Invertebrates play a huge but largely unseen role in the functioning of Rawcliffe Meadows: they recycle plant debris, flood refuse, rotting timber, small animal corpses and cow dung; they pollinate trees and flowers, ensuring production of seeds and fruits; they maintain soil structure; and they provide food for larger animals like amphibians, birds and mammals. The more we know about the ‘minibeasts’ that make their home on the Meadows, the better we can manage their habitats.
Further invertebrate surveys at Rawcliffe Meadows in 2015 were part-funded through the Yorkshire Wildlife Trust/Biffaward Flowering the Floodplain project. This year, work focused on habitats we know little about and was carried out by invertebrate specialists Bob Marsh, Martin Hammond and Andy Godfrey.
Some 209 species of beetle were found during the survey, bringing the total recorded since 1996 to a remarkable 584: over 14% of Britain’s beetles! Forty new species were detected during 2015. One hundred and ten other terrestrial invertebrate species were detected in addition to 43 aquatic species found during the pond survey.
The Copse Meadow, created from weed-infested agricultural grassland in 2007, has now yielded an impressive 108 beetle species. This shows that we have succeeded not only in re-creating flower-rich meadow but also a rich habitat for invertebrates. The magnificent Necklace Ground Beetle is clearly well-established in Copse Meadow with several records this year on top of those from 2013. This once-widespread predator will be listed as Endangered in a forthcoming Natural England review of British ground beetles. Hopefully, the newly-established Cornfield Meadow next door will allow the population to expand.
Fen vegetation in the north of the Flood Basin proved to be a rich and productive invertebrate habitat, with 123 species recorded. These included no less than four rare flies: the long-headed flies Achalcus bimaculatus and Thrypticus atomus, the grass-fly Chlorops planifrons and the tiny Stenomicra cogani. By contrast, tall vegetation adjoining the Tansy Mounds at the southern end of the site was a relatively poor habitat with few species of note.
Species-rich grassland within the fence surrounding the Southern Pond is cut late in the year, so should provide resources for invertebrates over a longer period than the adjoining hay meadows. The results from pitfall-trapping and vacuum-sampling were rather equivocal: there were fewer invertebrate species than might have been expected, and few which depend on flowers or seeds. However, two scarce fly species were recorded and it is probably beneficial to leave this small area to flower into late summer.
So what did we learn from the survey? As well as providing more information about the biodiversity of Rawcliffe Meadows, the results can guide how we manage the site:
- The report provides guidance for managing Copse Meadow for Necklace Ground Beetle. Establishing a similar, wildflower-rich sward in the adjoining Cornfield Meadow should also benefit this Endangered species and needs to be a priority in 2016.
- Fen vegetation in the Flood Basin is an important invertebrate habitat and is currently well-managed. If it becomes over-grazed, however, temporary fencing might be needed in late summer.
- Because tall vegetation adjoining the Tansy Mounds supports a relatively poor invertebrate assemblage, management to expand Tansy Beetle habitat is unlikely to be detrimental to other species of conservation concern.
- Species-rich grassland adjoining the Southern Pond should continue to be cut later than the meadows but does not necessarily have to be left into late October.
Other noteworthy insects found during 2015 have included a scarce sawfly whose larvae feed on Yellow Loosestrife and a small moth, Caloptilia semifascia, whose caterpillars make a protective tent for themselves by folding over the leaves of Field Maple. The latter was found by Yorkshire Naturalists’ Union moth recorder Charles Fletcher and proved to be only the third Yorkshire record.