Landres1999 Flashcards
Title
Overview of the use of natural variability concepts in managing ecological systems
Natural resource managers have used natural variability concepts since?
Early 1960’s
Natural variability concepts are being used for?
- Maintaining biological diversity
- Restore altered ecosystems
- Benchmarks for assessing anthropogenic change
Management use of natural variability relies on 2 concepts
- Past conditions and processes provide context and guidance for managing ecological systems today
- Disturbance-driven spatial and temporal variability is a vital attribute of nearly all ecological systems
Natural variability can be defined by a specific time period or spatial extent, T or F?
False
- No a priori time period or spatial extent should be used in defining natural variability
What are the drivers for selecting a relevant time period and spatial extent for defining natural variability?
- Specific goals
- Site-specific field data
- Inferences derived from data collected elsewhere
- Simulation models
- Explicitly stated value judgement
What must always be explicit parts of the definition and use of natural variability concepts?
- Clearly defined goals, objectives, assumptions, value judgements, and spatial and temporal bounds
Wide-ranging, legally-protected species must be evaluated at what scale?
- The scale of their range, even if it extends beyond local planning area
Range is often used to describe what? But?
- Natural variability and to evaluate when current conditions are beyond the bounds of natural conditions
- But, rare extreme events define these bounds and spatial and temporal limits usually are not defined in sufficiently explicit terms
What is a spike descriptor and what does it include?
- Spike descriptors quantify short-term, extreme, or high magnitude changes caused by discrete disturbance events and the relatively short term ecological responses to these events
- Include rate of change, severity, seasonality, and size and severity frequency distributions
When does the natural variability approach have little utility?
- When historical relationships between ecosystem components and their functions cannot be determined or restored
What needs to be done when the size, intensity, or effect of a disturbance on socio, political, or endangered ecosystem components (species) is so great as to be unacceptable?
- Other approaches to landscape management need to be employed that are outside of the historical regime/natural variability
What are the significant concerns that remain about the use of natural variability concepts?
- Relevance of the concepts to environments that are different today from what they were
- Amount and quality of information and understanding about natural variability may be insufficient
- Difficult of managing dynamic ecological systems, especially at large enough scales to be meaningful
What are 3 primary criticisms against natural variability?
- Native and contemporary people altered natural systems so that there are no pristine areas left, making info from the past irrelevant or difficult to interpret
- Dominant climate patterns continually change, past patterns and processes are largely irrelevant today or in future
- Management goals using natural variability see to recreate past envrs and maintain them in a static condition, not the dynamic of nature
What uncertainty in long-term trends makes analysis of trends difficult
- few data available further back in time
- Rare events increase with longer time frames, and skew data b/c intense and impacts longer lasting
- Earlier times limited info available about disturbance processes and interactions with dominant driving variables such as climate
