California’s amphibians, a group that includes frogs, toads, salamanders, and newts, are facing unprecedented threats to their survival due to human activities. These sensitive animals serve as indicators of environmental health, yet their numbers are declining at an alarming rate. The impact of human encroachment on natural habitats, coupled with the introduction of harmful chemicals and invasive species, has created a perilous situation for amphibians. Urgent action is needed to mitigate these threats and preserve the ecological balance that amphibians help maintain.

Like all animal classes, the survival of amphibians is threatened by the effects of global warming. However, amphibians are particularly susceptible due to their thin, permeable skin which they breathe and absorb chemicals through. Consequently, their bodies are extremely sensitive to environmental factors, such as disease, habitat destruction, temperature, and pollution.

Local change also plays a large role. The encroachment of urban developments and agricultural expansion have resulted in the degradation and fragmentation of amphibians' habitat, posing large threats to their survival. As California’s population grows, natural habitats continue to be converted into residential, commercial, and agricultural areas, severely limiting amphibians’ breeding and foraging grounds. Additionally, transportation poses a significant threat to amphibians’ survival, as the presence of wide roads and highways often creates impassable barriers to migration. 

“I ride my mountain bike around Lake Lagunitas every week,” said an anonymous Marin County Resident using the pseudonym Jane. “Especially in the wetter months, I see newts and frogs crossing the trail all the time. The species I probably see the most would be the orange-belly California Newt.”

While the California Newt is classified as a Species of Special Concern in California, it does not have federal protection. Habitat loss and destruction, particularly as a result from human alteration of the land, is a threat to newt populations throughout California.

“There are signs posted to warn people of newt crossing, but they are still stepped on and rolled over. I have run over one personally, and I felt terrible. Newts are run over every day, but I don’t see much being done about it,” Jane said. 

Matt Cerkle is the Senior Park Ranger of the Mount Tamalpais Watershed. The Mt. Tamalpais Watershed is the primary source of drinking water for the residents of central and southern Marin County. Consisting of multiple large bodies of water, the watershed is home to over 400 species of wildlife, including rare, threatened, and endangered species. Cerkle attributes the decline of the California Newt population in the Mt. Tamalpais Watershed to human activity.

“There is a fair amount of mortality due to human actions,” Cerkle said. “The number one threat [to the California Newt] is climate change, [and] we’re unsure whether the newt population will be able to adapt to its new climate and habitat. A secondary threat is recreational use, like hiking and biking, but this won’t stray the newts from the watershed.”

According to Cerkle, the Mt. Tamalpais Watershed has seen amphibious species go extinct in specific areas. The foothill yellow-legged frog is of the watershed’s vulnerable species. 

“The frogs have actually seen more impacts due to recreational use [of the Mt. Tamalpais Watershed] than the newts. Recreational use in the Cataract Creek area along Cataract trail, one of our most popular hiking trails, caused the local population of foothill yellow-legged to go extinct in the creek. People go into the pools of water, disturbing the egg sacs to the point [the yellow-legged frogs] could no longer breed successfully,” Cerkle said. 

Cerkle believes the California Newt plays a vital role in the ecosystem of the Mt. Tamalpais Watershed. 

“[The California Newt is important because] it's an indicator species, if the environment is healthy the newts will signal that, and if the newts were to disappear it would show that the ecosystem is suffering. Amphibians are a key component of the ecosystems they inhabit,” Cerkle said. “Not only do they help keep the insects under control, but they serve as a crucial part of the food chain.”

Of the amphibians affected by human actions, many have been classified as endangered. The California Tiger Salamander (Ambystoma californiense), a species that was once abundant in California, is experiencing a severe decline, causing the species to be listed as endangered since 2000. Years of research have revealed the decline of the California Tiger Salamander is primarily anthropogenic. The introduction of non-native species, habitat destruction, and pollution are all contributing factors to the decline. Invasive species such as the American Bullfrog and various fish prey on salamander larvae and compete with them for resources, further reducing their populations. Pesticide use in agricultural areas also contributes to their decline by contaminating their habitats and worsening the quality of their breeding ponds.

Like the California Newt, the threats to the California Tiger Salamander are predominantly local rather than global. Their limited range of travel means local geographical changes and conservation policies have a substantial impact on their populations. While global issues such as climate change may bear an effect on their habitat over time, the immediate threats stem from current human activities in California.

The extinction of the California Tiger Salamander would have significant repercussions for the  ecosystem it inhabits. The species plays a vital role in the food web as both predator and prey in controlling insect populations and providing a food source for birds and mammals. Their burrowing behavior also aids in soil aeration and nutrient mixing, contributing to the health of the grassland and woodland ecosystems they inhabit.

While their population is relatively small in comparison to other amphibian species, the decline of the California Tiger Salamander can serve as an indicator of broader environmental issues. Amphibians are often considered bioindicators due to their heightened sensitivity to environmental changes, and their decline signals potential problems in the ecosystem, such as pollution, habitat degradation, and the loss of biodiversity.

Although strategies have been implemented by California’s Government to mitigate the effects of climate change on amphibians, global populations continue to diminish. The IUCN’s Global Amphibian Assessment 2 revealed that amphibians are the most threatened vertebrate class (41% of species are globally threatened), and that “Agriculture is the most common cause of habitat loss and degradation threatening amphibians.”

The decline of California’s amphibians, including species like the California Newt and California Tiger Salamander, serves as a stark indication of our environment’s dwindling health. Whether it be from habitat loss, pollution, or otherwise, amphibians are struggling to adapt and survive. Immediate action is critical in mitigating the effects of human development and preserving these irreplaceable species.