Among the fish populations that could be harmed by the Xayaburi dam in Laos is the critically endangered Mekong giant catfish, considered by the Guinness Book of World Records to be the world’s largest freshwater fish. The fish, which grows to 650 pounds and about 10 feet long, is only found in the Mekong River. It is migratory, moving between downstream habitats in Cambodia upstream to northern Thailand and Laos each year to spawn. Some experts fear the Xayaburi dam could block the migration and drive the giant catfish to extinction. (Photo by Courtesy of Zeb Hogan/University of Nevada, Reno)

The Hubble Space Telescope is shown following its release from the space shuttle Discovery Wednesday, February 19, 1997. The Hubble Space Telescope, one of NASA'S crowning glories, marks its 25th anniversary on Friday, April 24, 2015. With more than 1 million observations, including those of the farthest and oldest galaxies ever beholden by humanity, no man-made satellite has touched as many minds or hearts as Hubble. (Photo by AP Photo/NASA)

An old locomotive train that was used for transporting coal is preserved as a monument at Ny-Alesund, in Svalbard, Norway, October 11, 2015. A Norwegian chain of islands just 1,200 km (750 miles) from the North Pole is trying to promote new technologies, tourism and scientific research in a shift from high-polluting coal mining that has been a backbone of the remote economy for decades. (Photo by Anna Filipova/Reuters)

A vendor sells chili peppers at his stall at a market in Bangkok, Thailand March 31, 2016. (Photo by Jorge Silva/Reuters)

A wildlife ranger strokes a northern white rhino, only three of its kind left in the world, ahead of the Giant Club Summit of African leaders and others on tackling poaching of elephants and rhinos, Ol Pejeta conservancy near the town of Nanyuki, Laikipia County, Kenya, April 28, 2016. (Photo by Siegfried Modola/Reuters)

In this Friday, January 9, 2015 photo, bathhouse worker Omid Riahi, 39, scrubs a man to remove dead skin, at the Ghebleh public bathhouse, in Tehran, Iran. The steamy air and curved tiled walls of Iran's famed public bathhouses, some rinsing and massaging patrons for hundreds of years, slowly may wash away as interest in them wanes. The bathhouses, known as “hammams” in Persian, find themselves in rough financial times as modern conveniences now allow showers and baths in most homes across the Islamic Republic. (Photo by Ebrahim Noroozi/AP Photo)

“Early morning in Mandawa, rural Rajasthan: it was the morning of Diwali and the streets were swept by smiling women in brightly coloured sarees as I took an early morning cup of chai. Celebrations started later, when darkness fell”. (Photo by Hamish Scott-Brown/Guardian Witness)

Kendall Jenner (L) and Hailey Baldwin attend Harper's BAZAAR Celebration of “ICONS By Carine Roitfeld” at The Plaza Hotel presented by Infor, Laura Mercier, Stella Artois, FUJIFILM and SWAROVSKI on September 8, 2017 in New York City. (Photo by Bennett Raglin/Getty Images for Harper's BAZAAR)