and global species extinctions (Figures SPM.2 
and 3) (well established) {4.3.1}. Invasive alien species 
have contributed solely or alongside other drivers of change 
to 60 per cent of recorded global animal and plant 
extinctions (established but incomplete) {Box 4.4, 4.3.1}, 
while invasive alien species are the only driver attributed to 
16 per cent of documented global extinctions (established 
but incomplete) {Box 4.4}. The majority of documented 
global extinctions (90 per cent) with invasive alien species as 
one of the major causes are reported from islands
(established but incomplete) {Box 4.4}. At least 218 invasive 
alien species have caused 1,215 documented local 
extinctions of native species across all taxa (Figure SPM.3)
(established but incomplete) {4.3.1}. Invasive alien species 
harm native species most often by changing ecosystem 
properties (27 per cent), for example soil and water 
characteristics, and through competition between species 
(24 per cent), predation (18 per cent) and herbivory (12 per 
cent) (established but incomplete) {4.3.1.3}. The majority of 
reports of the impacts of invasive alien species on native 
species document negative effects (85 per cent), primarily 
negatively impacting the growth, survival and reproduction 
of individuals, which lead to local population declines and 
local and global extinctions (well established) {4.3.1}. Some 
invasive alien species have a profound ecological impact 
that spans various levels, from individual species and 
communities to whole ecosystems, resulting in complex, 
undesirable and in some cases irreversible outcomes when 
the system has crossed a threshold beyond which 
ecosystem restoration is not possible (well established) {Box 
1.5, Box 4.12, 4.3.3}. For example, Castor canadensis
(North American beaver) and Magallana gigas (Pacific 
oyster) change ecosystem properties by transforming 
habitats, with cascading effects on a myriad of native 
species (well established) {4.3.2.1, Box 4.11}. On Christmas 
Island, the arrival of the invasive alien Anoplolepis gracilipes
(yellow crazy ant) caused the decline of the native Christmas 
Island Gecarcoidea natalis (red crabs), which resulted in the 
population explosion of the invasive alien Lissachatina fulica
(giant African land snail) (well established) {3.3.5.1}. 
Increased biotic homogenization (or loss of uniqueness) of 
biological communities is a major negative impact of invasive 
alien species (well established) {1.3.4}. The magnitude of the 
negative impacts of invasive alien species on nature 
depends on the context, and the factors that determine the 
highest magnitudes of impact are not well understood 
(established but incomplete) {Box 4.9, 4.3.2.1, 4.7.1}. For 
 <Section-header> A. Invasive alien species are a major threat to nature, 
nature's contributions to people, and good quality of li </Section-header> 

SUMMARY FOR POLICYMAKERS
19SUMMARY FOR POLICYMAKERS
BACKGROUND
A. Invasive alien species are a major threat to nature, 
nature's contributions to people, and good quality of li