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A Wonder through the Wonders: Species on the Edge explores the Keen of Hamar

Our Species on the Edge Shetland team were out and about enjoying Unstfest recently, the most northerly festival in the UK. This festival sees an exciting array of activities take place across Unst, ‘the island above all others’.

A group of people stood loosely in a circle, some looking at the plants on the ground and some looking through binoculars
Everyone enjoying getting up close to the wonders of the Keen with Mike and Robina to guide them, © Molly Harvey

Species on the Edge is a multi-partner species conservation programme dedicated to supporting vulnerable and threatened species found along Scotland’s coast and islands. Funded by The National Lottery Heritage Fund, the partnership consists of Amphibian and Reptile Conservation, Bat Conservation Trust, Buglife, Bumblebee Conservation Trust, Butterfly Conservation, NatureScot, Plantlife, and RSPB Scotland who are taking the lead here in Shetland.

Thankfully, we managed to dodge the rain on the Friday on our Wander through the Wonders of the Keen of Hamar. This lunar landscape of shattered serpentinite rock is home to the Plantain Leaf Beetle, one of Shetland’s priority species for Species on the Edge. There is a real sense of mystery around this elusive insect that was only recently found to have a population at the Keen of Hamar. The beetle can only be found at a handful of other sites around Orkney (where populations of up to 70 individuals have been encountered!) and saltmarsh at Loch Etive. Its bizarre distribution is the matter of much speculation and new behaviours and aspects of its ecology are just waiting to be discovered!

A small black beetle with red racing stripes crawls over sandy coloured rocks
The Plantain Leaf Beetle photographed at the Keen of Hamar in April 2023, © Molly Harvey

The Species on the Edge team encountered the beetle at the Keen of Hamar on several occasions throughout April and May before the beetles seemed to vanish. This was not surprising given that the beetle has been observed to have a diapause (a period of dormancy) on Orkney with a second emergence of presumably the new generation around late-May to mid-July in Orkney. This diapause and second emergence are something that has yet to be observed in Shetland. If there is a secondary emergence it certainly did not seem to coincide with our walk as no beetles were encountered. However, there was plenty of other wonders to enjoy on the Keen of Hamar!

A small white flower on a sandy/rocky background with a sign saying 'Edmonston's chickweed' in the foreground
The delicate Edmondston’s Chickweed is thought to be the rarest plant in the UK © Molly Harvey

Mike Pennington from NatureScot took us on a tour of the botanical treasures of the Keen which supports a unique assemblage of flowering plants. A highlight was the Edmondston’s Chickweed, also known as Shetland Mouse-ear. Mike explained that one flower (pictured above) was flowering for the second time this summer – something that has not previously been observed! Edmondston’s Chickweed is endemic to Unst and found nowhere else in the world making it a precious rarity. It is named after its discoverer, Thomas Edmondston who was just 12 when he discovered the plant in 1837. At 19 years of age, Thomas Edmondston published A Flora of Shetland and was appointed Professor of Botany at the Anderson University of Glasgow. A year later he set out to follow in the footsteps of Darwin as the naturalist on board HMS Herald, a vessel retracing the voyage of the infamous HMS Beagle. Tragedy struck with the accidental discharge of a gun striking Edmondston dead as he was disembarking from a boat on the coast of South America when he was just 20 years old. It is remarkable how much Edmondston was able to achieve and contribute to the field of natural history in his brief but incandescent career.

Meanwhile Robina Barton from the Shetland Geological Society provided fascinating insights into the geology of the Keen. The Keen is aptly named with the word Hamar old Norse for ‘rocky outcrop on the hillside’. The serpentinite rocks characteristic of the Keen are formed deep beneath the oceans and are not commonly found on land. They were hurled to the surface some 400 million years ago during a dramatic upheaval and have since weathered to produce a sparse soil that is among the oldest and poorest in Britain. It is a landscape that reflects how much of Northern Europe probably looked after the ice retreated following the last Ice Age some 11,000 years ago. So looking across the stark shattered landscape of the Keen is like looking back in time!

A moonscape landscape below a blue sky
Looking out on the lunar landscape of the Keen of Hamar is like looking back through time, © Tom Allen

The geology of the Keen explains a great deal of its natural and cultural heritage. The coarse debris and hillside location of the Keen makes it an incredibly dry habitat despite the prodigious rainfall experienced in Shetland! In fact, it is known as Britain’s most northerly desert and its extreme water shortage is posited to explain many of the unique botanical treasures that show adaptations and endemism to these extreme conditions. This includes the Sea Plantain species which is thought to be the preferred food plant of the Plantain Leaf Beetle. On the Keen of Hamar, and nowhere else, the Sea Plantain can be seen to be coated in dense fluffy hairs. These hairs act to trap water vapour reducing evaporation and resultant loss of water and so are a local adaptation to the extreme dry conditions of the Keen.

A delicate green plant with fluffy white fibres grows from rocky ground
The fluffy hairs on Sea Plantain on the Keen of Hamar are an adaptation found nowhere else © Mike Pennington

Meanwhile the existence of the nearby quarry and pony mill at Hagdale is due to the mineral richness of the site. One mineral present at the site was considered new to science at its discovery. Called Theophrastite this mineral was named for the Greek philosopher and writer Theophrastus who authored possibly the first mineralogy book in 315 BCE translated from Greek as ‘On Stones’.

 Chromite quarried from the area was ground at the pony mill and used for a diverse range of purposes; from explosives to providing yellow pigment for paint. Serpentinite was also quarried for use in lining furnaces due to its property of extreme hardening in reaction to the application of heat. There was even a pony railway that connected the quarries at Hagdale to the harbour at Baltasound for export.

The Hagdale pony mill is the only example of a mineral-crushing horse mill remaining in Britain © Molly Harvey

For more information about the Keen of Hamar you can visit the NatureScot website Keen of Hamar Nature Reserve - A miniature mosaic | NatureScot.

If the Plantain Leaf Beetle has sparked your curiosity, get in touch with Tom Allen, the Species on the Edge Project Officer for Shetland at tom.allen@rspb.org.uk. We would be very interested to hear about any sightings especially with photos and a what3words location! It is also encouraged to record sightings on the iRecord website. Follow this link for an easy step-by-step guide to iRecord Get started with iRecord... | iRecord.