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.
London
Amphibians are common in the capital, including smooth newts living by the Tate Modern, and common frogs, common toads, palmate newts and great crested newts. On the other hand, native reptiles such as slowworms, common lizards, grass snakes and adders, are mostly only seen in Outer London.