In the City of Gloucester, Massachusetts, 30% of the Soft-shell Clam (Mya arenaria) beds in a tidal inlet known as the Annisquam River are not harvestable owing to the discharges of untreated sewage from the surrounding area. A large proportion of the total area of the clam-flats has been closed to clamming because of exceedingly high levels of coliform Bacteria in the clams and in the water. These polluted areas represent a ‘loss’ of resources for the community, and they were surveyed in 1980 to determine the number and value of Clams which could have been harvested if only the sewage discharges had been controlled.

In the productive areas of the closed-to-fishing flats, which totaled 25.9 ha, the densities of Clams larger than 2.5 mm were found to be statistically the same on the 9 flats sampled and averaged 122.3 per m2. The average number of legally harvestable Clams (those with shells more than 51 mm in length) was 23.3 per m2, and the total yield that could have been harvested in 1980 was estimated at 6 × 106 Clams. Assuming that only 50–60% of the Clams would actually have been harvested in a year (i.e. 3.2 × 106 animals), the local community lost $332,400 in retail sales alone for lack of adequate sewage treatment facilities. Locally, 70% of the harvest goes into the restaurant trade where a bushel (35.2 1), which contains some 1,600 animals, retails for $210, and 30% is sold fresh at $64 per bushel.

Between late 1978 and mid-1979, two major coastal vegetation plantings were completed on dredge material in Tampa Bay, Florida. On the dredge material extension of Sunken Island, 1.64 ha of Smooth Cordgrass was planted via 12-cm ‘plugs’ on 1-m centres, in rows 2 m apart. After 14 months, this planting is showing 93.4% survival. On dredge-material island CDA-D, 0.52 ha of mangroves (63% Black and 37% White) was planted via 0.3–1.9 m transplants on 2-m centres. After 13 months, this planting is showing 73.3% survival.

The nature of these two plantings permits a comparison of their cost and man-power requirements. The labour requirements for Smooth Cordgrass were 995 man-hours/ha as opposed to 2,541 man-hours for mangrove transplanting. Smooth Cordgrass requires $4,566/ ha for plugs ($1.03/plug) while mangrove transplants cost $11,459/ha ($3.92/transplant). These costs are for comparison only, as they entail primarily labour and neglect most of the indirect costs that may be experienced.

An analysis of benefits for both salt-marsh and mangrove planting indicates that Smooth Cordgrass provides greater primary production on a g C/m2 basis than mangroves. Both plantings serve as colonial waterbird nesting habitat and source-areas for further planting, but Cordgrass does so in a shorter time-frame. When weighing the positive and negative aspects of both, Spartina alterniflora is preferred over mangroves where both are present.

Knowledge is needed of the geomorphological characteristics of stream-channels in urban areas in order to manage the streams for recreation, biota conservation, environment enhancement, erosion control, and the discharge of stormwater runoff. This study is concerned with how urban streams in Brisbane have been substantially modified by many different human activities, and how the future behaviour of the channels is likely to be very complex because of the diversity and magnitude of these modifications.

Major water-supply dams have been constructed on three of the streams, and some flood-detention storages are soon to be constructed on another. The earth embankment of the South-east Freeway fills the upper reaches of Norman Creek, and stormwater runoff is now carried in a man-made channel. Elsewhere in this catchment, flood-flows have been modified by culverts—where the Freeway and access roads cross the drainage channels, and where the Freeway embankment occupies a substantial part of the floodplain of the Creek.

The construction of Brisbane Airport has already modified the tidal reaches of Kedron Brook, and the proposed redevelopment of the Airport will replace the existing modification with a major new floodway.

Several of the stream-channels have been deepened, widened, and straightened, for flood-mitigation purposes, with 465,000 m3 of material removed from Breakfast Creek alone. Three of the stream-channels have been used as major sources of sand and gravel for building activities in the City. Flood characteristics of the streams appear to have been changed by increased runoff from impervious surfaces when these reached a critical threshold in the urban areas, and by increased velocities of flow in piped, lined, and other, artificial stormwater channels. Construction of new artificial channels amounts to some 15 km per year.

The modifications which have occurred differ among the urban streams in Brisbane, and each stream requires individual study to assess the long-term effects of the changes. All of the streams reported on in this study have been substantially modified by human activities.

Drought conditions in Northern California during 1975–77 caused widespread mortality in conifer forests mainly from attacks by disease organisms—including dwarf mistletoes and Fungi—and from epidemic outbreaks of various bark beetles. A federal survey has estimated the volume losses sustained through the affected four years (1975–79) as 9.6 thousand million board feet (45.3 million cubic metres) on 6.3 million acres (2.55 million ha) of national forest. As the dominant host species in afflicted forests is Pinus ponderosa, the most destructive agents have been the parasites of this species—primarily the Western Pine Beetle (Dendroctonus brevicomis) and the Western Dwarf Mistletoe (Arceuthobium campylopodum). However, interrelationships between many stress-inducing factors may be of more significance than the direct attack by any single parasitic species on a host.

Three approaches to the reduction of conifer losses have been studied. The first involves the use of silvicultural practices based on the elimination of susceptible, or high-risk, trees. This is most applicable in countering bark beetles which have the mobility and selectivity to reach potential hosts over large areas.

