We used the process-oriented niche model CLIMEX to estimate the potentialglobal distribution of serrated tussock under projected future climates.Serrated tussock is a drought-tolerant, wind- and human-dispersed grass ofSouth American origin that has invaded pastures in Australia, Europe, NewZealand, and South Africa. The likely effect of climate change on itspotential global distribution was assessed by applying six climate-changescenarios to a previously developed model. The projections of climaticsuitability under the current climate revealed considerable scope forspread, with the most suitable areas occurring adjacent to existingnaturalized populations in Australia, New Zealand, and Western Europe. Underfuture climates, projected to the 2080s, the land area suitable for serratedtussock contracts globally between 20 and 27%. Changes in projectedpotential area under the six scenarios were very similar in all geographicalregions apart from North America and New Zealand, where the projectionsrange from little change or contraction under the National Center forAtmospheric Research (NCAR) and Centre for Climate Research (MIROC) globalclimate models (GCMs) to expansion under the Commonwealth Scientific andIndustrial Research Organisation (CSIRO) GCM. Elsewhere, contractions occurin Australia, Asia, South America, and Africa under all six future climatescenarios. By contrast, for Europe, the area climatically suitable forserrated tussock increases under all six scenarios (average increase 47%)through expansions into eastern European countries that are currentlyunsuitable and through increases in the suitable area in England, Ireland,and Denmark. Since pastoralism is a dominant land use in these regions ofEurope, a prudent biosecurity strategy would be to contain the nascent fociof serrated tussock in southern France, along the west coast of Italy, andin the United Kingdom. This strategy could consist of a set of policies tolimit human-assisted dispersal of the species' seeds and to reducewind-borne spread through cultural control of the plant.
