Biologists from the University of California, Berkeley, have reported that salamander populations in parts of Central America have declined sharply in the past 40 years — and global warming could be the cause.

UC Berkeley researchers compared data of current salamander populations in western Guatemala and southern Mexico to data collected from the locations between 1969 and 1978. The team found that two of the most common species of salamanders in the areas 40 years ago are extinct, and several others have experienced large drops in number.

Amphibian populations have been declining worldwide, and experts have attributed the drops in other amphibian species — such as the well-documented plummeting of frog populations — to factors such as pesticides, predators and habitat destruction.

But according to David Wake, professor of integrative biology at UC Berkeley and the new study’s lead researcher, the salamanders in Guatemala lived on a controlled nature preserve, so neither outside predators nor human disturbance could have been responsible for their startling disappearance.

The nature preserve couldn’t guard the salamanders from the effects of global warming, however, and the climate conditions of salamanders’ habitat did change over the past 40 years. Salamanders are highly sensitive to climate and humidity, so even a slight increase in temperature could have caused them to seek higher elevations. Having thrived at their former altitudes for thousands of years, the salamanders were unable to adjust to these new habitats, researchers suspect.

Unlike other amphibians, salamanders are famously secretive creatures and often go unseen by all but keen, deliberate observers. Wake says salamanders’ effects in ecosystems do not go unnoticed, however: In forests, salamanders account for a large amount of biomass. Certain species even depend on salamanders for their own survival, such as the salamander-eating snake, which, according to Wake, is also showing signs of population decline.

See Science Daily's article for more information on Wake and his colleagues’ study, and check out A Wealth of Salamanders for more on these fascinating creatures and their unique presence in North America.

Photo by iStockphoto/Armin Hinterwirth

According to the World Health Organization, lead is unsafe at any level. At high exposure levels, lead poisoning can cause severe brain damage or death for both adults and children. At low levels, it can cause vomiting, learning difficulties, behavioral problems and even spontaneous abortion. Children are at higher risk for lead poisoning because their bodies are still developing; and they absorb a higher concentration of lead than adults (when exposed to the same amount).

Because of these risks, many dangerous products have been taken off the market, including lead paint and leaded gasoline. But one lead product that's still causing problems for both people and wildlife is lead ammunition.

In recent studies done by the Peregrine Fund and Washington State University, people that eat venison risk lead exposure. The study analyzed 30 white-tailed deer shot under normal hunting conditions in Wyoming with standard lead-based bullets fired from a high-powered rifle. Of the 30 deer carcasses that were studied, 80 percent of the processed meat contained metal fragments, and 92 percent of those fragments were lead. 

In the study, the carcasses were processed into packages of ground meat and boneless steaks at different commercial meat processors, using standard preparation practices. Although processors habitually cut and toss out meat around the wound and along the bullet’s path, a number of packages still contained lead fragments. Some of them contained up to nine lead fragments, while others had few or no fragments — leaving processors and consumers with no way to determine which packages will contain lead in the future.

And the risk of exposure isn't limited to humans. California condors are also suffering from exposure to lead ammunition. In December 2007, the California Fish and Game Commission passed a regulation that bans hunters from using lead ammunition in California condor territory in an attempt to reduce deaths of the endangered species. The birds have been dying for years, largely as a result of lead poisoning that they get from scavenging the carcasses of animals killed by lead bullets. At one point, the species was reduced to nine individual birds, but that number has significantly grown to 305 since the animal was placed on the Audubon and American Bird Conservancy WatchList. The lead ammunition ban should help boost their numbers further after it goes into effect July 1, 2008.  

The ban only covers the California condor territory, but officials think that, because the exposure to lead is so threatening to wildlife and humans, the ban will most likely spread to other areas around the country. Rick Watson, vice president of the Peregrine Fund, believes that copper bullets will soon be the bullet of choice for hunters nationwide. Until then, the lead-based bullets can still legally be used outside of California condor territory. So, for now, it’s an issue to be aware of for those who hunt or eat venison.