Nearly three-fifths of all animals with a backbone -- fish, birds, amphibians, reptiles and mammals -- have been wiped out since 1970 by human appetites and activity, according to a grim study released Thursday.

On current trends, stocks of global wildlife could plunge two-thirds by 2020, an annual decline of two percent, conservation group WWF and the Zoological Society of London warned in their joint biennial Living Planet report.