Agricultural intensification is critical to meet global food demand, but intensification threatens native species and degrades ecosystems. Sustainable intensification (SI) is heralded as a new approach for enabling growth in agriculture while minimizing environmental impacts. However, the SI literature has overlooked a major environmental risk. Using data from eight countries on six continents, we show that few governments regulate conventionally bred pasture taxa to limit threats to natural areas, even though most agribusinesses promote taxa with substantial weed risk. New pasture taxa (including species, subspecies, varieties, cultivars, and plant-endophyte combinations) are bred with characteristics typical of invasive species and environmental weeds. By introducing novel genetic and endophyte variation, pasture taxa are imbued with additional capacity for invasion and environmental impact. New strategies to prevent future problems are urgently needed. We highlight opportunities for researchers, agribusiness, and consumers to reduce environmental risks associated with new pasture taxa. We also emphasize four main approaches that governments could consider as they build new policies to limit weed risks, including (i) national lists of taxa that are prohibited based on environmental risk; (ii) a weed risk assessment for all new taxa; (iii) a program to rapidly detect and control new taxa that invade natural areas; and (iv) the polluter-pays principle, so that if a taxon becomes an environmental weed, industry pays for its management. There is mounting pressure to increase livestock production. With foresight and planning, growth in agriculture can be achieved sustainably provided that the scope of SI expands to encompass environmental weed risks.

Bio Protection Research Centre Lincoln University Lincoln 7647 New Zealand;

Centre for Invasion Biology Department of Botany and Zoology Stellenbosch University Matieland 7602 South Africa; and

Department of Environmental Studies and Centre for Environmental Management of Degraded Ecosystems University of Delhi Delhi 110007 India;

Department of Plant Pathology Physiology and Weed Science Virginia Tech Blacksburg VA 24061;

Facultad de Ciencias Forestales Universidad de Concepción Casilla 160 C Concepción Chile; Institute of Ecology and Biodiversity Chile;

Faculty of Law University of Technology Sydney NSW 2007 Australia

Institute of Botany Department of Invasion Ecology Academy of Sciences of the Czech Republic CZ 25243 Průhonice Czech Republic; Department of Ecology Charles University Prague CZ 12844 Prague Czech Republic;

National Environmental Research Program Environmental Decisions Group and ARC Centre of Excellence for Environmental Decisions Australia; Commonwealth Scientific and Industrial Research Organisation Land and Water Brisbane QLD 4001 Australia;

National Environmental Research Program Environmental Decisions Group and ARC Centre of Excellence for Environmental Decisions Australia; Fenner School of Environment and Society Australian National University Canberra ACT 2601 Australia;

National Environmental Research Program Environmental Decisions Group and ARC Centre of Excellence for Environmental Decisions Australia; Fenner School of Environment and Society Australian National University Canberra ACT 2601 Australia; School of Botany The University of Melbourne Melbourne VIC 3010 Australia; Department of Ecology Evolution and Behavior University of Minnesota Saint Paul MN 55108;

Comment In

Nature. 2014 Dec 4;516(7529):37. doi: 10.1038/516037e. PubMed

Comment In

Proc Natl Acad Sci U S A. 2015 Apr 7;112(14):E1696. doi: 10.1073/pnas.1500548112. PubMed

Comment In

Proc Natl Acad Sci U S A. 2015 Apr 7;112(14):E1695. doi: 10.1073/pnas.1424707112. PubMed

See more in PubMed

Steinfeld H, et al. Livestock's Long Shadow. Environmental Issues and Options. Food and Agriculture Organisation of the United Nations; Rome: 2006.

Alexandratos N, Bruinsma J. World Agriculture Towards 2030/2050: The 2012 Revision. Food and Agriculture Organization of the United Nations; Rome: 2012.

Godfray HCJ, et al. Food security: The challenge of feeding 9 billion people. Science. 2010;327(5967):812–818. PubMed

Foley JA, et al. Solutions for a cultivated planet. Nature. 2011;478(7369):337–342. PubMed

Herrero M, Thornton PK. Livestock and global change: Emerging issues for sustainable food systems. Proc Natl Acad Sci USA. 2013;110(52):20878–20881. PubMed PMC

Garnett T, et al. Agriculture. Sustainable intensification in agriculture: Premises and policies. Science. 2013;341(6141):33–34. PubMed

Lonsdale WM. Inviting trouble: Introduced pasture species in northern Australia. Aust J Ecol. 1994;19(3):345–354.

