About 71% of the birds, 87% of the reptiles, and 95% of the frogs are unique to Australia. Seven of the more than 755 known species of birds have become extinct since the beginning of European settlement, and another 35 are endangered or vulnerable. Of mammals, 20 are extinct and 63 are threatened. Of the 22,100 species of plants in Australia, more than 90 % occur naturally there. Some 850 species are threatened with extinction, and 83 have become extinct since the beginning of European settlement. around 2,000 plant species are introduced, or nonnative.