Nature conservation implications of hydraulic engineering schemes affecting British estuaries

Abstract

INTRODUCTIONEstuaries are generally more productive than adjoining marine, freshwater and terrestrial ecosystems, being equalled only by intensive agriculture. When conditions of light, temperature and nutrients are at an optimum, organic production in the estuarlne environment can be ten times more than that of most temperate crops. The diversity of primary producers -benthic and planktonic mlcrophytes and the attached macrophytes -are advantaged by the nutrients trapped by the system, the stirring action of the tides and the flushing of the estuary. A vast number of animals, particularly invertebrates, feed upon these plants. Estuaries are well known as the nursery grounds for young fish -many of commercial species -which are supported by this high biomass. Some of the invertebrates also provide important shellfisherles. In addition, the large number of winterin~ wildfowl and waders and other migrants, as well as the resident breeding birds depend on these invertebrates and plants for their food. The breeding birds also rely on the extensive saltmarshes in estuarlne areas for nesting, and in a few areas the common seal uses the saltmarshes for pupping.Estuaries therefore have a high value as reservoirs of wildlife which, in part, play a crucial role in sustaining shell fisheries and sea fisheries. However, these areas also attract man's attention as a convenient passage between sea and land, an amenity area and a useful drain for his waste ~roducts. These most important and unique interface areas thus have many potential uses and consequently many potential conflicts between the activities exist. This paper begins with a description of the range of impacts on estuarine areas and then attempts an analysis of the affects of hydraulic engineering schemes; selected aspects such as land reclamation and some water resource schemes are discussed in detail. Finally, a strategy for the conservation of estu, fine areas is outlined.

Effects of river regulation and diversion on marine fish and invertebrates

“…With continued modification of nearshore coastal regions from river regulation and other of man's activities such as land reclamation, dredging, building of harbours and breakwaters, etc., serious consideration should be given to protection of a series of natural marine reserves as proposed by Mitchell (1978).…”