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)

Scared of Heights. “Taken from the highest residential building in Asia: the Zenith in Busan. This was taken with official permission (which took me months to get) and safety measures were taken. I had to hang myself over the edge to get this shot. Not for the faint of heart! But when you’re at a height like this, the world below you just seems different. It takes away the fear one would normally have, and gives a sense of peace instead”. (Photo by Albert Dros/NatGeo Cities Travel Photographer of the Year 2017)

“Touring the Koko-en Gardens adjacent to the Himeji castle was an unexpected highlight of our visit”, wrote Jeff Solar, 64, of Silver Spring, Md., about his trip to Japan. “The fall colors were outstanding and the gardens were both amazing and a bargain (just a few Yen added to the cost of the Himeji Castle admission)”. (Photo by Jeff Solar/2017 Washington Post Travel Photo Contest)

“Mr Big Dipper”, Nicholas Roemmelt (Denmark). A stargazer observes the constellation of the Big Dipper perfectly aligned with the window of the entrance to a large glacier cave in Engadin, Switzerland. This is a panorama of two pictures, and each is a stack of another two pictures: one for the stars and another one for the foreground, but with no composing or time blending. (Photo by Nicholas Roemmelt/National Maritime Museum/The Guardian)

Participants hang from ropes as they learn how to use safety gears at an experience centre for construction safety training in Beijing, September 5, 2014. The centre which opened in June 2014 was established to educate workers about construction safety. According to the centre, about 1,000 construction workers undergo 3-hour classes which comprises of 33 modules every month. (Photo by Kim Kyung-Hoon/Reuters)

A man carries away an injured girl while walking through debris past in the Achrafiyeh district in the centre of Lebanon's capital Beirut on August 4, 2020, following an explosion at the nearby port of Beirut. (Photo by The Mega Agency/Stringer)

A woman poses for a photograph during Holi celebrations in the town of Barsana in the state of Uttar Pradesh, India, March 6, 2017. (Photo by Cathal McNaughton/Reuters)

Attendees wear a cardboard “Facebox” at the 2017 South By Southwest (SXSW) Interactive Festival at the Austin Convention Center in Austin, Texas, U.S., on Monday, March 13, 2017. The SXSW Interactive Festival features a variety of tracks that allow attendees to explore what's next in the worlds of entertainment, culture, and technology. (Photo by David Paul Morris/Bloomberg)