CLEVELAND, Ohio -- More than a half century of liberally salting Ohio's icy winter highways is turning our grassy roadsides into saltwater seasides.

Botanists like Jim Bissell of the Cleveland Museum of Natural History and Rick Gardner of the Ohio Division of Wildlife say not only are native plants dying off from a gradual buildup of salt and salt water, but that plants now thriving are species arriving from ocean estuaries or coastal salt marshes.

In fact, the harsh roadside environment has probably been gradually changing for as long as snow plow crews have been salting roads in winter -- and accelerating over the last four decades or so.

And the tide is turning -- in favor of species collectively known as halophytes, or plants that tolerate or demand salinity.

"We're not talking about a slight difference, either," Bissell said. "The salt creates a habitat more like the salt flats in the extreme southwest and only certain plants can live there. You see the leftover salt in the summer when the berms are all white."

So instead of finding the fescues and perennial rye grasses that grew roadside since before the paving of asphalt highways, Bissell, Gardner and others find seaside goldenrod, various salt grasses from the East Coast -- or even European salt-tolerant species Juncus compressus, commonly known as round-fruited rush.

"It's already an interesting and harsh ecosystem, if you think about it," said Gardner, a wildlife management assistant for the state for the last dozen years, but a botanist for more than two decades.

"It's a dry, open area with gravel and all of the compaction of soil for construction. You find a lot of interesting plants along roadsides already -- throw in all that salt and it gets even tougher for most plants to survive."

Tough for some, but not hardy species like black grass (Juncus gerardii).

The species, actually a member of the rush family, forms "dark green meadows along the tidal flats and salt marshes" along the East Coast from Maine to Georgia, but is not native to Ohio, Bissell said.

"But we've just recently found it in downtown Cleveland for the first time," Bissell said. "There's no reason it would be here other than it can live in the saline conditions along the side of the road."

There's no question where the salt comes from -- between 15 million and 18 million tons of sodium chloride is spread over the nation's highways each winter. But how do seeds from salt marshes in Florida or estuaries in Maryland make it to a ditch off Interstate 71?

They hitch a ride -- either in the belly of a bird or the tires of a car or truck -- although some might simply be windblown, as well, Gardner said.

"Travel by car and truck tire is the most likely explanation, though I don't think anyone has actually tracked it," Gardner said. "But we do know that if you map out the distribution of any of these plants, it's totally linear -- all along the highways, but not scattered inland at all."

With a few exceptions. A number of halophytes have colonized the area near the Morton Salt Plant near Mentor Headlands State Park because of the high saline content of the water and soil there.

Many of the saltwater tolerant plants began to show up in the 1970s, Gardner said, following the increase of road salt in the 1950s and 1960s. Prior to that, road crews used mostly cinders or sand to provide grip on winter roadways.

"So you only see this kind of thing in states where there is snow and where a lot of salt is put down -- all along Interstate 90 and the turnpike system from Pennsylvania, Ohio and Indiana," he said. "What we call freeway sedge here, for example, was actually a sedge found only in the mountains out west, but it has made its way east for years because of the saline conditions along the roadway."

Generally, the introduction of saltwater-tolerant plants along the side of the road isn't a major environmental concern, but the saltwater runoff into nearby streams is a growing problem, officials have said.

More than 40 percent of urban streams tested in Ohio and 18 other northern states by federal researchers showed dangerously elevated chloride levels likely related to salt runoff from road de-icing.

Elevated chloride can slow plant growth, damage the reproduction cycle for fish and smaller organisms and generally reduce diversity in streams, said John Mullaney, a hydrologist with the U.S. Geological Survey who authored the September 2009 study.

"Adding a high concentration of chloride from increasing uses of road salt, along with salt from other sources like wastewater treatment plants and farms, is particularly bad for the streams," he said when the study was released. "Eventually, it could affect drinking water for some areas."

That future fear -- salt contaminating the groundwater supply now used for drinking water by four out of 10 Americans -- is tempered by how much safer salting makes the roadways in winter.

"That's the greater concern, not whether salt-water tolerant plants are living on the berm," admitted Gardner. "Still, it's fascinating to see how we've created a new ecosystem by our use of roadside over the last 50 to 70 years."