A walker has left a handprint on a snow- covered tree trunk on Grosser Feldberg mountain in the Taunus mountain range, Germany, 16 January 2017. (Photo by Frank Rumpenhorst/DPA)

Tree trunks are seen in a forest on November 8, 2011 near Landau an der Isar, Germany. The German government is conducting a nationwide project to estimate the number, variety and geographic distribution of trees and forests in Germany, as well as their condition and health. Approximately a third of Germany is covered in woodlands, and though that territory has actually expanded since 1989, some analysts fear demand for wood will outstrip supply in coming years due to national growth in industry and bio-energy needs. (Photo by Johannes Simon/Getty Images)

Bonbibi, Treehouse Point, Fall City, WA. The Bonbibi is balanced on two steel yokes. The yokes spread out the load and allow for tree growth and movement in the wind. A small deck hangs from the beams below and uses the treehouse itself to shelter guests. (Photo by Pete Nelson)

CHINA: Customers eat at a restaurant as a cooked pig sits on a cart on the street outside in Hong Kong, China, December 12, 2016. (Photo by David Gray/Reuters)

NEPAL: A devotee is smeared with a vermillion powder while celebrating the “Sindoor Jatra” vermillion powder festival at Thimi, in Bhaktapur, Nepal, April 14, 2016. (Photo by Navesh Chitrakar/Reuters)

A man holds his umbrella during snowfall on the Areopagitou pedestrian street beneath the Acropolis hill during snowfall in Athens, Greece, January 10, 2017. (Photo by Alkis Konstantinidis/Reuters)

The North Side Skull & Bone Gang stand together during the wake up call for Mardi Gras, Tuesday, February 9, 2016, in New Orleans. Their costumes are intended to represent the dead and they bring a serious message, reminding people of their mortality and the need to live a productive and good life. (Photo by Brynn Anderson/AP Photo)