The movement of surface currents and the availability of coral prey are probably not responsible for the discontinuities in the distribution of Acanthaster (the Crown-of-thorns Starfish or Sea-star) in American waters. Temperature and salinity conditions are critical in development, and it is possible that these parameters are effective locally, for example in the Gulf of Panamá. There is a strong possibility that continuing field work will show that Acanthaster has a significantly more widespread distribution in the eastern Pacific than is currently known.

Adult Acanthaster and several species of coral prey exhibited an unusually high tolerance to varying conditions of temperature and salinity. The possibility of step-wise colonization to new areas, mediated by resistant adult populations that can become established during favourable seasons, should be considered in any plans to alter the existing freshwater canal in Panamá. For introductions can be environmentally dangerous.

The highest population densities of Acanthaster so far observed in the eastern Pacific, 1 individual/40 m2 to approximately 1 individual/100 m2, are comparable to population sizes in the Indo-Pacific region that are not considered to have a serious impact on coral communities. Coral destruction by Acanthaster can be significant in certain limited areas, but is usually less than that caused by other corallivores.

An analysis of coral community structure in relation to Acanthaster density failed to show a significant correlation with (a) number of species, (b) number of live coral colonies, (c) species diversity (H'), or (d) species evenness (J').

Prey preference data indicate that Acanthaster selectively destroys rare corals. Replacement of rare, predated corals by fast-growing species (Pocillopora spp.) has been observed in the field, showing that Acanthaster could have a negative effect on species diversity.

Visitors to Spurn Nature Reserve, located at the south-east tip of Yorkshire, England, were surveyed during the summer holiday season of 1970. It was estimated that about 3,400 groups of people visited the Reserve in the three months of July, August, and September. Only 17% of the visitors were members of the Yorkshire Naturalists’ Trust, which owns the Reserve, and only 12% of the visitors—mostly bird-watchers—came primarily for purposes of nature study. Pressure from the visitors was found to be concentrated, because of topographical and vegetational features, in areas where it could potentially do great harm to the wildlife and to the physical stability of the habitat itself. Examination was made of methods that might be used to control the total number of visitors and their effect upon the environment.

Economic analysis using the Clawson Demand Schedule, gave a Recreational Value for the Reserve of about £2,000 for the three months of this survey. The example would seem noteworthy for other comparable areas as population pressures and tourism increase.

The Lake Wingra Study is an integrated, interdisciplinary programme which has been developing mathematical models of the hydrological, biological, and nutrient, cycles in a man-modified lake-basin in Madison, Wisconsin, USA. Computer simulations based on these models promise to aid in the prediction of urban impact on the land-water systems within the Lake Wingra basin. Such information should also increase the effectiveness of environmental quality management in Lake Wingra and similar watersheds. So far, the greatest success has been the development of process models which describe individual components of highly complex ecosystems. Examples include models of nutrient cycling and the growth of Algae, aquatic weeds, and fish. Further work on synthesizing individual process models of the Lake, and integrating this information with data from other United States and foreign sites, will receive top priority from the Lake Wingra scientists during 1974.

Many small communities use septic tanks as a method of partial sewage treatment in situations where effluents may be satisfactorily discharged into the soil. These systems are also suitable for use in many situations where intermittent occupation occurs. Where effluents are discharged into streams in which serious pollution is likely, further treatment by secondary processes is necessary, and in many situations tertiary treatment processes are added as a final safeguard. Prefabricated or package-plant systems using variants of the activated-sludge process or special types of percolating filter, have become available and can be designed by the manufacturers to satisfy all of the purposes of primary and secondary treatment in specific situations. Maintenance requirements of most of these processes are small, but no system may be operated for long periods without a minimum of maintenance.

Some of the simplest systems of sewage treatment can provide excellent sanitary conditions and a high level of protection from health hazards and environmental deterioration if properly designed and operated. Package plants are compact and convenient but not necessarily more effective. They are usually dependent on a reliable power-supply, but have many advantages on restricted sites or sites requiring rapid development or expansion.

Travel in the Arctic is nowadays predominantly by aircraft or by specifically designed overland vehicles, as few roads exist. Terrain damage resulting from off-road vehicular movement in arctic areas is potentially serious—particularly in the wetter, ice-rich permafrost terrain. Detailed examinations of vehicle trails made in the 1940s indicate that natural recovery and stabilization of these trails has been relatively slow. Several recent controlled tests using a variety of vehicles suggest that long-term impact of the vehicles on the terrain is a function of time of year, type of substrate, vegetation, soil moisture, ground-contact pressure, type of vehicle propulsion (i.e. tracks, air-cushion, etc.), and operator technique.

Much of the published research on the effects of air pollutants on plants suffers from a lack of understanding of the relationship between the conditions employed and naturally occurring concentrations of pollutant. Frequently lacking is information as to the effective dosages of pollutants used in laboratory studies. The importance of dosage is discussed, as is its relation to concentration and flux. It is suggested that a greater interrelationship between observations from different research workers would be achieved by the simple expedient of measuring pollutant uptake by the plants under study, rather than merely describing concentrations in the surrounding air.

The pollution of the marine environment by plastics such as polyethylene, polyvinyl chloride, polystyrene, and polyurethane, is discussed. As plastic materials are relatively resistant to oxidative ageing and are generally not degraded by microorganisms, they will accumulate in coastal and oceanic waters. The origin of plastic pollutants, their distribution in the marine environment, and their persistence and ultimate fate, are largely unknown. The technology is available to manufacture plastic materials with a programmed service life which, if widely adopted, would reduce the accumulation of plastics in the sea. But their random distribution should be discouraged on behalf of the marine environment.