Transcript Chapter8

• Successfully addressing the problem of IAS
needs collaboration between different
economic sectors and disciplines.
• Cultural values and public perceptions need to
be addressed.
• Policymakers need to know that invasive
species pose a major threat to native
ecosystems and biodiversity and to economic
prosperity.
• Education is a key component of successful
prevention and management methods (GISP,
2004).
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• The management of invasive species changes according
to the management goal, time allocated, funding and
severity of the invasive species infestation (GISP 2004).
• Management is categorised into:
assessment
early detection
prevention
containment
strategies
eradication
control
mitigation
follow-up
biological control
integrated pest management
monitoring
Generalized steps in the invasion process and their
relationship to management of invasive species
(adapted from Kolar and Lodge, 2001)
PREVENTION
• Species may be excluded from countries according to quarantine
laws and regulations.
• A good predictor of invasiveness is whether a species has
invaded other (similar) areas where it has a longer history as an
alien (Richardson, 2001).
• The most common approach for prevention is to target individual
species.
PREVENTION cont.
• A more comprehensive approach is to identify major pathways
and manage the risks associated with these.
• Risk assessments can be done for pathways as well as for
individual species. In most countries, black lists are made of
the most notorious invaders, known to be pests in the country
or elsewhere. Prevention of these species from entering a
country is the goal of quarantine.
• Australia is well on its way to developing a promising
screening system (Daehler and Carino, 2000). This system uses
various types of information (e.g. life history, biogeography,
habitat characteristics and weed history) to classify a species
as either likely to be invasive, not likely to be invasive, or
requiring further research.
• The general public can also do their bit to prevent
introductions or further establishment of already
introduced IAS.
not taking spp. across borders
awareness
tolerance of aerial spraying
garden refuse disposal
planting indigenous spp.
not releasing pets into the wild
• These limited actions will make a difference to the
biodiversity of their countries, and will assist those
involved in management.
EARLY DETECTION
• Should be based on a system of regular surveys.
• Some surveys will need to focus on specific target species
known to be invasive under similar conditions, or species that
have been successfully eradicated before.
• A crucial part of early detection is a contingency plan, which
determines the action to be taken when an alien species has
been found.
• The longer an alien species goes undetected, the less
opportunity there will be to intervene, the fewer options will
remain for its control or eradication, and the more expensive
any intervention will become!
ASSESSMENT
depends on the:
management goal
extent and quality of the area
the invasive target spp.
the indigenous spp. under threat
• The management goal is usually the conservation or
restoration of intact ecosystems that support the delivery of
ecosystem services.
• Assessment will determine which eradication and control
options should be taken, if any based on the likelihood of
success, cost effectiveness and any potential detrimental
impacts.
ASSESSMENT cont.
• In South Africa, scientists are developing a “prioritization
system” for managing invasive alien plants (Robertson et al,
2003).
• This system is a means of assessing IAS, and directing control
or research options and funding towards the species that are
of most concern.
• Independent assessments are made per species on the basis
of invasiveness, spatial characteristics, potential impact,
potential for control, and conflicts of interest.
STRATEGIES: ERADICATION, CONTAINMENT,
CONTROL AND MITIGATION
• ERADICATION is the elimination of the entire population of
an alien species in the managed area.
• Eradication should only be attempted if it is feasible.
• If eradication of the invasive species is achieved, it is more
cost-effective than any other measure of long-term control.
• Early detection and rapid action, persistent efforts and good
understanding of invasion ecology can lead to successful
eradication of alien invasive species
STRATEGIES: ERADICATION, CONTAINMENT,
CONTROL AND MITIGATION cont.
Methods of ERADICATION vary, depending on the species:
hand-pulling
mechanical control
burning
fencing to exclude animals
electrical currents to control fish movements
STRATEGIES: ERADICATION, CONTAINMENT,
CONTROL AND MITIGATION cont.
chemical control
toxic baits against
invertebrates
spraying insecticides/herbicides
Control of disease in wildlife
Increase in willingness
to use herbicides
eg. mountain gorillas against
measles & chips against polio
biopesticides
eg. Bacillus thuringiensis (BT) sprayed against insect pests
STRATEGIES: ERADICATION, CONTAINMENT,
CONTROL AND MITIGATION cont.
