From the boat, the salt marsh looks pristine: cloud-dotted sky, brown-blue water, gold-green grass. As we motor along the coast, a flock of egrets flutters into the air, startled by the only humans in sight. Later, I’m equally startled to see an alligator lazing in the shallows.

It is easy, if you don’t know any better, to think that the world of the wetlands is simple, steadfast, still. That would be incorrect. A salt marsh is an exquisitely complex ecosystem. It is also a crucial one. In Louisiana, where wetlands make up one-third of the state by area, the landscape plays a pivotal role. These waving grasses along the Gulf of Mexico underpin Louisiana’s seafood industry, the country’s second-largest behind Alaska. They are home to key infrastructure, like the pipes that carry oil and gas from the largest US entry port for waterborne crude oil all the way up to Knoxville, Tennessee and Washington DC.

And although the precise magnitude of their effect is still being debated, they are a natural barrier against storm surge, hurricanes and flooding. The wetlands at Biloxi Marsh – a web of bayous, brackish and salt lakes in south-east Louisiana that give way to Eloi Bay, Chandeleur Sound and, finally, to the Gulf of Mexico – help protect even New Orleans, 45 miles away.