The second approach is direct control, or the physical removal or destruction of parasites. The steady spread of dwarf mistletoe, formerly contained by natural fire, can only be slowed through pruning, logging, or burning. Bark beetles can be directly controlled if the work is done before new broods hatch and mature. Toxic pesticides such as Lindane have proven ineffective—mainly for economic reasons, but also due to serious reservations among some foresters about detrimental effects on the forest ecosystem. Sex attractants have been used to draw bark beetles into trees of which the removal is planned.

The third approach, applicable to bark beetles, is biological control, or reliance on organisms—such as lizards, woodpeckers, predaceous beetles and their larvae, parasitic hymenopterans, and various Fungi, which in some cases the forester has options to encourage or discourage. At the very least these controls suppress bark beetle populations when normal precipitation patterns return.

Unfortunately, the ideal of a natural equilibrium being reached solely with the use of biological controls is unrealistic. The most fundamental stress on the commercial forests of California is human use, in spite of occasional drought-accelerated epidemic losses to parasites. Salvage must continue to be aggressively pushed upon a reluctant industry, but, above all, more flexible and immediate responses to the first signs of increasing bark-beetle activity, coupled with indirect, pre-epidemic silvicultural practices based on the broader lessons of forest parasitology, must be developed.

A survey of vegetation around an aluminium factory in Renukoot, Mirzapur, U.P., India, was made in the course of a study of the polluting effects on plants of gaseous hydrogen fluoride. These ‘pollugenic’ effects were analyzed by examining the chlorotic and necrotic symptoms of injury on the leaf surfaces, the plants then being classified into three categories on the basis of their sensitivity.

The study revealed the absence, from the vicinity of the factory, of certain plant species which are normally present in the surrounding unpolluted areas. The tree species were the first to be affected, followed by shrubs, grasses, and finally forbs. These differences in response could be attributed in part to differences between the ambient air and ground-level concentrations of the pollutant. The concentrations in the ambient air, being higher than those at ground-level, were responsible for the greater impact on trees, with less on shrubs and grasses, and least on forbs, this being in part a function of the exposure-height of the plant species.

The gradual improvement noted in the performance of the plants and the number of their species at increasing distances from the aluminium factory, was consequent on the gradual decrease in the concentration of the polluting hydrogen fluoride. Such a trend is clearly evident in the north-east direction, where the pollutant fallout was directed by the prevailingly southwesterly winds.

Collisions between birds and aircraft have caused damage to, or destruction of, aircraft and loss of human life for more than 68 years. Birds are attracted to airfields by the large open spaces which they provide and, often, by the availability of food, water, and shelter, on or near the airfield. Birds attracted by open space can be driven away by trained persons furnished with suitable bird-dispersal equipment, while removal of food, water, and shelter, can reduce the attraction.

Mass movements (migrations) by birds, especially large birds, create hazards for aircraft aloft. Air traffic control radar can show the abundance, speed, and direction of movement, of birds, while correlation of those movements with weather parameters permits development of bird movement hazard forecasts. Although the periods of high hazard are of short duration, use of these forecasts to make changes in flying training programmes has reduced losses of Canadian military aircraft through bird studies.

Automatic digital presentation of bird movement data gathered by radar has been tested at two airfields by air traffic controllers for possible use in vectoring scheduled civil aircraft away from hazardous concentrations of bird migrants. A decision on operational use of the technique has not yet been made.

Reduction of bird hazards to aircraft depends upon human motivation. The necessary habitat control, bird dispersal, and migration hazard forecasting, involve timeconsuming, rather dull work that is repeated at prescribed intervals. Unless the work is always well done, bird-strikes on aircraft will continue and human lives and aircraft will be lost.

Four samples of water were taken for analysis from Kala Shah Kaku Industrial Estate, near Lahore, Pakistan. These were:

I) ‘Pure’ water of the channel Dek Nullah,

II) Wastewater of Ravi Rayon Limited,

III) Wastewater of Ittehad Chemicals, and

IV) Dek Nullah ‘polluted’ water after the discharge into it of wastewater from two industries, namely Ravi Rayon Limited and Ittehad Chemicals.

The analysis of these waters showed that sample I was the best in quality (medium-salinity and low-sodium water: C2-S1), sample II was of the quality class C3-S1 (high-salinity and low-sodium water), sample III was found to be of the poorest quality (very-high-salinity and very-high-sodium water: C4-S4), while sample IV was of relatively bad quality (high-salinity and mediumsodium water: C3-S2). Only the wastewater of Ittehad Chemicals had some sediment in it, the qualitative analysis of which showed the presence of oxalates, sodium, iron, and magnesium.

The study of planktonic biota in Dek Nullah ‘pure’ and ‘polluted’ waters showed that they were more diverse in the former than in the latter; indeed, unless Bacteria are classed as fauna, there was no representative of these last in the ‘polluted’ water.

The industrial wastewater effluents are being discharged into Dek Nullah, and this ‘polluted’ water is being used for irrigation by the farmers operating along its downstream course. The effects of this water on Rice germination were studied, and it was found that such germination was significantly greater in Dek Nullah ‘pure’ water than in its ‘polluted’ water.

Dek Nullah ‘polluted’ water may deteriorate further with time, as more and more wastes are added to it, and it may have deleterious effects on soils when used for irrigation purposes—causing salinity and sodicity problems unless proper management techniques are adopted.