The winter months can bring difficult travel conditions, but these can be made safer with shovels, plows, and deicers such as road salt. Road salt can do a little to improve safety, but its use is not without consequences. Researchers from the College of Agriculture, Health and Natural Resources and the College of Liberal Arts and Sciences are working to better understand the many environmental effects of too much salt on roads and sidewalks.
Bigger frogs, more mosquitos
Department of Natural Resources and Environment Researcher Tracy Rittenhouse and her group are studying the effects of road salt on amphibians.
“Previous research has shown that tadpoles have a tendency to grow larger from salty wetlands and high-salinity conditions,” says Rittenhouse. “In general, we think bigger sizes are a good thing, but we’re not sure why they’re bigger or how they might differ physiologically.”
Rittenhouse explains that frogs that start living in salty conditions, although larger, seem to have no benefits later in life, while frogs from lower salt conditions started their lives smaller but grew much faster and larger over time. These results show that amphibians are not only amazingly salt tolerant, but that we still have a lot to learn. Despite the amount of salt getting into wetlands, this resilience is the reason we haven’t seen a massive decline in amphibian populations, says Rittenhouse.
Another experiment carried out by a student in her laboratory group showed that young frogs not only recognize whether the ground is salty, but also consistently avoid these conditions.
“This project opened up this whole arena where we should really look at the juvenile and adult frogs and how they might react to the salinity in the terrestrial environment,” she says.
Rittenhouse says the road’s heavy salting has other consequences, including disruptions in the food web, which can harm some members of the ecosystem while benefiting others.
“Salt, for example, generally kills most of the zooplankton,” says Rittenhouse. “Zooplankton eat phytoplankton and tadpoles eat phytoplankton. So with less zooplankton, the tadpoles have more food because these competitors are gone. There are shifts in the churches, but it’s not all negative for everything. Another thing that works well in high salinity wetlands is mosquito larvae. While many other things die in high salinity conditions, the mosquitoes can take this pretty well too. Maybe that would be a motivation to use less salt. “
Rittenhouse warns that if the “more salt is better” mindset does not change, we will see more negative effects.
Future changes in plant communities?
UConn researchers Beth Lawrence, Ashley Helton, and Gary Robbins recently published a study in Ecosphere Investigation of the potential effects of road salt on plant communities and biogeochemistry in wetlands. The road-dense, wetland-rich landscape of the northeast provides a perfect setting for this type of investigation, says Lawrence.
“Other studies have found a higher incidence of invasive species and a shift towards salt-tolerant species,” she says. “Surprisingly, we did not notice any major shifts in the vegetation even where we observed an increased salt content at the roadside. We saw that roadside invasive species could have a competitive advantage, and we’re not sure if this was caused by road salt. “
To get a better idea of possible salinity thresholds, the researchers examined the seed bank – dormant seeds in the soil waiting for optimal germination conditions. They collected soil from a nearby wooded wetland and exposed the piled seeds to different levels of salt in order to study the emergence of the seedlings under different conditions.
“We found that increased salinity decreased the number of germinating seeds, decreased the seeding density that came out of the ground, and decreased the diversity of regrowing species,” says Lawrence, “which suggests that there are some plants that are more tolerant and more. “able to germinate under conditions with higher salinity.”
Fortunately, according to Lawrence, these experimental salinity levels are higher than field conditions, which are currently not salty enough to produce a strong response.
“If high amounts of road salt continue to be applied, we could certainly cross this threshold and see major changes in the vegetation in the future.”
A sodium-lowering solution
Mike Dietz, extension educator and faculty member in the Department of Natural Resources and Environment, is working to counteract the high salt application rates. His research also monitors salinity in the UConn Storrs area, and he says the best time to review application rates is now.
“From some of the surveillance that we have here on campus with Eagle Brook once we implement it Green Snow Pro training, given by UConn’s T2 center, The application rates were greatly reduced, over the course of two years we began to see the salt concentrations in the stream, ”says Dietz. “In Connecticut, we have this ‘glacial’ ground through which the water moves very slowly. For example, it takes about 10 months for water to flow from Storrs Hall to Swan Lake. So it’s really a delayed response as we’re reducing application rates. It will be a year or two before we see a decline. “
The biggest hurdles include social factors and expectations, which, according to Dietz, are largely an unresolved issue.
“That is a big topic. In the 1980s and 1990s, we recorded a sharp increase in the amount of road salt applied. I think that was when expectations changed. While people used to stay at home after a winter storm, now everyone has to go out and get to work. There is a lot to think about, ”he says.
Dietz says this issue is attracting the attention of state legislators after a Road salt bill was proposed in 2021. Dietz and a nationwide chloride working group are now working with the legislature to work out the best possible bill for the upcoming session. The bill would oblige private contractors to do that Green Snow Pro Training that, according to Dietz, would be a step in the right direction.
“In New Hampshire, about 50 percent of salt freight is on private property,” he says. “Relief of liability to contractors and property owners taking this training would be huge and would really make a difference in the amount of salt used in Connecticut.”
Robbins, professor at the Department of Natural Resources and Environment and the Department of Earth Sciences agrees that this issue needs to be addressed and says Road salt pollution of the groundwater is one of the biggest problems caused by the excessive use of road salt.
“We’re not slowing down how much salt is applied,” he says. “The salt ends up in the groundwater, where elevated concentrations persist even in summer. It can take a very, very long time for the salt to come out. Over the years, we have examined a lot of groundwater for salt and found that the salt concentration has increased by an average of ten times its natural level. “
Everyone can do their part to reduce salt consumption at home, because there are alternatives to salt deposition, says Dietz. Plowing or shoveling driveways and sidewalks can allow the sun to warm the surfaces and melt the snow and ice. It is also important that the melt water can drain off so that it does not freeze again on the surface later. Dietz has been lucky with this method and says he doesn’t need to use salt at home. If you’re using salt, make sure you don’t overdo it, he says.