They can be good indicators of habitat diversity, biological variety, and local stressors on the environment. They are bathed in both water and air. They live outdoors on land and water, and their skin, larvae, and unshelled eggs are constantly exposed and in contact with the substances in their surroundings. Other species' populations have disappeared or are declining in numbers in Brazil, Mexico, Australia, India, Bangladesh, Portugal, Taiwan, the United States, and Norway. There is no one apparent cause for these declines.
Habitat destruction is one of the most serious threats to amphibian populations.
In 1988 on a West Michigan farm, frogs were nearly absent. A similar story exists on a ranch in Nutt, New Mexico. Where crayfish were abundant, leopard frogs were rare or absent, aquatic snails disappeared, and native aquatic plants and invertebrates were severely depleted. Acidification of habitat is also a possible cause for amphibian declines. Air has a great capacity for moving large amounts of pollutants over time and space.