Louisiana is losing the equivalent of a football field of land a day, totaling about 1,300 acres of land a year to coastal erosion.

We write in response to Dan Fagan's recent column, "Oil companies not the real culprits in Louisiana’s wetland Loss: It may be Mother Nature."

Is Mother Nature to blame for Louisiana’s Wetland Loss Crisis? River deltas naturally deposit sediment and build land in the form of delta lobes comprised mostly of wetlands. Rivers erode their channels and eventually abandon their course for a shorter route to the sea. The abandoned delta lobe erodes and subsides over time, allowing salt-water intrusion and excessive inundation to accelerate wetland loss. In exchange, a new delta lobe, nourished by sediments, nutrients and freshwater, is born and initiates the development of a new wetland complex. Within this geologic framework, hurricanes, faulting, drought-induced dieback, and other processes cause additional wetland loss. So, yes, some of Louisiana’s wetland loss is natural. But certainly not all of it.

We, as a society, have made drastic changes to the natural deltaic process by leveeing the Mississippi River. Although levees and other flood-control measures help protect coastal communities, they prevent the delivery of sediment that leads to new deltaic wetland formation and maintenance of existing wetlands. As a result, Louisiana is currently experiencing a net loss of wetlands rather than no loss or a net gain. Humans also have a role to play in sea-level rise. Greenhouse gas emissions are responsible for the rapid warming trend that cannot be explained by natural processes alone. Sea-level, which is rising around the world at a rate of just over an inch per decade, is caused by increased melting of glaciers and ice-sheets and thermal expansion as ocean water warms. This sea-level rise is contributing to the loss of Louisiana’s wetlands.

And while the canals dug by the oil and gas companies may not be the only culprit of wetland loss, they occupy an estimated length of 20,943 miles and directly replace wetlands. Also, spoil banks, created by the deposition of dredged material from canals, including those for navigation, smother adjacent marshes and can impede the natural exchange of water and sediment necessary for wetlands to avoid submergence. Fluid extraction can also contribute to land loss by increasing soil compaction and subsidence. Many of us from the scientific community, including John Day, professor emeritus at Louisiana State University, and Sean Graham, assistant professor at Nicholls State University, agree with these conclusions. Blaming Mother Nature and absolving the oil and gas companies and the role that society at large has played in Louisiana’s wetland loss crisis will only slow a successful remediation-response that necessitates assistance from all entities, private and governmental, that have contributed to the degradation and loss of one of the world’s preeminent ecosystems — the Mississippi River Delta.

Tracy Quirk

assistant professor 

Irving A. Mendelssohn

professor emeritus

LSU Department of Oceanography and Coastal Sciences

Baton Rouge