Category Archives: weeds and invasives

Is there no end to the pasture grass assault on the Australian environment?

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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:

Feed or weed? New pastures are sowing problems for the future

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.

 

Imported Weeds and Invasive Exotic Plant Species

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The use of “weedy” species, together with the use of non-local species of unknown weediness, incites very heated debate in permaculture circles, inspiring a lot of name-calling and pseduo-science.  My own view is that the promotion of known invasive, or potentially invasive, species as part of the permaculture approach is highly irresponsible and arguments for their use are often couched in language that approaches the mysticism or spirituality that is supposedly “banned” in serious permaculture.  (You can see my views on the use of Leucaena here.)

Of course, the topic of invasive species overlaps with the consideration of “weeds” as an element of food productions activities.  I’m not going to go into that here, but the eXtension website has an excellent article on weeds in agriculture (An Ecological Understanding of Weeds) that incorporates both the negative and positive aspects of weeds in agriculture.  Well worth reading – much of it reads as if it was written by an well-informed permaculturist.  In fact the author, Dr Mark Schonbeck, is credited by the the Virginia Association for Biological Farming as combining “deep scientific knowledge, practical farming technique and policy smarts”.  I recommend googling his name – it will turn up a plethora of interesting and informative articles.

Dr Schonbeck’s article also deals with invasive species, under the heading of Imported Weeds and Invasive Exotic Plant Species.  Among other things this part blows out of the water the permaculture argument that for a species to become invasive in an ecosystem there must have been a vacant niche in the ecosystem.

Below is the text of that part of the article (with what I think are the really telling points underlined by me), but I really recommend you read the whole article for its information about the place of weeds in food production systems.  Remember that the weed/invasive species referred to are in relation to the US, though it is interesting how many are familiar to us in Australia.

Many of a region’s most problematic weeds are those that are not native to the region, or even the continent. These exotic plant species often grow more vigorously in their new habitat than they do in their area of origin, where certain soil organisms, herbivorous insects, climate patterns, and/or competing vegetation keep them in check. Kudzu (Pueraria thunbergiana), imported from Japan as a forage crop, is one dramatic example whose enormous vines can cover and kill large trees in the southeastern US. However, a small (4–18 inches) perennial weed called purple nutsedge (Cyperus rotundus), which has invaded the southern United States, causes much greater losses in cultivated crops (even sugarcane and coffee trees), and is considered the world’s worst weed (Holm et al., 1991).

Some of our major agricultural weeds were intentionally brought to the United States from overseas to provide food or forage. European colonists carried common lambsquarters (Chenopodium album) to the New World as a vital source of early season greens that prevented scurvy and other nutritional deficiency conditions. Common lambsquarters has spread around the globe and is now listed as the world’s 10th worst agricultural weed. Livestock farmers imported bermudagrass (Cynodon dactylon, 2nd worst weed), johnsongrass (Sorghum halapense, 6th worst), and quackgrass (Elytrigia repens, a major weed of vegetable crops in the northeastern US) to this country for their utility as forages. Other serious exotic weeds were first planted as flowers and other ornamentals, and subsequently spread from cultivated gardens into surrounding farmland and/or natural ecosystems. Still others arrived by accident as a seed contaminant in imported crop seed, feed grain, foods, bedding plants, or other materials.

Many exotic weeds have become “naturalized” over time, and are now part of a region’s agricultural weed flora that must be managed (not necessarily eradicated) to protect crop yields. However, some newly introduced plants growing in the absence of the natural enemies with which they evolved may spread unchecked, choking out native vegetation as well as invading pastures or cultivated fields. Imported weeds that threaten natural ecosystems and/or rangeland over wide geographic areas are designated invasive exotic plant species or invasive exotic weeds, and often become the focus of regional or nationwide coordinated eradication efforts. Examples include water hyacinth (Eichhornia crassipes) and purple loosestrife (Lythrum salicaria) in wetlands; Canada thistle (Cirsium arvense), musk thistle (Carduus nutans), spotted knapweed (Centaurea maculosa), and St. Johnswort (Hypericum perforatum) in rangeland; and autumn olive (Elaegnus umbellata) and tree-of-heaven (Ailanthus altissimus) in eastern deciduous woodlands. Classical biological control—the introduction of herbivorous insects or microbial pathogens that are natural enemies of these weeds in their native lands—has been used with considerable success to combat some invasive exotic weeds.

Arrival of a new invasive exotic weed on an organic farm is one instance that may justify efforts to eradicate the new arrival. Early detection—combined with an understanding of the ecology of the weed—is vital for successful elimination of the invader.

Leucaena leucocephala – a tale of ongoing stupidity – or is it dishonesty?

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What, you may ask, is Leucaena leucocephala?  And why a blog about it in relation to sustainability in the Lockyer Valley?

Well, first let me admit that this is a bit of a “vent”, as they say.  It is also a reminder that misleading and stupid advice by government agencies is not something that was invented recently.

In the early ’80s I came back from the Northern Marianas Islands, where I’d been working on archaeological surveys to trace the history of the Chamorro people who were suspected of having been on the islands for up to 2000 years.  The Marianas are a group of about 15 islands in the northwest Pacific Ocean, southeast of Japan and about half way between Hawaii and the Philippines.  Only three of the islands are permanently inhabited: Saipan, Tinian and Rota.

Up until the Second World War the Marianas were under Japanese control as part of the South Pacific Mandate granted by the League of Nations.  They’re now a Commonwealth in Political Association with the United States of America, though why anyone would want such an association is beyond me.

