Tuesday, 28 April 2015

Past and Present Climate Change in the Severn Estuary: Sea Level Change and Mediterranean Visitors


As an archaeologist I have always been fascinated with the remains of past human societies which lie preserved in the ground beneath our feet. There are some areas in which archaeological remains are exceptionally well preserved. The Severn Levels is one such area. 
Within the clays and peats which line the banks of the Severn Estuary are the remains of settlement, hunting and fishing activities which stretch back thousands of years. Among the most evocative remains are the footprints of animals and humans, including those of small children, preserved in the estuarine silts. These footprints date from between 8000 and 6400 years ago, at a time when the ice caps still held large volumes of water, sea levels were lower, and oak forests grew in the areas which today lie within the intertidal zone.

Jethro, my artist partner, and I are interested in the connection between climate and sea level change, and so, with evidence of sea level change in the past, a trip to the Severn Estuary seemed a good place to start.

The Severn Estuary and the sediments which hold evidence of sea level change in the past
Initially I set out to find the blue/grey marine clays and peats which are evidence of changing sea levels and former periods of marine inundation. However, as I squelched my way through the mud, leaving deep-set footprints behind me, I began to think of the Mesolithic footprints, and all those which had marked the shoreline since. I started to look more carefully at the footprints in the mud around me; those of people, dogs and birds.
As I was photographing I had a chance encounter with another archaeologist walking the foreshore, whose research in this area has spanned well over a decade. In this time he has noticed changes not only to the archaeology, which erodes at an alarming rate, but also to the species living in the area today. I explained why I was photographing the footprints, and told him about our Paper Makers project, in response he informed me that he had seen Little Egrets while out walking- a species which had been rare when he started his work on the Severn Levels, but was now common.
When I got home I went through the day’s photographs, trying to identify what species were represented, and found that some of my photographs showed the tracks of the Little Egret:

Tracks of the Little Egret- I think!

After doing some more research I discovered that the species was once rare in the UK, being commonly found in the Mediterranean. 
However, it is thought that, due to climate change, the species has expanded its range and is now common along the south coast of England and Wales. Having set out to look for past evidence of sea level change, reflecting different climatic conditions, I had perhaps stumbled onto evidence for climate change going on today! I look forward to exploring the Severn Estuary further with Jethro, and investigating what other signs can be found within the mud. 

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