Invertebrates of the Tarras Valley

Often overlooked, invertebrates are the backbone of our planet. Insects and other invertebrates provide critical eco-system services on which we rely, including pollinating plants, breaking down detritus, and being a vital part of most natural food chains. Over half of the species on Earth are insects, 41% of which are at risk of extinction over the next few decades, and the rate of extinction in insects is 8 times higher than in vertebrates like birds or mammals. As said by Sir David Attenborough, ‘if the invertebrates were to disappear, the world’s ecosystems would collapse’.

Habitat loss is a driving factor in the decline of many species of insects, as well as other threats such as the increased use of insecticides and climate change. The switch from species-rich, diverse natural habitats to over-managed, polluted, monocultures means that the natural variation of insect species is being replaced by a few pollution-tolerant species.

Dumfries-based naturalist, Bob Merritt, has been surveying invertebrates on the Tarras Valley since the first community-buyout in 2021. Across 21 locations on the reserve, mainly freshwater habitats including different points along the River Tarras, and a variety of bogs, ponds and pools, along with some moorland, grassland and woodland habitats, where he found a total of 162 different species.

The methods used to collect samples were pond- and sweep-nets, and a vacuum sampler. The species found included 72 beetles (mostly water-related), 68 spiders, 11 water-bugs, 3 dragonflies, 2 stoneflies, 1 crustacean, 1 mayfly, 1 harvestman and 1 mollusc.

Of the 162 taxa, 11 species have a rarity/threat designation by JNCC greater than “Least Concern”. The JNCC (Joint Nature Conservation Committee) is a statutory body that deals with nature conservation issues in each of the 4 countries of the UK. Of these 11 taxa, 3 are designated Near Threatened (which is the lowest category of Red-listed species) and the remaining 8 taxa are Nationally Scarce. Species which qualify for this designation have been recorded from fewer than 100 hectads (100km squares) in Britain since 1990.

A recent increase in two of the Near Threatened water beetles, means that they are expected to be downgraded to Nationally Scarce in the next JNCC review.

Other individuals have also been recording invertebrate species on the reserve, such as local ecologist John Halliday, who has been recording moths for several years. His findings include over 170 species, including the first ever Dumfries and Galloway record of the Northern Drab moth.

One of the main ways to increase the population of invertebrates on a site, is by restoring the natural ecosystems. On the Tarras Valley, we are aiming for large-scale ecosystem restoration, encouraging natural regeneration and helping to restore natural processes. Regeneration, restoration and creation of natural habitats and processes will lead to a much more dynamic, diverse, and natural ecosystem with greater biodiversity.
We will be continuing to survey invertebrate populations on the reserve and will hopefully find that they increase over time. If you want to help invertebrates in your own area or garden, actions such as not using insecticides, growing wildflowers and leaving areas ‘un-mown’ can all help, and if you’d like to get involved with invertebrate monitoring and other citizen science on the reserve, please email hello@tarrasvalleynaturereserve.org