been adopted. Models have been developed, for example, to predict...
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