Environmental DNA or eDNA is any microscopic DNA from the skin cells, scat, mucus, and tissue that gets left behind on any surface like soil, water, or air. It is the least invasive way to collect data on animals, plants, fungi, bacteria, etc. It barely disrupts habitat, and you don't need to capture or observe the species. The data collected from eDNA is important because it tells us about the habitat and ecosystem of any location. Since eDNA gives you all of the plants and animal species in an area you can make inferences about the health and biodiversity of an ecosystem. Scientists collect the eDNA by getting a sample from water, soil, or air and running it through a filter that separates the DNA from the sample, and then preserving the DNA by freezing or in a buffer that keeps it for multiple years; finally, the sample goes to a lab to be analyzed.

The Contra Costa Resource Conservation District is using eDNA to study livestock ponds in California’s East Bay Area. They are trying to see how many amphibians and other invertebrates use the ponds for breeding and to monitor the population of red-legged and yellow-legged frogs. We collected water samples from five different pond points to ensure that we included all the species that use the ponds. We then run one liter of sampled pond water through the eDNA filter until the water reaches the red line or stops getting pumped through the filter. Then remove the sample from the pump, place it in a sealed bag, and label it with a date and location.