BSG Ecology was commissioned by Cadw to undertake a botanical survey of Chepstow Castle in south east Wales. This revealed a nationally rare plant, known as lobed maidenhair spleenwort Asplenium trichomanes spp. pachyrachis, growing in many places on the castle walls.
This rare subspecies is typically found on limestone cliffs and wasn’t recorded in the UK until 1987. The spleenwort is listed as being of principal importance for the conservation of biodiversity in Wales under the provisions of Section 42 of the Natural Environment and Rural Communities Act (2006). As a consequence, in specifying any works affecting the castle walls, Cadw has a responsibility to have regard to and consider potential impacts on the species.
Cadw engaged multidisciplinary consultants Opus International to provide advice on necessary renovation works. When the need to clear vegetation and repoint the castle walls was confirmed we were asked to provide specialist botanical survey skills and advice to ensure that the works didn’t compromise the status and distribution of the spleenwort that we had previously identified.
We made recommendations to retain the fern in situ wherever possible. In order to protect the plants during the work, BSG Ecology undertook two survey visits and, using scaffolding to access the walls, marked up discrete clusters or individual plants with high visibility tape secured into the adjacent mortar work with nails. This alerted site personnel to the presence of the rare subspecies allowing them to avoid disturbance and damage while removing other plants more damaging to the mortar of the walls. The methodology was agreed with Cadw in advance and discussed on site with the site foreman both prior to work commencing and whilst the building conservation work was ongoing.
In addition to protecting established plants BSG Ecology suggested that the simple inoculation of the mortar with spores from the fern would promote establishment of new plants. This was undertaken as a component of the works, allowing Cadw to promote conservation of the species without any additional expense.
This approach was well received by both Cadw and Opus International and successfully conserved the population of lobed maidenhair spleenwort at Chepstow Castle without compromising the extent or timing of the renovation works. In addition, during the survey work fronds were collected and sent to the Natural History Museum in London, allowing Cadw to extend its contribution to conservation by providing data for the UK fern DNA barcoding project.