National Geographic. Cat Island, Louisiana, was an important bird colony until oil from the Deepwater Horizon disaster caused it to fall apart, with only traces visible above the waves.

We're all familiar with the horrifying effects oil spills can have on marine life and birds. But the idea that oil can dissolve a whole island is far less intuitive. However, as this National Geographic video shows, that is exactly what happened after the Deepwater Horizon spill in 2010.

As Natalie Peyronnin of the Environmental Defense Fund explains. “The oil comes down, it kills the mangroves, which then kills the root system. And the root is holding together this island, and without that root system holding together, the sediment it just erodes away.” An island 5.5 acres in size (2 hectares) has largely vanished.

For birds that breed on the island, the results are devastating. And this creates a cost that draws far less attention than the animals clogged with oil, but potentially more long term.

Credit: National Geographic.