Upload
doanxuyen
View
217
Download
0
Embed Size (px)
Citation preview
��������� �������
��������� ��������
���������������
����� �������� � ������ ��
������ ������ � �� �� �����
��� ����������� ��� ����
��� ������ �����
��������
����� ���
supervising scientist
���� ���!�"�#����
$��� ����
ii
Managing invasive species impacts – feral animals and weeds
Talk presented to weed and feral animal control rangers at Kakadu National Park (4 April 2003)
By Peter Bayliss & Dave Walden
Environmental Research Institute of the Supervising Scientist
Registry File #
1
Seminar outline
Principles of population control to mitigate damage
Using integrated ‘Pest Control’ models Damage-density relationship
Cost-of-control curve
Population growth response
Examples Pigs on Kakadu
Buffalo on Kakadu
Mimosa on Oenpelli
Management & monitoring framework for invasive species
2
Managing invasive species impacts
(ferals & weeds)
THE 3 “TRUTHS” OF POPULATION CONTROL
• All animals have an impact on their environment.
• Damage occurs when that impact causes economic or environmental harm.
• How one defines “harm” depends on how one makes a living.
3
Managing invasive species impacts (weeds & ferals)
Involves making choices– how much management intervention at what cost ($) ?– what benefit is delivered ?
Challenge is to make choices that are– sensible– pragmatic– defensible
Requires benefits & costs to be balanced at least– past focus on “activity-based” management– need new focus on “damage-based” management within a budget– involves complex decision making - need to use modelling tools
Pest control
Pest density
Damagereduction
Economic inputs(costs of control)
Outputs(additional income or
improved public asset)
Benefit/cost analysis
Monetary benefit/cost analysisBenefit maximisationCost minimisation
Pest Control Modelling
4
POPULATION CONTROLHOW TO MANAGE IMPACTS OR “DAMAGE”
• Clearly define damage in first place
• Identify a socially acceptable level of damage & corresponding animal density
• Use modelling tools to improve efficiency of control operations within budgetary constraints – i.e. come up with the hard facts & figures
• There are only 3 key models to use ..........
1. DAMAGE - DENSITY RELATIONSHIP
0
20
40
60
80
100
120
140
160
0 2 4 6 8 10 12
Pest Density
Leve
l of D
amag
e
Socially acceptable?
Threshold
5
2. COST- OF- CONTROL CURVECHOOSING THE RIGHT “TARGET” DENSITY
Threshold dens ity – where damage firs t occurs or is measurable
Socially acceptable dens ity – damage level
Buffalo – Arnhem Land 1985
3. POPULATION GROWTH RESPONSE
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
0 2 4 6 8 10 12
Years
Den
sity
fera
l / k
m2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
0 2 4 6 8 10 12
Years
Den
sity
fera
l / k
m2
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
0 2 4 6 8 10 12
Years
Den
sity
fera
l / k
m2
RECOVERY RATE(usually rapid with pest species)
initial control
maintenance control
6
Helicopter duration (hrs / pig) = Cost $ / killKNP (1998 - 2001)
0.0
0.1
0.2
0.3
0.4
0.5
0 100 200 300 400 500 600 700
Index pig density (pigs shot)
hrs
/ pig
T = 1.9186 D-0.7861
R2 = 73%, R=0.8513n=58, P<0.001
PIG CONTROL – KAKADU – COST CURVE
NB: Still need to add all other costs – ammo, salary etc
Index density needs to be converted to “actual density”
NTU KCTWM FERAL ANIMAL MANAGEMENT CONTRACT KAKADU
• How do Traditional Owners view this “damage”?
• How do they value pigs & buffalo?
• Which cultural resources (assets) are being damaged or at risk? (habitats, species, sacred sites etc)
• How many & where (whose country & responsibility)?
• How do we manage these different views? - what are the “trade-offs”?
7
SIMULATED BUFFALO CONTROL monitoring performance
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
0 2 4 6 8 10
Years
Dens
ity fe
ral /
km
2rm = 17% p.a.Initial kill 80%maintenance kill 10%Target 2 / km2
7 years to exceed target again
COST-OF-CONTROL OR HARVEST / HABITAT Costs / km2 / yr Total $
Initial cost $36.91 $3,691Maintenance cost $113 $101,709Total cost fo 10 Years $105,400
SIMULATED BUFFALO HARVEST
For BUFFALOYear start 2003Year end 2023Simulation Years 10
Price $/head $150.0
Total Return $243,245Total Cost $105,400Net cost or benefit $137,845
Net annual Return $13,785 p.aTotal annual cost $10,540 p.a.
