A dramatic decline in insects in Europe has been recorded over the last few decades. Every study has shown falls in numbers, for example recent research at more than 60 protected areas in Germany showed flying insects have declined by more than 75% over almost 30 years. This pattern is repeated across the globe virtually wherever studies are undertaken. Insects are vital to the world’s ecosystem and it is no exaggeration to say that without them it would collapse. Life for humanity would become impossible. The main cause seems to be heavy use of pesticides, but loss of habitat and climate change are also strong influences.
Schemes to improve the situation such as green corridors and wildflower plantings exist and while these are effective and necessary they often require significant funding inputs and long-term funding for continued management. Addressing the use of pesticides is a matter for Government legislation. This project is intended as a compliment to any and all of these schemes while being flexible, low cost and requiring little or no maintenance. It has a simple, clear message and easily identifiable results. Most importantly it can be undertaken on an individual, community or corporate level and provides a manageable and hands-on teaching resource for schools. This means it can bring together all parts of our community in a common goal, create new connections and a greater appreciation of nature within an urban environment.
So how does it work? It begins with a native deciduous shrub/small tree: the Alder Buckthorn, Rhamnus frangula. Buckthorn is hardy, fast growing and versatile. It will grow in woodland, along woodland edge, alone, as part of a hedge or in a corner of a garden or park. It will cope with annual cutting or pruning as necessary, as part of a hedgerow or to manage its size as part of municipal planting or ornamental garden. It is easily planted as a “whip” in the winter months and will grow successfully on the clay soils of the Holderness Plain.
Next comes the star attraction – the focal point of the project – the Brimstone butterfly Gonopteryx rhamni, the male sulphur yellow and the female a pale lemon – both large and with wings shaped to resemble the leaves of the ivy in which it often chooses to hibernate. Its caterpillars feed on the leaves of the Alder Buckthorn and crucially this species is highly mobile, with females having been shown to be able to locate a solitary Buckthorn more than two miles from the next. This means that no extra habitat is required to create breeding conditions for these butterflies – unlike many species which require larger areas of a variety of plants. It makes the Brimstone an ideal urban butterfly.
While the Brimstone is the star, the Buckthorn has many other benefits. It produces a profusion of tiny, pale green flowers all through spring and summer. These flowers are highly attractive to bees, and the plant will hum with their activity as they go about their business. Providing nectar sources for bees – whose decline has made national news – can be a challenge in a city, but one that the Buckthorn meets with ease. The flowers and developing berries are also food for the caterpillars of the gem-like Holly Blue Celastrina argiolus, another mobile butterfly which will have no trouble finding the plant. Moths also benefit: caterpillars of The Tissue Triphosa dubitata, Pale Brindled Beauty Phigalia pilosaria and Willow Beauty Peribatodes rhomboidaria, all feed on Buckthorn and the adults have been recorded in the Hull area.
It does not stop there. Our world is a living web of connections. The humble House Sparrow is in decline: not because there is a lack of food for the adults because as a nation we are great at putting out feeders for the birds, but because the chicks require live food to grow. Most of the caterpillars on the Buckthorn will end up as food for growing chicks. In the autumn the copious small flowers produce a wealth of berries that are a further source of food for the fledglings as winter approaches.
Trees scrub pollutants from the air, draw down carbon dioxide as they grow, can help to lower temperatures and simply looking a them in an urban environment has been shown to reduce stress in the observer.
A “round-table” meeting was held on June 20 with attendees from all parts of the community. The response was overwhelming and massively positive. The first steps to creating a Butterfly City have been made. It is the intention to have the first “whips” planted this winter; bare rooted planting can only be done in the winter months. The project is developing and expanding rapidly as the news spreads and this page will aim to document its story as well as being a source of updates and information.