Grass cutting plan supports rare coastal moth population in north Essex

Fisher's estuarine moth. Picture: Essex Wildlife Trust

Fisher's estuarine moth. Picture: Essex Wildlife Trust - Credit: Essex Wildlife Trust

A strategic approach to cutting grass along a section of sea defence wall in north Essex has helped provide a boost for a rare species of moth.

Grass cutting the sea defence structure at Hamford Water

Grass cutting the sea defence structure at Hamford Water - Credit: Archant

The fisher’s estuarine moth has a distribution restricted to low-lying, coastal grassland habitats that support its sole caterpillar food plant, hog’s fennel, and have the long coarse grasses that the moth requires for egg laying.

As a result, the moth is only found in two areas - the north coasts of Essex and Kent.

The mainstay are found at Hamford Water, a Site of Special Scientific Interest between Harwich and Walton-on-the-Naze in Tendring, which supports the majority of the Essex population and is the most important UK site for this species, home to approximately 70% of the population.

The fisher’s estuarine moth is a European protected species, which means damage or destruction of its breeding sites and resting places is prohibited - a potential challenge for the Environment Agency, which maintains more than 30km of sea wall within Hamford Water. - a structure integral to protecting people, property and land in the area from coastal flooding.

In order to carry out inspections of the wall to ensure that it up to the required standard of defence, it is necessary for the vegetation growing on it to be cut. The optimum management regime for the moth is to carry out the minimum amount of cutting necessary to maintain a grassland habitat and prevent scrub encroachment.

Working with Dr Zoe Ringwood of Natural England, the Environment Agency has devised a cutting rotation for the site which enables the grass to be periodically cut to allow for inspection without damaging the moth or compromising its vital habitat.

Fishers estuarine moth Picture: Natural England

Fishers estuarine moth Picture: Natural England - Credit: Archant

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In any one year, no more than one third of the site is cut to ensure that the moth has sufficient long grass on which to lay its eggs which it does during its flight season in September/October.

All seawall cutting within the moth site takes place between August 1-25 as this is when the moth is either feeding as a larva or pupating underground within the hog’s fennel roots.

Naomi Boyle, a biodiversity officer in the Fisheries Biodiversity and Geomorphology team at the Environment Agency, said: “Our field team has done an excellent job of the cutting this year.

“Cutting this length of sea wall in such a short space of time is a big task, especially this year as the hot dry weather in July and at the start of August meant that cutting was delayed due to risk of fire.”

Dr Ringwood said: “The sea wall around Hamford Water is one of the most important sites in the UK for populations of the rare and highly protected fisher’s estuarine moth and its larval food plant, hog’s fennel.

“Natural England has been working with the Environment Agency to ensure the sea wall cutting required to maintain the sea defences is conducted in a way that will meet sea wall inspection requirements whilst being sympathetic to the conservation requirements of the moth.

“This is an excellent example of partnership working that has benefited populations of one of the UK’s rarest moths.”

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