Bioindicators are living things that, usually, reveal the presence of pollutants and indicate the health of an ecosystem. The best bioindicators are abundant and easy to measure, meaning they have a certain set of symptoms sparked by toxicity. Fungi, plants, and animals are all bioindicators. Fungi are bioaccumulators, meaning they absorb their environments, like frogs’ sensitive skin, and their colonies exist just about everywhere. Different varieties can monitor global moisture levels, soil composition, air quality, nitrogen levels, pH levels, and the list goes on. Because fungi are abundant, it’s also minimally invasive and usually the most cost-effective way to start environmental monitoring projects. And they roll up their sleeves to get the job done… Take the Cortinarius caperatus and some Boletus mushroom species, for instance. They effectively absorb radioactive compounds, like cesium-137 from the soil. Cesium-137 typically takes 30 years to decay on its own. In the last three decades, radiotrophic fungal colonies have sprouted around the desolate Chernobyl Nuclear Power Plant, using melanin to thrive in high-radiation environments.