Researchers describe how “environmental DNA” (eDNA)—genetic material shed by organisms into water, sand, or air—can be detected from very small environmental samples. By collecting a cup of river water and analyzing the DNA fragments it contains, scientists can infer which species are present and where they have been, including wildlife that has migrated through the area. The approach also supports monitoring of environmental conditions linked to human activity. Multiple outlets note that eDNA can be used to detect indicators of pollution and to identify biological signatures associated with pathogens, allowing surveillance of disease-causing organisms in waterways and surrounding environments. Because the method does not require direct observation or capture of organisms, it can provide a broader view of biodiversity and ecosystem use across time and space. Together, the sources emphasize that eDNA offers a multi-purpose tool: it can contribute to tracking species, assessing contamination-related biological evidence, and surveying pathogens using DNA signatures extracted from routine environmental samples.