THE THEMATIC ASSESSMENT REPORT ON INVASIVE ALIEN SPECIES AND THEIR CONTROL
35SUMMARY FOR POLICYMAKERS
although there are examples of successful eradication of 
invasive alien plant species with limited distributions (well 
established) {5.5.3}. Also, rapid response to incursions, 
detected early, of some invertebrates have been successful, 
for example, eradication of Solenopsis invicta (red imported 
fire ant) in New Zealand (well established) {Box 5.14}. There 
are examples of larger-scale eradications, such as Ondatra 
zibethicus (muskrat) and Myocastor coypus (coypu) from the 
United Kingdom (well established) {5.5.3}. However, 
large-scale eradications are difficult and unlikely to be 
feasible in many cases (well established) {5.5.3}. In addition 
to the extent of the area invaded, the success of eradication 
programmes depends on the support and engagement of 
relevant stakeholders and Indigenous Peoples and local 
communities (well established) {5.4.2.2.a, 5.5.3, 5.6.2.1, 
5.6.2.2}. Eradication programmes are aided by a rapid flow 
of information on the extent and location of invasive alien 
species, which can be provided by people who live nearby 
(well established) {5.4.2.2.a, 5.5.3}. Evidence suggests that 
there have been no fully successful eradication programmes 
for established invasive alien species in marine ecosystems 
(well established) {5.5.3}. While eradication programmes can 
only be achieved with access to upfront cost, they are 
generally cheaper than long-term and permanent control 
cost and impacts (well established) {5.5.3}.
C20 When eradication is not possible for different 
reasons, invasive alien species can be contained 
and controlled, particularly in terrestrial and closed 
water systems (well established) {5.4.3, 5.4.4, 
5.5.4, 5.5.5}. There are many examples of successful 
containment and control of invasive alien species in 
terrestrial and closed water systems and aquaculture (e.g., 
containment of Styela clava (Asian tunicate) invading the 
aqua-cultured blue mussel in Canada) (well established)
{5.5.4}, but most attempts in marine and open water 
ecosystems have been largely ineffective (established but 
incomplete) {5.5.4, 5.5.5}. Containment of invasive alien 
species can be achieved with physical, chemical and 
biological control actions or in combination (Table SPM.1)
(well established) {5.4.3.2, 5.5.4}. Physical and chemical 
control options are mostly effective at a local scale but can 
also be effective at larger scales; these control options are 
limited by labour costs and generally provide short-term 
suppression but not sustained control (well established)
{5.4.3.2.a}. Furthermore, chemical control may have 
non-target impacts, needs to be implemented under 
regulatory compliance requirements and has decreasing 
societal acceptability (well established) {5.4.3.2.b}. Biological 
control has been very effective in controlling some invasive 
alien plants, invertebrates and, to a lesser extent, plant 
microbes and a few invasive alien vertebrates, but it may 
have non-target impacts if not well regulated (well 
established) {5.5.5.3}. To reduce the risks of unintended 
consequences, including non-target impacts, from biological 
control, international standards and risk-based regulatory 
frameworks (developed under the International Plant 
Protection Convention) have been applied and continue to 
be effective across many countries (well established) {5.5.2}. 
The use of biological control for invasive alien plants and 
invertebrates has been successful in more than 60 per cent 
of documented cases (Box SPM.3), with one third of the 
alien plant species requiring no further form of control, while 
also leading to benefits to biodiversity and ecosystem 
resilience (well established) {5.5.5.3}. Classical biological 
control to suppress invasive alien species populations at 
landscape scales has been effectively practised for more 
than 100 years (well established) {5.5.5.3}.
C21 Adaptive management, including ecosystem 
restoration, can improve the management of 
invasive alien species and support the recovery of 
nature's contributions to people in terrestrial and 
closed water systems (well established) {5.3.3, 
5.4.4.3a, 5.5.6, 5.7}. The integration of site- and/or 
ecosystem-based management, including ecosystem 
restoration, can improve management outcomes, enhancing 
ecosystem function and resilience to environmental change, 
including future invasive alien species, especially under 
climate and land-use change (Box SPM.4) (well 
established) {5.3.1, 5.3.2, 5.4.3, 5.5.6, 5.6.1.3}. The 
success of any applied adaptive site- or ecosystem-based 
Box SPM 3 Classical biological control of Mikania micrantha (bitter vine): an example of 
effective suppression of a widespread invasive alien species.
Classical biological control uses host-specific natural enemies 
(biological control agents) of invasive alien species (target) to 
suppress and control such species. Mikania micrantha (bitter 
vine), a native species of Central and South America, is one of 
the highest-impact fast-growing {2.5.2.1} invasive alien plants 
within the agricultural systems and natural and planted forests 
of the Asia-Pacific region {Box 5.21}, affecting the livelihoods of 
farmers and rural communities, including women {4.5.1, 4.6.1}. 
In the native range of Mikania micrantha, a rust fungus (Puccinia 
spegazzinii) specific to this invasive alien plant causes necrosis of 
leaves and cankers on the stem and petioles {Box 5.21}. Starting 
in 2006, Puccinia spegazzinii was introduced as a classical 
biological control agent and established in five countries in the 
Asia-Pacific region, where it has provided effective control of 
Mikania micrantha {Box 5.21}. However, in India the rust fungus 
failed to survive in the field following introduction {Box 5.21}.
35SUMMARY FOR POLICYMAKERS
19SUMMARY FOR POLICYMAKERS
BACKGROUND
Table SPM 1 Objectives and actions for managing biological invasions. 