The Great Barrier Reef of the Americas: Coastal Lessons from the Past

01.08.2018 | In Wildlife & Birds
By Richard S. Condrey, Louisiana State University (retired)

This is part 1 of a two-part series concerning Richard Condrey and Natalie Peyronnin’s recent paper, “Using Louisiana’s coastal history to innovate its coastal future,” published in Shore & Beach, Fall 2017. See part 2 here.

They were there, billions of oysters on the Great Barrier Reef of the Americas (GRBA), along the southern coast of Louisiana – a dangerous impediment to navigation. Just three to four feet under the surface of the water, though visible when the winds blew from the north, with only narrow and intricate channels along a nearly continuous coast with passage only for pirogues. 

They were there in 1492, when Columbus sailed into his New World. They bathed in the nutrient and oxygen-rich waters of the Gulf of Mexico, sweetened by subsurface and surface freshwater discharges of the Mississippi River Basin – continuing the efforts of uncounted generations of oysters to create and maintain a vast marine ecosystem, while protecting a majestic, growing delta.

Figure 1. Estimated extent of the Great Barrier Reef of the Americas (GBRA, gray area) in 1785-1807 based on the surveys conducted by Evia (1968, dashed lines) and Dumain (1807, dotted line) and the consistency of their measurements with the observations reported in Chaves (ca. 1537), Barroto (1687), Gauld (1778), and Audubon (1838). Coastal points: a, Cheniere au Tigre; b, Vermilion Bay; c, Cote Blanche Bay; d, Atchafalaya Bay; e, Point au Fer; f, estimated extent of Last Island in 1800; g, Ship Shoal. The reef, while a major impediment to navigation, played a vital role in coastal protection and advance until its demise in first half of the 1800s, likely as the result of human alterations in ground- and surface-water discharges of the Mississippi River Basin. No pre-1840 surveys have been located which contradict this interpretation.

They were there in the 1530s, providing Spanish sailors with a safe offshore harbor once they had located the Cape of the Cross (now Cheniere au Tigre, Figure 1) and entered the western end of the GRBA near the western most mouth of the River of the Holy Spirit (now Vermillion Bay's Southwest Pass).

They were there in 1543, lying just under the surface, as the remnants of De Soto’s men sailed out of the River of the Holy Spirit, over the Great Reef, and headed for Mexico, escaping the wrath of the natives of North America’s heartland. 

They were there in 1687, trapping huge drift trees as Barroto sailed across the Great Reef in his search for La Salle and his group of French invaders of Spain’s Americas. 

They were there in 1696, as Bisente drew his map of the Gulf of Mexico, based on Barroto’s accounts.

They were there in 1699, as Iberville, empowered by Bisente’s map, “discovered” the lower Mississippi River, making alliances with its native people as England plotted their genocide.

They were there in 1778, as Gauld surveyed the Spanish coast for her deadly rival, Great Britain.

They were there in 1785, as Evìa mapped the Great Reef and camped in the shelter of its western port.

They were there in 1806, as Lafon completed his map of Louisiana and in 1807 as Dumain completed his coastal survey – both under President Thomas Jefferson's orders.

They were there in 1811, as Pichardo defended Spain’s claims to Texas.   

They were there in 1837, dead and dying, their shells piled high along the Louisiana coast, as John James Audubon made his transformative journey along the coast into the new Republic of Texas.

But they were gone in 1853, when Sands completed his survey for the Ship Shoal Lighthouse, likely the victim of human alterations in the subsurface and surface discharges of the Mississippi River Basin.

They are elsewhere, ready to restore the functions of the Great Barrier Reef of the Americas, once the Gulf of Mexico’s waters are sweetened by subsurface and surface discharges of the Mississippi River Basin.

Imagine that you were there with these explorers. Imagine what it would look like to see this massive oyster reef. We can learn a lot from the past about how to restore coastal Louisiana into the future. We can build new great reefs, which will create and maintain vast marine ecosystems while protecting our coasts from climate change’s rising seas.