What's In the Water? Mapping Global Wastewater Nitrogen

The tendency for most of us when it comes to human wastewater is out of sight, out of mind. But Cascade Tuholske and our team turned our attention to this overlooked topic and its impacts on global coastal ecosystems.

The study, published in PLOS One, is the first to map nitrogen and pathogen inputs from wastewater across 130,000 watersheds worldwide. We also created a data visualization that maps the sources and destinations of nitrogen globally.

“The motivation behind this research was a desire to have a fine-grain understanding of how wastewater is impacting coastal waters worldwide,” Cascade said. “This isn’t the first study to produce a global wastewater model, but it is the first study to map the inputs of nitrogen and pathogens from wastewater across 130,000 watersheds across the planet.”

The findings surprised us: “Nearly half as much nitrogen comes from wastewater as agricultural runoff globally,” Cascade said, “which is a huge fraction.” As diets shift toward more animal-based proteins in developing countries, even more nitrogen shows up in wastewater. As Cascade put it: “The more burgers people are eating, the more nitrogen is getting into the ocean.”

Read the full story at UCSB Current →