Stretching across some of the most remote, arid places on Earth is one of humanity’s largest built objects: the “dog fence,” a nearly 3,500-mile-long barrier erected to keep wild dingoes away from the sheep that graze on some of Australia’s most populated regions.
Up close, the fence isn’t much to look at: four feet high or so, made out of chickenwire, lying like a long metal snake across the red sand of the desert. But it’s responsible for a newly discovered ecological phenomenon. By keeping dingoes out of the southeastern part of the country, it has created two versions of the same landscape—a world with top predators and one without. And you can feel the difference in your feet.
Mike Letnic, a field ecologist in sunglasses, shorts, and a battered felt hat, has spent years crisscrossing the dog fence when not at his desk at the University of New South Wales in Sydney. For a long time, he felt that the landscape was clearly different on the two sides of the fence, but “it was very hard to put a finger on it,” he says. Eventually, he realized that on the side of the fence without dingoes, the desert sand was mounded into tall dunes with plants growing on their crests. On the side with the tawny canines, vegetation was sparser, and dunes were bald and short and prone to shift under his boots.
“It is a little bit harder to walk on the dingo side because the sand is looser. You do a lot more trudging,” Letnic says. On the other hand, it is also “easier to see” because there are fewer trees and bushes.