The Global Atlas of Human Sewage

Scientists from the University of California and Columbia University have released a new interactive map which visualizes the impact of human sewage on the world's coastlines. It is fairly well known that nitrogen from agricultural run-off (from fertilizers and livestock waste) contribute to harmful algae blooms which effect the amount of oxygen in rivers and along coastlines. This run-off is therefore very harmful to coastal species and ecosystems. What is less well known is that human waste also contributes around 40% of the total nitrogen contributed by agricultural run-off.

The interactive Global Wastewater Model map shows where human wastewater from 130,000 watersheds discharge nitrogen and pathogens into the sea across the world. The nutrients in human waste discharged into the oceans can create phytoplankton blooms. These algae blooms block sunlight and deprive water of oxygen. They can therefore suffocate sea life. The toxins produced by some algae blooms can also enter the food-chain, which then becomes harmful to human health. 

You can read more about the global wastewater model used to create the interactive map in the paper Mapping global inputs and impacts from human sewage in coastal ecosystems. The model uses global population data, data on national protein consumption, data on wastewater treatment facilities and global watershed locations to model where nitrogen effluent and pathogens are entering the world's oceans. The amount of nitrogen in human waste increases when the consumption of meat increases. The higher the level of consumption of protein from meat then the higher the levels of dangerous nitrogen in the wastewater.