C.F. Mason

An assessment of the total external costs of UK agriculture

This trans-disciplinary study assesses total external environmental and health costs of modern agriculture in the UK. A wide range of datasets have been analysed to assess cost distribution across sectors. We calculate the annual total external costs of UK agriculture in 1996 to be £2343 m (range for 1990‐1996: £1149‐3907 m), equivalent to £208/ha of arable and permanent pasture. Significant costs arise from contamination of drinking water with pesticides (£120 m/year), nitrate (£16 m), Cryptosporidium (£23 m) and phosphate and soil (£55 m), from damage to wildlife, habitats, hedgerows and drystone walls (£125 m), from emissions of gases (£1113 m), from soil erosion and organic carbon losses (£106 m), from food poisoning (£169 m), and from bovine spongiform encephalopathy (BSE) (£607 m). This study has only estimated those externalities that give rise to financial costs, and so is likely to underestimate the total negative impacts of modern agriculture. These data help to identify policy priorities, particularly over the most eAcient way to internalise these external costs into prices. This would imply a redirection of public subsidies towards encouraging those positive externalities under-provided in the market place, combined with a mix of advisory and institutional mechanisms, regulatory and legal measures, and economic instruments to correct negative

Spatial and seasonal variation in heavy metals in the sediments and biota of two adjacent estuaries, the Orwell and the Stour, in eastern England

A study was made of the concentrations of the elements As, Cd, Cu, Hg, Mn, Ni, Pb and Zn in the sediments and biota of two adjacent estuaries, the Orwell and Stour, in eastern England. The Orwell Estuary, with its urbanized head, was more contaminated with heavy metals than the Stour Estuary. Generally, in both estuaries, concentrations of metals were highest towards the head and the mouth. Saltmarsh sediments accumulated higher concentrations of most metals than mudflat sediments. Metal concentrations in the biota showed marked interspecific differences; Mytilus edulis had higher concentrations of Cd, Littorina littorea higher concentrations of Cu and Mn and Arenicola marina higher concentrations of Hg. Invertebrates from the Orwell had higher metal concentrations than those from the Stour. Algae had generally lower levels of metals than invertebrates. Metal concentrations were greatest and more variable in the top 10 cm of sediment. Metals were at greatest concentrations in winter and lowest in summer in sediments, algae and invertebrates. Mercury concentration increased with size in the three invertebrate species studied, but Cd and Zn generally were at higher concentrations in younger animals. Comparisons of sediments with average shale values indicated anthropogenic enrichment with several metals but it was considered that only Pb, at some sites, and possibly Hg posed potential threats to the ecology of the estuaries.

Mercury, cadmium and lead in eels and roach: The effects of size, season and locality on metal concentrations in flesh and liver

Mercury, cadmium and lead were measured in the liver and flesh of 885 eels and 338 roach collected from four sites on the Rivers Brett and Chelmer, eastern England, over the period November 1985 to November 1987. Concentrations of metals in liver and flesh of both species were highly correlated at all sites. Generally, mercury in flesh and liver was correlated with fish length in both species. There were fewer significant relationships between length and the concentrations of cadmium and lead. Site differences in mean concentrations were recorded. Seasonal variations in metal concentrations were largely restricted to eels from the more polluted Site 4. The significance of the concentrations of metals to the status of the fishery is discussed.

Mercury, cadmium and lead concentrations in five species of freshwater fish from eastern England

A total of 146 samples of five species of fish were examined between March and November 1986 in four sites from the Rivers Brett and Chelmer in eastern England. Variations in heavy metals concentrations between sites and species were related mainly to size differences of fish. Mercury levels in the flesh were higher than in the liver, while cadmium and lead levels were higher in the liver.

Factors influencing phosphate exchange across the sediment-water interface of eutrophic reservoirs

The results of a survey of the sediment chemistry of 7 East Anglian reservoirs are presented as part of a regional study on the assessment and control of eutrophication. The influence of water quality (dissolved oxygen, pH, temperature) on phosphate (PO4) adsorption by sediment from hypertrophic Ardleigh Reservoir is also examined. Extractable phosphate-P (extr.-P) varied between 92 and 383 mg kg−1 dry matter. Extractable P varied between 5.3 and 16.6% of the total phosphate-P (Tot. P) content and increased with the concentration of dissolved reactive phosphate-P (DRP) in the overlying water column. Organically complexed iron (organic Fe) was the determinand which correlated most closely with phosphate adsorption capacity, PAC (r = 0.8). Organic Fe was also related inversely to Extr. P. The rate and extent of PO4 adsorption by Ardleigh Reservoir sediment increased with the initial concentration of DRP and adsorption equilibria were reached after 24 h. The equilibrium DRP concentration, [DRP], was 0.7 mg P 1−1 under aerobic conditions indicative of a high potential for PO4 exchange. The rate and extent of PO4 adsorption was greater at 7 °C than at 22 °C PO4 adsorption increased markedly with dissolved oxygen status. Ardleigh sediment exhibited a marked buffering capacity to a change in pH; however, PO4 adsorption was greatest at an equilibrium pH of 5.6 and decreased progressively either side of this pH value.Options for the artificial control of sediment PO4 release are discussed in relation to the seasonal variation in sediment PO4 exchange observed for Ardleigh Reservoir.