Richardson DM, et al. Naturalization and invasion of alien plants: Concepts and definitions. Divers Distrib. 2000;6(2):93–107.

Silvério DV, et al. Testing the Amazon savannization hypothesis: Fire effects on invasion of a neotropical forest by native cerrado and exotic pasture grasses. Philos Trans R Soc Lond B Biol Sci. 2013;368(1619):20120427. PubMed PMC

Simberloff D, et al. Impacts of biological invasions: What’s what and the way forward. Trends Ecol Evol. 2013;28(1):58–66. PubMed

Gilbert B, Levine JM. Plant invasions and extinction debts. Proc Natl Acad Sci USA. 2013;110(5):1744–1749. PubMed PMC

Mack RN, et al. Biotic invasions: Causes, epidemiology, global consequences, and control. Ecol Appl. 2000;10(3):689–710.

DiTomaso JM. Invasive weeds in rangelands: Species, impacts, and management. Weed Sci. 2000;48(2):255–265.

Pimentel D, Zuniga R, Morrison D. Update on the environmental and economic costs associated with alien-invasive species in the United States. Ecol Econ. 2005;52(3):273–288.

Sinden J, et al. The economic impact of weeds in Australia. Plant Prot Q. 2005;20(1):25–32.

Setterfield SA, et al. Adding fuel to the fire: The impacts of non-native grass invasion on fire management at a regional scale. PLoS ONE. 2013;8(5):e59144. PubMed PMC

Grice AC, Friedel MH, Marshall NA, Van Klinken RD. Tackling contentious invasive plant species: a case study of buffel grass in Australia. Environ Manage. 2012;49(2):285–294. PubMed

Quinn LD, Barney JN, McCubbins JSN, Endres AB. Navigating the “noxious” and “invasive” regulatory landscape: Suggestions for improved regulation. Bioscience. 2013;63(2):124–131.

Davis AS, et al. Screening bioenergy feedstock crops to mitigate invasion risk. Front Ecol Environ. 2010;8(10):533–539.

Lindenmayer DB, et al. Avoiding bio-perversity from carbon sequestration solutions. Conservation Letters. 2012;5(1):28–36.

Richardson DM, Rejmanek M. Trees and shrubs as invasive alien species: A global review. Divers Distrib. 2011;17(5):788–809.

Bradley BA, et al. Global change, global trade, and the next wave of plant invasions. Front Ecol Environ. 2012;10(1):20–28.

Hulme PE. Weed risk assessment: A way forward or a waste of time? J Appl Ecol. 2012;49(1):10–19.

Warren RJ, Ursell T, Keiser AD, Bradford MA. 2013. Habitat, dispersal and propagule pressure control exotic plant infilling within an invaded range. Ecosphere 4(2):art26.

Kempel A, Chrobock T, Fischer M, Rohr RP, van Kleunen M. Determinants of plant establishment success in a multispecies introduction experiment with native and alien species. Proc Natl Acad Sci USA. 2013;110(31):12727–12732. PubMed PMC

Nunez MA, Moretti A, Simberloff D. Propagule pressure hypothesis not supported by an 80-year experiment on woody species invasion. Oikos. 2011;120(9):1311–1316.

Neto AB, et al. Italian ryegrass establishment by self-seeding in integrated crop livestock systems: Effects of grazing management and crop rotation strategies. Eur J Agron. 2014;57:77–83.

Fensham RJ, Donald S, Dwyer JM. Propagule pressure, not fire or cattle grazing, promotes invasion of buffel grass Cenchrus ciliaris. J Appl Ecol. 2013;50(1):138–146.

van Kleunen M, Weber E, Fischer M. A meta-analysis of trait differences between invasive and non-invasive plant species. Ecol Lett. 2010;13(2):235–245. PubMed

Keller RP, Kocev D, Dzeroski S. Trait-based risk assessment for invasive species: High performance across diverse taxonomic groups, geographic ranges and machine learning/statistical tools. Divers Distrib. 2011;17(3):451–461.

Marco A, Lavergne S, Dutoit T, Bertaudiere-Montes V. From the backyard to the backcountry: How ecological and biological traits explain the escape of garden plants into Mediterranean old fields. Biol Invasions. 2010;12(4):761–779.

