THE THEMATIC ASSESSMENT REPORT ON INVASIVE ALIEN SPECIES AND THEIR CONTROL
32SUMMARY FOR POLICYMAKERS
species has been both successful and cost-effective 
for terrestrial and closed water systems, especially in 
biogeographically isolated areas such as small islands 
and lakes (well established) {5.3.1, 5.3.2, 5.5.4}. While 
some management approaches can be applied at multiple 
scales across terrestrial and closed water systems (well 
established) {5.1.1, 5.3.1.4.}, pathway management (e.g., 
ballast water and biofouling; Box SPM.2) is by far the 
Management objectives
Prevention and 
preparedness Early detection and 
eradication
Containment Control and 
restoration
Absent Establishment Spread Widespread
Introduction
Lag phase
TIME
Conceptual invasion curve without management
Conceptual invasion curves with management
AREA IMPACTED
A) Terrestrial and closed water systems
Absent Establishment Spread Widespread
Absent Establishment Spread Widespread
Managing pathway
Management target - Relative importance (white highest)
Managing species
Managing site/catchment
Managing ecosystem/catchment
Actions to achieve objective
Border
biosecurity/
quarantine
Preparedness
Risk assessment, prioritization & decision-making
Surveillance and monitoring
Chemical, physical, and biological controls
Adaptive management
Management objectives
AREA IMPACTED
Absent Establishment Spread Widespread
Lag phase
TIME
Conceptual invasion curve without management
Conceptual invasion curves with management
Prevention and 
preparedness Early detection for 
low-mobility organisms, 
eradication
Post-establishment
management is
largely ineffective
B) Marine and connected water systems
Introduction Absent Establishment Spread Widespread
Absent Establishment Spread Widespread
Management target - Relative importance (white highest)
Managing pathway
Managing species
Managing sites
Border
biosecurity
Risk assessment, prioritization and decision-making
Surveillance and monitoring
Actions to achieve objective
Preparedness
Figure SPM 6 Conceptual diagram of management-invasion continuum. 
Management objectives panels A and B show the generalized invasion curve without management and the expected changes 
in the trajectory of the invasion curve with appropriate management actions in (A) terrestrial and closed water systems (including 
lakes and coastal systems such as salt marshes) and (B) marine and connected water systems (including rivers). Post-establishment 
management actions (such as containment and control) are not shown in panel B as they are generally not achievable in such 
systems. In a management context, the first detection (introduction point), lag phase and exponential spread phase are important 
points at which to implement an early detection and rapid response management plan. This figure is conceptual, and the curves do 
not represent actual population dynamics of invasive alien species. In the Management target panels, the white boxes indicate 
the optimal management options at each stage of the biological invasion process. The colour gradient of the managing pathway, 
managing species, managing site and managing ecosystem boxes show how the relative importance of each changes as a biological 
invasion progresses (managing ecosystems is not applicable in marine and connected water systems). In the Actions to achieve 
objective panels, the white boxes indicate the typical management actions needed to achieve each management objective. 
SUMMARY FOR POLICYMAKERS
19SUMMARY FOR POLICYMAKERS
BACKGROUND
C. Invasive alien species and their negative impacts can 
be prevented and mitigated through effective management