THE THEMATIC ASSESSMENT REPORT ON INVASIVE ALIEN SPECIES AND THEIR CONTROL
30SUMMARY FOR POLICYMAKERS
RELATIVE IMPORTANCE
DIRECT ANTHROPOGENIC DRIVERS OTHER DRIVERS INDIRECT DRIVERS
Transport Introduction Establishment Spread
STAGES OF INVASION
Economic
Science and technology 
Policies, governance
and institutions
Land-/sea-use change
Extraction of natural 
resources 
Climate change
Invasive alien species
Sociocultural and 
social values
Demographic
Pollution
Biodiversity loss
Natural drivers
Minimal Minor Moderate Major Massive
Figure SPM 5 Relative importance of different drivers of change in nature in facilitating 
biological invasions across biomes per different stages of the biological invasion 
process (transport, introduction, establishment and spread), as determined 
through expert assessment, based on the evidence in chapter 3 {3.6.2}. 
These estimates are summarized across ecosystems and terrestrial biomes at the global scale. Drivers are classified according to the 
IPBES conceptual framework as direct or indirect drivers {3.1.3, Table 3.1}. Additionally, other drivers are included, namely biodiversity 
loss and natural drivers, as they can increase native ecosystem vulnerability or in other ways facilitate biological invasions {3.1.3}. 
Note that the role of invasive alien species as a driver refers to their role in facilitating other invasive alien species {3.3.5} and that 
this analysis focuses on the unintended consequences of policies, governance, institutions and technologies in facilitating biological 
invasions {3.2.4, 3.2.5}. The relative importance of drivers for each stage of the biological invasion process accounts for multiple, 
29SUMMARY FOR POLICYMAKERS
19SUMMARY FOR POLICYMAKERS
BACKGROUND
Box SPM 2 The International Convention for the Control and Management of Ships' 
Ballast Water and Sediments: an example of international collaboration to 
prevent biological invasions.