With thanks for this report to Fiona MacGillivray of the Islay Natural History Trust.
The Islay Natural History Trust has just released its report on Islay’s roadside verge project a collaboration with the Islay Pollinator Initiative. It has been a two-year study supported and funded by The Botanist Foundation, Bruichladdich Distillery.
Just under 100km of verges throughout the Rhinns of Islay were surveyed during the summers of 2017 and 2018 recording flowering plants and associated pollinators (butterflies, bumblebees, honey and solitary bees, flies and other flower visiting insects). Every 200m section of verge had a separated survey count with a quadrat recording flower species and the numbers of flowers available for insects and counting the number of insects visiting flowers in each 200m section. The project employed one full time botanist for four months and supported two part time roles through the summers with assistance from four volunteers. Identification of bumblebees was a real learning bonus for at least two Islay residents.
The wealth of the biodiversity of flowering plants was analysed according to location and associated habitat and management. All routes were surveyed twice across the season – giving 877 quadrats and 9307 species records for the biological records database, over 86 1km OS map grid squares. 167 flowering species were identified, the most diverse sections went through natural habitats, but where verges were left to develop regularly over time, these provided more flowers. Grazing and early mowing frequently resulted in lower flowering abundance, although grazed swards actually provided some of the most diverse species compositions, these sections however did not enable plants to reach or fulfil their flowering potential.
1673 butterflies were counted and 4147 bumblebees. The Green-veined White butterfly was the most numerous, being seen consistently throughout the season. And the Common Carder Bee was the most numerous bee species, closely followed by Garden Bumblebee and White tailed Bumblebee. Flies not necessarily considered as prominent pollinators were recorded in flowers through 93% of the survey sections. We had records for six solitary bee species and good populations of the rarer Moss carder Bee and Heath Bumblebee.
The abundance of pollinators positively reflects increases in flowering across all genera, indicating that verges with more flowers are favoured by more pollinators. This provides a scientific impetus that the goal of more flowers will aid pollinator usage; this has high importance through areas of low floral diversity such as sheep grazed pasture and barley crops. A floral rich verge would provide a corridor of forage for pollinators through these areas. Argyll and Bute Council are supportive of the work we have undertaken and are agreeable to changing their management and cutting practices for Islay’s verges.
The Botanist Foundation have agreed to help fund this development work and an initial plan for verge management has been drawn up, which involves an introduction of grass suppressing plants (Yellow Rattle, a native annual flower which must seed each year to remain in the sward), introduction of Islay sourced grassland seed stock and late cutting of some sections.