Invasive species management • 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). http://news.bbc.co.uk/media/images/39350000/jpg/_39350125_bush_ap.jpg
Management categories • 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 eradication control strategies follow-up mitigation biological control integrated pest management monitoring
Steps in the invasion process Generalized steps in the invasion process and their relationship to management of invasive species (adapted from Kolar and Lodge, 2001)
Prevention 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. 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.
What can the public do? • The general public can also do their bit to prevent introductions or further establishment of already introduced IAS. • These limited actions will make a difference to the biodiversity of their countries, and will assist those involved in management. not taking spp. across borders awareness tolerance of aerial spraying planting indigenous spp. garden refuse disposal not releasing pets into the wild
Early detection 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 ASSESSMENT • depends on the: • 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. management goal extent and quality of the area the invasive target spp. the indigenous spp. under threat
Assessment cont. 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 STRATEGIES: ERADICATION, CONTAINMENT, CONTROL AND MITIGATION • ERADICATIONis 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
Mechanical control STRATEGIES: ERADICATION, CONTAINMENT, CONTROL AND MITIGATION cont. Methods ofERADICATIONvary, depending on the species: hand-pulling mechanical control burning fencing to exclude animals electrical currents to control fish movements
Chemical control STRATEGIES: ERADICATION, CONTAINMENT, CONTROL AND MITIGATION cont. toxic baits against invertebrates chemical control Increase in willingness to use herbicides spraying insecticides/herbicides Control of disease in wildlife eg. mountain gorillas against measles & chips against polio biopesticides eg. Bacillus thuringiensis (BT) sprayed against insect pests
Other methods of eradication STRATEGIES: ERADICATION, CONTAINMENT, CONTROL AND MITIGATION cont. Hunting of invasive vertebrates (mammals and birds) Cultural methods e.g. crop rotation, tillage practices, barriers, hedgerows Habitat management e.g. grazing and prescribed burning OTHER METHODS OF ERADICATION
Eradication cont. 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.
Containment 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
Control 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).
Methods of control STRATEGIES: ERADICATION, CONTAINMENT, CONTROL AND MITIGATION cont. ConventionalCONTROL methods for animals include: trapping Baiting in Australia done using 1080 – a natural poison found in indigenous plants baiting shooting fencing Indigenous herbivores have evolved a high tolerance to it used to control feral animals (goats, pigs, horses etc) guidelines for humane treatment and removal should be adhered to
Mitigation 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 • 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. 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).
Biological control cont. BIOLOGICAL CONTROL cont. • 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: 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) the proposed field trials of a GM insect (caged populations of the pink bollworm Pectinophora gossypiella), itself an alien pest of cotton (UCS, 2001) the emergence of naturally occurring herbicide-resistant canola plants descended from GM parents (Ellstrand, 2001) Immuno-contraception is a new approach to biocontrol that controls fertility instead of killing the pests
Pros & cons of biological control BIOLOGICAL CONTROL cont. Table 1. Advantages and disadvantages of classical biological control (Fowler et al, 2000)
Biological control examples 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 weevilCyrtobagous salviniae
Biological control examples 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)
Failed biological control 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 biocontrol fail? 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 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. 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. INTEGRATED PEST MANAGEMENT cont. • 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 Lamreys attached to a trout http://www.genome.gov/Pages/News/Photos/Science/sealamprey_image.jpg
Monitoring and follow-up 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
Links to other chapters Next Chapter 1Definitions Chapter 2History, globalisation and GMOs Chapter 3The 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 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.