L22: Baselines, patterns, & processes II

Question 1

Changes in climate/other impacts will affect at many levels

Answer 1

• Physiological and behavioral response of organisms
• Population growth
• Community structure
• Biome distribution, extinction (next week lectures!), migration
• Productivity and nutrient cycling

Question 2

Define resilience

Answer 2

”Resilience is the capacity of a system to absorb disturbance and still retain its basic function and structure” (Holling, 1973)

Question 3

Three uses of ‘resilience’ framework for conservaIon biogeography

Answer 3

• Biodiversity conservation: aim to create ‘resilient’ species/population /communities
• Ecosystem service: ‘persistence of resilient ecosystem services’
• Restoration ecology: what are the alternative stable states and how quickly can a system switch back to a preferable state?

Question 4

Information needed in order to manage and create resilient ecosystems

Answer 4

1) Determination of the alternative stable states of an ecosystem
2) Understanding how close an ecosystem is to an alternative stable state
3) Determining the triggers that cause switch to alternative stable state
4) Identification of factors that enhance resilience
5) How resilient is a landscape to environmental perturbation?

Question 5

Which parts of the landscape are close to a threshold event? (i.e. which parts have lost resilience?)

Two potential methods:

Answer 5

1) Use long-term records to determine trend in variability (example on the leS)
2) Use present-day spatial patterns in combination with environmental variables to predict landscapes closest to threshold events (next example)

Question 6

Does the resultant vegetation pattern look any different between a resilient and a non-resilient site?

Answer 6

Patterned vegetation and associated patchiness results from spatial self- organisation

Emerges from fine-scale interactions e.g. positive feedback between plant growth and availability of water

Proposed the hypothesis that imminent regime shifts in ecosystems can be predicted by self- organised patchiness

Question 7

How resilient is the landscape to environmental disturbance?

Recovery rates of tropical forests to disturbance events

Answer 7

• Faster recovery following larger infrequent events such as cyclones and earthquakes.
• Slower recovery following small- scale human-induced impacts such as burning!

Question 8

Summary

Answer 8

• To date, much of the focus has been on describing the processes & mechanisms leading to abrupt ecosystem change
• A major research challenge is to now quantify and spatially define ecological resilience on ecosystems at scales relevant for policy & management