• Alarmingly, nearly one-fifth (19%) of extant vertebrate species are threatened with extinction (Hoffmann et al., 2010); the true value of this estimate falls between 16% (assuming no Data Deficient species are threatened) and 33% (assuming all Data Deficient species are threatened).

• Habitat destruction is the most widespread threat to mammals, affecting 37% of all extant and recently extinct species, followed by overexploitation (17%), invasive species (6%), pollution (4%), and diseases (2%).

• Spending on less endangered species meant a shortterm loss for a long-term gain; in the short-term, there would be relatively fewer species extant when compared with spending on more endangered species, whereas at longer time periods, there would be relatively more species extant (Fig. 2).