Salt Marshes and Climate Change

By Charles Croydon

 

What is happening locally due to climate change? We do not live in Chamonix in France where one can see the glaciers melting & retreating. Neither are the changes as dramatic as in Antarctica where earlier this century the Larsen B ice shelf broke up and without the ice shelf acting as a ‘cork’ the glaciers are now pouring into the sea 4 to 5 faster than 10 years ago. So what is happening around here?

 

Because of the current 6mm annual rise in sea levels, the salt marshes in our local rivers are being covered with water more frequently. The salt marshes only used to be covered at spring high water and the more frequent covering is affecting the plants. Without getting into too much detail the plants whose roots hold the salt marsh together are going and the salt marsh is eroding. As the salt marsh absorbs 40% of the wave action on the river walls, the river walls will erode faster than we can afford to repair them and there will be flooding. 

 

The strength of any salt marsh lies in the bulk of its root mass, which is usually pretty ancient and therefore is strongly resistant to erosion. It is basically peat. This is what you see that underlies the humps and bumps where salt marsh growth has gone altogether. The process of decay is promoted by small channels becoming larger and eventually isolating pockets of growth and eventually eating it away from all sides.

 

There are various causes of the original demise of certain characteristic salt marsh plants and the increasing frequency of inundation at high tide doesn't help. A healthy salt marsh will have a good covering of grass, which was the case at Loders Cut near Woodbridge on the River Deben, and this is Sea Couch.

 

The other plants that are no longer actively there are Sea Lavender and Sea Vetch. There are of course more, but these are usually indicators of a good even covering of vegetation. What we now see is mainly Spartina Grass, which is a well known pioneer species and Sea Aster, which is a survivor, both of which give a "leggy" appearance to the place and also provide residual strength on the clumps where they remain. Also, seasonally you will see samphire, which is a pioneer species, but will only lead to a further stage of colonisation if the conditions are appropriate; otherwise it will continue to appear on those levels recently vacated by more robust growth. Right now you can see it here and there as livid pale green and red patches on the slightly lower levels.

 

In Ipswich we are taking some precautions. The new housing by the docks has no one sleeping on the ground floor. The new University building with a sloping grass roof has all its electric cables & systems at least 2 feet above the floor. There are plans for a new flood barrier.

 

Another issue is insulation. Now with a chill in the air we think about insulating our homes to keep warm, but it is actually the heat that kills. In the last hot summer thousands of old people died in France from the heat.