Cowan, E, Chester, P, Wittkuhn, R & Wood, B 2026, 'From angles to amendments: learnings from field trials to improve rehabilitation practices', in AB Fourie, G Boggs, J Heyes & M Tibbett (eds), Mine Closure 2026: Proceedings of the 19th International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 1-15, https://doi.org/10.36487/ACG_repo/2615_66
(https://papers.acg.uwa.edu.au/p/2615_66_Cowan/)
Abstract: Rio Tinto strives to deliver quality rehabilitation outcomes across its mining operations in the Pilbara, Western Australia. Successful rehabilitation of the Pilbara is challenging due to factors including variable rainfall, high temperatures, poor growth medium quality and challenges with returning native species. Therefore, to inform evidence-based rehabilitation practices, Rio Tinto established a suite of field trials. Here we discuss 3 trials that demonstrate both the breadth of current research and the complexity of conducting successful rehabilitation in the Pilbara. The first trial relates to the seeding rates and timing necessary to promote diverse vegetation communities. For this trial we found low plant densities where seed was not applied but high variation in the different seed rates. The effect of seasons was unable to be determined due to differences in seeding methodologies. These findings allow for more targeted seed rates and investigations into seeding methodologies. The second trial tested different amendment types and watering regimes for tubestock of Eucalyptus leucophloia, an iconic tree species that has low establishment from seed in rehabilitation. We found that water at the time of planting substantially increased survival and no consistent effect of amendments, with these findings important for future planting techniques. The third trial investigates slope angle effects on vegetation establishment. Here we tested the effect of irrigation and slope angles at 16, 18 and 20° on vegetation establishment. So far there appears little effect from slope angle but a strong effect of irrigation on perennial densities. Collectively these trials highlight the critical role of fieldbased evidence in shaping effective rehabilitation prescriptions and improving long-term outcomes, with findings applicable to rehabilitation in the Pilbara more broadly.  

Keywords: Pilbara, field trials, seed rates, seed timing, tubestock, landform design