Newt
Newts, as with salamanders in general and other amphibians, serve as bioindicators because of their thin, sensitive skin and evidence of their presence (or absence) can serve as an indicator of the health of the environment. Most species are highly sensitive to subtle changes in the pH level of the streams and lakes where they live. Because their skin is permeable to water, they absorb oxygen and other substances they need through their skin. Scientists study the stability of the amphibian population when studying the water quality of a particular body of water.
Newt
Although some species, such as the rough-skinned newt ("Taricha granulosa") in North America or the smooth newt ("Lissotriton vulgaris") in Europe, are still relatively common, populations of newts throughout their distribution range suffer from habitat loss, fragmentation, and pollution. This affects especially the aquatic breeding sites they depend on, but also their land habitats. Several species, such as the Edough ribbed newt ("Pleurodeles poireti"), Kaiser's spotted newt ("Neurergus kaiseri"), or the Montseny brook newt ("Calotriton arnoldi") are considerered threatened by the IUCN, and the Yunnan lake newt is a tragic example of a newt species that has gone extinct recently.