Long-term trends in water quality and their impact on macroinvertebrate assemblages in eutrophic lowland rivers

Long-term trends in water quality in eutrophic lowland rivers in eastern England were investigated and their impact on macroinvertebrate assemblages studied. Dissolved oxygen (DO) declined significantly in eight rivers in Essex and Suffolk over 40 years to 1998. Chloride concentrations significantly increased during the same period in most rivers. Total oxidized nitrogen and soluble reactive phosphorus increased until the 1980s, then began to decline. Biotic scores (Lincoln Quality Index) generally increased over 14 years to 1998 and there were significant positive relationships between biotic scores and several nutrients. Invertebrate families and environmental variables sampled over the eight rivers in a dry year (1997) and a wet year (1998) were subjected to multivariate analysis. River stretches were grouped according to substrate requirements of indicator invertebrates. In the dry year, those river stretches behind mills or immediately downstream of sewage treatment works (STW) were grouped. In the wet year, there was only one separate group, comprising sites downstream of STWs. Nutrients, DO and low flows have a much greater influence on water quality, and hence invertebrate assemblages, during drought years than during wet years.

Habitat characteristics and the distribution of Odonata in a lowland river catchment in eastern England

The influence of habitat characteristics on the distribution of larval and adult Odonata communities in a lowland river in eastern England was studied. There was a longitudinal distribution of Odonata, with larval assemblages being influenced directly by marginal flow velocity, biochemical oxygen demand (BOD) and phosphate concentrations and indirectly by shade and cover of floating vegetation. Adult populations responded directly to shade, reed cover, amenity-managed land use and bank height, and indirectly to BOD and ammonia concentrations. Distribution patterns were strongly associated with both natural changes along the river system and management impacts. River management practices locally disrupted the natural displacement of species along the river, but whilst some forms of human interference on river systems were beneficial to species richness, the effects on stenotopic species were disadvantageous. To conserve Odonata management emphasis should be on the maintenance of suitable conditions for river specialists.

Impact of road run-off on receiving streams in Eastern England

Invertebrate samples from nine East Anglian rivers were collected above and below crossings of the A12 and A14 trunk roads in spring and summer 1996 to assess any impact due to road run-off discharges. The Biological Monitoring Working Party (BMWP) score, average score per taxon (ASPT) and Shannon diversity index values were compared between upstream and downstream sites. Only the BMWP score was significantly lower in summer at downstream sites in those rivers crossed by the A12. Zinc, lead and cadmium concentrations in sediments and invertebrates (Asellus aquaticus, Gammarus pulex, Sialis lutaria) did not differ significantly between upstream and downstream sites. There was a significant relationship between metal concentrations in sediments and invertebrates only for lead. Road run-off from these trunk roads appears to have no major impact on the receiving streams.

Growth in Otter (Lutra lutra) Populations in the UK as Shown by Long-term Monitoring

Abstract European otters declined dramatically from the 1950s, disappearing from many rivers. We report here on longterm monitoring (from 1977) in 3 catchments in western Britain that were recolonized naturally and in 2 catchments in eastern England that were reinforced by captive-bred otters. A minimum of 16-years data was collected on each river until 2002. At a series of sites in each study river, the percentages which were positive for otters and the number of spraints per sprainting site were recorded and combined to produce an annual index of population. One western river, naturally recolonized, showed rapid early population growth for 5 years, followed by slower growth, while growth was steadier in 2 catchments which already held some otters at the beginning of the study. Colonization on the eastern rivers was slower, with greater fluctuations over time. Annual population growth rates were estimated at 1–7%, higher in the earlier years. A strategy for annual monitoring of otters is recommended.

Responses of ground flora to coppice management in an English woodland – a study using permanent quadrats

Changes in the ground flora in sweet chestnut (Castaneasativa) woodland were studied over 11 years usingpermanent quadrats in two coppiced plots and one plot in a ride widened by treeremoval. Light and temperature were also recorded. The temperature range wasgreater in the ride than in the coppice plots. Light reaching the woodland floorin summer fell to less than 1% of incident radiation at later stages of thecoppice cycle. Species richness peaked in the second and third year aftercoppicing and then declined in both the coppice plots and the ride. A similarpattern was seen in total percentage frequency of cover. The dominant species,Anemone nemorosa, showed little response to the coppicecycle in terms of frequency, but showed a fourfold increase in floweringintensity in the second and third year following coppicing. Other speciesgenerally declined in frequency through the coppice cycle, and flowering waslargely suppressed in the later stages. The results are discussed in relation toalternative methods of woodland management.