Weed Risk Assessment- Galapagos · Galapagos Not Present in Galapagos. High Risk. High Risk...
Transcript of Weed Risk Assessment- Galapagos · Galapagos Not Present in Galapagos. High Risk. High Risk...
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Alan Tye
Weed Risk Assessment- Galapagos
Johanna Mader
Chris BuddenhagenHawai’i
Invasive Species Council
Paul Pheloung
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•
Someone proposes to introduce a new ornamental plant or crop species. Do you permit it to enter?
What decisions do we mean?
•
You have 500 introduced plant species in your country, and you know the top 10 invaders. But which of the many plants in people’s gardens might become the next problem?
•
You have a plant known to be a serious weed on other islands, but it is still only found in small areas in your country. Can it be eradicated completely?
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A process:
1. Weed inventories
2. Evaluate invasiveness and impact, or risk of it, for each species.
3. Decide if and how to manage each species.
4. Start eradication-
reassess feasibility as you go.
Some principles for Weed Risk Assessment and Weed Management
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Small number of introduced species-
good baseline before 450 (2001)
812 total 542 cult. 270 wild 62 NaQ
0
100
200
300
400
500
600
700
Genov
esaSan
ta Fé
Pinzón
Fernan
dina
Pinta
Españo
laSan
tiago
Florean
a
Isabela
San C
ristób
alSan
ta Cruz
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Not Present in Galapagos
Not Present in Galapagos
High RiskHigh Risk
ExcludeExclude
Low RiskLow Risk
Determine action?
Feasibility of Eradication (effort required)
Feasibility of Eradication (effort required)
Present in Galapagos
Present in Galapagos
Size of infestationSize of infestation
Number of searchesNumber of searches
Attempt eradication
Attempt eradication
High RiskHigh Risk
Weed Risk AssessmentWeed Risk Assessment
2 Steps to Managing Plant Introductions2 Steps to Managing Plant Introductions
1. WRA
2. Action
re-assess
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Environmental focus (but include agricultural, forestry, health etc considerations).
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Intended to permit review of all known introduced plants; species not yet introduced which could be a risk.
• Produce an risk index for each species.
•
Classify each species into one of five invasiveness impact/risk categories.
• Easily adaptable for any island or archipelago.
Features of the Galapagos and Galapagos WRAs:
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Changes to questions and in Galapagos section
Naturalization -
Viable seed production
Naturalization -
Evidence of seedlings produced without human assistance
Naturalization -
Evidence of two or more generations of adult plants
Invasiveness -
Evidence of long distance propagule
dispersal and establishment
Invasiveness -
Evidence of establishment in natural ecosystems (with little human disturbance)
Invasiveness -
Current status
Already growing wild in the National Park in the arid zone
En la zona húmeda del Parque Nacional
Presente en dos o más islas
Presente en islas no habitadas
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Five invasive status categories:
A Transformer: already
a habitat transformer
in Galapagos
(includes hybridizers with endemics).
B Potential
transformer:
naturalized
in Galapagos
and known as a habitat transformer elsewhere-or early signs of impact potential.
C Integrator: naturalized in Galapagos
but integrating into native vegetation without causing major habitat change (mainly small weeds).
D Potential invader: not naturalized in Galapagos
but a potential invader (based on behaviour elsewhere).
E Probably harmless: only cultivated in Galapagos
(not naturalized) and not known as an invader elsewhere.
8
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12 Key Questions that influence the environmental impact categorization:
Behaviour elsewhere:
3.04
Environmental weed that is a transformer in natural areas (elsewhere)
3.05
Other species in same genus are serious invaders elsewhere,
or are native or naturalised
in Galapagos
Potential environmental impact:
5.04
Smothering growth habit. 5.05
Forms dense thickets,
particularly woody perennials. 5.06
Is a tree, woody perennial shrub, grass,
geophyte
or vine.
6.03
Capable of interspecific
hybridization. 6.04
Endemic congeneric
species present in
Galapagos.
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Present in
Galapagos?
[Yes
or no]
Behaviour in Galapagos:
9.01
Viable seed production 9.02 Evidence of seedlings produced without human assistance 9.03
Evidence of two or more generations of adult plants 9.07
Current invasive status [Don't
know, Integrator, Transformer, Potential
transformer]
12 Key Questions that influence the environmental impact categorization:
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Management options for plants already introduced:
• Do nothing –
(E Harmless; C Integrators)
For Transformers, Potential Transformers and Potential Invaders:
• Eradication
• Containment/Exclusion
• Site-specific control
• Biological control
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>2000 ha
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RubusRubus megalococcusmegalococcus August 2000August 2000
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Weed Eradication Feasibility Analysis
Oscar Cacho & Paul PheloungSchool of Economics
University of New EnglandAUSTRALIA
Collaboration: Danny Spring, Susie Hester, Dane Panetta, Chris Buddenhagen
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ISSUES
a) How can we measure weed detectability?
b) How many search/control missions are required to eradicate an invasion?
c) How intensive should these missions be?
d) What is the probability of eradication in x years if we invest y dollars?
e) How do attributes of the weed and the environment affect all this?
