The fourth annual BigPicture Natural World Photography Competition aims to celebrate the diversity of life on Earth, and encourages people to protect and conserve it. Here: “The Salmon Catchers”. Terrestrial Wildlife. To capture this view of a mother grizzly bear and her cub, photographer Peter Mather set up a camera trap on a log that he knew the bears tended to traverse while fishing for salmon, in the Yukon River watershed in Canada. (Photo by Peter Mather/BigPicture Natural World Photography Competition 2017)

Shoppers walk down stairs featuring a five-metre-high reproduction of Vincent van Gogh's signature painting “Sunflowers”, at the entrance to Ocean Terminal in Hong Kong July 15, 2013. A premium three-dimensional reproduction of works of Van Gogh, the RELIEVO collection, approved by the curators of the Van Gogh Museum in Amsterdam, is on display at a gallery inside Harbour City shopping mall attached to the terminal. (Photo by Bobby Yip/Reuters)

A bird is cleaned at the International Bird Rescue in Fairfield, California January 20, 2015. A gooey, unknown material discovered on the eastern shores of San Francisco Bay is clinging to the feathers of birds, and more than 100 birds, mostly species of oceangoing, diving ducks, have died after their feathers were fouled by the viscous substance now undergoing testing at state labs in Sacramento. (Photo by Robert Galbraith/Reuters)

A store mannequin with a protective mask stands before a clothes store as they open for the first time since March during the novel coronavirus (COVID-19) pandemic on April 22, 2020 in Berlin, Germany. Small to midsized-shops are opening across Germany this week as state authorities follow a recommendation by the federal government to ease restrictions imposed in March meant to slow the spread of the coronavirus. Some schools are also planning to reopen soon, as are museums and hair salons in coming weeks. (Photo by Maja Hitij/Getty Images)

Netherlands Antilles Sint Maarten – Boeing 747-400 of KLM in approach for the “Princess Juliana” airport on July 2, 2002. (Photo by LUPOO/Ullstein Bild via Getty Images)

Sunset is seen through smoke from the Wallow fire June 8, 2011 in Springerville, Arizona. Hundreds of thousands of acres have burned in eastern Arizona prompting evacuations by residents. Smoke loomed over the twin towns of Eager and Springerville, home to about 7,000 people north of the fire. (Photo by Eric Thayer/Getty Images)

Princess Charlene poses after the arrival of the Riviera Water Bike Challenge in support of the Princess Charlene of Monaco Foundation, in Nice, France, June 4, 2017. (Photo by Eric Gaillard/Reuters)

Climbers place a huge 80x80 metres (262x262 feet) Swiss national flag on the western face of the north-eastern Swiss landmark Mount Saentis, Switzerland on July 31, 2018. (Photo by Arnd Wiegmann/Reuters)