Open Cut » Environment
STAGE 1
The Queensland state regulator and the mining companies that operate open-cut coal mines in central Queensland would both like to see domains of successfully rehabilitated mine land formally certified as having been returned to a sustainable end use acceptable to stakeholders and thereby of no further liability to the companies. This study addresses issues of risk were cattle-grazing is to be the end use.
The research investigated the management of rehabilitated sites if placed under the stewardship of graziers, in particular, the way graziers' characteristics and circumstances influence their land management practices, and hence the risks that grazing - especially over-grazing - may incur. Graziers' 'within-person' characteristics (values and attitudes), the capital structure of the business, operational business circumstances, and the external economic and climatic environment were found to influence their land management practices. The research found key elements affecting risks of degradation to be the degree of conservatism in the grazier's approach to stocking rates and the operational flexibility afforded by the business.
A further factor relates to the possible role of management caveats in regulating stocking rates. Since ongoing compliance with such caveats would be required, this is tantamount to an enduring business relationship being forged between the miner (and regulator) and the grazier. In business-to-business relationships, the level of trust and commitment existing between the parties is crucial. Graziers' expressed a willingness to comply with caveats. However, the research found that several critical precursors to trust and commitment were wanting.
A preliminary risk assessment model incorporates management factors with biophysical factors using a framework of conditional probabilities (Bayesian Belief Networks). Where mining companies purposefully pursue grazing as an end use, they could consider several interventions to reduce risks. These are: to ensure site architecture and surface rehabilitation techniques will result in a biophysical environment conducive to productive pasture growth; to construct grazable domains of a configuration suited to commercial cattle production, and to build trust between the company and landholders so that an enduring relationship, committed to sustainable grazing is achieved.
STAGE 2
This research provided a framework for considering end use and custodianship options for mined land. Though the source data and results are specific to existing open-cut coalmines of the Bowen Basin of central Queensland, the process of investigation is applicable to early stages of mine planning and to other regions.
Mining in the region had disturbed in excess of 55,000 ha of erstwhile agricultural land by the turn of the 21st century. The rate of disturbance will increase in ensuing decades. Companies seek to achieve an acceptable end use for the various domains of rehabilitated domains of disturbed land. Furthermore, the regulator encourages certification of completed rehabilitation on a progressive basis. This path is appealing to mining companies because liabilities are reduced and experience of 'sign-off' is gained.
This research investigated risks of cattle-grazing as an end use for mined land. A risk assessment model was developed that incorporates site-based factors with the style of land management that a future custodial grazier may employ. Various characteristics and circumstances of graziers were identified from prior research as drivers of management style and were included as draft components of the model. A survey of the prevalence of these factors among Bowen Basin graziers was then conducted. This process ascertained the prior probabilities of the elements being modelled, and refined the model's structure. The influence of the factors in shaping land management style was then estimated using a process of expert opinion. The resulting predictive model estimates the likelihood of conservative and sensitive land management under various scenarios of site characteristics and grazier-based factors.
The model for the central Queensland situation identified graziers' financial stability as the most influential driver of likely land management style, followed closely by a set of actions that mining companies could take to build graziers' commitment to specified sustainable grazing practices. The next ranked sets of influencing factors are where a grazier strongly seeks tenure of the mined land for reasons that go beyond financial gain, and where graziers hold conservation values, rather than being motivated by lifestyle or economic values. The operational nature of the business and the influence of the external climatic and economic environment were of least importance.
The model can be used to assess the risks of using currently available domains of mined land for grazing, and to identify actions that mining companies could take to manage such risks. The model may also guide future rehabilitation work by encouraging the purposeful construction of domains specifically suited for cattle production - or by purposefully and transparently planning for grazing not to be the designated end use.
The process of consultation with prospective end-users, using expert opinion as a means of linking drivers with outcomes, and embedding the resulting data in a Bayesian Belief Network was shown to have value in this context. The process could be applied to other regions, and to higher-order decisions associated with mine closure options.