Farmers and perverse outcomes: The quest for food and energy security,emissions reduction and climate adaptation

Victorian farmers have experienced significant impact from climate change associated with drought and more recently flooding. These factors form a convergence with a complex of other factors to change production systems physically; and farmers’ decision making is variously described as adaptive or maladaptive to these drivers of change. Recently updated State Government policies on farming, climate and water have immediate and long term implications for food production systems but are not readily interpreted at a local scale. Further, peak oil and energy security are only partially integrated into either climate or water policy discourse. In effect, despite some far-sighted words about the meaning of climate change, uncertainty is largely met with a ‘business as usual’ mantra. Farmer narratives are used to demonstrate their systemic and increasing vulnerability and likelihood of perverse outcomes. The Future Farming strategy and Our Water Our Future are briefly analyzed, as are potential implications of the rhetoric of newly elected conservative government. Using ideas from Bourdieu and Bhabha we suggest that the reliance on farmers being able to innovate and take up opportunities associated with the uncertainty of large scale changes in climate and energy availability are misguided. It is more likely that current policy directions entrench the values of the global market and its elite, leaving farmers locked-in to historical structural responses that will not be successful in the long-term and will diminish their ability to imagine radical and diverse ways of avoiding the maladaptive structures currently surrounding their production systems.     

Spinifex biogeochemical expressions of buried gold mineralisation: The great mineral exploration penetrator of transported regolith

A major challenge for mineral explorers is to efficiently detect mineralisation beneath the weathered cover that extends across the landscape. Determination of the elemental composition of plants (biogeochemical exploration) can aid in the detection of buried ore deposits due to their root penetration through the weathered cover. At the coyote prospect in Western Australia a range of plant species were sampled traversing a buried Au orebody. Here it is shown that the soft spinifex (Triodia pungens) accumulated important pathfinder elements related to the mineralisation, which produced a multi-element surficial expression of the underlying ore deposit. Spinifex grasses are one of the most widespread grasses over the Australian continent and have vertical root systems that can extend for many 10s of metres through sedimentary cover and interact with buried mineral deposits and alteration zones in the underlying substrate. Spinifex biogeochemistry therefore has potential to be a low cost, low environmental impact, sampling medium for mineral exploration programs across large parts of arid Australia. The examination of similar grasses from other semi-arid and arid regions from around the world therefore also warrants further investigation.     

Komatiites and nickel sulfide ores of the Black Swan area,Yilgarn Craton,Western Australia. 3: Komatiite geochemistry,and implications for ore forming processes

The Black Swan komatiite sequence is a package of dominantly olivine-rich cumulates with lesser volumes of spinifex textured rocks, interpreted as a section through an extensive komatiite lava flow field. The sequence hosts a number of nickel sulfide orebodies, including the Silver Swan massive shoot and the Cygnet and Black Swan disseminated orebodies. A large body of whole rock analyses on komatiitic rocks from the Black Swan area has been filtered for metasomatic effects. With the exception of mobile elements such as Ca and alkalis, most samples retain residual igneous geochemistry, and can be modelled predominantly by fractionation and accumulation of olivine. Whole rock MgO–FeO relationships imply a relatively restricted range of olivine compositions, more primitive than the olivine which would have been in equilibrium with the transporting komatiite lavas, and together with textural data indicate that much of the cumulus olivine in the sequence was transported. Flow top compositions show evidence for chromite saturation, but the cumulates are deficient in accumulated chromite. Chromite compositions are typical of those found in compound flow-facies komatiites, and are distinct from those in komatiitic dunite bodies. Incompatible trace element abundances show three superimposed influences: control by the relative proportion of olivine to liquid; a signature of crustal contamination and an overprint of metasomatic introduction of LREE, Zr and Th. This overprint is most evident in cumulates, and relatively insignificant in the spinifex rocks. Platinum and palladium behaved as incompatible elements and are negatively correlated with MgO. They show no evidence for wholesale depletion due to sulfide extraction, which was evidently restricted to specific lava tubes or pathways. The lack of correspondence between PGE depletion and contamination by siliceous material implies that contamination alone is insufficient to generate S-saturation and ore formation in the absence of sulfide in the assimilant. Contamination signatures in spinifex-textured rocks may be a guide to Ni-sulfide mineralisation, but are not entirely reliable in the absence of other evidence. The widespread vesicularity of the sequence may be attributable to assimilated water rather than to primary mantle-derived volatiles, and cannot be taken as evidence for primary volatile-rich magmas. The characteristic signature of the Black Swan Succession is the presence of highly localised disseminated sulfide within a sequence showing more widespread evidence for crustal contamination and interaction with its immediate substrate. This has important implications for the applicability of trace element geochemistry in exploration for komatiite-hosted nickel deposits.Electronic Supplementary Material Supplementary material is available in the online version of this article at Editorial handling: Peter Lightfoot     

