Timbuktu: A UN peacekeeper from Burkina Faso stands guard at the Djinguereber mosque, built in the 14th century, during a visit by a UN delegation on election day in Timbuktu, Mali, July 28, 2013. (Photo by Joe Penney/Reuters)

A student from the union territory of Pondicherry prepares to take part in the inaugural session of the national Balrang Festival 2017 in Bhopal, India, 20 December 2017. More than 500 participants from 26 states across the country take part in the three-day long cultural event to showcase their performances. The festival organised by Madhya Pradesh School Education Department and Indira Gandhi Rashtriya Manav Sangralaya. (Photo by Sanjeev Gupta/EPA/EFE)

In this June 29, 2016 file photo, boats docked at Central Marine in Stuart, Fla., are surrounded by blue green algae. The 153-mile-long Indian River Lagoon has been plagued by harmful algae blooms. Water quality testing data analyzed by the AP showed the average phosphorous level – a byproduct of fertilizers and human waste that algae thrive on, rose nearly 75 percent between 2000 and 2016. (Photo by Greg Lovett/The Palm Beach Post via AP Photo)

As an airliner prepares to land, a bird takes off at the Gravelly Point park near Reagan National Airport in Arlington, Va. on December 23, 2018. (Photo by Michael S. Williamson/The Washington Post)

Photographer Gregg Segal travelled the world to document children and the food they eat in a week. Partly inspired by the increasing problems of childhood obesity, he tracked traditional regional diets as yet unaffected by globalisation, and ironically, found that the healthiest diets were often eaten by the least well off. (Photo by Gregg Segal/The Guardian)

The band “Baby In Vain” and the dancegroup Corpus perform at the Gloria Stage at Roskilde Festival on July 3, 2019. (Photo by Helle Arensbak/Ritzau Scanpix/AFP Photo)

A view through mist shows the Kirk of Saint Mary Magdalene in Primorsk, Leningrad Region, Russia on March 24, 2019. (Photo by Anton Vaganov/Reuters)

Hundreds of pumpkins lie on a field near Frankfurt, Germany, after sunset on Wednesday, October 16, 2019. The autumn vegetable heralds the approach of halloween. (Photo by Michael Probst/AP Photo)