Sustainability like many other words has been hijacked and its meaning has been perverted. However, when it comes to the environment our future wellbeing, it really isn’t a difficult concept to grasp.

The Brundtland definition is good. The Wikipedia definition is good too: the capacity to endure. And I would add the bit that I often express on OLO: the ongoing balance between supply and demand, with a big safety margin.

Agriculture in Australia is basically sustainable... if you accept that enormous ecological damage that has been done, in the WA wheatbelt for example, and you accept the fertilizers and the fossil fuel energy needed to plough, sow and harvest the crops, and you accept soil salinity, loss of topsoil and erratic and diminishing rainfall, which has often led to no crops or the large-scale sell-off or agistment of sheep and cattle.

In other words, it isn’t really all that sustainable. Or at least a good part of it isn’t.

What a load of rubbish.(not you, Ludwig).
Borlaug's wonderful Green Revolution was and is in the final analysis, a system of 'robbing Peter to pay Paul'; enriching farmland in one part of the world by mining, synthesising and trucking nutrients from another part.
Has the author not heard of “Peak Phosphorus”? Or will he contend that mines are inexhaustible and sustainable.
Farm losses MUST be replaced, period. All sales of product off farm are -to the ecology of the farm- losses. Chemical fertilisers simply represent the most cost effective replacement, -at current pricing.
Since most chemical fertiliser is made, not only with, but from, fossil fuels, we can safely expect the price of fertilisers to keep on rising.
The old farm mentioned in the article managed to produce (an admittedly lower number of) livestock with virtually no off farm inputs; in today's terms, that's money for nuthin', chick(en)s for free.
In order to make modern farming sustainable, we would need to look at the entire producer/consumer system holistically, and bring back all the 'waste' products to the farm -including the water.

Nothing is 'sustainable' indefinitely. Continents move, technologies change, population figures rise and fall, stars explode, galaxies collide -- and yes, climate changes, through natural causes. So the first thing to ask someone making a claim about 'sustainability' is "How long for?" If it's my lifetime, that's great. If it's the lifetime of me and my children and (potential) grandchildren, that's better still.

Going beyond that, though, really doesn't add anything. I'm not foolish enough to think that the people of, say, 2150 are going to have to rely on our half-baked attempts to try and imagine what their lives might be like. That would be like someone in 1850 setting up a huge free-range horse ranch in Britain, to 'sustainably' supply transportation for the next millennium. Aren't you glad they didn't?

An interesting but over-simplistic article which ignores two salient facts: 1. The accelerating rate of global population increase and therefore increase in demand for food and, more importantly 2. The effects of global warming on all living species – including homo-sapiens and the food crops needed to sustain them.

Most of these species require an environment where climate is stable, predictable and largely devoid of weather extremes. Yet what we know of global warming is that as average global temperature rises, the incidence of extreme weather events increases with disastrous effects on both food crops and human life. A recent example is the 2010 Russian heat-wave which killed 50,000 people and 25% of the national grain crop.

Prolonged droughts and fire affecting Texas and the mid-west, flooding of northern India-Pakistan and an increasing incidence of wind events occurring world-wide are crop destroying. No amount of genetic engineering enable crops to withstand such events, something Mr Leyonhjelm knows but ignores. Anyone can put forward a glowing (and misleading) picture of increasing sustainability – provided they ignore the real world in which we live and the need for a little intellectual rigour

'Totally sustainable' - wish you were right David but it needs to be qualified by 'for how long?'. Unfortunately modern agriculture -100 cows where there were 20 - is totally reliant on fossil fuels to produce the nitrogen and other fertilizers that enable this. Fossil fuels are finite and so is the capacity of the atmosphere to take the pollutants while maintaining habitable climates.

There is also the problem of exponential population growth and climate change......

Yes there is much that is good about modern agriculture but its not sustainable. We need to change the 'western way of life' considerably and also further adapt agricultural systems. If we go 'business as usual' the demise of human civilization will be soon rather than later

There is much in what you say David.
However, what you seemed to have missed is the parasites that are killing farms and or farmers.
No not the insect variety, just the humans that earn all their money polishing leather or shuffling paper?
Its the exponentially rising cost of things like fuel, transport water; and industry destroying foreign investment that are making farms unsustainable.
We see an Asia that is demanding more and more food, yet we here are bulldozing generational family orchards.
Why?
Well because we are no longer smart enough to re-engage the cooperative model.
If Ardmona, Golden circle and a few other were still co-ops, were resumed and then recreated as co-ops, they could be re-jigged to simply break even, while they grew and grew our Asian markets, assisted by FTA's that encouraged this production and exports. Eventually profits and massive economies of scaled up production, would create the next boom, or the dining boom!
We the people must de-privatise and invest in water and transport infrastructure.
Like very rapid rail and roll on roll off fast ferries that could take Australian fresh picked very early in the morning and deliver it chilled the same night to Singapore, Malaysia and Indonesia?
Family farms ought to be encouraged rather than tax avoiding corporate farmers, simply because the family farm model, John Howard and a few other conservative or flawed thinkers,(same diff) tried to destroy; is the most productive model!
I mean 85% of the income earned by farming, is done on family farms, which may only be 20% of the industry?
Rhrosty.