An Afghan girl carries water on her back as she climbs a hill in Kabul, Afghanistan February 20, 2017. A growing population is straining water supplies in Afghanistan's capital, forcing those who can afford it to dig unregulated wells ever deeper to tap a falling water table. Finding water in arid Afghanistan is virtually always a challenge, but a drop in the groundwater level in Kabul caused by overuse and drought is making it even more difficult for residents, especially the poor. (Photo by Omar Sobhani/Reuters)

Lindsay Heimbach goes airborne while sledding down a hill on Mt. Lemmon December 27, 2008. (Photo by James Gregg/Arizona Daily Star)

Members of security forces secure Tahrir Square in Cairo, Egypt, November 11, 2016. Egypt imposed a big security clampdown in its cities on Friday as mass demonstrations called to protest against austerity measures failed to take place. Riot police and armored vehicles filled the otherwise empty streets of central Cairo, but most people stayed at home. (Photo by Mohamed Abd El Ghany/Reuters)

Anti-pollution protesters wearing traditional costumes and contemporary gas masks ride bicycles in the Qingming Grand river park in Kaifeng, Henan Province, China on January 1, 2017. The Beijing Municipal Environmental Protection Bureau extended an “orange alert” for heavy air pollution for three more days. (Photo by SIPA Asia/Rex Features/Shutterstock)

The International Garden Photographer of the Year is one of the world’s premier competitions specialising in botanical photography. There are 11 main categories and numerous special awards including Young Garden Photographer of the Year, and the mobile-only category Gardens on the Go. Here: Winner, Wildflower Landscapes category. Alto Paraíso de Goiás, Goiás, Brazil. (Photo by Marcio Cabral/The Guardian)

“People of the River”. This is a Karo tribe family; father, mother, two sisters and two brothers. The tribe, who live along the Omo River in east Africa, incorporate rich symbolism into their rituals by using ornate body art, headdresses and body scarification to express beauty and significance. (Photo by Jatenipat Ketpradit/International Portrait Photographer of the Year)

“A girl arrives at the parking lot wearing tiny leather shorts and sits on the back of a bike with a horse power of more than 1,000 CC. Next to her a man gets ready to ride, wearing a skeleton mask. It’s more than a fashion show, it’s an extravaganza on two wheels along Chinese roads”. – Carlos Barria. Photo: A couple rides their motorcycle at the Qian Dao Lake rally, on May 11, 2013. (Photo by Carlos Barria/Reuters)

Sap runs out of a frankincense tree near Mader Moge, Somaliland, a breakaway region of Somalia on August 4, 2016In a tradition dating to Biblical times, men rise at dawn in the rugged Cal Madow mountains of Somaliland in the Horn of Africa to scale rocky outcrops in search of the prized sap of wild frankincense trees. (Photo by Jason Patinkin/AP Photo)