Analyses of environmental impacts, and descriptions of methodologies for conducting them, have not always been explicitly cognizant of the subjective value-judgements that must be made in the process of collecting, refining, assessing, and presenting, objective scientific information. This paper has outlined the types of objective and subjective judgements that are made in each of the following major steps of the analysis: identifying major activities; selecting environmental components; selecting types of impacts; assessing the possibilities and/or probabilities of occurrences; determining the degree of the impacts; determining the time-frame of impacts; designating impacts as positive, neutral, or negative; and determining trade-offs among activities and impacts.

The subjective judgements that must be made are based on values, feelings, beliefs, and prejudices, and are functions of the personal, institutional, professional, and societal, contexts of the analyst. If great care is not taken in making these judgements, and in making very explicit the value-framework used, the effectiveness and credibility of the analyst may be sharply reduced. There is also the danger that society and its decision-makers will be presented with an analysis having so many built-in biases that the legitimate role of the decision-makers in assessing the analysis and then making important value trade-offs is seriously compromised. This paper has attempted to make the nature of the process of analysis explicit with respect to the introduction and treatment of values, so that these problems can be understood and, it is hoped, properly managed by both scientists and decision-makers.

The use of current money-lending rates as the basis for economic calculations involving long-term assets such as growing timber, agricultural land, or species of wildlife, is unrealistic and can be very damaging to the interests of the environment. An alternative method, using an assessment of risks together with an assessment of the expected ratio of investment: income, is proposed.

Pb, Zn, and Mn, levels in sediment and common estuarine plants and animals colonizing dredge-spoil disposal areas were compared with levels occurring in the same materials from a natural salt-marsh. Finegrained dredge-spoil had considerabily higher levels of all three metals than did natural salt-marsh sediment, and large differences in the metals content of the spoil were observed, depending on sediment type.

Pb levels in the Grass Shrimp (Palaemonetes pugio), Mummichog (Fundulus heteroclitus), Common Reed (Phragmites communis), Saltmarsh Cordgrass (Spartina alterniflora), and Saltmeadow Hay (Spartina patens), from dredge-spoil areas, were significantly higher at the 0.01 confidence level than in these species from the natural salt-marsh. Zn concentrations were significantly higher at this confidence level in the three plant species growing in dredge-spoil compared with those from the natural marsh. Mn content in Grass Shrimp from ponds in dredge-spoil disposal areas was significantly higher (0.05 confidence level) than in those from the natural marsh. Thus, dredge-spoil containing heavy metals, even though disposed of in specially designed diked containment areas, may act as a source of certain heavy metals that are potentially toxic to the biota.

Data on the transfer of Pb and Mn in simple foodchains of the dredge-spoil pond ecosystem are presented and discussed in relation to feeding behaviour. Decreasing concentrations with increasing tropic level were observed for Pb and Mn, but no consistent pattern was noted with Zn.

During the period 6 December 1974 to 20 January 1975, the R/V Westward circumnavigated the Mediterranean Sea and took quantitative samples of pelagic tar at 48 stations. These have been compared with a similar survey made in 1969 by the R/V Atlantis II and with some data published in the USSR. In the ‘Ionian Sea’ (between Crete and the Strait of Sicily) the geometric mean of tar concentration has decreased significantly—from 60 mg/m2 in 1969 to 5 mg/m2 in 1974–75. In other regions of the Mediterranean, no significant changes were found. However, in both the ‘Tyrrhenian Sea’ west of Italy and the ‘Alboran Sea’ along the Algerian-Moroccan coast, tar concentrations have increased by about a factor of two, roughly corresponding to the relative increase in tanker traffic in the Mediterranean as a whole. In the ‘Balearic Sea’, 1975 levels were lower than those of 1969, but the data may not be comparable because of the different geographic regions covered.

At present, the total standing stock of pelagic tar in the Mediterranean is lower than in 1969, due to the decrease in pollution of the eastern basin. With the reopening of the Suez Canal, changes in the amounts of tar should be carefully monitored as a measure of pollution control effectiveness.

Imported species of plants or animals tend either to fail or to flourish in a new environment, and it is nearly inevitable that ranch-fenced exotic ungulates will escape to the wild. Successful introduced species tend to spread into all suitable areas, and the likelihood that exotic species will be damaging is great. Prior study of prospective imported species cannot insure either a successful importation or a beneficial result. Yet a thorough preceding review by qualified ecologists and the effective regulation of ungulate importations by national and international agencies, are the only present safeguards against serious economic and environmental damage. Some general truths are proposed to serve as guiding principles for the future.

Surveys of visitors to a moorland Nature Reserve in Yorkshire, England, were carried out in 1968 and 1973. The major change during the five-years' period is that visitors have increased their interest in conservationally desirable improvements, such as the construction of hides, and have reduced their demand for such amenities as tea-rooms and toilets. It is concluded that the establishment of a picnic site and the creation of a nature trail have made the area more accessible to the general countryside user while not destroying the wildlife conservation potential of the habitat.

A preliminary survey of thirteen Latin American nations indicated that both the number and rate of importations of wild hoofed animals from Europe, Asia, and Africa, has increased rapidly in recent years. This is especially true for Mexico, Argentina, and Chile. In nearly every instance reported, the original stock of hoofed game was held under fence and no importer intended that animals should escape from his control. From these and other instances around the world, it seems that eventual escapes of captive ungulates held under normal ranching conditions are a virtual certainty. As the full effects of imported species on the plants and animals in their new environment cannot be predicted with certainty, guideline principles to govern species introductions are sorely needed.