$ cost helicopter/hr $1,0001,000
6,000
11,000
16,000
21,000
26,000
31,000
36,000
2002 2006 2010 2014
Year
Cost
or b
enef
it ($
)
Total benefits ($)Total costs($)Net benefits ($)
8
But we also need current information on feral animaldistribution & abundance – many methods e.g. aerial
survey (Bayliss 1985)
Blocks
Transects
Buffalo Pigs
Or use methods related directly to control program e.g. Catch-out fisheries method (Pigs – 1999 Kakadu)
"Catch-out" Method
N = 2,674
0
10
20
30
40
50
60
70
80
0 500 1000 1500 2000
Sum of previous number shot
New
pig
s sh
ot/h
r
More cost effective – but requires CONSISTENT collection of the RIGHT sort of effort data (time spent searching & killing in an AREA; # killed, #
bullets/kill)
9
RULES OF ENGAGEMENT OF PEST CONTROL
• Keep focused on damage management, not numbers killed
• Searching an area is just as important as killing – e.g 2 pigs killed in a high priority control area (with threatened habitat) is more important that a 1,000 pigs killed in a low priority area.
• A reduced population will quickly recover – control is “forever” - so need a cost-effective maintenance program using the best kill proportion & time interval to keep density below target (e.g. 30% of what’s left every 2 years).
• So absolutely essential that you collect consistent effort & cost data for each control area, to monitor your performance in relation to DAMAGE control.
Pig impacts on EleocharisPhD student Robert Bednarik – NTU
supported by TOs, Parks & Eriss
Eleocharis dulcis -Bunda
10
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
0 10 20 30 40 50
TIME (YEARS)
POSS
UM
DEN
SITY
(ha
-1) &
HI
NAU
IND
EX (x
10)
POSSUM
HINAU FRUIT
K
Introduced possum in NZ & damage to native forests
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
0 10 20 30 40 50 60 70 80
YEAR
POSS
UM
& H
INAU
DEN
SIT
Y
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
0 10 20 30 40 50 60 70 80
YEAR
POSS
UM
& H
INAU
DEN
SIT
Y
Target = 10% reductionTarget = 80% reduction
DENSITY- DAMAGE THRESHOLD
Possums Hinau
What target density is needed to restore natural “masting” cyclein hinau fruit production?
11
Mimosa Risk Assessmentnorthern Australia
Wetlands across northern Australia potentially at risk of mimosa infestation, based on 1:250K topographical wetland data & potential distribution using CLIMEX
Dave Walden et al. (2002): A Risk Assessment of the Tropical Wetland Weed Mimosa pigra in Northern Australia
Potential impact mimosa on magpie geese nest numbers in Top End (1983-1989)
y = - 0.01Area2 + 71.4Area - 35410R2 = 96%, n=6, P<0.01
01000020000300004000050000600007000080000
0 500 1000 1500 2000 2500 3000 3500
Area Floodplain or mimosa (km2)
Tota
l num
ber n
ests
(los
t)
POTENTIAL DAMAGE CAUSED BY MIMOSA TO WATERBIRDS
12
Impact of mimosa on floodplain plant biodiversity (CSIRO study Oenpelli 1993)
Loss = 0.90 MC - 2.81R2 = 90%, n=4, P<0.05
0
20
40
60
80
100
0 20 40 60 80 100
% Cover mimosa
% S
peci
es lo
ss
DAMAGE CAUSED BY MIMOSA TO WETLAND PLANT DIVERSITY
MIMOSA & PARAGRASS DESTROYS BUSHTUCKER HARVESTS
& ANY POTENTIAL FOR COMMERCIAL USE
13
Mapping Paragrass & other weeds on the Magela
New (2003)Old (1991)
Cost-of-control curve MimosaOenpelli 1991 - 1997
y = 30150x-0.7109
R2 = 93%, P<0.001
$0
$100
$200
$300
$400
$500
$600
$700
0 2000 4000 6000 8000
Mimosa control area (ha)
$ Co
st /
ha
Mimosa control on Oenpelli Floodplain
14
MIMOSA CONTROL OENPELLI(1991 – 1997)
0
5000
10000
15000
20000
25000
30000
35000
0 2 4 6 8 10 12 14 16 18 20
Years
Area
mim
osa
(ha)
1991
C osts/h a T o ta l Co sts
In iti a l co st ($ /h a ) $ 0 $ 0M e a n a n n ua l m a in t c ost ($/ h a / y r $ 0 $ 0To ta l co st ( $ /h a ) for $ 0 $ 013 Y e a r s
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
0 2 4 6 8 10 12 14 16 18 20
Years
Area
mim
osa
(ha)
1991
Costs/ha Total Costs
Initial cost ($/ha) $51 $404,162Mean annual maint cost ($/ha/yr) $218 $247,707Total cost ($/ha) for $1,139 $1,642,696
ABUNDANCE MANAGEMENT FRAMEWORK
ABUNDANCE APPROACHDominates pest control, is a single species, single method & single location approach - inefficient
PIGS CONTROL
DAMAGE(ground disturbance or eat yams)
15
IMPACT MANAGEMENT FRAMEWORK
DAMAGE APPROACHFocus is on the "damage", not the animal; allows use of social & economic values in management decisions - more efficient & realistic
PIGS DAMAGE CONTROL
GROUND SOCIAL & ECONOMICDISTURBANCE VALUES