THE THEMATIC ASSESSMENT REPORT ON INVASIVE ALIEN SPECIES AND THEIR CONTROL
34SUMMARY FOR POLICYMAKERS
most effective option for managing biological invasions in 
marine and connected water systems, and can be achieved 
by enhanced international and regional cooperation (well 
established) {5.5.1, 6.3.2.2}.
C16 There are effective decision-making 
frameworks and tools that can support 
management of biological invasions (Table SPM.1) 
(well established) {5.2.1, 5.2.2}. Frameworks and tools 
have been developed based on evidence from practice, 
science and other knowledge systems, including those of 
Indigenous Peoples and local communities. These can 
underpin impact assessment, monitoring and prioritization of 
intentional and unintentional introduction pathways, species 
and sites for the successful management of biological 
invasions (well established) {5.2.2}. Although many 
knowledge and data gaps exist (Table SPM.A1), the tools 
enable management actions to proceed under a risk 
assessment and risk management framework in line with a 
precautionary approach, as appropriate, using inclusive 
decision-making that leads to the review of all the measures 
(well established) {5.2.2.1, 5.2.2.3, 5.2.2.4, 5.3.3, 6.4.1}. 
Decision-making may be challenged by multiple sources of 
uncertainty, such as projections in other drivers of change, 
which can be recognized, quantified and documented to 
contextualize decisions (well established) {5.6.2.5}. Many 
sources of accessible literature and information (including 
open-access data), analytical tools and other types of 
knowledge can be used to support decision-making for all 
countries, which could lead to coordinated management 
outcomes globally (Table SPM.A3) (established but 
incomplete) {6.6.1.5}.
C17 Preventing the introduction of invasive alien 
species is the most cost-effective management 
option (Figure SPM.6) (well established) {5.5.1}. 
Prevention measures through pathway management, 
including strictly enforced pre-border quarantine, import 
controls and border biosecurity, have increased interception 
rates and slowed the rate of invasive alien species arriving 
and establishing globally (well established) {5.4.3.1, 5.5.1}. 
For example, in Australasia, the number of interceptions of 
Halyomorpha halys (brown marmorated stink bug), 
recognized as a major threat in the agricultural sector, have 
declined following implementation of a systems-based 
pathway management approach (well established) {5.5.1}. 
Measures to address escape from confinement are also 
necessary (established but incomplete) {5.3.1.1}. It is, 
however, difficult to prevent further natural dispersal of 
invasive alien species from a previously invaded range (well 
established) {5.5.1, Box 1.6}. Prevention is important on 
islands and in ecosystems where eradication poses 
significant technical challenges (well established) {5.3.2}. 
Effective prevention measures depend on adequate and 
sustained funding, capacity-building, technical and scientific 
cooperation, transfer of technology, monitoring, and relevant 
and appropriate biosecurity legislation and enforcement, 
which is supported by strong infrastructure, quarantine and 
inspection facilities, including diagnostic support services 
(well established) {5.4.2, 5.6.2, 5.6.2.2, 5.7}. Risk 
assessment could be used by businesses to engage 
different sectors in the prevention and management of 
biological invasions (established but incomplete) {5.6.2.1}. 
Adoption of regulated species lists with explicit prohibition of 
or permission for the importing of specific alien species, 
underpinned by risk analysis, has been an effective 
prevention strategy (well established) {5.6.2.1, 6.3.1.4}. It is 
estimated that nearly 70 per cent of marine invasive alien 
species established worldwide were introduced via
biofouling (established but incomplete) {5.5.1}.
C18 When prevention fails or is not possible, 
preparedness, early detection and rapid response 
are effective at reducing rates of invasive alien 
species establishment in terrestrial and closed 
water systems, and critical for marine and 
connected water systems (well established) {5.4.2, 
5.5.1, 5.5.3, 5.5.2, 5.6.3.3}. Horizon scanning and risk 
analysis are examples of the many decision-support tools 
used to identify and prioritize emerging invasive alien 
species to support preparedness (well established) {5.2}. 
Such tools can inform the development of rapid response 
plans in advance of an incursion to guide action effectively 
following the detection of priority invasive alien species (well 
established) {5.2.2.1.a, 5.2.2.1.b, 5.5.1}. Early detection of 
invasive alien species can enable rapid intervention to 
contain and eradicate invasive alien species before they 
spread (well established) {5.1.1, 5.3.1.1, 5.5.2}. General 
surveillance strategies (e.g., through citizen science, sentinel 
sites, and remote sensing) for detecting new invasive alien 
species can also underpin effective preparedness 
(established but incomplete) {5.3.1.1, 5.4.2.1.a, 5.4.2.2.a, 
5.5.2, Box 6.20}. For example, in Africa, Asia and Latin 
America, the PlantwisePlus programme assists smallholder 
farmers with the identification of pests and damaged crops, 
contributing to early detection of invasive alien species 
outbreaks (well established) {5.5.2}.
C19 Eradication has been successful and costeffective for some invasive alien species, 
especially when their populations are small and 
slow-spreading in isolated ecosystems such as 
islands (established but incomplete) {5.5.3}. Over the 
last 100 years, there have been 1,550 documented 
examples of eradication on 998 islands, with success cited 
in 88 per cent of cases (well established) {5.5.3}. One of the 
many examples is French Polynesia, where Rattus rattus
(black rat), Felis catus (cat), Oryctolagus cuniculus (rabbit) 
and Capra hircus (goat) have been successfully eradicated 
(well established) {Box 5.8}. Eradication of invasive alien 
plants is particularly difficult because of the longevity of 
dormant seeds that can persist in soil (i.e., soil seed bank), 
SUMMARY FOR POLICYMAKERS
19SUMMARY FOR POLICYMAKERS
BACKGROUND
Table SPM 1 Objectives and actions for managing biological invasions. 