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As system-level concerns increasingly dominate thinking and questions to do with resource management it is necessary to include an expanding list of processes, scales and drivers. This poses a large number of challenges when dealing with model components with different resolutions and native scales. Differential equations and other 'classical methods' are well suited to the representation of large bodies or large areas, but often fail when fine scale detail is critical. In contrast, individual based models (IBMs) are well suited for fine scale questions but are inappropriate (typically due to computation demands) for representing all components of a regional system-level model. Bringing both of these model types together in one framework shows great promise not only for representing ecological systems, but for addressing management questions. Lessons learnt from such an exercise on the Ningaloo Reef system (Western Australia) highlights the pitfalls and potential of taking marine management to regional, multiple use and fully dynamic scales. In particular, the work highlights how failing to take such approach can compound a failure to appreciate tradeoffs in the system with the human tendency to underestimate the impact of cumulative non-linear impacts.

Ningaloo-Exmouth region is an area of exceptional beauty and productivity that is supporting a diverse range of local activities (e. g. farming, fishing and oil and gas exploration), while also attracting national and international tourists. The proximity of Ningaloo reef to the coastline and the presence of Cape Range National Park in the same area mean that any development or growth of industries (including tourism) needs to be done with sustainability foremost in mind and with a minimum of unintended effects.

Avoiding unintended consequences is particularly important given the vulnerability of the area to cumulative impacts and the implications for pressure on water resources in such an arid area. The greatest influences on coastal systems like those in the Ningaloo-Exmouth region are: climate change; eutrophication and associated nuisance algal blooms; habitat degradation and destruction; species extinctions and introductions; pollutants; changes in water cycles; disturbance of biogeochemical cycles and physical properties like temperature, salinity and pH. Individually, each of these pressures can pose serious management challenges, but in combination their cumulative impacts can rapidly degrade the state of a system.

The new set of environmental conditions likely to be created in the Ningaloo-Exmouth region under global climate change (e. g. changes in weather patterns and oceanic water column properties like temperature and pH) are likely to impact the availability of water in the region and may also affect the resilience of the reef to other pressures. This makes any decision that may affect water or the reef of potential concern to the community, management bodies and every industry in the area. Regardless of what the final set of decision is, there will be tradeoffs between sectors and system components and potentially even between generations when addressing questions regarding

the use open or restricted access (by area or activity) for managing load on the system;

the speed of infrastructure and coastal development; and

the relationship between environmental load, eco-efficient practices and technology, the sustainability of regional development and the carrying capacity of the area.

Preliminary results show that due to the location, isolation and the distribution of resources in the region, just a few decisions separate a possible future where governance and development encourages growth and sustainable industries, and a possible future where the capacity of the system is exceeded, at great environmental, social and economic cost.