Ecological Survey of Independent Quarry, Portland
Bob Ford, January 2004
1. Introduction
This report attempts to list the likely species that could colonize Independent Quarry over the next 20 years or so. It assumes that the parties involved, namely Albion Stone and Portland Sculpture and Quarry Trust, deliver a restoration process that is sympathetic to the natural regeneration of the quarry. Much depends on how the landscape is left after quarrying operation cease, and the specific restoration techniques employed. Many of the species listed in this report will require a particular micro-climate that will in turn depend on the topography of the land-forms created. Excessive use of re-seeding could exclude many species that are not able to compete with species in the seed mix. Such seed mixes, whilst containing suitable species, are likely to contain genetic strains different from those normally found on Portland. This could lead to taller plants, which could be too exposed to provide food for the island's unique population of butterflies. The use of local topsoils would also limit the ecological value of the site due to the high nitrogen content of the soil and the presence of seeds of agricultural weed species.
The restoration plan recommended by the Portland Sculpture and Quarry Trust includes the following key points:
- Any landscaping in the quarry should be carried out to maximize south facing slopes.
- Materials used in landscaping should be confined to limestone rubble, surfaced with limestone fines.
- Topsoil should not be used in landscaping operations, but reserved for areas targeted for tree planting.
- Re-seeding with commercial seed mixes should be avoided altogether in the main area of the quarry, and should be limited to less ecologically-sensitive areas such as bunds fronting main roads and car park surrounds.
- A limited amount of planting and re-seeding of native herbaceous species will take place, using locally-derived material. In general the landscape should be allowed to regenerate naturally and slowly.
- A freshwater habitat should be created and allowed to be naturally colonized by local species with no deliberate introductions.
- Tree planting should be confined to native species, sited so as to avoid shading of south-facing slopes.