THE THEMATIC ASSESSMENT REPORT ON INVASIVE ALIEN SPECIES AND THEIR CONTROL
47SUMMARY FOR POLICYMAKERS
APPENDIX 2
Synthesis of knowledge 
and data gaps
CATEGORY GAP IMPLEMENTATION 
CHALLENGE
POTENTIAL GAIN
Estimated research costEstimated scientific challengeFor taking management actionFor better understanding biological invasions
Gaps in 
biomes, units 
of analysis and 
species groups
Incomplete or lack of inventories of invasive alien species in marine, 
tropical and Arctic ecosystems {2.5.2.1, 2.5.2.4, 2.5.2.5, 2.5.4}
Incomplete or lack of inventories of invasive alien microorganisms 
and invertebrates {2.3.1.11, 2.3.3.3}
Lack of understanding of the drivers of change that facilitate 
biological invasion for some animal groups (notably invertebrates), 
fungi and microbes {3.6.1}
Lack of understanding and synthesis of the impacts of invasive 
alien microbes {4.7.2}
Poor understanding of drivers of change that facilitate biological 
invasions in aquatic and marine systems {3.6.1}
Lack of data on successful restoration attempts in terrestrial and 
marine systems {5.5.6, 5.6.2.1}
Regional gaps 
in data and 
knowledge
Comparatively incomplete inventories of invasive alien species in 
Africa and Central Asia {2.4.2.5, 2.4.5.5}
Comparative lack of understanding of the drivers of change that 
facilitate biological invasions in developing economies {Box 3.12}
Lack of data and knowledge of the drivers of biological invasions in 
sub-Saharan Africa, tropical Asia and South America {3.6.1}
Incomplete data on the impacts of invasive alien species across 
Africa and Central Asia {4.7.2}
Interoperable 
data for 
monitoring 
invasive alien 
species and 
effects of drivers 
of biodiversity 
change
Lack of standardization of terminology for invasive alien species 
monitoring {2.4.4.5, 6.6.2.3, 6.6.2.7}
Lack of information on the role of indirect drivers, especially 
governance and sociocultural drivers, in affecting biological 
invasions {3.1.5, 3.6.1, Box 3.13}
Lack of understanding of the net effects of multiple interacting 
drivers in shaping and promoting biological invasions {3.5, Box 
3.10, 3.6.1, Box 3.13}
Lack of knowledge on interactions and feedback across drivers in 
promoting invasions {3.1.5, 3.6.1}
Table SPM A 1 Table of knowledge and data gaps 
Synthesis of the most important knowledge and data gaps identified and collated through the assessment. Confidence levels in the 
summary for policymakers were allocated with full consideration of the gaps listed in the table; closing those gaps would strengthen 
the understanding of biological invasions. Experts have assessed the estimated cost and scientific challenge of closing these gaps, as 
well as the potential gain in increasing understanding of and successfully tackling biological invasions globally (from very low to very 
high). The listed gaps may not be relevant at local or regional scales. 
SUMMARY FOR POLICYMAKERS
19SUMMARY FOR POLICYMAKERS
BACKGROUND
Figure SPM A 1 The four-box model for the qualitative communication of confidence. 