global extinctions, and are the only driver in 16 per cent of 
the documented global animal and plant extinctions. Biotic 
homogenization, whereby biological communities around the 
world become more similar, is a major negative impact of 
invasive alien species, with consequences for the structure 
and functioning of ecosystems. Changes in the properties 
of ecosystems, such as soil and water characteristics, 
account for more than a quarter of documented impacts. 
The magnitude and types of impacts vary for different 
invasive alien species and across ecosystems and regions. 
The majority of documented global extinctions attributed 
mainly to invasive alien species have occurred on islands 
(90 per cent), and local extinctions account for 9 per 
cent of documented impacts of invasive alien species on 
islands. Some areas, despite being protected for nature 
conservation or being remote, are also vulnerable to the 
negative impacts of invasive alien species.
SUMMARY FOR POLICYMAKERS
The thematic assessment report on
INVASIVE ALIEN SPECIES
AND THEIR CONTROL
KM-A1 People and nature are threatened by 
invasive alien species in all regions of Earth 