Below are excerpts from this article about damage to the Louisiana coast from oil drilling activities.

Verdin, a commercial fisherman, says back then, some places here were so thick with trees you could barely see through them. When the oil industry cut canals into the area to get to its drilling sites, he says, things started changing. He says those canals brought the equivalent of poison into the marsh: salt water from the Gulf of Mexico.

“The water flows in and brings all that salt water,” Verdin says.

[….]

“Before oil and gas, even after the main river levees, we were holding our own,” Professor Oliver Houck says. “Once we started drilling, we started collapsing.”

You can see the damage from the air. You see vast, open waterways that began as canals, sliced into the marsh.

“There are 10,000 miles of those canals through the marshes now,” Houck says.