Global wildlife populations will decline by 67% by 2020 unless urgent action is taken to reduce human impact on species and ecosystems, warns the biennial Living Planet Index report from WWF (World Wide Fund for Nature) and ZSL (Zoological Society of London). From elephants to eels, here are some of the wildlife populations most affected by human activity. Here: The maned wolf is among the large mammals in the Brazilian Cerrado that are threatened by the increasing conversion of grasslands into farmland for grazing and growing crops. (Photo by Ben Cranke/Nature Picture Library/Alamy Stock Photo)

A four-year-old bulldog named Goldie wearing spectacles and a nightcap. (Photo by Fox Photos/Getty Images). 9th January 1960

1974: American boxer Muhammad Ali, formerly Cassius Clay, strikes an aggressive pose at a press conference on November 29, 1974. (Photo by Harry Dempster/Express/Getty Images); American actor Will Smith at the Royal Premiere of the film Ali in London on December 11, 2001. Smith starred as Muhammad Ali in the film. (Photo by Dave Hogan/Getty Images)

#1: Superman. According to McAfee, 16.50% of Web searches for Superman led to sites with viruses and other malicious software. Pictured here: The Superman costume that was worn by Christopher Reeve in “Superman: The Movie” on display at Profiles In History in Calabasas, northwest of downtown Los Angeles, on July 19, 2012 in California. (Photo by Frederic J. Brown/AFP Photo)

Young man making the O.K. sign. (Photo by George Marks/Retrofile/Getty Images). Circa 1950s

A Palestinian man carries a lion cub as he shows it to children in Rafah refugee camp in the southern Gaza Strip on December 4, 2019. (Photo by Ibraheem Abu Mustafa/Reuters)

An elephant with a shackled leg is pictured at the Hanoi Zoo in Hanoi on August 16, 2023. Legs in iron chains and unable to roam freely, the treatment of two elderly elephants at the Hanoi public zoo has drawn outrage from animal lovers across Vietnam. (Photo by Nhac Nguyen/AFP Photo)

Children play football on March 10, 2022 on a concrete slab in Mukuru Kwa Njenga informal settlements, where structures have been demolished in November 2021 to pave the way for the construction of the Nairobi Expressway. (Photo by Simón Maina/AFP Photo)