2016-08-18
Chris Johansen
Ever since humans have practiced sedentary agriculture there has been a loss of evolutions finely crafted biodiversity and the ecosystem services that support that biodiversity. Forests have been cut down to plough the land and biodiverse grasslands grazed to leave a climax vegetation of a few hardy species best able to survive regular defoliation and trampling. The agricultural regions of Western Australia provide a stark example of this, where European-style agriculture was imposed on an already frail landscape – frail in the sense nutrient-poor soils and largely marginal and unreliable rainfall, with little scope for irrigation. I grew up exposed to the agricultural landscape of the 50s and 60s, went away for 45 years, coming back after a long enough time to see changes in the agriculture and landscape in which it is conducted.
My Grandfather farmed north of Merredin in the 20s and early 30s, until wiped out by the depression and an extended drought then. He described, and showed photos of, how he cleared the land with teams of horses and how that land yielded well initially, but patches quickly turned “sour”. That sourness was the now well understood phenomenon of dryland salinity, where vegetation removal reduces transpiration resulting in a rising water table which brings salts once at equilibrium deep in the soil to the surface. Ironically, my Grandfathers last enterprise was mining salt from the salt lakes of Rottnest!
To what extent my Grandfathers stories inspired me to study agriculture at UWA, and undertake post-grad research on how plants regulate uptake of salt ions, Ill never really know. From my early agricultural studies there is one piece of advice I did take notice of and carried with me through my career – that “a good agriculturalist necessarily needs to be a good environmentalist”. There was, by the way, also another snippet of wisdom – “dont ever try to actually practice agriculture (its too risky), just tell others how to do it”!
The importance of agriculture to the WA economy has gradually declined over the last century, giving way to mining and secondary and tertiary industry. Agriculture, forestry and fishing now (2014-15) stand at only 2% of nominal value added for WA, at $4.5b pa. Nevertheless, how we pursue agriculture into the future will have a big influence on the general well-being of the state. We have a comparative advantage of being able offer quality products of temperate agriculture, such as wheat, barley, pulses, oilseeds, fruit, wine, dairy, etc., to a nearby growing, largely tropical, Asian market. We need a sustainable agricultural system not only to maintain and build on this comparative advantage but also to maintain a healthy ecosystem for tourism and recreation purposes and maintenance of ecosystem services for the survival of urban areas at least (e.g. fresh water supply).
When examining a particular agricultural region anywhere in the world, as I have been doing through my career of telling other people what they should be doing, I first do a constraint analysis. Some of the major environmental constraints confronting SW agriculture (the region to which Ill confine my comments; its a huge state with all manner of actual and potential agricultural pursuits) seem to have worsened over the last 50 years, and do not seem to be being adequately addressed.
Of course the major constraint is climate change. When I returned to WA some 10 years ago most spokespeople for the Liberal and National Parties denied climate change, even though the region of SW WA was globally famous for having one of the largest declines in rainfall over the last 50 years. According to the Bureau of Meteorology (for which some of our new senators want a royal commission into, along with CSIRO!) average annual rainfall in SW WA was around 750 mm in the 60s but is now 600mm, a decline of >20%, with increased year-to-year variability. May not seem that much but it makes a huge difference if you are trying to grow rainfed crops. There are now less strenuous assertions from conservative quarters in WA that this is not a distinct trend, rather than a random aberration, but they appear unwilling to whole-heartedly address remedial possibilities, one oft-cited reason being the claim that 'climate change (should it indeed actually exist) is a Commonwealth rather than State responsibility.
Of course, the extent to which SW WAs rainfall keeps declining, and temperatures increasing, does depend on the global response to climate change, which depends on the extent to which everyone, especially rich polluting nations like Australia, pulls their weight. But what can be done is a realistic reassessment of land use, which takes into account the inevitable contraction of wheatbelt boundaries. If the outer wheatbelt is to continue to be cropped without increasing risk, rather than reverting to just pastoralism, then new crops and cropping practises would be required. New crops could include arid zone adapted ones like jojoba (oil), jujube (fruit), agave (fibre), date palm, plantation forestry with adapted species (e.g. oil mallee), etc. If existing crops like wheat, barley and chickpea are to be continued then that would depend on development of varieties of shorter duration and more drought resistant than currently available, but inherently low yielding due to those traits. It would also require sharpening of 'response farming techniques, whereby cultivation practice is closely synchronised with the vagaries of incident rainfall (e.g. fertilizer amount and timing determined by in-season rainfall).
Ah-ha you say, why, if rainfall is in decline, are trends in total WA wheat production and yield continuing to rise? Reasons are regular release of improved varieties, improving agronomy (e.g. minimum tillage), warmer winter temperatures boosting yield in higher rainfall areas, (perhaps) higher carbon dioxide levels boosting photosynthesis and large season-to-season variation masking long term trends. The outer wheatbelt is most at risk but I do not have recent data on that.
Harking back to my Grandfathers 'sour soil problem, soil salinity continues to insidiously spread across the landscape in the WA wheatbelt. The ultimate solution is to lower the water table, by revegetating affected areas with salt tolerant species and then trees. This has been done sporadically but not enough, it appears, to remain one step ahead of salt creep. Growing strips of oil mallee across salt affected or threatened fields is one such locally developed innovation to lower the water table. Oil mallee can provide biofuel, biomass for electricity generation and biochar (a soil conditioner), however the necessary processing infrastructure has not been developed and thus this promising multipurpose technology languishes.
Another serious soil threat, that has increased in severity over the past 50 years, is soil acidity. This has been mainly caused by use of ammonium fertilizers and, disappointingly, clover based pastures. I once thought that a prime example of sustainable agriculture was the leguminous pasture-wheat rotation as widely practiced in SW WA before I left. A pasture phase of a few years would add fixed atmospheric nitrogen, organic matter and animal dung to the soil to benefit several following wheat crops. However, a hitherto unrealized (by me at least) downside was this acidifying effect of legumes. Soil acidity can be countered by adding lime but this is costly and usually uneconomic in a short term perspective.
Another problem that threateningly grew in my absence was that of weeds and their increasing resistance to herbicides. In the 60s ryegrass was revered as a nutritious pasture grass which complemented clovers. Now it is feared as a herbicide resistant weed in cereal crops. This is because of the decline of the pasture ley system, due initially to declining wool prices, and the explosion in use of herbicides with minimum till farming (ploughing no longer an option for weed control). Repeated exposure of almost any living organism to a toxic compound leads to evolution of resistant strains which then come to dominate the population (as in a news item of the other day – medicated shampoos for head lice no longer work because said lice are now resistant to active ingredients).
And there are a host of other physical, biological and socioeconomic constraints that farmers have to confront, but I mention those above as they really need a coordinated, holistic, long-term approach that cannot be left to market forces alone. Technical solutions do exist but government involvement in terms of legislative and funding support is needed if these generic agricultural problems are to be effectively addressed. Thus a reversal of recent trends of both federal and state government support for sustainable agriculture is needed if a viable agriculture and healthy rural environment is to be contemplated.
Photos: Header – Nature watering a wheat crop near Moora Jordan Cantelo; Salinity in a valley near Bruce Rock Willem van Aken, CSIRO; Oil mallee intercropping Cliff Winfield