Hunting of invasive vertebrates
(mammals and birds)
Habitat management e.g.
grazing and prescribed
burning
OTHER
METHODS OF
ERADICATION
STRATEGIES: ERADICATION, CONTAINMENT,
CONTROL AND MITIGATION cont.
• Small populations of invasive species can sometimes be
ERADICATED if action is immediate.
• eg. rabbits in Haleakala National Park in Hawaii (Loope et
al, 1992) and a fire ant in Galapagos (Abedrabbo, 1994).
• However, once reproduction, dispersal and adaptation
have occurred, control becomes problematic and
eradication highly unlikely.
STRATEGIES: ERADICATION, CONTAINMENT,
CONTROL AND MITIGATION cont.
• CONTAINMENT aims to restrict the spread of an alien
species and to contain the population in a defined
geographic range.
• The methods used for containment are the same as those
described for prevention, eradication and control.
• Usually the population is suppressed along the border of a
defined area, and individuals spreading beyond this are
eradicated.
• Introductions into areas outside the defined containment
area are prevented
STRATEGIES: ERADICATION, CONTAINMENT,
CONTROL AND MITIGATION cont.
• CONTROL aims for the long-term reduction in density and
abundance to below a pre-set acceptable threshold.
• The weakened state of the invasive species allows indigenous
species to regain ground and possibly further diminish the
abundance of the alien species.
• Control methods include those in eradication, as well as
biological control. All control methods, except biological
control, need long-term funding and commitment (GISP, 2004).
STRATEGIES: ERADICATION, CONTAINMENT,
CONTROL AND MITIGATION cont.
Conventional CONTROL
methods for animals include:
Baiting in Australia done
using 1080 – a natural poison
found in indigenous plants
baiting
shooting
trapping
fencing
used to control feral animals
(goats, pigs, horses etc)
Indigenous herbivores have
evolved a high tolerance to it
guidelines for humane treatment
and removal should be adhered to
STRATEGIES: ERADICATION, CONTAINMENT,
CONTROL AND MITIGATION cont.
• MITIGATION the last resort is to “live with” this species in
the best achievable way, and mitigate impacts on biodiversity
and endangered species.
• It differs from containment and control in that the activity
undertaken does not directly affect the invasive species in
question, but rather focuses on affected indigenous species
(GISP, 2004).
BIOLOGICAL CONTROL
• Biological control is the introduction of a natural enemy
(predator, parasite or disease) to control invasive alien
species, often from the IAS’ indigenous range.
• Biological control can be a self-sustaining and cost-effective
tool for the management of invasive species (Fowler et al,
2000).
• However, a biological control agent is also an introduced
species, and many survive without controlling the target pest.
Some may attack non-target organisms.
BIOLOGICAL CONTROL cont.
• Numerous biological control introductions have adversely
affected non-target indigenous species.
• Risk assessment for biological control is difficult because of
how hard it is to predict community- and ecosystem-wide
impacts of introduced species and because introduced
species disperse and evolve (Simberloff and Stiling, 1996).
• Many early biological control projects used generalized
predators that subsequently attacked non-target species
(Simberloff, 1992).
the emergence of naturally
occurring herbicide-resistant
canola plants descended from
GM parents (Ellstrand, 2001)
the proposed field trials of a
GM insect (caged populations
of the pink bollworm Pectinophora
gossypiella), itself an alien
pest of cotton (UCS, 2001)
GMO Atlantic salmon in aquaculture
(escapes of thousands of fish
per year are documented) and where
the genetic impacts of escaped
farmed fish on rare wild populations
are unclear (Naylor et al, 2000)
• As biotechnology develops, scientists hope for new ways to
control invasive species for which there are few other options.
But controversy is common in areas where issues related to
invasive species and genetically modified organisms (GMOs)
overlap (UCS, 2001). Recent debates involve:
BIOLOGICAL CONTROL cont.
BIOLOGICAL CONTROL cont.