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Weed Eradication Feasibility Analysis
Oscar Cacho & Paul PheloungSchool of Economics
University of New EnglandAUSTRALIA
Collaboration: Danny Spring, Susie Hester, Dane Panetta, Chris Buddenhagen
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ISSUES
a) How can we measure weed detectability?
b) How many search/control missions are required to eradicate an invasion?
c) How intensive should these missions be?
d) What is the probability of eradication in x years if we invest y dollars?
e) How do attributes of the weed and the environment affect all this?
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Modelling eradication feasibility
Modelling eradication feasibility
Mature PlantsMature Plants
Seed bankSeed bankYear …Year …Year 3Year 3Year 2Year 2Year 1Year 1
Juvenile PlantsJuvenile PlantsYear…Year…Year 3Year 3Year 2Year 2Year 1Year 1
Search +Control
efficiency
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MODELLING STRATEGY
Search theory
Population dynamics(stage matrix model)
Economic theoryOptimisation techniques
Demographicparameters
Input requirements(labour, chemicals)
Input costs
Invasion costs(environmental
services)
Probabilities
Searchparameters
proportion detected and killed
size of invasionsize of seedbank
Optimal strategies:search effort,
cost of control program,years to eradication,
allocation of limited budget
control feedback
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SEARCH THEORY
• initially developed to improve success rate in detecting military targets
• relates search effort to probability of detection of an object
• the concepts of Coverage (c) and Effective Sweep Width (R) are key features of the theory
ATRSc =
S = search speed (m/h)T = search time (h)R = effective sweep width (m)A = search area (m2)
R measures the detectability of the object in the given environment
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0.0
0.2
0.4
0.6
0.8
1.0
sear
ch p
ath
(A) (A)
(B) (B)
Effective Sweep Width
Lateral range (m)
Prob
abili
ty o
f det
ectio
n
LATERAL RANGE CURVES
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0.0
0.2
0.4
0.6
0.8
1.0
0.0 0.5 1.0 1.5 2.0
definite range
parallel tracks
random search
Coverage (c)
Prop
ortio
n de
tect
ed (p
d)
PROBABILITY OF DETECTION
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PROJECTION MATRIX
A =
0 0 0 15000.251 0.251 0 00.026 0.026 0 0
0 0 0.050 0.464
new seedsseedbankjuvenilesmature
xt =x1
x2
x3
x4
xt+1 =A xt
λ = 1.5
(λ = er)
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Parameter Value Description T 1.0 Time searching (h/ha) S 1,000 Speed of search (m/h) R 20 Perceptual range (m) K 0.95 Effectiveness of control agent
Parameter Value Description f31, f32 0.05 Germination rate f43 0.02 Juvenile survival f1n 1,500 Fecundity MT 2 Time to maturity (yr) SL 5 Seed longevity (yr) MS 1.0 Size of adult (m2)
Search parameters
Biological parameters
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0102030405060708090
100
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
Year
s to
era
dica
tion
Search time (h/ha)
YEARS TO ERADICATION VS SEARCH EFFORT
(3) perennial, long-lived seeds
(1) annual
(2) perennial, base
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INPUTS FOR WEED CONTROL
Data from Budenhagen and Yanez (2005)
0
100
200
300
400
500
600
700
800
900
1,000
0 10,000 20,000 30,000 40,000
Stems per ha
Labo
ur In
put (
h)
0
10
20
30
40
50
60
0 10,000 20,000 30,000 40,000
Stems per haH
erbi
cide
inpu
t (l)
Labour Chemicals
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Measuring detectability
Harris, Brown and Timmins (2001), p.13
Habitat type Weed growth form Visibilitya
(m) Forest climbing vine 1-100b ground creeper 1-7 shade-tolerant shrub or tree 1-7 Shrubland vine 1-100 b tree or tall shrub 1-100 b Short vegetation short weed 1-3 shrub or tree 1-20 Wetland short weed 1 shrub 1-30 tree 1-100 b Open habitat short weed 1-3 taller weed 1-20
a depends on plant ageb depends on vantage point
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Lateral range (m)
Cum
ulat
ive
coun
t
detectionsnon-detections
½ ESW
Measuring detectability (ESW)
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MODELLING STRATEGY
Search theory
Population dynamics(stage matrix model)
Economic theoryOptimisation techniques
Demographicparameters
Input requirements(labour, chemicals)
Input costs
Invasion costs(environmental
services)
Probabilities
Searchparameters
proportion detected and killed
size of invasionsize of seedbank
Optimal strategies:search effort,
cost of control program,years to eradication,
allocation of limited budget
control feedback
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