Since the 16th century, at least 680 species of vertebrates have become extinct.[13] By 2016, among mammals, more than nine percent of livestock breeds were extinct, and another 1,000 breeds are threatened with extinction.[14] The authors have coined the expression "dead species walking" for the more than 500,000 species that are not yet extinct but, due to changes in, or reduction of, their habitats, have no chance of long-term survival.[15]