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Landscape-scale risk assessment for the ARR

The International Science Panel (ISP) in its 2000 examination of whether the Kakadu World Heritage status was at risk from impacts of uranium mining, recommended landscape and ecosystem analyses and called for a comprehensive risk assessment within the context of the Kakadu World Heritage area.

Maintenance of the natural World Heritage Values of Kakadu National Park (KNP), as they pertain to pressure from mining-related activities, underpins the landscape analyses undertaken by eriss. To ensure the protection of the region from the effects of uranium mining, and to encourage best practice in ecosystem management and conservation it is important that managers and regulators understand the relative importance of all potential ‘threats’ to World Heritage values. 

Environments of the region are subject to change from multiple threats that operate over differing spatial and temporal scales. All have some potential to diminish World Heritage values.  Exotic feral animals and weeds, and the potential for landscape level change induced by climate change and subsequent sea level rise and altered fire regimes are considered among the more serious threats to these values. Uranium mining activity poses but one point-source for contaminants that can potentially enter the surrounding environment of KNP.

The aim of this program is to broaden the contaminants risk assessment of Ranger mine to include key non-mining stressors at the landscape-scale, thereby placing contaminant issues for Ranger mine within an integrated risk assessment framework. The initial assessment focused on threats to world heritage values of the Magela floodplain (eg measured damage to natural habitats) and incorporates quantitative information on risks from both mining and non-mining threats (Figure 4). A secondary aim is that this risk assessment model be developed for use as a decision support tool for assessing and managing multiple ecological risks at multiple scales.

Initial results from the risk assessment are summarised in Table 2 and are elaborated in more detail in Section 3.10 of the Supervising Scientists Annual Report 2005-2006. Two key results from the integrated assessment are:

• Non-mining landscape-scale risks are currently several orders of magnitude greater than mining risks (Table 2), although that difference may reduce when on-site water management systems at Ranger mine change in the transition between mine production and mine closure and rehabilitation; and
• Para grass weed (Urochloa mutica) is currently the major ecological risk on the Magela floodplain because of its extent (10% cover), effect (a monoculture that displaces native vegetation and wildlife habitat) and rapid spread rate (14% per annum). Note the risk posed by para grass has been examined in greater detail by combining a Bayesian habitat suitability model with a spread rate model, therefore encompassing current and future risk to floodplain habitat diversity depending on distance to source and invasion pathways.

Table 2  Comparison of landscape and minesite ecological risks to the Magela floodplain, and their relative importance rank

Category	Pathway	Hazard	Risk rank	Action	Time frame
LANDSCAPE	Park-wide Park-wide Floodplains	Para grass weed Pig damage Unmanaged fire Total ecological risk =	1 2 3 0.21	Take active control Research effects Research effects	In perpetuity In perpetuity In perpetuity
MINESITE	Surface water Magela Ck	Uranium Sulfate Magnesium Manganese Total ecological risk = Ra-226	4 5 6 7 0.00009 8	Watching brief Watching brief Watching brief Watching briefWatching brief	2006 2006 2006 20062006
	Airborne/wind	Radon (Ra-222)	9	Watching brief	2011

NB: Ra226 and Ra222 (Radon) are included also

The overall findings from the landscape ecological risk assessment suggest that non-mining landscape-scale risks to Magela floodplain should from now on receive the same level of scrutiny as applied to uranium mining risks, including an assessment of what appropriate level of investment would be needed to manage these risks.  The ultimate challenge however, is linking the costs of reduction in ecosystem health “damage” to perceptions of socio-economic and cultural benefits in order to optimise management investments under budgetary constraints. At the end of the day decision support tools need to be realistic, pragmatic, defensible and provide management options that at least balance costs and benefits.

For more information, contact Dr Peter Bayliss (tel +61 (0)8 89201170)