Even before the ocean caught a fever and reached temperatures no one had ever seen, Australia’s ancient giant kelp was cooked. Rodney Dillon noticed the day he squeezed into a wet suit several years ago and dove into Trumpeter Bay to catch his favorite food, a big sea snail called abalone. As he swam amid the towering kelp forest, he saw that “it had gone slimy.” He scrambled out of the water and called a scientist at the University of Tasmania in nearby Hobart. “I said, ‘Mate, all our kelp’s dying, and you need to come down here and have a look.’ “But no one could do anything about it.” Strands of bull kelp at Shelly Point in Tasmania. The Tasman Sea is warming, and once plentiful giant kelp forests have rapidly declined. Indigenous artists rely on a kelp habitat for traditional jewelry and basket making. […]