Advantages
Disadvantages
Target specificity
Initially high research costs
Continuous action
Relatively long time until impacts
noticeable
Long-term cost-effectiveness
Uncertainty over ultimate scale of
impact
Often a gradual effect, so
environmentally non-intrusive
Uncertain “downstream” effects
(difficult to predict and measure)
Self-dispersing (self-sustaining)
Lack of control of agents
Irreversible
Table 1. Advantages and disadvantages of classical
biological control (Fowler et al, 2000)
BIOLOGICAL CONTROL cont.
• Successful biocontrol is not expected to eradicate IAS, but it
will reduce their numbers, growth and reproduction. Some
examples of successes in biocontrol include:
• introduction of the Australian ladybird into California to
control the cottony cushion scale
• control of cassava mealybug in Africa with an encyrtid wasp
from South America
• control of salvinia with a weevil Cyrtobagous salviniae
BIOLOGICAL CONTROL cont.
• control of Opuntia spp. (prickly pear) with the moth
Cactoblastis cactorum
• the virus myxomatosis, released in 1950 was believed
to have killed more than 90% of feral rabbits in six
months
• the fungus (Uromycladium tepperianum) that galls the
buds of the Port Jackson willow (Acacia saligna)
• the weevil (Melanterius ventralis) and a wasp
(Trichilogaster acaciaelongifolia) released in to attack
long-leaved wattle (Acacia longifolia)
EXAMPLES OF FAILED BIOLOGICAL CONTROL
• control of mahogany shoot-borer, world-wide
• control of western flower thrip in Australia
• biocontrol of lantana has been a success in Hawaii, but a
failure in Australia
• introduction of cane toad in Australia in 1935 to control two
insect pests of sugar cane. The cane toad itself became an
invasive species
• introduction of the rosy wolf snail (Euglandia rosea) to Hawaii
to control the previously introduced giant African snail
(Achatina fulica), which led to extinctions of at least 15
endemic snail species on Oahu, and 24 endemic snail species
on Mauritius
vs
WHY DOES BIOLOGICAL CONTROL FAIL?
Failure in biological control can be attributed to the failure of an
unsuccessful agent or to a whole programme in which the density
of the target weed has not declined.
Agents fail when:
(1) they do not become established,
(2) they become established but remain at low density or
geographically restricted,
(3) they become established and reach high density but do not
have a negative impact on the density of the target species, or
(4) when the biocontrol agent attacks non-target hosts.
INTEGRATED PEST MANAGEMENT
• Satisfactory control of invaders is usually only achieved when
several complementary methods are carefully integrated
(Richardson, 2001).
• The term “Integrated Pest Management” implies the integration of
approaches and methods into a pest management system, which
takes into consideration the ecology of the environment and all
relevant interactions that pest management practices may have
on the environment.
INTEGRATED PEST MANAGEMENT cont.
• Since IPM considers all applicable methods, it is assumed that
emphasis on chemical methods may be reduced when effective
non-chemical alternative methods are available.
• IPM consists of approaches, methods and disciplines to
minimize environmental impact, minimize risks, and optimise
benefits.
• An integrated approach to IAS management is required, with a
range of methods to deal with the problem. It is important to
accumulate the information available, assess all potential
methods (as above), and use the best method or combination of
methods to achieve the target level of control.
INTEGRATED PEST MANAGEMENT cont.
Lamreys attached
to a trout
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• For example, in response to the sea lamprey problem in the
Great Lakes, the Great Lakes Fishery Commission developed a
programme that combined a number of methods for
management: barriers to block the migration of adult sea
lamprey upstream to spawn, a selective lampricide (TFM) to kill
larval sea lamprey; sterilization of male sea lampreys; and the
potential use of pheromones to lure adult lamprey into traps
MONITORING AND FOLLOW-UP
• Monitoring and follow-up is an essential last
step to any management, to determine
whether the programme is/was successful and
the management goal reached
Chapter 1 Definitions
Chapter 2 History, globalisation and GMOs
Chapter 3 The human dimension
Chapter 4 Pathways of introduction
Chapter 5 Characteristics of invasive alien species
Chapter 6 The ecology of biological invasions
Chapter 7 Impacts of invasive alien species
Chapter 8 Invasive species management
Next
Chapter 9 Predicting invasive spp. occurrence and spread
Chapter 10
Chapter 11
Chapter 12
I hope that you found chapter 8 interesting and that you
will enjoy chapter nine.