To protect Mersea harbour from becoming too rough to use and washing away. The harbour only exists because of the shelter it gets from the fragile saltmarsh of Old Hall Point, Cobmarsh and Packing Marsh Islands that are in the harbour mouth and stop big waves coming in the harbour, and all these are washing away allowing more big waves into the harbour each year.

Why are the islands washing away?

The Islands have been washing away for hundreds of years as Southern England gradually adjusts to the last Ice Age, which only ended about 12k years ago. The weight of ice sitting on the land in the last ice age pushed Scotland “down’ and caused southern Britain to “rise’. As the ice melted so the process was reversed, just like a “see-saw”. Also the seas and oceans have been very slowly warming since that time, so the combined effect is about 300mm, or one foot of tide rise every century. As sea level rise waves wash away the mudflats and saltmarsh that protect the outer harbour.

Is this sea level rise the same as climate change?

No. These are all natural changes that are thousands of years old. Climate change is the theory that the Earth is warming due to man burning fossil fuels, which trap harmful carbon gas, which stops the Earth naturally losing heat, hence what is called the “greenhouse effect”. 

The extra heat in the Earth’s atmosphere will cause the oceans and seas to get warmer, and if you heat anything it expands, so sea levels will rise more and Mersea harbour will wash away even faster. The best estimate by experts is that the sea level will rise about 500mm or two feet six inches over the next 100 to 200 years.

What are the long term impacts of this erosion on Mersea harbour?

  • Within 70 to 100 years Old Hall Point, Cobmarsh and Packing Marsh will have washed away and much bigger waves will come in the harbour.
  • The jetty will probably be too unsafe to use within 15 to 20 years.
  • The mudflats will be washed out and that mud carried up the creeks of the harbour so they will be too shallow for larger boats.
  • The oyster layings will all be smothered in mud and no longer useable.
  • The sea walls to the RSPB Old Hall bird reserve and Feldy Marsh will probably breach and huge amounts of tidal water will flood them every day.
  • The properties along the harbour frontage will be under increasing threat of bigger waves.

Importance to Wildlife

Apart from protecting the harbour the recharge areas will prove very important for local marine wildlife.

They will form natural looking beaches that unlike the majority of our coast will not be very accessible to disturbance by people and in spring and early summer will provide safe nesting sites for a range of birds including the endangered Little Tern, Oystercatcher and Ringed Plover. In winter these same areas will become roost sites at high tide where birds can rest up and preen.

Rare plants will quickly establish, from the elegant Yellow Horned Poppy, the prickly Sea Holly and the delicate Sea Campion. With little disruption from too many trampling feet they will establish communities that will be able to spread their seed to other parts of the Blackwater coastline.

One of the key features of the whole project is to provide shelter to the beds and nurseries of the local Mersea Native Oyster, a nationally scarce creature that thrives in our muddy estuary waters, is delicious to eat and helps provide a living for the local oystermen, as it has done since Roman times.