Thomas Thwaites, a 34-year-old researcher from London, has spent the past year creating prosthetics that allow him to roam around on all fours like goat.

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)

In this photo taken Wednesday, March 8, 2017, a woman herder sits with her goats in a remote desert area near Bandar Beyla in Somalia's semiautonomous northeastern state of Puntland. Somalia has declared the drought a national disaster, part of what the United Nations calls the largest humanitarian crisis since the world body was founded in 1945, and with animals being central to many the drought threatens their main sources of nutrition and survival. (Photo by Ben Curtis/AP Photo)

Revellers cool themselves in the Danube River during the Sziget music festival on an island in Budapest, Hungary August 12, 2015. The event is one of the biggest cultural events of Europe, offering art exhibitions, theatrical and circus performances and music concerts. Almost 200 performers from 47 countries will entertain the hundreds of thousands of visitors from 11 to 18 August. (Photo by Laszlo Balogh/Reuters)

Dancer Elizabeth Suarez, 29, gets ready to perform at the backstage of a cinema where the “Cuerda Viva” (Live Strings) alternative music festival is taking place, in Havana, February 26, 2016. (Photo by Alexandre Meneghini/Reuters)

“Chewbacca Mom” Candace Payne attends the 2016 CMT Music awards at the Bridgestone Arena on June 8, 2016 in Nashville, Tennessee. (Photo by Kevin Mazur/WireImage)

Allie Labutis wears a painted “Merica” on her thigh during the fifth annual Made in America Music Festival in Philadelphia, Pennsylvania September 3, 2016. (Photo by Mark Makela/Reuters)

Singer Ariana Grande performs during the 2014 MTV Europe Music Awards at the SSE Hydro Arena in Glasgow, on November 9, 2014. (Photo by Toby Melville/Reuters)