Global wildlife has declined by two-thirds in the past 50 years

Global wildlife populations have declined by more than two-thirds in nearly 50 years, according to a new report from the World Wildlife Fund. The report looked at more than 20,000 animals from more than 4,000 different species around the world. Population sizes of mammals, birds, fish, amphibians and reptiles have declined by an average of 68 percent since 1970. The report warns that this "catastrophic decline" shows no signs of slowing and that humans are destroying nature at an "unprecedented rate".