Hot Topics in Ecology

Weed risk set to rise

New plant varieties bred for pasture will worsen the weed problem
Synthesis by Don Driscoll, Australian National University, and Jane Catford, University of Melbourne.
  • Many plants introduced for livestock production have become weeds of native ecosystems with major environmental, social and economic costs.
  • New varieties of pasture plants that are already weeds in Australia can be developed and released without consideration of environmental consequences.
  • Because these new varieties are bred with characteristics that are typical of invasive plants, their release will likely increase the impacts and exacerbate the spread of environmental weeds.
Buffelgrass, used widely by the pasture industry, is also an ecosystem transformer, carrying hot fires that kill woody plants. photo by DD

Australia already pays a high price for introducing hundreds of exotic plant species for livestock pasture production. Many of these species have become weeds with major environmental, social and economic impacts. Some introduced grasses increase fire intensity, transforming natural savanna woodlands to exotic-dominated grasslands. Gamba grass, introduced to northern Australia, has increased flammable biomass from six to ten tonnes per hectare, with the cost of fire management now nine times higher.

Many new pasture plants have a high risk of becoming invasive weeds. One of the most reliable predictors of a species’ invasiveness is whether or not it is invasive elsewhere. Globally, over 90% of plants developed for pasture are regarded as weeds, and one third are classed as weeds in the country in which they are sold.

If new varieties of existing weeds are introduced, the weed problem could escalate. New varieties are bred to increase pasture production, but also possess characteristics that increase invasion risk. Some are inoculated with bacteria or fungi that increase reproduction and growth, or can interact with the soil to increase nutrient availability, which could exacerbate weed invasion. Pasture varieties that resist disease, tolerate drought or grow in poor soils can become more successful than their less tolerant relatives, increasing the threat to ecosystems with high conservation value. Introducing additional genetic variation into existing weed populations can enable weeds to invade new habitats, and to take advantage of changing climates.

Although proposals to introduce new species are scrutinized for potential environmental and economic impacts, the likely impacts of new varieties of permitted exotic species are not considered. Without regulations that take into account the environmental impacts of new pasture varieties, existing weeds will likely become more invasive.

Hot Topic Lead Author: 
Name: Dr Don Driscoll
Phone: 02 61258130

ID Title Location Type
7242 Setterfield S. A., Rossiter-Rachor N. A., Douglas M. M., Wainger L., Petty A. M., Barrow P., Shepherd I. J. & Ferdinands K. B. (2013) Adding Fuel to the Fire: The Impacts of Non-Native Grass Invasion on Fire Management at a Regional Scale. Plos One 8, e59 Batchelor, Northern Territory, Australia pre-existing gradient/contrasts
7243 Pauchard A., Kueffer C., Dietz H., Daehler C. C., Alexander J., Edwards P. J., Arevalo J. R., Cavieres L. A., Guisan A., Haider S., Jakobs G., McDougall K., Millar C. I., Naylor B. J., Parks C. G., Rew L. J. & Seipel T. (2009) Ain't no mountain high enoug global Review
7222 Driscoll D. A., Catford J. A., Barney J. N., Hulme P. E., Inderjit, Martin T. G., Pauchard A., Pyšek P., Richardson D. M., Riley S. & Visser V. (2014) New pasture plants intensify invasive species risk. Proceedings of the National Acadamy of Science USA global Review plus survey of agribusinesses and legislation
7223 Lonsdale W. M. (1994) Inviting trouble - introduced pasture species in northern Australia. Aust. J. Ecol. 19, 345-54. na Review
7225 Fensham R. J., Donald S. & Dwyer J. M. (2013) Propagule pressure, not fire or cattle grazing, promotes invasion of buffel grass Cenchrus ciliaris. J. Appl. Ecol. 50, 138-46. Central Qld, Australia landscape-scale survey and a field experiment
7226 Uchitel A., Omacini M. & Chaneton E. J. (2011) Inherited fungal symbionts enhance establishment of an invasive annual grass across successional habitats. Oecologia 165, 465-75. near Ordoqui, Buenos Aires province, Argentina manipulative experiment
7227 Godfree R. C., Woods M. J. & Young A. G. (2009) Do virus-resistant plants pose a threat to non-target ecosystems? II. Risk assessment of an Australian pathosystem using multi-scale field experiments. Austral Ecol. 34, 525-44. ACT, Australia manipulative experiment
7228 Rout M. E., Chrzanowski T. H., Westlie T. K., DeLuca T. H., Callaway R. M. & Holben W. E. (2013) Bacterial endophytes enhance competition by invasive plants. Am. J. Bot. 100, 1726-37. north-central Texas, USA observation and growth trials
7229 Ellstrand N. C., Prentice H. C. & Hancock J. F. (1999) Gene flow and introgression from domesticated plants into their wild relatives. Annu. Rev. Ecol. Syst. 30, 539-63. na Review
7230 Lu B. R. & Snow A. A. (2005) Gene flow from genetically modified rice and its environmental consequences. Bioscience 55, 669-78. na Review
7231 Lavergne S. & Molofsky J. (2007) Increased genetic variation and evolutionary potential drive the success of an invasive grass. Proc. Natl. Acad. Sci. USA. 104, 3883-8. Czech Republic (4 populations), France (3 populations), USA (Vermont, North Carolina, 3 populations each) Genetic survey, transplant, glasshouse and field experiments
7232 Grossman J. D. & Rice K. J. (2014) Contemporary evolution of an invasive grass in response to elevated atmospheric CO2 at a Mojave Desert FACE site. Ecol. Lett. 17, 710–6. Mojave Desert USA manipulative experiment
7234 Prober S. M. & Wiehl G. (2012) Relationships among soil fertility, native plant diversity and exotic plant abundance inform restoration of forb-rich eucalypt woodlands. Divers. Distrib. 18, 795-807. Wheatbelt, Western Australia pre-existing gradient/contrasts
7235 Grice A., Friedel M., Marshall N. & Van Klinken R. (2012) Tackling Contentious Invasive Plant Species: A Case Study of Buffel Grass in Australia. Environmental Management 49, 285-94. Australia review and opinion piece
7236 Cook G. D. & Grice A. C. (2013) Historical perspectives on invasive grasses and their impact on wildlife in Australia. Wildlife Society Bulletin 37, 469-77. Australia review and opinion piece
7237 Clarke A., Lake P. S. & Dowd D. J. (2004) Ecological impacts on aquatic macroinvertebrates following upland stream invasion by a ponded pasture grass (Glyceria maxima) in southern Australia. Marine and Freshwater Research 55, 709-13. West Gippsland, Victoria, Australia (37°55′S, 146°00′E) pre-existing contrasts
7238 Bunn S. E., Davies P. M., Kellaway D. M. & Prosser I. P. (1998) Influence of invasive macrophytes on channel morphology and hydrology in an open tropical lowland stream, and potential control by riparian shading. Freshwater Biology 39, 171-8. wet tropics of far north Queensland, Australia (145°59.8′E, 17°34′S) manipulative experiment
7239 Weber J., Dane Panetta F., Virtue J. & Pheloung P. (2009) An analysis of assessment outcomes from eight years’ operation of the Australian border weed risk assessment system. Journal of Environmental Management 90, 798-807. Australia comparison of model performance and expert judgement
7240 van Kleunen M., Weber E. & Fischer M. (2010) A meta-analysis of trait differences between invasive and non-invasive plant species. Ecology Letters 13, 235-45. global meta-analysis

Further information about this topic contact:

Dr Don Driscoll
02 61258130

Chair, Hot Topics Editorial Board
Dr Brett Murphy