The invertebrates of Prosperous Bay Plain, St Helena a survey by Philip and Myrtle Ashmole September – December 2003 Commissioned by the St Helena Government and financed by the Foreign and Commonwealth Office

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7.5 Mitigation

7.5.1. Background

In general, it is preferable to avoid environmental problems, rather than to rely on developers providing money to try to make amends afterwards. Money and machines can rarely rectify environmental damage and in this instance it has taken millions of years to create the special environment of Prosperous Bay Plain.

However, even if the principles and procedures outlined above are adhered to, airport construction will inevitably involve substantial damage to the natural environment. It will mar some magnificent natural scenery, both in Prosperous Bay Plain itself and in places affected by the construction of access routes, and will destroy large areas of habitat with their native plants and animals. There is a strong case, therefore, for expecting that in a budget of many million pounds, some mitigation funds should be designated for efforts to restore and enhance the natural environment of the island.

Our opinion is that the most effective single contribution would be the funding of a post (full-time or part-time) for a qualified biologist to promote initiatives relating to conservation of endemic plants and animals on St Helena and restoration of their habitats. Such a post should be endowed for a substantial period (e.g. 10 years) and should be quite separate from the suggested short-term government post to ensure monitoring of the activities of the contractors (see Section 7.4.2.a above).

Experience within the UK suggests that there are advantages in this type of funding being channelled through NGOs rather than government, partly because it generates a somewhat independent expert voice on conservation issues, and thus tends to improve the quality of government decision-making. On St Helena there would be a case for funds being made available to the St Helena National Trust (ring-fenced for the stated purpose), since it would then be explicitly an addition to – rather than substitution for – the conservation personnel currently employed within SHG.

One of the first responsibilities of the person appointed to this post could be establishment, in cooperation with the airport contractors, of a modest interpretation centre within the airport terminal. This could focus on Prosperous Bay Plain and its invertebrates, but also on the other outstanding natural habitats of the island, thus promoting the idea that the wildlife of St Helena is a good reason to make a visit.

A third important possibility is the launch of a project to restore native plant communities (as opposed to amenity planting related to buildings or roads) in some parts of Prosperous Bay Plain. The Millennium Forest initiative has made a fine start in restoring Gumwood forest at Horse Point, but a separate initiative would be appropriate to re-establish stands of Scrubwood and Boxwood in suitable areas on Prosperous Bay Plain and increase the populations of St Helena Tea along the cliffs. Reinstatement of the Salad Plant should also be a high priority. However, it would be inappropriate to attempt establishment of any of these shrub species within the Central Basin.

In some places it may be feasible combine ecological restoration with the use of native plants to supplement engineering methods of erosion control. West-facing (landward) newly constructed banks (for instance in Dry Gut) will be extremely arid, so that establishment of native plants on them would be very difficult, though Samphire could be appropriate and feasible in some places. However, banks facing the sea and subject to condensation from rising air (for instance near the waterfalls at the eastern end of Dry Gut) could be suitable for limited planting with the endemic shrubs Scrubwood and St Helena Tea (there is already a tiny relict stand of the latter species near here).

Any plans for initiatives in ecological restoration should be undertaken in the closest cooperation with SHG environmental authorities and the St Helena National Trust.

A third exciting possibility for mitigation – particularly appropriate in the context of the re-establishment of seabirds on Ascension Island after eradication of feral cats – is an initiative to improve the lot of St Helena’s seabirds. This idea was discussed with the St Helena Agriculture and Forestry Department in 1995-96, and is outlined in Ashmole & Ashmole (2000: 166-167). Since removal of cats from St Helena is not considered practical, the idea is to create a cat free zone where seabirds can breed in safety.

The natural site for such an initiative is on Gill Point, one of the few places on the island where fairly level land is present close to the sea, and immediately opposite Shore and George Islands, where there are already crowded colonies of boobies and other seabirds. There is evidence that Sooty Terns have nested on the point within the last few decades, and petrels have clearly also done so in the past.

It should be noted that this area is more than 100 m below the level of the proposed runway (as well as being well to the side) and that the seabirds concerned normally fly at this level or lower, and along the coast, and thus would pose no threat to aircraft. All that is needed is construction of a cat-proof fence round a substantial area (perhaps 3 hectares) as close to the sea as possible just north of Gill Point. Designs for such a fence have been discussed in the past with the contractors responsible for cat eradication on Ascension. The main logistic problem would be transport of materials, but with careful pre-planning this could be overcome on any occasion when a helicopter was available. Provision for long-term monitoring of the birds and the fence would of course be needed, and this could be carried out by the person appointed under 7.5.2.a.

Such an initiative would be best carried forward after consultation between government authorities, the St Helena National Trust and RSPB/Birdlife International. It offers the possibility of bringing about another major success in ecological restoration, and would thus be a most appropriate way of offsetting damage to the ecology of St Helena that will inevitably be caused by airport development.

7.5.2. Suggested actions

a. Funding of a St Helena terrestrial conservation post. A mitigation fund should be created, to establish a long-term position in terrestrial conservation and ecological restoration, preferably within the St Helena National Trust.
b. Interpretation centre. Establishment of a modest interpretation centre in the airport terminal building, relating to all types of wild life on the island. Display material could be developed by the person appointed under Section 7.5.2.a.
c. Restoration of plant communities. Planting of Gumwood, Boxwood, St Helena Tea and Salad Plant should be carried out in appropriate places on Prosperous Bay Plain and the seaward cliffs, in cooperation with local conservationists. In some places such planting could play a role in control of erosion on new artificial banks.
d. Restoration of seabird communities. A safe haven for breeding seabirds should be created on about three hectares of land at Gill Point, by construction of a cat-proof fence. Monitoring would be by the person appointed under Section 7.5.2.a.

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