In most cases, sampling the local environments where the frogs are found shows nothing amiss. We compare the samples with relevant chemical standards for air, water, land, and everything seems to be fine. Yet the frogs are saying, look again. Frogs were one of the indicator species she was using in that work, along with insects, plant life, and other amphibians. Malformed frogs consumed much of her work time for several years.
Wetlands provide a good example.
People see a wetland, with geese on the water and lily pads, and they'll think it looks pretty healthy. A lot of wetlands really get hammered by stormwater, and when you look closer you see the turbidity and sediment. We see a big response to the level of disturbance in a wetland. Helgen cites a pair of ponds she and colleague Mark Gernes studied in a Twin Cities suburb. Water chemistry showed each had the same level of chlorides, most likely from road salt.