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)

Coulpe in bed, secret lover hiding. (Photo by Peter Cade/Getty Images)

A skydiver dressed as Santa Claus prepares to leap out of a plane as 155 tandem skydivers set a new Guinness World Record over eight hours, over the Australian city of Wollongong, December 17, 2016. (Photo by Jason Reed/Reuters)

In northwest Russia, in a small village called Alekhovshchina, Nadia Sablin's aunts spend the warmer months together in the family home and live as the family has always lived, chopping wood to heat the house and making their own clothes. Sablin's book of photographs, “Aunties: The Seven Summers of Alevtina and Ludmila”, is published by Duke University Press. Here: “Two-Handed Saw, 2014”. (Photo by Nadia Sablin)

One of the most significant challenges related to cancer in Nepal is the lack of awareness around the prognosis of the disease, as many patients, their families and even healthcare professionals consider cancer to be an incurable disease at any stage. This results in significant delays in bringing patients to hospitals, and high rates of advanced stage cancers and mortality. (Photo by Omar Havana)

Figurines representing French Brigade of Lancers are seen on a 40-square-metre miniature model of the June 18, 1815 Waterloo battlefield, in Diest, Belgium, in this picture taken on April 29, 2015. Waterloo enthusiast Willy Smout said he spent 40,000 hours and around 150,000 euros over the past 40 years, to recreate the battlefield as closely as possible in a purpose-built room in his house. (Photo by Francois Lenoir/Reuters)

Buns are stamped the Chinese characters “Ping An”, meaning peaceful and safe, inside a bakery, at Hong Kong's Cheung Chau island, China May 17, 2015, ahead of the upcoming Bun Festival on May 25. The festival celebrates the islanders' deliverance from famine many centuries ago and is meant to placate ghosts and restless spirits. (Photo by Tyrone Siu/Reuters)

Doris Dean of Chicago, Ill., sits with her gun shortly after she won a 50 meter, 40-shot event for women with a perfect 400 score at the National Rifle Association (NRA) matches at Camp Perry, near Toledo, Ohio, September 7, 1941. (Photo by AP Photo/DW)