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Identifying
Dutch elm disease ‘danger-spots’
on the Isle of Man
with an agent-based model
Bruce Mitchell a, Joana Barros b, Daniel Wendel c
Email a: [email protected]
b: [email protected] c: [email protected]
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Suffolk, 1984
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StarLogo TNG - code blocks
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The Isle of Man in TNG
SpaceLand
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Objective
Is there a relationship between where
a beetle cluster originates and the
number of agent elms that die?
If so, might that relationship be used
to map the island to reveal locations
where an infestation might potentially
be more or less damaging?
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Isle of Man -
Relief• Scolytus beetles can only thrive
where elms prosper
• Landscape determines elm
habitats
• On Man, there is an ‘elm-line’ of
ca. 160 metres a.s.l..
• Two ranges of hills exceed this
elevation, restricting the flow of
the disease across the island
• In the model, a ‘beetle-line’ was
set at an arbitrary 25 % higher
(200m) than the elm-line.
The combination of DEM, elm-line
and beetle-line places elevation
at the model’s centre.
• Beetles operating out of any
given disease epicentre will find
some areas accessible, others
out of range.
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A single model run …
Sets up tree, beetle, forester, bird
agents
‘Infects’ up to 1.5% of elms with
beetles
Runs an elm census at game turn
(GT) 0
Generates a single beetle cluster
Runs a beetle census at GT 60
Continues to GT 1,000
Exports results to .csv file
Resets to GT 0 and introduces next
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Model agent flow chart
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The agents
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Model system flow chart
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SL-TNG Output
For each run:
◦ cluster originates in random location;
◦ number of elms surviving to GT1000
varies
.csv run results ported to MapInfo and
SPSS for processing, then transferred
to ArcGIS Spatial Analyst
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RCNS Calculation – step one
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RCNS Calculation – step two
RCNS zones
and regions
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Data processing flowchart
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Frequency of
cell inclusion
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Cluster
median
centres and
elm survival
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Modelled
danger-spots
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Identifying Dutch elm disease ‘danger-spots’ on
the Isle of Man
with an agent-based model
Bruce Mitchell
Data Visualisation Centre
Methodology Directorate
Office for National Statistics
Joana Barros
Department of Geography, Environment and Development Studies,
Birkbeck, University of London,
Malet Street, London, WC1E 7HX
Daniel Wendel
Lead StarLogo TNG DeveloperScheller Teacher Education Program
Massachusetts Institute of Technology
Boston, MA, USA
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