At left, a woman holds the saffron crocus during the saffron harvest in Herat, Afghanistan. At right, saffron flowers are collected in Saint Hippolyte, eastern France. Since the stigmas need to be picked from the flowers by hand, saffron is the world's most expensive spice. Majid Saeedi/Getty Images; Maxppp /Landov hide caption

itoggle caption Majid Saeedi/Getty Images; Maxppp /Landov

Gorillas in Virunga National Park in Democratic Republic of Congo, in 2013. Great apes like the gorilla have become increasingly threatened by the expansion of palm oil production in Africa. Brent Stirton/WWF/Canon/Getty Images hide caption

itoggle caption Brent Stirton/WWF/Canon/Getty Images

Doughnuts at a Krispy Kreme store in Washington, D.C. An environmental coalition says leading doughnut companies like Krispy Kreme source palm oil from suppliers who are clear-cutting rain forests and destroying wildlife habitat. Meredith Rizzo/NPR hide caption

itoggle caption Meredith Rizzo/NPR

Kellogg, maker of Pop-Tarts, announced Feb. 14 that it will buy palm oil — an ingredient in Pop-Tarts — only from companies that don't destroy rain forests where palm trees are grown. Andrew Burton/Getty Images hide caption

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Dunkin' Donuts plans to go green by committing to purchasing all of its palm oil from sustainable sources. Andrew Huff/via Flickr hide caption

itoggle caption Andrew Huff/via Flickr