System Disturbances

To improve the resilience of a system, potential perturbations must be identified along with their foreseen effects. Managers will not be able to identify all the disturbances that a system can undergo or the effects that could result. Surprise events are inevitable and could be beyond the scale of influence of managers.

Tables 2, 3 and 4 show some of the environmental, social and economic disturbances that can and do affect the Port Phillip Bay system. The kind and duration of the shock is listed as to give an idea of how the system may be affected.

Below: Table 2: Environmental disturbances, type, frequency and possible effects

Disturbance	Type	Frequency	Effects
Drought	Pulse	Annual/Decadal, Can Last a Single or Several Years	Reduced Runoff results in Bay and River Nutrient Input Reduction
			Tourism and Water Based Recreational Activities Suffer
			Social Impacts – Personal Water Restrictions and Creates Unrest
			Potential Loss of Tax Revenue as Business and Industry Suffer
			Need for Greater Government Spending to Deal With Crisis
			Forest Fire Potential Increase Coupled With Wildfire Disease
			Water Quality Effects, No Water Cycling and Freshwater Input
			Potential Media, Social, Political, Environmental and Economic Conflicts
			Increased Water Production and Transport Costs
Increased Rainfall in Wet Years	Pulse	Rare	Increased Agricultural Production and Runoff Leading to Increased Nutrient Inputs
			Water Dominated Businesses, Industry and Recreation Flourishes
			Increased Potential for Flash flooding

Bioturbation	Press	Rare but sustained	Reduction in Secchi Depth and Photosynthetic Activity at Lower Depths
			Oxygen profile changes
			Algal bloom stimulation leading to eutrophication
			Destruction of Sea grass and kelp bed habitats
			Toxicant release effects pH balance and enters the food chain
			Reduction in water body aesthetics effects tourism and land values
			Sight reliant food locating species effected
Temperature Increases	Press	Gradual Increase	Thermal expansion of water creates erosional problems on coasts
			Bay temperature profile changes effects metabolic rates and decreases pH
			Increasing demand for water and Health Impacts
			Increased drought potential and evaporation rates
Sea Level Rise	Press	Gradual but small increase	Threatens current beaches and thus tourist and recreational activity
			Increased cliff failure and erosional events
			Flooding potential increased
			Loss of property value
Spills and Dumping	Pulse	Unpredictable	Poisoning of food chain
			Increased eutrophication and loss of aesthetic value
			Health impacts from physical contact and marine food consumption

Below: Table 3: Social disturbances, type, frequency and possible effects

Disturbance	Type	Frequency	Effects
Population Dynamics	Press	Very Slow but Constant	Increased demand for goods and services when population growing
			Pressures on environment such as agriculture and water supplies
			Increasing use of and demand for local businesses and government services
			Increased urbanisation and fertiliser use
			Increasing Traffic creates pollution and health problems
Terrorist Event or Global Pandemic	Pulse	Unpredictable and Effects could be sustained	Keeps tourists and capital investment away from areas
			Can affect local attitudes
			Local health of population could be effected
			Potential infrastructure and business market destruction
Institutional Changes	Pulse and Press	Greatly depends of type of change	Policy and jurisdictional changes can result in management practise changes
			Potential social, economic and environmental changes
			Budget changes can have positive or negative effect
			Could potentially have effects at all scales

Below: Table 4: Economic disturbances, type, frequency and possible effects

Disturbance	Type	Frequency	Effects
Financial Instability	Pulse and Press	Unpredictable, can last years or even decades	Reduced demand for goods and services
			Reduced demand for shipping and imported goods
			Reduction in disposable income effects recreation and tourism
			Higher energy and production costs
			Exchange rates and land values effected
			Government revenue reduced impacts on departmental budgets
Exchange Rate Dynamics	Press	Constantly Fluctuating	Currency devaluation promotes tourism and exports
			Currency appreciation promotes imports and puts tourists off
			Effects demands for goods and thus shipping and transport
Environmental Budget Cuts	Pulse	Depends on Government changes and priority shifts	Effects management practises
			Can produced ineffective environmental assessments
			Research and development affected
			Could amplify any current impacts if interventions are scaled back

Some disturbances are known to reoccur. El Nino, exchange rate fluctuations and institutional based changes will occur time after time. The issues lie in that the details cannot be predicted as easily. The timing of an El Nino event cannot be predicted (Chen et al., 2004) and the amount the Australian dollar will fluctuate on any given day is unknown. What I critical is the idea that surprise events will occur that result in surprise effects. The following tables highlight some of the disturbances that could affect Port Phillip Bay.

The disturbances listed here are not exhaustive and a merely a guide for managers on the range and types that Port Phillip Bay could be subjected to.

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Next: Stable States and Thresholds

References

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System Disturbances

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