Print this page

What are the REAL environmental weeds?

 by Ian Menkins

"As an amateur botanist I always enjoy trips into the field. I recently had the opportunity to search for several native species of plants in the wilds of Central Queensland. The future existence of these plants is somewhat precarious, as they are slowly but surely being obliterated by Buffel grass (Cenchrus ciliaris), as well as Guinea grass (Panicum maximum), and an assortment of other exotic pasture grasses.

After many hours of searching I found a few of the native species and brought back cuttings and seed to perpetuate them in cultivation and hopefully start up some ex situ populations in future. It would be good to try to establish them elsewhere where the buffel grass is mostly absent.

The thing that constantly amazes me is that the DPI and Biosecurity Australia keep harping on about the urgent need to eradicate feral cacti when the worst environmental weeds by far are exotic pasture grasses.

These grasses are of great detriment to brigalow and softwood scrubs in particular, where fire had once been excluded. Nowadays the ground cover is dominated by these highly flammable grasses. The grasses form a dense impenetrable swathe in which few native species can successfully compete. These grasses also have a very high propensity to turn tinder-dry and burst into flames after just a few weeks of dry weather. These factors have combined to virtually decimate all of the original indigenous flora, not only in the ground cover and mid-stratas, but the ecosystems as a whole.

So I am forced to ask this poignant question. Why are feral cacti always regarded as the number one weed to be eradicated from these areas, when the fact remains that they are not highly flammable?

Those in the hallowed halls of government seldom like to be told this simple truth either. Is this because these were the same people who had once introduced and promoted these grasses en masse? In fact they were still introducing them up until 10 years ago and are STILL promoting their cultivation today, e.g. the highly invasive Indian runner grass (Bothriochloa pertusa). This grass is set to completely replace our native couch grass around this area within the next decade or so. Sadly, it is a far inferior grass too, in terms of quality and nutritional grazing value!

The Department of Main Roads are no better. They still use the exotic Angleton grass (Dichanthium aristatum) and other exotic grasses in their rehab work. These grasses are rapidly replacing many of our native Dichanthium sericeum grasslands.

Native grasslands had made their last stand on road reserves and stock routes, but it seems that even these areas are now being taken from them by swathes of marauding exotic grasses. These exotic grasses often form dense monocultures in a very short space of time. Native biodiversity frequently gets reduced to zero in just a few years.

But it is far easier to target big spiny things like cacti I guess. These are far better "propaganda tools" and easily capture the imagination of the ignorant masses. It would be hard to get anyone too excited about grasses. Few people can identify or even recognize grass species whenever they drive around the countryside. But if you show people a big spiny cactus, regardless of the species, they immediately associate it with spines and pain and all things bad. In the battle of good against evil, a cactus can be SO easily portrayed as inherently "evil", and portrayed as "the enemy" of humans and nature alike. Unlike grass species, which, as far as most people are concerned, are... well, "just grass"!

In a few places on my trip I also noticed that feralcacti were actually helping to create niches where the few remaining native species could persist. In these places the cacti offered relative protection against those highly competitive (and highly flammable) exotic grasses.

In one such place,a highly endangered species called Xerothamnella herbaceae was just barely clinging to existence. The plant would have almost certainly been extinct at this site long ago if not for the fact that providence (or sheer dumb luck) had provided it with a safe harbour beneath the very spiny, interlacing branches of an Harrisia martinii.

Here then exists a major problem, because we have the unthinkable scenario of a Class 2 noxious exotic weed protecting an endangered native species! Obviously this juxtaposition would not compute to a zealous weed warrior, who is blindly determined to eradicate every noxious weed from existence!! But clearly any attermpt to remove this feral cacti by those ill-equipped to identify rare native species could be an environmental disaster in the making.

The Xerothamnella site is an important case in point. It showed me just how easily a rare native species could be obliterated by some well-meaning weeds officer on a crusade to rid the world of exotic cacti. Clearly if this officer was to spray out the cacti he would not be able to miss also killing the rare plant, or any other native species in the vicinity. Manual removal of the cacti would also almost certainly rub out the rare plant. Another downer in this scenario is that the reduction of the cacti population would free up competition and then simply permit the exotic grasses to take hold and flourish!

I fear for the safety of our natural environment because those in authority often seem blind to the REAL environmental weeds that are causing untold damage to our native ecosystems. They really need to open their eyes to what is out there, take a few steps back, and re-focus their attention away from desktop bureaucracy and mere propaganda. by Ian Menkins

In central Queensland, Opuntia streptacantha is usually found as solitary individuals across the landscape. It is mid-winter in this photo, and the exotic grasses and legumes that form most of the ground cover are tinder-dry. The only non-flammable plant in the landscape is the Opuntia.


Previous page: Calandrinia in Cultivation
Next page: Ant Plants