“Cassowaries are large, flightless birds related to emus and (more distantly) to ostriches, rheas, and kiwis”, writes Olivia Judson in the September issue of National Geographic magazine. How large? People-size: Adult males stand well over five foot five and top 110 pounds. Females are even taller, and can weigh more than 160 pounds. Dangerous when roused, they’re shy and peaceable when left alone. But even birds this big and tough are prey to habitat loss. The dense New Guinea and Australia rain forests where they live have dwindled. Today cassowaries might number 1,500 to 2,000. And because they help shape those same forests – by moving seeds from one place to another – “if they vanish”, Judson writes, “the structure of the forest would gradually change” too. (Photo by Christian Ziegler/National Geographic)

A wheelbarrow loaded with two butchered pigs is seen at La Saline slaughterhouse in Port-au-Prince, Haiti, March 19, 2015. Reuters photographer Andres Martinez Casares: “The grunts of a pig or the bleating of a goat are one thing. Then there's the sound of animals about to be killed. That's something else. If you haven't heard that before, it's quite something... (Photo by Andres Martinez Casares/Reuters)

A dog walker on Longsands beach before sunrise in Tynemouth, UK on April 1, 2016. (Photo by Owen Humphreys/PA Wire)

A general view shows smoke and volcanic ashes billowing from volcano Cotopaxi in Pedregal, Ecuador, late 07 October 2015. (Photo by Jose Jacome/EPA)

In 2002 photographer Corey Arnold left behind a poor economy in San Francisco and headed up to Alaska to try his luck at his longtime passion of fishing. Arnold, who had worked summers during college on a salmon boat in Alaska, signed onto the f/v Rollo, a crabbing boat that fishes in the dangerous Bering Sea. While working long, strenuous hours on the Rollo, Arnold often stole away with the captain’s permission to grab his camera and photograph the crew and the ship. Arnold eventually put together “Fish Work: Bering Sea”, a documentation of his seven adventurous and dicey crab seasons aboard the Rollo. (Photo by Corey Arnold)

Teachers carry children away from Briarwood Elementary school after the tornado destroyed the school in south Oklahoma City. (Photo by Paul Hellstern/The Oklahoman)

Super-cell thunderstorms, whirling tornados and lightning bolts illuminating the sky – these photos capture the terrifying brilliance of American storms. (Photo by Brandon Goforth/Solent News & Photo Agency)