Martin LJ, Murray BR. A predictive framework and review of the ecological impacts of exotic plant invasions on reptiles and amphibians. Biol Rev Camb Philos Soc. 2011;86(2):407–419. PubMed

te Beest M, et al. The more the better? The role of polyploidy in facilitating plant invasions. Ann Bot (Lond) 2012;109(1):19–45. PubMed PMC

Uchitel A, Omacini M, Chaneton EJ. Inherited fungal symbionts enhance establishment of an invasive annual grass across successional habitats. Oecologia. 2011;165(2):465–475. PubMed

Rout ME, et al. Bacterial endophytes enhance competition by invasive plants. Am J Bot. 2013;100(9):1726–1737. PubMed

Catford JA, Jansson R, Nilsson C. Reducing redundancy in invasion ecology by integrating hypotheses into a single theoretical framework. Divers Distrib. 2009;15(1):22–40.

Godfree RC, Woods MJ, Young AG. 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. 2009;34(5):525–544.

Ellstrand NC, Prentice HC, Hancock JF. Gene flow and introgression from domesticated plants into their wild relatives. Annu Rev Ecol Syst. 1999;30:539–563.

Lu BR, Snow AA. Gene flow from genetically modified rice and its environmental consequences. Bioscience. 2005;55(8):669–678.

Lavergne S, Molofsky J. Increased genetic variation and evolutionary potential drive the success of an invasive grass. Proc Natl Acad Sci USA. 2007;104(10):3883–3888. PubMed PMC

Matesanz S, Horgan-Kobelski T, Sultan S. Contrasting levels of evolutionary potential in populations of the invasive plant Polygonum cespitosum. Biol Invasions. 2014;16(2):455–468.

Rice K, Gerlach J, Jr, Dyer A, McKay J. Evolutionary ecology along invasion fronts of the annual grass Aegilops triuncialis. Biol Invasions. 2013;15(11):2531–2545.

Reid CR, Goodrich S, Bowns JE. Cheatgrass and red brome: History and biology of two invaders. In: Kitchen SG, Pendleton RL, Monaco TA, Vernon J, editors. Proceedings–Shrublands Under Fire: Disturbance and Recovery in a Changing World. US Department of Agriculture, Forest Service, Rocky Mountain Research Station; Fort Collins, CO: 2008. pp. 27–32.

Grossman JD, Rice KJ. Contemporary evolution of an invasive grass in response to elevated atmospheric CO(2) at a Mojave Desert FACE site. Ecol Lett. 2014;17(6):710–716. PubMed PMC

Pauchard A, et al. Ain't no mountain high enough: Plant invasions reaching new elevations. Front Ecol Environ. 2009;7(9):479–486.

Grattan SR, et al. Evaluation of salt-tolerant forages for sequential water reuse systems: I. Biomass production. Agric Water Manage. 2004;70(2):109–120.

Mesleard F, Ham LT, Boy V, Vanwijck C, Grillas P. Competition between an introduced and an indigenous species - the case of Paspalum paspalodes (Michx) Schribner and Aeluropus littoralis (Gouan) in the Camargue (southern France) Oecologia. 1993;94(2):204–209. PubMed

Li H, Qiang S, Qian YL. Physiological response of different croftonweed (Eupatorium adenophorum) populations to low temperature. Weed Sci. 2008;56(2):196–202.

DAISIE . A Handbook of Alien Species in Europe. Springer; Berlin: 2009.

Perrings C, Dehnen-Schmutz K, Touza J, Williamson M. How to manage biological invasions under globalization. Trends Ecol Evol. 2005;20(5):212–215. PubMed

Yokomizo H, Possingham HP, Hulme PE, Grice AC, Buckley YM. Cost-benefit analysis for intentional plant introductions under uncertainty. Biol Invasions. 2012;14(4):839–849.

Ross A, Dovers S. Making the harder yards: Environmental policy integration in Australia. Aust. J. Pub. Admin. 2008;67(3):245–260.

Bundred S. Solutions to silos: Joining up knowledge. Public Money Manage. 2006;26(2):125–130.

