Last week, Floris and I wrote a commentary in the newspaper, building on some of the research Floris is doing and related to the to Cubbie or not to Cubbie question. Anyway, you can read it here. But, while writing this article, I was reminded of another question that I have not yet solved: whether Australia is better off growing annual cops under irrigation or perennial crops. I will explain.
Many of the recent comments about the sustainability of irrigated agriculture in Australia have pointed out that Australia should concentrate on growing “high value crops” as this would give the highest return on the water used. All too often the examples of “high value crops” that are given are perennials: grapes, horticulture etc.
The question I struggle with is whether we are not better off not growing any perennial crops at all. The specific nature of perennial crops is that they grow over several years and thus would need water every year, even if the need less water than an annual crop. In contrast an annual crop can be grown whenever water is plentiful.
In the Netherlands, a concept called “living with floods” has been developed. This concept is really related to flood management and not to irrigation. The concept says that it is better to accept that floods occur and thus that a river needs space (i.e. don’t build any houses on the floodplains) than to try and fight floods by increasing levees. I feel this concept is applicable in relation to irrigation water and crop choices in Australia.
A key characteristic of the Australian climate is the high variability (“droughts and flooding rains”), which means that the river will be dry for years followed by a massive flood. Climate change is suggested to bring even more of this variability. In the article that I mentioned above, we already calculated, based on the last 80 years of data, that good flows in the Lower Balonne river system only happen once in every 4 years.
What is more unnatural in such a system than a dam to collect runoff, what a typical human idea (or engineering idea)! Yes, dams and river regulation allow the river to be controlled and floods to be diminished and dry years to be overcome. But if the variability increases or changes the system is difficult to change (this is called resistant), exactly as we are seeing now: licences have been given out and investments (and bank loans!) have been made based on these licences.
Perennial plantings will now require water every year and are difficult to change (resistant) and so are huge investments in irrigation layouts which require regular annual profits to pay of bank loans.
What we really need is an agricultural system that is resilient, a system that can adapt to changes in the climate, from year to year and from decade to decade and from century to century. I feel that annual crops have a better opportunity to fit into such a system than most perennial plantings, as planting decisions can be changed from year to year and these crops can be interspersed with rainfed crops. Alternatively we could look for perennial plantings that do not need water every year (and might not give a crop every year). Such systems could harvest irrigation years in plentiful flood years, similar to floodplain graziers (and of course not harvest too much) and in the end we might not need dams at all! But this requires a total change in thinking, and I am not sure we can do this yet.