Resilience Part 1 & 2 Flashcards
Define resilience
the ability to bounce back from catastrophe
what is the optimization approach?
o Get a system into some particular optimal state and hold it there.
o Believed it will deliver maximum sustained benefit.
o The approach is to find the optimal path for the state of the system.
o Sometimes referred to as the maximum sustainable yield or optimal sustainable yield paradigm.
How does the optimization approach work?
Optimization does not work as a best-practice model because this is not how the world works.
The systems we live in and depend on are usually configured and reconfigured by extreme events, not average conditions.
It takes a two-year drought, to kill perennial plants in the tropical savannas, and it takes extremely wet periods for new ones to be able to establish.
Explain the Everglades case in relation to resilience thinking
Disturbance events characterized the Everglades over thousands of years were also the forces that vitalized the ecosystem.
Regulating the system to optimize its short-term human returns was shutting down natural cycles that sustained its wealth and allowed it to recover from extreme events.
Define threshold
Level of controlling variables where feedbacks to the rest of the system change
What word do you use to define a system?
State.
Define a Two-dimensional system
consists of 2 variables (ex: number of fish and the number of fishers).
Define the ball in a basin system
The ball is the state of the social-ecological
system.
The basin is the set of states which have the
same kinds of functions and feedbacks,
resulting in the ball moving toward
equilibrium.
Define the lake example in relation to the ball in a basin system.
o Receives phosphorus from runoff from a field.
o Phosphorus is a plant nutrient and encourages growth of algae.
o This algal growth can turn clear water murky.
o After runoff event by a big rainstorm, phosphorus levels in the water increase, algal growth increases and the clear lake goes murky.
o If the phosphorus in the sediment is low, then the sediments will absorb phosphorus in the water.
o When the water near the sediments has plenty of oxygen, the phosphorus gets bound up in the sediment in a form that has low solubility.
o Then little gets released back to the water.
o The algae therefore lose their source of nutrients, and the lake returns to a condition of clear water.
o If the phosphorus in the lake sediments is low, it draws the phosphorus levels in the water down.
o And so–the lake has a degree of “resilience” to shocks caused by nutrient inputs of phosphorus.
o The lake cannot recover to its former clear state. It has a new stable state.
o In this new regime algal growth proceeds unchecked.
o The water becomes murky and smells, fish die, and the system no longer provides the ecosystem services it once did to the surrounding population
What sequence of events caused the shift of the Sea Otter and Marine Ecosystem of the Pacific Rim to shift outside the threshold?
o Sea Otters were hunted to near extinction.
o Sea otters feed on sea urchins and shellfish, keeping the populations in check.
o Sea urchin populations grew unchecked.
o Sea urchins grazed heavily on kelp, leaving little food or shelter for fish.
o Harbor seals which fed predominantly on fish also declined in number.
How do thresholds define resilience?
o Resilience is the capacity of a system to absorb disturbance, undergo change, and still retain essentially the same function, structure, and feedbacks—the same identity.
o Resilience refers not to the speed with which a system will bounce back after a disturbance so much as the system’s capacity to absorb disturbance and still behave in the same way.
What are the Key Points on Resilience Thinking
o Though social-ecological systems are affected by many variables, they are
usually driven by only a handful of key controlling (often slow moving) variables.
o Along each of these key variables are thresholds; if the system moves beyond a
threshold it behaves in a different way, often with undesirable and unforeseen
surprises.
o A system’s resilience can be measured by its distance from these thresholds. The
closer you are to a threshold, the less it takes to be pushed over.
o Sustainability is all about knowing if and where thresholds exist and having the
capacity to manage the system about these thresholds.
Is it easy to cross back over a threshold once it has been crossed?
No, it is usually difficult (or impossible) to cross back.
Define the Goulburn-Broken Catchment
- Provenience in Victoria, Australia.
- Heavily reliant on agricultural, food processing, forestry, tourism.
- 120 mm of rain annually, but has periods of drought
Explain the layers of the Goulburn-Broken Catchment
Layers: soil, salt layer, water table 25-50 mts below the salt layer.
Tap roots that could go down and tap into the water table. A thick layer of soil helped to keep moisture.
The threshold can be broken if enough water fills and mixes with the salt layer.
o Water catchments to catch the water during drought years, will collect a water reserve.
o Technology must keep the catchments from exploding. Ensuring slow variables can keep these systems level.
