Perversity in the pasture 

Guarding against new pasture varieties becoming tomorrow’s environmental disasters

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.

Consider African lovegrass. It was used to ‘improve pasture’ in Australia for almost 100 years, but is now declared a weed in four Australian states and the ACT. It has been of little value in pastures, poses a substantial fire risk and threatens a range of native species. Similarly, Gamba grass was widely promoted in northern Australia by the cattle industry and government. It is now listed as a Weed of National Significance. Gamba grass increases fire intensity five-fold, which transforms native woodlands into exotic-dominated grassland and increases the cost of fire management by an order of magnitude.

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 ongoing loss of our natural heritage.

The latest block buster from the Don Driscoll production house (who could forget The matrix in Ecology and Cannibal Horses of Australian Alps) tells the compelling story of how pasture varieties are taking over the world. Youtube:

New varieties of trouble

So, we’ve learnt our lesson, right? The problem of deliberately introduced plant species going rogue is both well known and well documented. Consider the box on ‘inviting trouble’ (it’s based on a survey published over twenty years ago).

Well, as incredible as it seems, we don’t seem to be learning at all. Agribusinesses still develop and promote new varieties of species that are known invasive weeds.

Our global survey of pasture plants (Driscoll et al., 2014; Driscoll & Catford, 2014) revealed 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.

Although these weed species already occur throughout much of Australia, the environmental risk escalates when new varieties of those species are released. They may belong to the same species, but these varieties can be quite distinct from their parents – just think of the differences among dog varieties like Chihuahuas, Dalmatians and wolves. The impacts of new pasture varieties in the environment can be substantial.

Weeds by design 

New varieties can be created by cross-breeding different varieties or different species. Another trick to create better performing plants is to manipulate the symbiotic bacteria and fungi that live inside the plants. Engineering plants in any of these ways can lead to varieties with higher reproduction, higher growth rates, better resistance to disease and higher tolerance of environmental extremes. Unfortunately (but perhaps not surprisingly), these are the same characteristics associated with invasive species. New varieties of pasture plants are bred to grow great pasture, but at the same time, they are inadvertently bred to be super-weeds.

Once these souped-up plants have been bred, they are matched to the environments in which they are most likely to succeed. To make matters worse, because of the nature of pasture production, these new varieties will likely be planted widely across the landscape. Combined with new weedy characteristics, environmental-matching and widespread planting means that pasture plants can spread very easily, rendering nearby native vegetation extremely vulnerable to invasion. Because new pasture varieties can be planted very quickly over massive areas, it will be very expensive to try to control invasion once a weed has got away and the problem noticed. Pre-emptive action makes sense.

Unregulated development and release of new varieties of existing weeds will make the weed problem worse, potentially a lot worse.” 

Under the radar 

Australia has world-leading biosecurity. However, risks from new pasture varieties are not considered by current regulations. At the moment, Australia only considers the weed risk of new exotic species that may be imported. Exotic species that are already present in Australia are not assessed but are permitted ongoing entry, even if they are known to cause harm. This is a major flaw in our system: it suggests that if a species is already here, the damage, if any, is done, and ongoing use is a reasonable course of action. New varieties of these permitted exotic species can be developed, released and spread widely across Australia’s pastoral areas, without any scrutiny of their potential to (1) become new weeds, (2) increase the impacts of existing weeds or (3) spread into new areas.

In a nutshell, Australia already has an enormous weed burden that is destroying 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.

But – there are solutions.

  1. Account for full environmental, social and economic benefits of new varieties A key problem to address is the widespread conflict within government, where one section of government lists pasture plants as a threatening process (eg, see Victoria’s list of threatening processes), and other parts promote invasive pasture plants for use by the livestock industry (eg, tall wheat grass). This conflict reflects a lack of integration across sections of government, with different motivations and cultures in primary industry sectors compared with environment sectors. Analyses that account for social, environmental and economic costs and benefits may be one mechanism that would help promote integration across these sectors. Multi-criteria approaches to weighing up costs and benefits are already well developed and enable both monetary and non-monetary values to be transparently included in decision-making. Traditional economic analysis is not up to this challenge because it discounts future impacts, and struggles to consider non-monetary values like species and the amenity value of biodiversity.
  2. A list of prohibited and permitted species based on varieties. This would enable distinctions to be made between varieties of pasture species that are benign and those that are invasive.
  3. Apply weed risk assessment to new varieties. Government could expand its world-leading weed risk assessment protocols to apply them to new varieties that are proposed for either import or release after development within the country.
  4. Monitor new varieties and respond rapidly if they become invasive. A program to monitor new varieties that are released and, if they become invasive, to rapidly respond to eliminate the threat. (And who would pay for this? We suggest that government needs to implement a polluter-pays scheme.)

This last point about who should pay is critical. The likely reason that agribusiness and government agricultural departments don’t consider the weed risk of their products is that they are not held accountable for the environmental damage their products cause, or the cost of managing invasive pasture species. A polluter-pays system might include industry-wide levies, insurance and bonds; mechanisms that are already widely used in Australia.

Getting business on board 

While government must play a lead role, the solutions are not up to government alone. Agribusiness could take up opportunities to integrate weed risk assessment into their development programs, with the aim of developing varieties with low weed risk. The former Future Farms Cooperative Research Centre pioneered this approach, proving that development for agriculture can work together with environmental responsibility.

Agribusiness could also tap into environmentally-aware markets by developing a weed-free certification scheme for their products, and the same potential exists for certified farm products. Farmers could also contribute to improving stewardship of their land by refusing to buy new pasture varieties that have a high weed risk.

Although we focus on the weed threat from new pasture varieties, the risk posed by industry-driven spread of exotic plants is not confined to the livestock sector. The same risks, and likely solutions, apply to other industries including bioenergy, carbon-sequestration, forestry and horticulture. With this array of industries releasing new varieties of plants, many of which are already invasive weeds, now is the time for governments to provide industry with appropriate incentives to consider the weed risk of their products.

As our tropical savannahs succumb to Gamba-grass fires, as our arid woodlands vanish under buffel-grass wastelands, and as native species vanish from the few remaining box-gum woodlands degraded by introduced pasture plants, it seems like common sense to stop making these kinds of problems worse.

Inviting trouble – when will we learn?

Back in 1994, ecologist Mark Lonsdale surveyed the history of exotic pasture introductions in northern Australia to compare the rate of introduction of useful species with that of weeds. Between 1947 and 1985, 463 exotic grasses and legumes were intentionally introduced into the region, the grasses predominantly from Africa, and the legumes from Central and South America. Of these, only 21 (5%) came to be recommended as useful, while 60 (13%) became listed as weeds. Seventeen of the useful plants were in fact also weeds, leaving only 4 species (<1%) that were useful without causing weed problems. They were far outnumbered by the 43 species (9%) that were weeds but had no recorded use.


Londsdale WM (1994). Inviting trouble: Introduced pasture species in northern Australia. Australian Journal of Ecology 19: 345–354. 

More info: Don Driscoll 


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 

Driscoll D & J Catford (2014b). Invasive plants: New pasture plants pose weed risk. Nature 516: 37.

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