One of the things that really depresses me when I think seriously about the mangement of our 33 hectares of native bushland is the problem of pasture grasses gone feral.  Green Panic is the major problem here, but we have a number of others, including Rhodes Grass.  Both were introduced into Australia as pasture plants.

The Green Panic (Panicum maximum var. trichoglume) is still touted as a good pasture grass.  The story when it was introduced was that it would not spread and become a pest because it needs plenty of moisture and will not grow under shade. Did the agronomists not know about evolution? Did they not know that a grass often has weedy characteristics because it is inherently capable of rapid adaptation to different environments.

Just in case there are agronomists or botanists who were involved in the introduction of this wonder grass among my readers: We have a new variety of Green Panic – Lockyer Valley Green Panic.  It has adapted and evolved (surprise!) and now grows even on dry ridges and under semi-closed woodland trees.  And, like all Green Panic, it grows dense and tall when it isn’t grazed, so that it crowds out the native grasses and by the middle of summer when it has dried out it forms a near explosve compact mass of cellulose that will send flames into the tree canopy.  Where previously there was a carpet of low green Kangaroo Grass on the woodland floor, now in parts of the Lockyer Valley Region we have dense tall brown monocultures of Panic.  Kangaroo Grass is unusual because it has green growth at the height of summer, and with this and its short tussocks it not only makes for some of the most beautiful Australian woodland that I know of, it also burns cool and recovers fast. [sorry for the lack of photos, for the moment I can’t find any pics of our Kangaroos Grass areas].

One of my fondest dreams is that I will see the day when communities across Australia come together in a class action against government agencies and agricultural companies, claiming massive damages for the harm done to the Australian environment by non-native pasture grasses.  So you can see why I was very heartened to see an article in todays Australian edition of The Conversation about the harm pasture grassed do.

Here’s an excerpt:

Weeds cost Australian farmers around A$4 billion every year — and they are likely to do a similar amount of damage to the environment.

In a new global survey published this week in Proceedings of the National Academy of Sciences, we show that new pasture plants, such as grasses, present a substantial weed risk.

And despite the risk, new varieties of plants that are known to be invasive are still widely developed and sold in Australia, with little regulation from government.

So, how can we tighten control to prevent the future spread of invasive plants?

Grasses out of control

African lovegrass was used to “improve pasture” in Australia for almost 100 years, but now it is a declared weed in four Australian states and the ACT. African lovegrass 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 by the cattle industry and government in northern Australia, but is now listed as a Weed of National Significance. Gamba grass increases fire intensity five-fold, which transforms native woodlands into exotic grassland and increases the cost of fire management by an order of 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.

Have we learned our lesson?

Not yet. Agribusinesses still develop and promote new varieties of species, which are known invasive weeds.

Our new survey of pasture plants reveals that over 90% of taxa 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, these species include Orchardgrass (Dactylis glomerata), Canary-grass (Phalaris species), Tall fescue (Schedonorus arundinaceus), and sub-terranean clover (Trifolium subterraneum). These species are all recognised weeds in Australia, and all promoted by agribusiness for pasture.

Inadvertently breeding super-weeds

These species have already spread throughout much of Australia. But new varieties of the same species can be just as bad, if not worse.

Although they belong to the same species, these varieties can be quite distinct from their parents – just think of the differences between dog varieties like Chihuahuas, Dalmatians and wolves.

The impacts of new pasture varieties in the environment can be substantial, as emphasised in a report “Weed risk set to rise”, to be published this week by the Ecological Society of Australia.

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, perfectly-matched to their environment and planted widely across the landscape.

Producing enormous amounts of pollen and seeds, these new pasture plants can spread quickly and over vast areas, making them very expensive to control if and when they become invasive. So it makes sense to nip the problem in the bud.

You can read the whole article here.