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 per cent, conservation group WWF and the Zoological Society of London warned in their joint biennial Living Planet report.