The long-term impact of urbanisation on aquatic plants: Cambridge and the River Cam.

Historical and contemporary records have been used to assess the impact of urbanisation on the aquatic plants of the River Cam and its narrow floodplain in Cambridge. Of the 62 native aquatic plant species which have been recorded in the study area since 1660, 40 (65%) were still present in the period 1985-1999 whereas 22 (35%) are apparently extinct. There is a striking relationship between the fate of species and their trophic requirements, with species of less eutrophic habitats having suffered disproportionately. Historical records demonstrate that the River Cam became grossly polluted by sewage from Cambridge in the 19th century, but the chemical and biological quality of the river improved from 1897 onwards. However, the majority of the species recorded from the river and nearby ditches persisted until after maximum incidence of sewage pollution, which may even have stimulated the growth of 'weed' in the river. Losses of aquatic plant species from two riparian commons, Coe Fen (35%) and Sheep's Green (50%), have been particularly great. The level of these and other areas of low-lying common land by the river has been systematically raised by the controlled tipping of waste in hollows, followed by levelling and resowing. The main effects of urbanisation on the flora therefore arose from the transformation of riparian pastures into suburban open spaces. Commons which are used purely for amenity purposes have lost almost all their aquatic plant species. Those which are still grazed retain more, and continuance of grazing is probably essential if a varied aquatic flora is to be maintained. The interpretation of botanical records in terms of recorded management history is likely to throw further light on the processes of urbanisation, although the number of sites with a sufficiently detailed botanical record may be limited.

Assessing stock and change in land cover and biodiversity in GB: an introduction to Countryside Survey 2000.

Countryside Survey 2000 (CS2000) is the latest in a series of surveys designed to measure and evaluate stock and change of land cover, landscape features, freshwaters, habitats and the vegetation of Great Britain. The ideas behind CS2000 developed during the 1960s and 1970s and culminated in the first survey of vegetation and land cover in 1978. One kilometer sample squares were selected at random using an environmental stratification. Subsequent surveys took place in 1984, 1990 and 1998, revisiting the original sample locations, whilst progressively expanding in scope and sample size; CS2000 included soils, breeding birds, remotely sensed imagery, freshwater biota and hydromorphology. Countryside Survey data may be interpreted using the pressure-state-response model, by selecting indicators of process and quality, and by identifying models of expected responses to different pressures. Thus, results showing losses of hedgerows between 1984 and 1990 stimulated new protection for these features. Ideally, CS2000 data should be used to stimulate experiments to distinguish between different pressures, in order to ensure that policy and management responses are both appropriate and achievable.The experience from CS2000 may prove helpful for the design and management of other large scale monitoring programmes of ecosystems. In particular, the scope of the survey, and the use to which the data are applied, have evolved through time, and yet continuity was essential for change to be detected efficiently. These objectives were reconciled by collecting the data in a disaggregated form, allowing a high degree of flexibility in both analysis and reporting.

Dredging the Tyne: an institutional perspective on process management

The increase in the size of steam vessels, and consequent need for the considerable enlargement of navigation channels, meant the years at the turn of the 19-20th centuries were of pivotal importance in harbour construction. This paper draws on the surviving archives for the Tyne estuary in north-east England in illustrating the inter-relatedness of both the physical and political processes, by which such adaptation and improvement were achieved.

'Deadwells', Urban growth and the threat to public health: an interwar perspective.

The paper reviews the range of threats to public health arising from large-scale housing development in those areas beyond the reach of mains drainage. Citing the limited number of legal precedents available, the paper traces the response made by the City of Norwich, when the purity of its water supplies was found to be threatened in the late 1920s by the cesspools being constructed on the estates near, or just beyond, the city limits. Insights are gained into the administrative and technical devices available to local and central government, as they sought to pioneer improvements in the standards of sanitation and, thereby, the degree to which water supplied could be given protection.