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 worker lays rails across the bed of a drained area of a lake used for the production of salt at the Sasyk-Sivash lake near the city of Yevpatoria in Crimea, October 5, 2014. The area has a long tradition of salt production, prepared from salt flats flooded with water from the Black Sea. (Photo by Pavel Rebrov/Reuters)

A motorcycle modified to run on rails is seen inside a tunnel connected to the Altiplano Federal Penitentiary and used by drug lord Joaquin “El Chapo” Guzman to escape, in Almoloya de Juarez, on the outskirts of Mexico City, July 15, 2015. U.S. law enforcement officials met with agents of the Mexican attorney general's office this week to share information related to the escape from prison of Guzman and coordinate efforts to apprehend him, a Mexican government official said on Wednesday. (Photo by Edgard Garrido/Reuters)

A menacing swarm of locusts that entered southern Israel earlier this week has been largely smitten, according to the Israeli government and local reports. But some of the insects' ilk may be back later this week. (Photo by Eliyahu Hershkovitz)

The newly-discovered gaseous planet Kepler-16b orbits it's two stars. NASA's Kepler Mission discoverd the world orbiting two Stars, the larger a K dwarf and the smaller a red dwarf. (Photo by NASA/JPL-Caltech/T. Pyle via Getty Images)

“The Sumatran tiger (Panthera tigris sumatrae) is a rare tiger subspecies that inhabits the Indonesian island of Sumatra. It was classified as critically endangered by IUCN in 2008 as the population is projected to be 441 to 679 individuals, with no subpopulation having an effective population size larger than 50 individuals, with a declining trend”. – Wikipedia

This photo taken on July 25, 2012 one of 14 preserved bodies of critically-endangered Sumatran tigers seized as members of the Indonesian national police and the special crime unit inspect the scene at a warehouse in Cibubur, south of Jakarta. Indonesian police seized 14 preserved bodies of critically-endangered Sumatran tigers in a raid on a house near Jakarta, a spokesman said on July 19. (Photo by Bay Ismoyo/AFP Photo)

The report, prepared by the Sustainable Development Solutions Network (SDSN) and the Earth Institute at Columbia University, showed Syria, Afghanistan and eight sub-Saharan countries as the 10 least happy places on earth to live. The top 10 this year were Denmark, Switzerland, Iceland, Norway, Finland, Canada, Netherlands, New Zealand, Australia, and Sweden. Denmark was in third place last year, behind Switzerland and Iceland. The bottom 10 were Madagascar, Tanzania, Liberia, Guinea, Rwanda, Benin, Afghanistan, Togo, Syria and Burundi. The United States came in at 13, the United Kingdom at 23, France at 32, and Italy at 50. Here: #8. NEW ZEALAND: A woman dives from a platform into a giant air bed at a park in Palmerston North September 29, 2011. (Photo by Marcos Brindicci/Reuters)