In the 1980s, microbiologists from the University of Montana implanted E. coli and salmonella in human faeces, which were then buried in the soil at various depths around the Bridger Mountains. The scientists followed the microbial levels in these samples for several seasons. Based on these investigations, they found that high levels of pathogens persisted for more than a year, regardless of the depth of the samples or the quality of the soil.

When these pathogens from human faeces leach into the soil, they multiply and increase using the nutrients produced in the faecal. Then, they begin utilizing the water source and spread it throughout the ecosystem. This problem has become more severe due to the modern human lifestyle. Human faeces contain increasingly complex substances such as chemicals, hormones brought on or triggered by pharmaceuticals, drug-resistant germs, etc. Laura C Scott, a geneticist with the U.S. Geological Survey, collected soil and water samples from national parks in 2016, and the results were quite surprising. All samples showed the presence of drug-resistant bacteria. This phenomenon is directly linked to the increase in human activity.

Lara Jacobs, a recreation ecologist and PhD candidate at Oregon State University who studies the impact of human waste on the outdoors, suggest that compared to the last 80s and 90s, the number of people in the backcountry has become so high nowadays, simply getting the poop out of sight was not sufficient anymore.