Salamanders are on the run

Study finds increasing drought, development force amphibians’ migration in N.C.

CorrespondentNovember 11, 2012 

  • How many are there? The number of salamanders in North Carolina is unknown, though Wake Forest biology professor Robert Browne estimates it’s in the millions. More than 50 species of salamanders can be found in North Carolina. Steven Price calls the state a “global hot spot” for salamander diversity, especially in the Appalachian Mountains. Many species can also be found in the Piedmont and coastal plain.

Following salamanders throughout North Carolina was an eye-opener for Steven Price. He hopes what he learned will be the same for others.

The former Wake Forest graduate student led a recently published study that indicated major salamander populations could start to wane in some N.C. habitats, potentially upsetting the fragile balance of our stream and forest ecosystems and making it crucial for communities and developers to plan for safeguards.

“There have been a number of previous studies that have correlated how many salamanders are in an area versus how much development there is in the area,” says Price, now an assistant professor of stream and riparian (river) ecology at the University of Kentucky. “My work was the first to follow these salamander populations through the development process.”

Exceptional drought from September 2007 to September 2008 highlighted the 2005-2009 study in Cabarrus, Gaston, Iredell, Lincoln and Mecklenburg counties by biologists at Wake Forest and Davidson College. The findings appear in the scientific journal Herpetologica.

Researchers studied the migration patterns of the northern dusky salamander and two-lined salamander in 30 small streams. Because more drought and development are predicted for the region, their goal was to learn how salamanders respond to those conditions.

Price says the adult salamander has about a 90 percent month-to-month survival rate under normal drought conditions. But their larvae, which must be in water for development and metamorphosis, disappeared from an average 30 percent of sites during the exceptional drought year, in which stream levels dropped to 110-year lows in Mecklenburg County.

“Droughts are rated (by the North Carolina Department of Environmental and Natural Resources) on how much water is available,” Price said. “It’s rated from 0 to 4, 4 being the most extreme. We were at 4 for several months.”

Climate change models show droughts will become more prolonged. Robert Browne, a Wake Forest biology professor who oversaw the salamander research, says “the most likely, reasonable scenario is that we’ll get much more extensive droughts so that much of the United States, including the Southeast, will get periods of droughts that are two to three times longer than in the past 150 years.”

Forced alternatives

Researchers found that as water disappears in stream beds, the northern dusky salamander and two-lined salamander – both abundant in the western Piedmont – seek refuge in high-humidity areas. Price says it’s unclear where they go.

“We’re not entirely sure. That’s a good question,” he says. “These guys spend most of their time either within a stream or really close to a stream, within a meter of the stream. They usually don’t move up into the woods. ...

“What they’re probably doing is moving down into crayfish burrows that get down into where the water table is. They can find big rocks that take longer for the water to dry up underneath them. They can get way up underneath the bank.”

Browne cites two results of urbanization that limit the salamander’s migration options.

“Salamanders go out and forage outside the stream bed itself, in moist, sponge-like areas ... They’ll come back, immerse themselves in water and rehydrate again. But if those areas are gone because of development, where developers have come very close to the stream, that foraging zone (called a riparian buffer zone in the study) has now diminished rapidly.

“The other major problem besides the reduction of that buffer zone is that so much of the land is going to be filled in with silt. The silt comes in and fills up the stream bed and then dries out like hardened mud – almost like concrete. That fills in basically all the interstitial areas, and the salamanders can’t really live in there.”

Any number of organisms are affected by climate change and development. “But the reason amphibians like salamanders are good to study is, changes in their numbers indicate the conditions of the aquatic environment pretty well,” Price says.

“When we think of these small … streams that I studied, throughout the landscape those small streams make up the majority of the fresh water on the surface. These larger aquatic systems like rivers wouldn’t function very well if you removed all these small streams from the environment.”

Salamanders are most numerous in these small streams, Price says. He adds that salamanders are important predators of pesky invertebrates such as snails and bloodworms, and are important food sources for other animals that inhabit these areas.

Imperfect storm

Rampant development in the Charlotte area during the middle of the past decade provided ideal conditions for research.

He said that in testing survivorship, he alone marked well over 3,000 adult salamanders in a 100-meter stretch of stream.

“I was able to get out there, assess the salamander population at the site before development took place, and then track how the population responded to development over time,” he says.

“What I found was that salamanders respond pretty quickly to urbanization. In one year after a site was developed, we saw lower abundances of the northern dusky salamander and the two-lined salamander. Within a couple years we saw there were fewer adults, probably because there were ultimately fewer larvae that were going through metamorphosis and entering the population.”

Price and Browne emphasize that the vast majority of salamander species aren’t in danger of extinction: “The salamander is very widespread and pretty flexible,” Browne says. “So what we would see instead is that its range would reduce considerably, and its occurrences would probably decrease to about 50 percent of the areas where you find it now.”

He says one species that’s in danger is the northern pygmy salamander – Desmognathus organi– “a new species that only occurs on four mountaintops in North Carolina. Because of the drought and other environmental parameters, I would probably name that species as one that’s going to be extinct within 50 years.”

Planning solutions

Price says protecting and widening riparian buffer zones and stormwater ponds – the ponds can catch sediment at construction sites – can stem the reduction in salamander numbers. There’s hope, he says.

He cited the success story of a nature preserve in the Summers Walk neighborhood in Davidson.

“We worked with the Davidson Land Conservancy as well as with some other local groups to educate folks in Davidson about the importance of this wetland, and how the animals in this wetland use the terrestrial environment and how that terrestrial environment is so critical for population persistence. We talked with the developer a lot.

“What ended up happening was, Mecklenburg County bought a large part of that Summers Walk property to maintain a large buffer zone around this wetland to make sure the integrity of that wetland stayed intact and that the animals that used that wetland remained.”

Everyone can benefit by preserving ecosystems, Price says.

“I think we need to realize that water is a critical resource for a lot of animals and people. We need to maintain the aquatic systems in an urban environment just like we do anywhere else. We should probably be thinking about planning in a way that is more sustainable in general.”

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