THE THEMATIC ASSESSMENT REPORT ON INVASIVE ALIEN SPECIES AND THEIR CONTROL
9
Figure SPM 1 Key concepts within the biological invasion process.7
Invasive alien species are one of the main direct drivers of change in nature. The biological invasion process comprises the following 
stages: transport, introduction, establishment and spread (or dispersal). Definitions of native, alien, established alien and invasive alien 
species are provided. Indirect and other direct drivers of change facilitate biological invasion.
7. This assessment acknowledges that national and local legislation to 
address biological invasions differ between countries and may include 
different definitions appropriate to specific national and local contexts.
Biological invasion - a process that transports (moves) and introduces a species outside of its natural range, 
"
intentionally or unintentionally by human activities to new regions where it may become established and spread."
1. Transport - Human activities 
move a species, intentionally 
or unintentionally, through
introduction pathways 
beyond barriers that define
its natural range
2. Introduction - Arrival at a new location 
outside of its natural range through 
human activities
3. Establishment - Production of a viable, 
self-sustaining population
4. Spread - Dispersal 
and/or movement in a new
region or range
Invasive alien species - A subset of established 
alien species that spread and have a negative 
impact on biodiversity, local ecosystems and
species. Many invasive alien species also have 
impacts on nature's contributions to people 
(embodying different concepts, such as 
ecosystem goods and services and nature's gifts)
and good quality of life
Introduction pathways - The many ways in which
species are moved from one location to another by 
human activities that give rise to an intentional
or unintentional introduction
Drivers - Factors that directly or indirectly cause 
changes to nature and may facilitate biological invasion
Negative impacts - Negative changes to nature, 
nature's contribution to people and/or good quality 
of life caused by invasive alien species
Biological 
invasion process 
Established alien species - A subset of alien 
species that have produced a viable, selfsustaining population and may have spread
Alien species - A species whose presence in a 
region is attributable to human activities that have 
enabled it to overcome the barriers that define 
its natural range
Native species - A species (animal, plant or 
other organism) within its natural range, including 
shifting its range, without human involvement
THE THEMATIC ASSESSMENT REPORT ON INVASIVE ALIEN SPECIES AND THEIR CONTRO
The thematic assessment report on
INVASIVE ALIEN SPECIES
AND THEIR CONTROL
DEFINITIONS, CONCEPTS
AND THE CONTEXT OF 
THE ASSESSMENT