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


Airport location and access: environmental considerations



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7.2 Airport location and access: environmental considerations




7.2.1. Background

Our recommendations under this head are based on a conviction that environmental considerations should be taken on board at the start of the detailed planning for air access and not grafted on when key decisions have already been made. The prime need is for consultants and government negotiators to be fully aware of the key environmental issues before undertaking serious talks with potential contractors.

It seems essential that during negotiations, clear guidelines should be provided on protection of the natural environment of the site. Some of the issues are indicated in Section 6.3 and below, but the list should not be regarded as comprehensive. We hope that the significance of the Central Basin of Prosperous Bay Plain, as explained in Section 6.2, 6.3 and elsewhere in this report, will be highlighted at all stages.

The line on the maps delimiting the Central Basin (see Plate 2b) generally follows the contours in the south, where the rim clearly defines the natural boundary of the basin. In the north and east the boundary is somewhat arbitrary and is shown as a dashed line on the maps. If this part of the boundary impinges on the edge of a planned runway footprint or access route, it could in principle be modified in discussion with potential contractors.

We recognise that one or more access routes from the main part of the island to the airport site will be needed before, during and after completion of the construction phase. These access routes have the potential to cause much damage, but careful routeing of roads (see also Section 6.3) and rigorous control of off-road activities by construction vehicles should enable this to be avoided.

To maximise public support for both the airport and conservation measures, it will be important to show sensitivity towards people using traditional access routes in this remote part of the island. At present fishermen (sometimes with donkeys) and walkers routinely cross the Central Basin, often using vehicles, on their way to Gill Point and fishing rocks along the eastern seaboard. If access by these routes is no longer feasible, alternatives will need to be provided.

The possibility that a road from Prosperous Bay to the airport will be required to provide access by heavy plant and for emergencies led us to undertake sampling at Prosperous Bay (Site 18) and in the major gully leading to it from the area west of the Signal Station (Sites 19 and 13). The results suggest that construction of a road down the upper part of the gully would be unlikely to endanger any of the endemic species, since the habitats traversed appear to be adequately replicated elsewhere.

However, from the point of view of the invertebrates, the hinterland of Prosperous Bay itself is of greater importance. It is an unusual habitat, since there are few places on St Helena where there is flat land close to the sea. Our Site 18 just behind the beach was one of only two where we found the new species of lepismatid thysanuran. There is a case for more sampling to learn more of the range of this species, but we would anyhow recommend extreme caution in construction work at Prosperous Bay: the habitat is very restricted and could be severely damaged by heavy plant.

On general environmental grounds we have strong reservations about the Prosperous Bay route. The bay, with the Fishers Valley canyon that leads to it, is one of the scenic wonders of St Helena. Furthermore, the path to it – though challenging in places – is a practicable route for most walkers, and is one of the most attractive on the island. It also provides access to a sea-level rock platform and cliffs that are of great geological interest. We believe that in most parts of the world this area would be designated as an area of great landscape value, and given special protection. It would be ironic if construction of an airport – partly in order to promote tourism – spoiled one of the features of the island most attractive to visitors.

Environmental impact assessment will of course be part of the development process. We hope that the results of our survey will provide all necessary information on invertebrate populations. Our work has necessarily involved collection of substantial numbers of invertebrates and we doubt whether additional collection is justifiable except on a very local basis to answer specific questions (for instance as indicated in Section 2.1.4).



7.2.2. Suggested actions



a. Location of airport and associated facilities. It should be clearly recognised that environmental considerations preclude the building of the runway, the siting of permanent buildings, or the location of a temporary work camp within the Central Basin of Prosperous Bay Plain, and that access routes to the construction site and the airport itself should avoid crossing this basin.
b. Access to potential airport sites during the negotiation phase. A firm protocol about short-term access to the potential airport sites should be established immediately, before any potential contractors come out to make their investigations. This should insist upon vehicles using only established routes across the Central Basin in the pre-construction phase.
c. Marking of short-term access routes. Appropriate SHG personnel should mark with posts the two main established tracks across the Central Basin of Prosperous Bay Plain, one in the north roughly parallel with Fishers Valley, and one across the south of the basin connecting with the path to Gill Point.
d. Access routes during and after airport construction. It should be recognised that no long-term access routes to the construction site or the operational airport can run across the Central Basin, but should skirt it to the north and/or south. Before any work on the airport itself is started, the main route(s) to the site should be created and adhered to. This will allow closure of existing vehicle routes across the basin, providing immediate benefit to the environment.
e. Local access. Care should be taken during the construction and operational phases to maintain reasonable access for fishermen, local walkers and visitors to places beyond the airport site, such as Prosperous Bay, the Signal Station and Gill Point.
f. Prosperous Bay road and port facilities. Careful consideration should be given to the environmental impact of construction activity at Prosperous Bay, before a decision is made to undertake any work there.


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