The Great Linford Wildfowl Research Project - A Case History.

Abstract

The particular nature of any gravel pit is a result of a combination of variables such as basin shape, water source, water quality, stability and depth, the ratio of open water to vegetated areas, shore line slope and contour, the ratio of shore length to water area and the plant. species diversity. The manipulation of these variables has been widely practised in management of wetlands for wildlife where the usual aim is to preserve an ecologically interesting area in a 'natural ' state, while maintaining high productivity.

The species competition and size of the fauna populations is influenced mainIy by the degree of heterogeneity of the vegetation resulting from the variation of the physiographical and hydrological features of the wetland. Generally speaking, species richness is assumed to indicate habitat quality (although of course there can be habitats of high quality for a limited nuraber of species) and Patterson (1976) showed that waterfowl production was related to wetland heterogeneity.

Leaving a gravel pit to colonise and develop naturally results in the establishment of a plant community dominated by one or two species, usually Willow, with a low floral diversity, and Milne (1974) showed that a decline in bird species at an unmanaged gravel pit after a few years was due to increasing uniformity of vegetation as naturally colonising vigorous species of plant became dominant.

Thus, where there is scope to alter the physical features during construction of a lake, as in the restoration of wet gravel workings, changes can be made which have profound effects on the composition and size of their eventual wildlife populations.

The result of the creation and management of waterfowl habitat at the Great Linford gravel pits has been to create a 'lacustrine oasis' of wildlife within the wetland complex created as a by-product of sand and gravel extraction. The reserve regularly supports greater numbers of breeding, wintering and moulting waterfowl, passage migrants and passerine species of birds than the surrounding lakes which are not managed for wildlife (Tables 1 & 2) . As this paper shows, these waterfowl populations provide an ideal opportunity for ecologists to study their precise habitat requirements and population ecology so that the 'ecological engineering undertaken to create new habitat from worked out gravel pits can be more effective.

The exploitation of gravel deposits is currently producing large areas of wetland. If left alone the new wetlands will eventually develop a stable but limited wildlife population, and they really do need careful development and management if they are quickly to attain their maximum potential as waterfowl production areas.

The British Isles are of major importance as winter quarters for a large proportion of the European waterfowl  populations, but by Continental and North American  standards, Britain supports a high density (low numbers) of  breeding duck. With careful management, however, the new wetlands created by gravel extraction can function as winter refuges and as 'duck production areas' for use by breeding birds.

In conclusion, gravel extraction could have a vital role to play in ensuring the continued well-being of the populations of common waterfowl species, provided that at least some of the new wetlands are correctly developed and managed. They are by no means the complete answer to the problems of wetland conservation, and we still have a great deal to learn, but with care and sufficient enthusiasm their potential could be fully realised so that the contribution of the new wetlands could be of great significance.