The word “amphibian” means “double life,” and refers to the tendency of most amphibians (frogs, toads, and salamanders) to have an aquatic, gill-bearing larval stage (i.e. tadpole stage for frogs) and an air-breathing adult stage that may live partially or almost entirely on land. However, adults must return to the water to reproduce. Amphibians are vertebrate ectotherms that have delicate skin that can absorb water. They need moisture in order to breathe through their skin (subcutaneous respiration), and some amphibians lack lungs altogether. Because of this, water-borne pollutants and pathogens can cause serious damage to amphibian populations. Amphibians include frogs and toads (Order Anura, meaning tail-less) and the tailed Order Caudata (salamanders and newts). The combination of mountainous, forested areas and high rainfall in the Pacific Northwest has resulted in a high amphibian species diversity and endemism. Amphibians depend upon moist terrestrial habitats such as gullies, riparian areas and wet depressions. Some species need standing water, while others require only moist environments. The permeable skin and exposed (shell-less) eggs of amphibians make them vulnerable to impacts that affect aquatic and terrestrial environments. Most adult amphibians remain within two hundred metres of breeding sites, and juvenile dispersal among populations is believed to be limited to less than one kilometre for most species, so populations can become easily isolated from each other. This makes riparian corridors very important for seasonal migrations and/or for dispersal.