Fault location and fault activity assessment by analysis of historic level line data, oil-well data and groundwater data, Hollywood area, California

Transecting the Los Angeles metropolitan area in a general E-W direction are major north-dipping reverse faults comprising the Santa Monica—Raymond Hill fault zone, a segment of the frontal fault system separating the Transverse Ranges from the Peninsular Ranges geomorphic provinces of southern California. Pleistocene or Holocene movement is evident along some segments of these faults, but urban development precludes accurate location and assessment of Quaternary movement by conventional mapping techniques. At present no conclusive evidence of Holocene surface rupture has been found onshore west of the Raymond Hill segment of the fault zone, but the geologic conditions and urban development in the area are such that the possibility of Holocene movement cannot be excluded at this time. Groundwater barriers in Pleistocene sediments are indicative of Quaternary faulting on the Santa Monica fault segment west of the Newport—Inglewood fault zone. Most literature indicates that movement along the Beverly Hills—Hollywood segment east of the Newport—Inglewood fault zone terminated in Late Miocene or Pliocene time, and there is no general agreement on the location of faults in this segment. However, recent work by the Division of Mines and Geology, by Geotechnical Consultants, Inc., and others suggests that the Santa Monica fault transecting the Hollywood area is associated with a zone of differential subsidence that varies from 100 to 400 m wide, depending on the resolution of repeated leveling survey data and with a groundwater barrier determined from analysis of oil-well and water-well data. Additional exploration is essential to test our present geologic model and to evaluate the earthquake hazard and seismic risk of faults in the area.     

Determining extreme parameter correlation in ground water models

In ground water flow system models with hydraulic-head observations but without significant imposed or observed flows, extreme parameter correlation generally exists. As a result, hydraulic conductivity and recharge parameters cannot be uniquely estimated. In complicated problems, such correlation can go undetected even by experienced modelers. Extreme parameter correlation can be detected using parameter correlation coefficients, but their utility depends on the presence of sufficient, but not excessive, numerical imprecision of the sensitivities, such as round-off error. This work investigates the information that can be obtained from parameter correlation coefficients in the presence of different levels of numerical imprecision, and compares it to the information provided by an alternative method called the singular value decomposition (SVD). Results suggest that (1) calculated correlation coefficients with absolute values that round to 1.00 were good indicators of extreme parameter correlation, but smaller values were not necessarily good indicators of lack of correlation and resulting unique parameter estimates; (2) the SVD may be more difficult to interpret than parameter correlation coefficients, but it required sensitivities that were one to two significant digits less accurate than those that required using parameter correlation coefficients; and (3) both the SVD and parameter correlation coefficients identified extremely correlated parameters better when the parameters were more equally sensitive. When the statistical measures fail, parameter correlation can be identified only by the tedious process of executing regression using different sets of starting values, or, in some circumstances, through graphs of the objective function.     

An improved method of least-squares parameter estimation with pumping-test data

Least-squares estimation of storativity and transmissivity from pumping-test data has been concerned with finding the lowest point on a mathematical surface. Since there is no guarantee that such surfaces do not contain local minima, the accuracy of the estimate may be dependent upon the selection of “good” initial values.

An improved estimation procedure can be obtained by converting the two-dimensional minimisation problem into an equivalent form in one dimension. The resulting line function can then be easily evaluated through any given feasible interval. This approach avoids the requirement of initial estimates and always returns the true estimates after a single computation sequence.

Examples are given of the application of the method to both drawdown and recovery data, together with a simple model for the determination of estimation error.     

Effect of Bioremediation on the Microbial Community in Oiled Mangrove Sediments

Bioremediation was conducted in the field on a mature Rhizophora stylosa mangrove stand on land to be reclaimed near Fisherman’s Landing Wharf, Gladstone Australia. Gippsland crude oil was added to six large plots (>40 m²) and three plots were left untreated as controls. Bioremediation was used to treat three oiled plots and the remaining three were maintained as oiled only plots. The bioremediation strategy consisted of actively aerating the sediment and adding a slow-release fertilizer in order to promote oil biodegradation by indigenous micro-organisms. Oil addition stimulated the numbers of alkane-degrading bacteria slightly to levels of 10⁴–10⁵/g sediment. Bioremediation of the oiled sediment had a marked effect on the alkane-degrading population, increasing the population size by three orders of magnitude from 10⁵ to 10⁸ cells/g of sediment. An effect of bioremediation on the growth of aromatic-degraders was detected with numbers of aromatic-degraders increasing from 10⁴ to 10⁶ cells/g of sediment. Active aeration and nutrient addition significantly stimulated the growth of hydrocarbon-degraders in oiled mangrove sediment in the field.