THE THEMATIC ASSESSMENT REPORT ON INVASIVE ALIEN SPECIES AND THEIR CONTROL
27SUMMARY FOR POLICYMAKERS
A GLOBAL DISTRIBUTION OF ESTABLISHED ALIEN SPECIES Established alien marine species
0 50 100 150 >200
0 6,000 12,000 >18,000
Established alien terrestrial and 
freshwater species
No data
Distributions of terrestrial data gaps
Few Many
B TEMPORAL TRENDS IN THE NUMBER OF ESTABLISHED ALIEN SPECIES ACROSS TAXA
0
500
1000
1500
2000
0
100
200
300
0
50
100
150
200
250
0
100
200
300
400
0
100
200
300
400
1500 1625 1750 1875 2015
0
100
200
300
1500 1625 1750 1875 2015
0
100
200
300
400
1500 1625 1750 1875 2015
0
1000
2000
3000
4000
5000
0
20
40
60
80
100
120
Mammals
ALIEN SPECIES
Birds Fishes
Africa
Americas
Asia and the Pacific
Europe and Central Asia
Insects Crustaceans Molluscs
Vascular plants
YEAR YEAR YEAR
Algae Fungi
Figure SPM 4 Global distribution and temporal trends in established alien species. 
(A) Total numbers of established alien species (terrestrial and freshwater) in the 18 IPBES subregions and marine ecoregions (marine) 
are indicated. White denotes missing information {2.2}. A gap analysis was conducted to identify data gaps for terrestrial regions, 
which are indicated in the inset {2.1.4, 2.2.3}. The data gap analysis could not be done for marine regions (white) and Antarctica 
(grey). (B) The temporal trends in the number of established alien species from 1500 to 2015 are shown for mammals, birds, fishes, 
insects, crustaceans, molluscs, vascular plants, algae and fungi, for the four IPBES regions {2.1.4, 2.4.1}. 
(Figure SPM.3) (established but incomplete) {2.2.1}. 
The number of alien species has been rising continuously for 
centuries in all regions (well established) {2.2.1} and is 
expected to continue increasing in the future (well 
established) {2.6.1}. Global exploration and colonialism 
beginning in 1500, with the associated movement of people 
and goods, and industrialization from 1850 resulted in the 
transport and introduction of alien species and were 
historically important. Increases in global trade since 1950 
have resulted in unprecedentedly high and increasing 
27SUMMARY FOR POLICYMAKERS
19SUMMARY FOR POLICYMAKERS
BACKGROUND
B. Globally, invasive alien species and their impacts are 
increasing rapidly and are predicted to continue rising in 
the future