蜜芽传媒

Only half of the world's vertebrate population is alive now compared to forty years ago, according to a joint report by the Zoological Society of London and the environmental group WWF. They say the reason for this dramatic decline is human activity, although some conservationists have questioned the study's methodology. Heather Sohl is WWF's Chief Adviser on Species.

(Photo: African elephants. Credit: WWF)