Transcript Slide 1

Disturbance Ecology
Top 5 Questions,
Answers,
and
Future Directions
Lindsay Berk
December 9, 2005
In the beginning…
Questions for the Semester
•
•
•
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What have we learned?
What generalities can we make?
What are the obstacles to generality?
What are the interesting and important
questions?
Lecture by Peter White: September 9, 2005
The Top 5
People & Nature
5
Definitions
4
Criticality
2
Disturbance Topic
Restoration & Management
11
Invasives
1
Large-Scale
1
HRV
3
Disturbance-Recovery
3
Pattern, Process, & Scale
5
Diversity & IDH
8
Generalities
2
Other
2
0
2
4
Number of Questions
6
8
10
n=47
12
What is it?
“A disturbance is any relatively discrete
event in time that disrupts ecosystem,
community, or population structure and
changes resources, substrate availability,
or the physical environment.”
(White and Pickett 1985)
What is it?
• Is there an acceptable and universal
definition of what constitutes a
disturbance?
• How do we define disturbance intensity?
• If a disturbance is “any relatively discrete
event in time…”, are humans a
disturbance?
Diversity & IDH
• What is the relationship of diversity and
disturbance?
• How common is the diversity-disturbance
relationship that is predicted by the IDH?
When and why does it not hold?
• What characteristics define the best
disturbance regime for maximizing
both productivity and diversity?
Diversity & IDH II
• Do intermediate disturbance levels
produce the best levels of carbon
sequestration and nutrient cycling
compared to no disturbance or large,
frequent disturbances?
• Instead of asking what the effects of
disturbances are on diversity, is there an
effect of diversity on disturbance
regimes? (i.e. does diversity help to
stabilize ecosystems?)
Diversity & IDH III
• If IDH does operate, what is its effect on
diversity relative to other effects?
• Does ecological complexity increase
resilience following disturbance events?
Or, said another way, does reduced
diversity increase restoration resistance in
degraded systems?
Pattern, Process, & Scale
• Pattern or process? Which are we trying
to restore?
• What about the effects of Process on
Process and Pattern on Pattern? (e.g.
Parasites & Fire, Floods & Landslides) and
(Ecological Memory)
• How do we untangle the issue of scale
and disturbance (severity, time, extent)?
• Is there a relationship between the scales
of these three ranges?
HRV
• Is historic range of variability a worthwhile
concept?
• Is the alternate stable state concept
worthwhile?
• In what ways and on what scales does the
variability of disturbance characteristics in
time and space influence ecosystem
function?
Large-Scale Interactions
• What are the long-term effects of multiple,
compounded disturbances on
ecosystems? Do they just take longer to
recover compared to ecosystems
experiencing single disturbances?
Invasives
• How do we (or CAN we) manage
disturbance to mitigate for the effects of
exotic invasions?
Criticality
• Does the effect of disturbance intensity on
community structure and/or function
increase smoothly or are there thresholds?
• If there are thresholds are they universal
or site specific?
Disturbance-Recovery
• What is the role of disturbance-recovery cycles
in the ecology-evolution connection?
• Are disturbance-recovery systems complex
adaptive systems, and if they are, what are
the implications?
• What is the connection between disturbancerecovery cycles and stability/
resilience/persistence? Can we formulate a
theory that describes disturbance-recovery
parameters that result in these properties?
Restoration & Management
• How can management mimic variability in
disturbance, given the constraints under which
managers often operate?
• Can we predict what impacts climate change will
have on disturbance regimes and how
does it impact our management of these
regimes?
• Because of long-term departure from historic
disturbance regimes, reintroduction of
disturbance may lead to undesirable, novel
results. Is there a way to predict these novel
results?
Restoration & Management II
• What should be the guiding principles for
managing disturbance if we cannot mimic the
historic regime?
• To what extent should we try to replicate the
HRV in disturbance regimes for managed lands
(given that we can agree on what their HRV
should be)?
• How can humans engineer "disturbed" systems?
Restoration & Management III
• Given that species respond to disturbance in
novel ways, how do we manage systems at both
landscape and regional spatial scales? In
particular, how do we protect species of
conservation concern yet still meet landscape
restoration (management) targets?
• How do we know the appropriate level and type
of disturbance to manage for "natural"
conditions, considering the likely changes to
disturbance regimes from climate change?
Restoration & Management IV
• Are we doing an adequate job in our
conservation planning of setting aside
enough land to manage for minimum dynamic
area?
• At what temporal and spatial scale is restoration
an attainable goal?
• How do we preserve systems with intact
disturbance regimes? or how do we restore
disturbance regimes or manage systems to
simulate natural patterns of disturbance?
People & Nature
• How are human caused and non-human caused
disturbances different? Can the same
theoretical approach be applied to both?
• What anthropogenic disturbances are the most
detrimental to natural systems and how can the
effects of these be mitigated? What are the long
range prospects?
• How will climate change affect disturbance
regimes and in turn their stability and richness of
ecosystems?
People & Nature II
• Given the difficulty of predicting the
impacts of “natural” disturbance regimes
(e.g. fire, flood, hurricanes), how can we
ever truly predict the impacts of
anthropogenic climate change?
• What is the contribution of human
activities to (changes in) non-human
disturbance cycles? (past, present,
future?)
Others
• To what degree is the "suddenness" of the
disturbance important?
• Is there a relationship between
disturbance and stability? That is, are
systems with a well-established
disturbance history (and not the
anthropogenic kind) more stable? More
productive?
Generalities?
• What generalities can we make in
disturbance ecology?
• Are there a few variables (ideally,
measurable) that can describe the
ecologically important properties of any
disturbance-recovery system, regardless
of system type, size, location, or other
dynamics?
Thought Exercise
• Given $xx million to spend on disturbance
research addressing any of the Top 5
questions, which would you choose and
why?
Future Directions
• Where is disturbance ecology headed as a
field?
Have we gotten any closer?
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What have we learned?
What generalities can we make?
What are the obstacles to generality?
What are the interesting and important
questions?
Best of…
Disturbance Figures from Biology 255
or
The Search for Generality
Pascual & Guichard 2005
Pascual & Guichard 2005
Mackey & Currie
2001
Shiel & Burslem 2003
Shiel & Burslem 2003
Peterson 2002
Peterson 2002
Peterson 2002
Schoennagel et al
Hobbs & Huenneke 1992
Brooks et al 2004
Turner MG, Baker WL, Peterson, CJ, and Peet
RK. 1998. Factors Influencing Succession:
Lessons from Large, Infrequent Natural
Disturbances. Ecosystems 1: 511-523.
White et al. 2000
Photo Credits:
nature.org
earth.esa.int
nasa.gov