Just as there are two sides to every story, scientists are split on the issue. There are those who feel this is a natural cycle, that there are normal fluctuations of the frog population. On the other side are scientists who believe the decline is the direct result of human actions. The scientists who claim that this is a natural part of the ecosystem make a valid point that our research is shortsighted, with a large portion of the data coming from studies done only since this alarm went off in 1990. Frogs have been around for approximately 180 million years and we are basing our concern on a millisecond of their existence. Skepticism also stems from reports from sites where there are both declining and thriving species in the same habitat. If they claim human disturbance harms the frogs, then why do some species manage to do so well? Scientists from the opposing viewpoint raise many issues to repute the skeptics. They believe some frogs are better adapted. These changes range from increased UV light to decreased wetland areas to wide-spread use of pesticides to the introduction of non-native fish. Many say the frog is to the global ecosystem what the canary is to the coal mine. Frogs live both in the water and on the land, in their life cycle progressing from herbivores to carnivores. They also have a thin, highly sensitive skin, which helps classify them as an indicator species.