General Impact of Humans on Amphibians
Climate change is not the only stressor on amphibian populations. Amphibians are more susceptible to pollution than other groups because their skin is permeable. For this reason, toxins are able to invade critical amphibian organs. Experimental and field studies suggest that amphibians are highly susceptible to common insecticides, pesticides, and herbicides such as Roundup. Chemicals cause a number of developmental problems including external deformities such as the formation of extra arms and legs, and the tendency of frogs to become hermaphroditic (the same individual bearing male and female reproductive organs), as well as damage to the central nervous system. Finally, increasing UV-B radiation is thought to cause genetic damage in amphibians. Many of the environmental changes and pollution don’t themselves cause the amphibians to become extinct, a related pathogen, fungus or disease provides the final blow, similar to the Golden Toad. For example, drought may weaken the amphibian population, but a drought-related pathogen may be the ultimate cause of the frog extinction. For pesticides, the developmental or neurological problem does not appear to kill the amphibians but it weakens them to a fungus that can cause a disease outbreak.
Human impact on amphibiansClick the images above to see full-size versions and complete source information.
So, all of this points to a very perilous picture for the amphibians. This inconspicuous group is at ground zero of the Anthropocene mass extinction. With extinction rates over 200 times the global average and potential threatened species loss of over 25,000 times that average, coinciding with a general lack of stewardship needed to fully understand the root causes of their extinction, the amphibians will likely be the major casualty of climate and other anthropogenic activities. However, the story doesn’t stop there. And their loss may also have a direct impact on a lot of other species. Amphibians are an important part of the diet of a number of species of reptiles, birds, and mammals, as well as the main predator for a number of groups of insects, thus their extinction will have profound impacts on a broad part of the food chain. That is why many ecologists believe that the amphibians are the “canary in the coal mine” for the impact of human activities on global diversity.