Stopping new pasture varieties becoming tomorrow’s weeds

Jane Catford with Don Driscoll in dense sward of canary grass. This species is a known invasive plant but new varieties are still being developed for pasture. (Photo by Stuart Hay)

Jane Catford with Don Driscoll in dense sward of canary grass. This
species is a known invasive plant but new varieties are still being
developed for pasture. (Photo by Stuart Hay)

Hundreds of the invasive plant species that now inflict major environmental and economic damage in Australia were originally developed and distributed as pasture species. What a perverse outcome. What’s worse, we don’t seem to have learnt from these mistakes.

Agricultural weeds cost Australia an estimated $4 billion every year, and the environmental damage is thought to be of a similar magnitude. Introducing these pasture species was a big mistake that Australians will continue to pay for indefinitely. We face increased fire risks, increased management and weed control costs, as well as threats to our natural heritage.

Don Driscoll and Jane Catford undertook a global survey of pasture plants (Driscoll et al., 2014) revealing that over 90% of plant species developed and sold by agribusinesses are weeds somewhere in the world, and on average 30% are weeds in the country in which they are promoted. In Australia, species promoted by agribusiness include orchard-grass (Dactylis glomerata), canary-grass (Phalaris species), tall fescue (Schedonorus arundinaceus), and sub-terranean clover (Trifolium subterraneum). These species are all recognised weeds in Australia, weeds that degrade native communities such as threatened box-gum woodlands.

In a nutshell, Australia already has an enormous weed burden that is threatening our natural heritage, increasing fire risk, and multiplying the costs of land management. Unregulated development and release of new varieties of existing weeds will make the weed problem worse, potentially a lot worse.

The researchers recommend:

  1. Account for full environmental, social and economic benefits of new varieties.
  2. A list of prohibited and permitted species based on varieties.
  3. Apply weed risk assessment to new varieties.
  4. Monitor new varieties and respond rapidly if they become invasive.

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Reference

Driscoll DD, JA Catford, JN Barney, PE Hulme, Inderjit, TG Martin, A Pauchard, P Pysek, DM Richardson, S Riley & V Visser (2014). New pasture plants intensify invasive species risk. PNAS 111: 6622–16627, doi: 10.1073/pnas.1409347111 http://www.pnas.org/content/111/46/16622

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