Aiding Cork City’s Urban Biodiversity

Cities have their own peculiar biodiversity, with habitats of animal and plant species shaped by their aspects, locations and (overarchingly) the impact of humans. The areas we choose to build in, the areas we do not, the materials we use and the plants we use to beautify our urban areas all influence the plants and animals that choose to make their homes near ours. Cork is no different and has a suite of plants and animals that, while not individually specific to the city, are unique in the collection that they present.

Cork City is built on out-hanging crops of old red sandstone that would in normal conditions give rise to acidic soils. The sandstone is, however, interspersed with instances of limestone and this, supplemented with more quarried from the city suburbs, makes up a large percentage of the city’s walls. Limestone is naturally basic and therefore gives a niche to base loving plants. This is most evident in the five fern species that populate the city’s walls, namely Rustyback, Wall Rue, Maidenhair Spleenwort, Hart’s Tongue Fern and Common Polypody.

Garden escapes, that is alien plant species planted in gardens that have established outside of the intended settings and become naturalised, are very common in city environments. In Cork, one of the most common to be seen is the delicately flowered Ivy Leaved Toad Flax. Native to the Mediterranean, it was introduced as an ornamental to Ireland where it soon spread due to its ability to utilise waste areas unsuitable to other species. Again, this species can be seen throughout the limestone walls of the city, its ivy shaped leaves pointing to the origin of its name.

Ivy leaved Toadflax Cymbalaria muralis 3

Ivy-Leaved Toad Flax

Many of the trees planted in Cork are non-natives, planted for beautification and shade requirements rather than to support any biodiversity. But support them they do, most notably a little insect called the horse chestnut scale. Despite its name, this bug colonises a wide range of trees. Originally from Asia, it came to Europe around the 1960’s with the first Irish record being in 2000 and feed on plants by piercing them with their needle like mouth parts to consume sap. The females are much larger than the males and can be seen on the numerous poplar and sycamore trees throughout the city as ovoid, brown, scab like growths. These are in fact the outer shield of the now dead females that are used to protect the egg sacks underneath.


Horse Chestnut Scale

So while certain species adapted to city life can find a foothold in Cork, it would be wonderful to see more of the wonderful native Irish flora and fauna within the city. With this in mind, in the new year Mad About Cork will continue to create as many new green spaces as possible in the city. However, the focus will shift from conventional herbaceous bedding annuals to native species such as cowslip, knapweed and the spotted orchid.

While everybody loves a petunia, as non-native they (as well as other flowers planted regularly around the city) cannot be utilised by native insects and result in pretty but sterile, ecologically dead environments. Therefore planting of native Irish flowers will provide more benefits to the biodiversity of the city. Not only will these plantings serve to highlight the beauty of our native botanical resources, but they will, over time, build up semi-natural communities within the city that will encourage the proliferation of more butterflies, ladybirds, bees and other insects throughout the city. Ireland is home to 101 native bee species, but some 42 of these have seen their numbers reduced by more than 50% with a further 11 declining by 30-50%. As Irish agriculture becomes more intense, native bees are losing their rural habitats, starving from lack of available flowers and being poisoned by increased pesticide use. Cities offer a viable alternative, due to their lack of pesticide use and few large herbivores to affect flower numbers. By increasing the variety of floral forage for bees in the city, we aim to make Cork City a refuge for insect pollinators. The project will begin at the Mad About Cork vegetable garden, where already native tree species have been planted, and continue with native species planters along the length of the pedestrian Shandon Bridge.