Event-Driven or Continuous; Which Is the Better Model for Managers?

Abstract

Over the past ten years or so, discussion of vegetation change in rangeland science has emphasised event- driven or episodic processes, occurring on timescales measured in decades or longer. Management recommendations arising from this literature have stressed that management must also be event-driven. This paper cautions against the uncritical acceptance of such a world view into management philosophies. We conclude that for management purposes, appropriate models of change in rangeland systems should include a balance between the effects of infrequent, unpredictable events and the effects of more continuous processes, measured in timescales of years or less. This may involve explicit recognition of multiple timescales in a hierarchical model system. We arrive at these conclusions from a number of perspectives. Firstly, a substantial proportion of total demographic change in shrub populations occurs between events. Secondly, managers are best able to devise appropriate management strategies by a process of adaptive management. This can only be successful if the adaptive cycles have a short return time. Thirdly, it is important that managers think of change as being continuous. Mental models held by managers must acknowledge the value of continuous change. This provides the best opportunity for acquiring knowledge through experience and helps prevent management inertia when faced with an event outside previous experience. Finally, management can take best advantage of a given event by 'conditioning' the resource. This can be thought of as managing within states, say by building up a seedbank, and provides the opportunity to alter the probability of a given event occurring.

Improving Field-Based Experimental Research to Compliment Contemporary Management

“…We have acknowledged this tension in the past, and understand that what we learn from science is provisional and we will continue to learn. 18 At issue here is the reconciliation of existing scientifi c evidence with a perceived understanding accumulated from either personal or generational experiences, or accumulated over time at specifi c sites.…”

State and Transition Models: Theory, Applications, and Challenges

“…Major concerns included strategies for communication using models and their role in management; the ability (or inability) to define quantitatively both states and transitions for specific plant communities; and incorporation of spatial processes, such as water flow (Brown 1994;Grice and MacLeod 1994;Scanlan 1994). Shortly afterward, Watson et al (1996) questioned the strong focus on event-driven processes and abrupt change and suggested that a model of more continuous, cumulative change was just as appropriate to describe vegetation dynamics in many systems. Further, they suggested an emphasis on the management of vegetation within an ecological state to either prime it for a desired transition or protect it from an undesired transition.…”

Science to Support Management of Receiving Waters in an Event-Driven Ecosystem: From Land to River to Sea

“…These events may occur infrequently or unpredictably, which can lead to uncertainty about the extent and frequency of monitoring required to encapsulate the full range of event characteristics and associated ecological responses. Further, their effects on receiving waters are often superimposed on seasonal or inter-annual changes in receiving-water quality and ecology, all of which require management consideration that is underpinned by detailed scientific understanding [1]. In addition, poor land use decisions are more likely to be made during long dry spells (e.g., encroachment of urban areas into floodplains), unpredictable flow events may occur when farmed floodplains are most vulnerable to erosion (e.g., when they have been recently plowed and seeded), and infrastructure such as levees and channelization that are implemented to deal with extreme flows can destabilize channels, leading to further problems during high flow events.…”