Table 1.

Number of native, nonnative, extirpated, and threatened species at the realm and world scales

	No. basins	No. native species	No. species occurring in basins outside their native range*	Translocated nonnative species, %	No. species encountering at least one extirpation	Species evaluated by the IUCN, %	No. threatened species	Threatened species among species evaluated, %
Afrotropical	109	2,333	44	59	29	40	237	25
Australian	179	404	52	37	4	19	30	40
Nearctic	207	694	224	79	47	23	96	60
Neotropical	155	3,900	70	61	11	2	35	43
Oriental	59	1,606	56	48	27	3	24	56
Palearctic	345	1,011	169	82	29	25	110	44
World	1,054	9,722	444	75†	145	16	524	35

IUCN, International Union for Conservation of Nature.

*Translocated species (nonnative species introduced in river basins belonging to a realm where they are present as native) and exotic species (nonnative species introduced in a realm where they are not present as native).

^†Only 25% (111 species) have been introduced in at least one realm where they historically did not occur.