shortcuts badge

Is gritting the roads bad for the environment?

Where do all those thousands of tonnes of rock salt end up? And is the salt bad for animals and plants?
    • The Guardian,
    • Jump to comments ()
Gritting roads
In high concentration, sodium chloride can harm plants and animals – just ask any slug. Photograph: Jeff J Mitchell/Getty Images

Over the past few weeks, the nation has developed an unhealthy taste for rock salt. Have we got enough of the stuff to see us through winter? When are the emergency orders placed abroad due to arrive? Why hasn't my road been salted yet?

But when the big thaw comes, expect this new-found interest to melt faster than the snow itself. One important question does remain, though: where do the thousands of tonnes of rock salt dumped on our roads during every cold snap actually go once they are washed away?

Sodium chloride (sand and anti-caking agents are often added to the grit, too) can have a deleterious impact when it comes into contact with plants and animals in high concentration – just ask any slug. Logic suggests, therefore, that dumping rock salt on our roads isn't exactly good news for neighbouring wildlife, or the rivers that will be the ultimate destination for much of the saline runoff.

In places such as Canada and the US, where cold snaps regularly out-trump anything the UK's climate can muster, this issue is taken seriously and studies have shown that road salt can damage, or even kill, vegetation and trees growing on the verges, as well as amphibians that can suffer acutely due to their permeable skin. Migratory birds are said to be at risk, too, with seed-eating species reportedly finding it hard to distinguish between gritty salt crystals and the mineral grit their diets require. As a result, measures are taken in some states to limit the use of de-icing salt.

The Environment Agency says it is not unduly concerned, though. "While there are minimal short-term impacts to the ecology of watercourses, the salt intake is not prolonged enough to cause significant long-term damage," says a spokeswoman. "As salt from roads tends to enter watercourses during a thaw, the salt is diluted relatively quickly. We do sample streams in the spring and have found no evidence of significant impact on wildlife from river salt intake."

Today's best video

Today in pictures