The birth and death of a landscape

Justin Nobel writes: To reach the youngest land in the United States you need a boat. Robert Twilley still vividly remembers the first time he made the trip. The Louisiana State University coastal ecologist piled into a 24-foot Boston Whaler with a bunch of geomorphologists from Minnesota and motored out to an arc of spongy islands along the central coast of Louisiana called the Wax Lake Delta. It was the best place to learn about how a delta develops. The way the land eventually stabilizes and becomes home to a unique ecosystem that changes as the delta gets older is a process that ecologists call succession. “Succession is one of the most fascinating concepts in ecology,” said Twilley, “though one of the hardest to study. But in the Wax Lake Delta you can see it all. Biologic communities link up A to Z; it is the holy grail of ecosystem succession.”

What is remarkable for scientists like Twilley is that with good muck boots, a small boat, and a non-aversion to intense sun, freak thunderstorms, biting insects, and devastating humidity, the aging process of this new land can be studied in a human lifespan. In just over 40 years, the Wax Lake Delta has grown from nothing to an area twice the size of Manhattan. Meanwhile, since the European settlement of North America, the Mississippi River Delta has lost approximately one-third of its original wetland area. A delta that was once about twice the size of Delaware and on maps resembled a head of cauliflower now looks more like a string bean. The slow death of the Mississippi River Delta has severe consequences, including reduced hurricane protection for cities like New Orleans. Not only an important food source for humans and wildlife, this rich habitat also helps filter pollutants and absorb excess nutrients that would deplete the oxygen in the Gulf of Mexico’s water.

As one delta dies, another one grows. The budding Wax Lake Delta has allowed Twilley and his team of researchers to study how a delta ages. First, the nascent delta takes shape as lobes of sediment accumulate below the water. The delta is born when it breaches the surface of the water. Colonized by plants that gradually enhance the soil’s organic content and raise its elevation, it rolls through childhood. And eventually, it grows into a landscape able to support large shrubs and black willow trees. “The delta is almost like an organism,” says Twilley, “There is a birthing, there is an aging process, and there is a death.” [Continue reading…]

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