What’s this got to do with Leucaena or sustainability?  Well … read on.  The islands of the Marianas were part of the chain of island “stepping stones” utilised by the US on its path to the eventual conquest of the Japanese mainland.  Some of the most violent battles of the World War II were fought there.  Saipan and Tinian were bombed, shelled and fought over until they were, across large areas, bare cratered earth.  The battles were so fierce that when I was there you could pick up about ten bits of shrapnel or actual bullets per square metre on parts of the bare limestone on the coast of Tinian.  There were larger bits of bomb casing sticking out of some of the few remaining trees, and in places bits of war debris, including sometimes aircraft parts, were mixed in with 2000 year old archaeological layers.

When the war finished the nearly denuded islands of Saipan and Tinian were in danger of literally having most of their topsoil washed into the sea in the wet season.  The surviving Chamorro people were at risk of losing the agriculture which was the basis if their existence.  Rota was spared invasion and destruction because it had no strategic value, lacking major Japanese fortifications or areas where airstrips could be built.  The troops stationed there were cut-off and left to starve until they surrendered, so the island was spared the destruction visited on Saipan and Tinian.

So what to do?  The quick, and as it turned out “dirty”, solution was to bomb the islands with huge quantities of the seeds of Leucaena leucocephala, a fast-growing member of the Mimosa family (like our Acacias) that originated in Central America.  They got the seeds from the Philippines where it had become naturalised and was widely distributed.  Leucaena is very well adapted to the tropics and sub-tropics.  It grows in dense stands as a small (up to six metres or so), whip-stick tree which produces seeds prolifically.  The stands are often so dense that nothing else can grow under them.

Leucaena grows in dense stands

Prolific seed production by Leucaena

Having done field work on Rota, Tinian and Saipan I had seen both the original lush, tropical vegetation of Rota, which luckily had not needed post-war soil stabilisation and is rich in species and wildlife, and the widespread, mono-species stands of Leucaena across Tinian and Saipan with very little wildlife.  The farmers on those islands spent a lot of their time in controlling the Leucaena regrowth, often to the point that agriculture became uneconomic, and in the towns it was even a pest in the lawns, growing faster than the grass.  Clearly the species was a mega-weed.

Arriving back in Australia, one of the first things I read in the newspaper was about how the Queensland Department of Primary Industries was promoting the planting of Leucaena as a cattle fodder, ideally adapted to tropical and sub-tropical areas with poor soils and monsoonal rainfall patterns.  Unbelievable!

Very concerned, I phoned the DPI to find out more and to share my observations of what Leucaena can do to the environment.  The agronomist I spoke to heard me out, then said that this might be the case in places where the seed was distributed willy nilly across the landscape, but I had to understand that what DPI was advocating for Queensland was “controlled” use of Leucaena in pasture – where it would never grow to seed-bearing stage because it would be grazed off before that.  Seriously.  Like the cattle were going to be in the paddocks the whole time, never turning their backs in case a plant set seed?

I was under the impression that Leucaena was being introduced into Australia at that time (remember this was before the internet and Google, and I’m not an agronomist), and that perhaps they really didn’t believe that it could become a pest.  But according to the UN Food and Agriculture Organisation (FAO) Leucaena had been introduced into Australia in the late 19th century and it was naturalised in parts of northern Australia by 1920.  So there should have been plenty of evidence that it was a very potent pest species.

Despite this, during the 1970s and early 1980s, Leucaena was being touted around the world as the ‘miracle tree’ because of its worldwide success as a long-lived and highly nutritious forage tree according to FAO, and the Queensland DPI were right there on the bandwagon and not about to listen to any contrary views.

Fast forward to the present:  According to the Biosecurity Queensland Factsheet on Leucaena it is “A very troublesome weed of waterways and roadsides in tropical and sub-tropical regions. It is also found in open woodlands, gardens, parks, waste areas, disturbed sites and on coastal foreshores and offshore islands.” and is “… widely naturalised and relatively common in the coastal and sub-coastal districts of northern and eastern Australia. It is most common in south-eastern, central and northern Queensland and in the northern parts of the Northern Territory. Also present in the coastal districts of northern and central New South Wales, in the coastal districts of Western Australia, on Christmas Island and on the Cocos Islands”.

So we come to the Lockyer Valley.  Try keeping a careful watch on the roadsides in the Valley, as well as between Toowoomba and Brisbane, including along Mt Crosby Road if you take that route into Brisbane – there’s no doubt that Leucaena is well and truly established in Southeast Queensland.

In fact, the Queensland Department of Agriculture, Forestry and Fisheries (DAFF) is now warning that “Unless heavily grazed or otherwise controlled, it is able to rapidly spread to adjacent areas”.

And this wasn’t bleeding obvious in the early 1980s to anyone who wanted to take more than a narrow, rose-coloured view of the species?  Give me a break.  Was I the only person who had noticed that it was a very noxious weed?

The cat, as they say, is now out of the bag – though in this case, given the number of other highly environmentally impacting species that have been introduced or promoted by government agencies across Australia, it might be more appropriate to say that Pandora’s Box is well and truly open.

Has anything changed?  Well, Leucaena is now well recognised as a problem here in Australia.  But is it really?

The Australian Government, through the Australian Centre for International Agricultural Research (ACIAR, which funds and advises on a lot of our foreign aid policy and projects) is running a website called Tropical Forages: An interactive selection tool, in partnership with the CSIRO, the Queensland Government and a number of other organisations.  This website advises that Leucaena “Will not normally spread under grazing as cattle relish young seedlings.  Some thickening up of grazed stands has occurred in eastern Australia where leucaena is left ungrazed during the growing season for provision of autumn feed.”  Is my 1980s agronomist friend now working in Australia’s international aid industry?

This ongoing level of ignorance and stupidity is beyond belief.  I hope to see the day when there will be major legal class actions in Australia against government agencies for the massive damage done to our environment and economy as a result of the lack of proper consideration of plant introductions.