Maritime motorways

[Wild-Woman]

We have discussed this before but with the amount of salt being distributed along roads and motorways this year (all necessary, I know) I suspect a steep rise in salt tolerant plant species creeping inland along central reservations and verges. I wonder if the effect will be immediate during the spring, or once some seeds from the tyres of cars have been dropped in the next year or so?
It'll be interesting to see what happens.

Ps- I would think the rivers and water table would have higher salt levels too?

What do the botanists amongst you think?

[Jim Ford]

I was told by someone involved in a new (at the time) local 'link road' that they plant salt tolerant species on the roundabouts and verges.

Jim

[Paul mabbott]

This has actually been happening for decades. I recall that Danish scurvy grass (Cochlearia danica) was one of the first. I can't find a comprehensive list for UK although I'm sure there have been studies - mainly by botanists in traffic jams!

Distance should be no problem. In a Swiss study various northern littoral species have gradually made there way to Switzerland, including:
Cochlearia danica – Danish scurvy-grass; Plantago coronopus – buck’s horn plantain; Catopodium loliaceum – sea fern-grass; Spergularia salina – salt sandspurry; Puccinellia distans – weeping alkali grass

[The Woodman]

You're right paul, Danish scurvy grass was one if not the first halophitic (?) plants noted alongside our motorways. I attended a Highways Agency biodiversity plan launch meeting a couple of years ago and there was mention of the way it spreads by seed attached to tyres.

In some places the central reservation is matted with the stuff.

As for studies and references I have a copy of the HA BDP if you want me to have a look.

[Wild-Woman]

Originally Posted by Paul mabbott

Distance should be no problem. In a Swiss study various northern littoral species have gradually made there way to Switzerland, including:
Cochlearia danica – Danish scurvy-grass; Plantago coronopus – buck’s horn plantain; Catopodium loliaceum – sea fern-grass; Spergularia salina – salt sandspurry; Puccinellia distans – weeping alkali grass

Amazing. A country land-locked with a sea plant population.

Can a population of salt tolerant plants be sustained, if in the future, the salinity is diluted eg by heavy rainfall?

[Paul mabbott]

Originally Posted by Wild-Woman

Amazing. A country land-locked with a sea plant population.

The wonders of human manipulation of nature ....

Can a population of salt tolerant plants be sustained, if in the future, the salinity is diluted eg by heavy rainfall?

I suspect not for long once application of salt was terminated. Sodium chloride is very soluble and, in most cases, is probably continuously leached from the soil surface into drains, rivers &c.. Stop aplying salt and in most places the salt would reach low enough levels for non-halophile species to recolonise - I'd guess at about ten years.

We shouldn't forget that while these plants have evolved physical and chemical processes which allow salt-tolerance, their proliferation is also in large part due to absence of competition from other, non-tolerant species. It's an equation with two sides!

[Dorts]

Danish scurvy-grass is now not only along virtualy all major routes that recieve winter salt, but also along many B roads.
It would be interesting to hear if anyone has found it on an inland 'unclassified' road?
Dorts.

[Ukwildlifeo]

Slightly off topic but when in Romania I visited a site far in land that not only had saltmarsh plants but a saltmarsh! Where salt rock (halite) is exposed in a basin and the lakes are brackish salinity. Lots of brine shrimp there too!

So inland saltmarsh plants arn't always unnatural, in Europe at least. If there were any exposed halite deposists they were probably mined long ago in the UK

[wanlock dod]

Originally Posted by Wild-Woman

Can a population of salt tolerant plants be sustained, if in the future, the salinity is diluted eg by heavy rainfall?

I am not sure that being salt tollerant means that these plants would be intollerant of fresh water, although I expect that they would be out competed by less salt tollerant plants in a less salty setting

Originally Posted by Wild-Woman

I would think the rivers and water table would have higher salt levels too?

I am not aware of any seasonallity to things like conductivity in surface waters. If there were an effect it would probably be most noticeable in a catchment with lots of treated roads, a relatively insoluble bedrock, and little groundwater input to surface waters. Most water sampling is probably not able to catch any difference bacause the salt will (probably) wash away quickly with the first flush of rain. The samples would usually be taken at fortnightly or monthly intervals, although some rivers in the UK do have continuous water quality monitoirng for a few things.

I am aware of a few situations where changes to the water chemistry (in terms of dissolved salts) has had an observable effect on the ecology, but none which are related to common salt (NaCl). The most obvious case would be liming of soft-water catchments to prevent the effects of acid rain, which can shift the local ecology towards one more typical of a harder water.

[Wild-Woman]

Originally Posted by wanlock dod

The most obvious case would be liming of soft-water catchments to prevent the effects of acid rain, which can shift the local ecology towards one more typical of a harder water.

That's interesting, I didn't know that was done.

Thanks for the information wanlock.