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)

Hidden Britain category winner. Garden Spider by Alan Smith from Reading, Berkshire. (Photo by Alan Smith/British Wildlife Photography Awards/PA Wire Press Association)

The Invasion. A quiet street in Macau. Modernization around is quickly changing the city, as documented by Paul Tsui. (Photo by Paul Tsui/National Geographic Travel Photographer of the Year Contest)

Best portfolio winner. Roseate Spoonbill, Platalea ajaja, by Petr Bambousek, Czech Republic. (Photo by Petr Bambousek/2018 Bird Photographer of the Year)

Professional conceptual category winner. Greetings from Mars, by Julien Mauve, France. Mauve says: “I have always wondered what it would be like to discover a totally different world ... and to photograph it for the first time as if I was Ansel Adams. So I came up with this project, which is about space exploration and discovery. But it’s also about our behavior in front of landscapes and how we create pictures that will share our personal story with the world”. (Photo by Julien Mauve)

Pangolins in Crisis: Brent Stirton, South Africa; 1st place, Natural world and wildlife. “Pangolins are the world’s most illegally trafficked mammals, with an estimated one million trafficked to Asia in the last 10 years. Their scales are used in traditional Chinese and Vietnamese medicine, and their meat is sold as a high-priced delicacy. As a result, pangolins are listed as critically endangered and anyone who trades or consumes them is breaking the law. This body of work exposes the trade, while exploring aspects of illegality and celebrating the people who are trying to save these animals”. (Photo by Brent Stirton/Sony World Photography Awards 2020)

U.S. Army soldiers with the 1st Battalion, 501st Infantry Regiment deployed to Combat Outpost Sabari, Afghanistan scan their area as they begin a multi-day air assault mission near the Pakistani border of eastern Afghanistan's Khost province May 2, 2012. (Photo by Staff Sgt. Joshua L. DeMotts/U.S. Air Force)

“Honorable Mention”. An Indian rhinoceros, far from home and stuck inside with late-winter blues at the Toronto zoo. Photo location: Toronto, Ontario, Canada. (Photo and caption by Stephen De Lisle/National Geographic Photo Contest)