Gwent Levels Invertebrate Study

By Head of Nature Recovery, Gemma Bodé

In April 2019, I commissioned Paul Whitehead, a landscape consultant and field entomologist, to carry out invertebrate surveys in the remaining traditional orchards on the Gwent Levels as part of our Orchards Project and the Living Levels Partnership Scheme. His initial findings were so interesting that we decided to continue these surveys on an annual basis, and this year Paul produced a report summarising his three years of ground-breaking work.

The landscape of the Gwent Levels has been well documented especially in Wild About Gwent over the years so I hope everyone reading this is already well versed in its importance!

Many of its designations are due to the nationally-important insects living in and around the reen and ditch network, but little was known about the assemblages of wood-inhabiting insects present in the area.

The Gwent Levels and Monmouthshire used to be as important as the neighbouring county of Herefordshire for traditional orchards. According to maps dating back to the early 1800s, there were at least 521 orchards but recent work has shown that at least 300 of these have been lost, mostly within the past 60 years; acres and acres of orchards gone, together with their amazing wildlife and cultural traditions. Working with the landowners of those that remain has been vital to help protect and enhance their continued value for wildlife into the future.

The Living Levels Orchard Project covered 81 orchards and our Project Officer, Beccy Williams, has been very busy over the last couple of years providing management advice, planting local varieties of fruit trees, helping with habitat management work, arranging fruit variety identifications using DNA analysis, running training courses for landowners in pruning and grafting and of course providing the opportunity for orchard owners to have Paul look at the insects lurking in their trees!

Over the three years Paul surveyed 20 orchards, returning annually to those which he felt were particularly special. Last year we requested that he looked at driftwood in several areas of the foreshore on the Gwent Levels to see what wood-inhabiting insects might be found there and this produced some fascinating results. Many of the orchards that remain are havens for wildlife including some with only a few trees left. Some of these still towering fruit trees have enormous trunks and provide a glimpse of how long they have stood for.

Paul’s ability to identify insects is astonishing and a previous article in WAG alluded to this when Beccy accompanied him last year on one of his study days. A life’s work of study and learning has enabled him to identify insects even if they have been consumed and crushed into a Jackdaw pellet! 

Insects were recorded from a number of key habitats within the orchards including tree crowns and foliage, branches and twigs, cavities, fallen dead wood, fungi and on the ground.  The survey covered many taxonomic orders of insects ranging over 172 families, the most common being that of beetles, Coleoptera, followed by true bugs, Hemiptera.

Spatial distribution of the invertebrates found in Paul’s study showed quite clearly how, of 84 ‘invertebrates of interest’ 76% were confined to just one orchard and that only 12 species, or 14%, occurred in two orchards. Clearly, these insect populations are worryingly isolated now but it also implies how these orchards, the varying ages of the trees and habitat management being carried out in them, provide specific niches for some very fussy insects. These orchards provide a relict habitat once widespread but now fragmented across the area, and attempts to increase this faunal biodiversity must focus on connecting these sites to support insect dispersal and connectivity across a far larger area.

Six species of insect were recorded by Paul not previously recorded in Wales and many others were recorded that were, in British parlance, ‘Nationally Rare’ or ‘Nationally Scarce’.  The specific requirements of many of these insects and their larval stages are often highly niche specific.  When old orchard fruit trees develop cavities they may vary greatly in their fine details and each may develop a distinctive invertebrate fauna. Cavities may vary greatly in size, shape, depth and fill and in the shade and shelter they provide. Some examples of such fastidious species include the woodmould specialist tenebrionid beetle Prionychus ater; little-known in Wales it utilises cavities predominantly in apple trees. 

Seven species of lichen and algae-feeding barkflies, Psocoptera, were recorded in the orchards.

The predatory snipefly Rhagio scolopaceus uses tree boles as vantage points from which to launch aerial attacks! The rare ptinid beetle, Gastrallus immarginatus, found in three orchards new to Wales is a specialised occupant of galleries cut inside thick exfoliating bark, most usually of veteran pear trees and Field Maple.

Paul’s work looking at invertebrate assemblages in driftwood on the foreshore at Wentlooge and Magor Pill confirmed linkage with the orchards and produced some surprises and several Nationally Rare and Nationally Scarce species. Many questions still remain unanswered but Paul was able to show that some coastal insects found in Iron Age sediments at Goldcliff still live on the foreshore today!  Paul recorded the Nationally Rare elaterid or ‘click’ beetle Ischnodes sanguinicollis breeding in drifted Acer wood here new to Wales although recorded further up the River Severn. He also noted two species of elm-associated scolytine weevils in rafted elm trees on the foreshore, with Scolytus multistriatus having both an orchard and driftwood presence.  Paul demonstrated how important tidal driftwood may be for connecting tree-inhabiting insects to the orchard environment, especially when located near to the coast.

It would be disingenuous of me to suggest I have even briefly summarised Paul’s findings in this article, so I urge you to read the full report (below.)

What is clear from Paul’s work is how vital dead wood of all types is for so many species of invertebrate; which is why it should be retained wherever possible.  Of the 18 Nationally Scarce and Rare insects associated with veteran fruit trees, 67% were found to be intimately connected to wood decay processes.  This doesn’t just apply to old orchards. If we are going to help to contribute to nature’s recovery, our invertebrate assemblages make up one of the most important elements of the food chain. Even in your garden make wood count, standing dead wood, fallen dead wood, even wet dead wood in a pond! The more insect niches you can create the better, and the more insects there are, the more wildlife there is.

Huge thank you to Paul Whitehead for all the time he put into this fascinating study carried out for us.