How do road salts impact Chesapeake critters?

Nearly every winter, road salt is applied to roads and sidewalks to melt snow and ice. It is certainly effective at keeping us safe, but the environmental impacts of road salt are far reaching for humans and wildlife.

What is road salt and how does it impact the environment?

The most common road salt is sodium chloride, the same type of salt you use to cook with. Road salt is effective at lowering the freezing point of water and therefore preventing ice formation. Road salt use began in the 1950’s and its popularity has dramatically increased over time. We now use an average of 10 to 20 million tons of road salt every year in the United States.

The salt applied to our roads washes off into the waterways, and also accumulates in the soil, where it soaks into groundwater. Even if we stopped applying road salt today, we would see a release of it for decades!

This can have major impacts on the freshwater habitats of the watershed, like certain rivers, lakes, ponds and wetlands. The salinization, or the increase in salts, of freshwater is one of the biggest threats to the wildlife who live in these habitats.

Wildlife impacted by road salts

Zooplankton

Zooplankton living in the lakes, pond and wetlands of the Chesapeake Bay watershed require relatively fresh water to hatch their eggs. Species of zooplankton have different abilities to handle salinization, but in order to have a successful hatch, their habitat needs to return to normal salinity levels. Road salts secreting from the soil or running off the land can delay or disrupt this critical time for zooplankton, causing a decline in the population. This decline can have a ripple effect throughout the entire ecosystem. They are an important food source for fish and insects, and they also eat phytoplankton, which when left unchecked, lead to harmful algal blooms.

Amphibians

Amphibians are particularly vulnerable to pollutants like road salts because they absorb them through their skin. Wood frog tadpoles are highly suspectable because they emerge in early spring and are therefore exposed to the road salts applied during winter for longer periods of time. Road salts can also impact the male to female ratio of wood frogs, which can endanger their long-term reproductive rate. Spotted salamanders are another amphibian that’s significantly impacted by road salts. For this species, freshwater salinization causes delayed hatching, increased instances of deformities, reduced size and shorter lifespans.

Fish

The Chesapeake Bay is brackish—or a mix of fresh and salt waters—but the rivers that lead to the estuary are mostly fresh. Road salts can spike the salinity of these freshwater habitats and make them less suitable spawning ground for migratory fish. The species who are most tolerant to salt may begin to outcompete less tolerant ones, which throws off the ecosystem. Spikes in salinity from road salts can even impact the development of fish, causing certain species to be smaller and weigh less.

In lakes, ponds and wetlands, salinization from road salts can impact the mixing of the water column, which can harm fish. Salty runoff can form a heavy layer that prevents oxygen, heat, carbon and nutrients from being dispersed to different layers of the water. This impacts where fish can survive and can fuel harmful algal blooms which can also kill fish.

Humans

Road salts are even a threat to our drinking water. The Potomac River is a drinking water source for five million people and it is showing a 200% increase in salinity over a 30-year period. Wastewater treatment plants do not have desalination equipment and once salt is in our environment it is very difficult to remove. Road salts can also corrode pipes and release toxic metals into drinking water. In rural areas, road salt is absorbed into groundwater and can seep into wells. In terms of infrastructure, the U.S. Environmental Protection Agency estimates that damage from road salts costs $5 billion in annual repairs across the country.

What you can do

Road salt isn’t going away entirely any time soon. It is still a necessary measure for public safety and alternatives to road salt come with their own risks. To help lessen the problem, make sure to properly apply road salt on your property. Share information about proper application with family, friends, neighbors and coworkers. Join a community science program like the Izaak Walton League’s Salt Watch to monitor your local waterway for impairments such as high salinity levels.

Salinization is becoming an increasing issue in the Chesapeake Bay watershed. It threatens marine life, harms forests and wetlands, and can even mobilize harmful chemicals like radon, mercury and lead. And it doesn’t just come from road salts. Construction, agriculture, mine drainage, sewage leaks and weathering infrastructure are also causing salt to enter waterways and coastal areas. We’re not at the point where salinization is causing tumors on fish or hundreds of them washing up on beaches, but the warning signs are there. To improve the health of the local ecosystem and waterways, we must remain vigilant of our land use year-round.