The tendency for most of us when it comes to human wastewater is out of sight, out of mind. Rarely do we consider what happens after we flush that toilet or turn off that tap.

However, researchers at UC Santa Barbara have turned their attention and considerable computational power to the subject and its impacts on global coastal ecosystems. The results aren’t pretty, but they are enlightening.

“The motivation behind this research was a desire to have a fine-grain understanding of how wastewater is impacting coastal waters worldwide,” says Cascade Tuholske, the lead author of a paper that appears in the journal PLOS One. While research on terrestrial threats to coastal marine ecosystems often focuses on agricultural runoff and what happens when fertilizer and livestock waste winds up in the ocean, he says, few studies investigate what happens when human sewage does the same.