Howes M, et al. Towards networked governance: Improving interagency communication and collaboration for disaster risk management and climate change adaptation in Australia. J Environ Plann Manage. 2014 doi: 10.1080/09640568.2014.891974. DOI

Keller RP, Lodge DM, Finnoff DC. Risk assessment for invasive species produces net bioeconomic benefits. Proc Natl Acad Sci USA. 2007;104(1):203–207. PubMed PMC

Springborn M, Romagosa CM, Keller RP. The value of nonindigenous species risk assessment in international trade. Ecol Econ. 2011;70(11):2145–2153.

Witt ABR. Biofuels and invasive species from an African perspective: A review. GCB Bioenergy. 2010;2(6):321–329.

Born W, Rauschmayer F, Brauer I. Economic evaluation of biological invasions - a survey. Ecol Econ. 2005;55(3):321–336.

Hanley N, Spash CL. Cost-Benefit Analysis and the Environment. Edward Elgar Publishing Ltd.; Cheltenham, UK: 1993.

Essl F, et al. Socioeconomic legacy yields an invasion debt. Proc Natl Acad Sci USA. 2011;108(1):203–207. PubMed PMC

Cook DC, Fraser RW, Waage JK, Thomas MB. Prioritising biosecurity investment between agricultural and environmental systems. J Consum Prot Food Saf. 2011;6:3–13.

Davies AL, Bryce R, Redpath SM. Use of multicriteria decision analysis to address conservation conflicts. Conserv Biol. 2013;27(5):936–944. PubMed

Grechi I, et al. A decision framework for management of conflicting production and biodiversity goals for a commercially valuable invasive species. Agric Syst. 2014;125(0):1–11.

Meyerson LA, Mooney HA. Invasive alien species in an era of globalization. Front Ecol Environ. 2007;5(4):199–208.

Barney JN. Bioenergy and invasive plants: Quantifying and mitigating future risks. Invasive Plant Science and Management. 2014;7(2):199–209.

Maron JL, Vila M. When do herbivores affect plant invasion? Evidence for the natural enemies and biotic resistance hypotheses. Oikos. 2001;95(3):361–373.

Houseman GR, Foster BL, Brassil CE. Propagule pressure-invasibility relationships: Testing the influence of soil fertility and disturbance with Lespedeza cuneata. Oecologia. 2014;174(2):511–520. PubMed

Eskelinen A, Harrison S. Exotic plant invasions under enhanced rainfall are constrained by soil nutrients and competition. Ecology. 2014;95(3):682–692. PubMed

Leung B, et al. TEASIng apart alien species risk assessments: A framework for best practices. Ecol Lett. 2012;15(12):1475–1493. PubMed

Gordon DR, Onderdonk DA, Fox AM, Stocker RK. Consistent accuracy of the Australian weed risk assessment system across varied geographies. Divers Distrib. 2008;14(2):234–242.

Strayer DL. Eight questions about invasions and ecosystem functioning. Ecol Lett. 2012;15(10):1199–1210. PubMed

Cousens R. Risk assessment of potential biofuel species: An application for trait-based models for predicting weediness? Weed Sci. 2008;56(6):873–882.

Tobey JA, Smets H. The Polluter-Pays Principle in the context of agriculture and the environment. World Econ. 1996;19(1):63–87.

Dawson W, Burslem DFRP, Hulme PE. The suitability of weed risk assessment as a conservation tool to identify invasive plant threats in East African rainforests. Biol Conserv. 2009;142(5):1018–1024.

Crossman ND, Bryan BA, Cooke DA. An invasive plant and climate change threat index for weed risk management: Integrating habitat distribution pattern and dispersal process. Ecol Indic. 2011;11(1):183–198.

Bhattarai GP, Cronin JT. Hurricane activity and the large-scale pattern of spread of an invasive plant species. PLoS ONE. 2014;9(5):e98478–e98478. PubMed PMC

Hulme PE, et al. Grasping at the routes of biological invasions: A framework for integrating pathways into policy. J Appl Ecol. 2008;45(2):403–414.

Stone LM, Byrne M, Virtue JG. An environmental weed risk assessment model for Australian forage improvement programs. Aust J Exp Agric. 2008;48(4):568–574.

Curbing the major and growing threats from invasive alien species is urgent and achievable

Economic use of plants is key to their naturalization success

Naturalization of European plants on other continents: The role of donor habitats

Reply to Proença et al.: Sown biodiverse pastures are not a universal solution to invasion risk