America's lakes are becoming increasingly salty due to use of road salt to de-ice highways.

America’s lakes are becoming increasingly salty due to use of road salt to de-ice highways. Photo by Aaron Burden via Unsplash.

Many lakes in North America are becoming saltier thanks to road salt. A recent study looked at 371 lakes in the Midwest and Northeast, and found that 44 percent of them were undergoing long-term salinization. This process means that these lakes have increasing amounts of chloride in them, which is bad for the ecosystems of those lakes.

The main cause of this is road salt, used to deice roads in colder areas so that people can drive safely.

“These results are likely an underestimation of the salinization problem, as a number of regions with heavy road salt application, such as Quebec or the Maritime Provinces of Canada, had no long-term data available” said study co-author Sarah Bartlett, a graduate student at the University of Wisconsin-Milwaukee.

The problem is that this salt has to go somewhere, and it ends up in freshwater lakes, either directly or through the watershed. Many of these states have regulations to protect lakes to some degree, but few bother to extend those protections more than 300 meters from the water, when in reality, runoff within 500 meters stands a chance of ending up in the lake. Even if only 1 percent of the surfaces within those 500 meters are impervious, meaning pavement into which salt cannot seep, it can lead to an increase in salinization.

In fact, if current salinization trends continue, the study’s authors report, North American lakes will surpass EPA-recommended chloride levels in 50 years.

Elevated chloride levels can harm fish and other creatures that occupy lake ecologies, and can even prevent lake water from mixing, which causes low-oxygen regions that can suffocate aquatic life. Higher chloride means less biodiversity and less life in general.

Unlike rivers and streams, water stays in lakes for a long time, meaning that minerals like salt stay in them for a long time as well. This allows for the buildup of chloride. The study’s authors recommend better lake and shoreline management practices as a preventive, but the reality is that many lakes lack the necessary monitoring equipment to adequately track the health of those lakes.

“We need to manage and monitor lakes to ensure they are kept ‘fresh’ and protect the myriad of services they provide, from fisheries and recreation to drinking water supplies,” said study co-author Kathleen Weathers, an ecosystem scientist at the Cary Institute of Ecosystem Studies.