By these several citations from the topics before this Second International Congress of Ecology, I have tried to suggest the need and the feasibility for this discipline to play a more active role in the continuing development and improvement of the quality of human life on this planet.

The international system which is now preparing for the Development Decade of the 1980s, and the developing countries which seek their own paths—as many as are needed to match their varying environmental, social, economic, and cultural, endowments—are open to advice as to what to do in the general scientific, and most particularly in the ecological, context in which all continuing life must operate.

The United Nations Conference on Desertification was the first occasion on which the nations of the world turned their concerted attention to the need for a comprehensive plan to halt and reverse desertification. The global annual loss to desertification is in the order of 60,000 km2. It is Man's action that degrades the land by misuse as he seeks to wrest a living from fragile ecosystems. A change to a more arid climate could be another cause, but no firm evidence is available that the climate is so changing. The Conference concluded that both the causes of desertification and the technical solutions to combating it are known. The key to combative measures is to be found in proper land-use. If desertification is to be brought to a halt by the end of the century, considerable financial resources will, however, be necessary.

The paper includes a comprehensive summary of the unpublished statements of the various national governments and some international agencies regarding their problems, an analysis of the findings of the Conference, and a brief discussion of action taken since its conclusion.

There are numerous instances where, through injudicious use, Man has contributed to desertification of the agricultural environment by increasing the aridity and decreasing the ability of the soil to support vegetation. This may come through erosion, even in areas with very high rainfall (e.g. Amazonia). But in many arid regions dedesertification has occurred under the influence of Man (e.g. Imperial Valley in California, Hungry Desert in Uzbekistan, 90-Miles Desert in Australia).

However, under certain conditions, such as those of fog-drip, an irreversible desertification can be caused by removal of the original vegetation (e.g. Central Chile).

Dew may be an important source of water for plants even in deserts, where there is a shortage cf liquid water for plant growth.

In April 1975, the Walking Catfish (Clarias batrachus) was known to be established in ten counties of Florida. The present range of this exotic species covers 18 counties or somewhat more than 25 % of the freshwater area of Florida, and this has happened in the ca ten years since the first specimens were found in the wild. Severely cold winters have failed to stem range expansion, and future northward migration in peninsular Florida can be expected.

Birds, struck during flight by fast-moving modern aircraft or getting ingested in jet engines, cause numerous serious accidents of which some involve human deaths. Gulls of various species are the birds involved in a considerable proportion of these accidents due to bird-strikes.

Gull-strikes of aircraft in flight may be expected:

1. When there is a chronic attraction such as a concentrated worm or insect population, a high mouse population, or some other biological attractant;

2. When there is lack of care in disposal of food-wastes;

3. When drainage on an airfield or on flat-roofed buildings is not properly designed or is not functioning well; or

4. During the early autumn when large numbers of inexperienced, immature gulls are in flight.

This paper examines the concept of environmental education as it relates to engineering education. The main area of applicability is considered to be in the continuing and postgraduate education areas, although some environmental input into undergraduate degree programmes is thought to be desirable.

The interdisciplinary nature of environmental problems necessitates a certain amount of formal coursework which should be coupled with a project to provide experience in solving real problems. The course-work should contain both broadening elements to introduce students to the relevance of disciplines outside their undergraduate experience and a specialization in a particular multidisciplinary area such as air pollution control or water resources engineering.

The criteria for environmental programmes in engineering are developed with special reference to the new Environmental Engineering Postgraduate Programme at the University of Melbourne.

A massive fish-kill at a trout hatchery located below the discharge of a seasonally stratified impoundment provided a unique opportunity to examine mechanisms of toxicity (using in situ water) by means of a largescale experiment at the hatchery itself. In order to assess the relative impact on the fish of a number of water constituents such as heavy-metals and organic materials, a variety of dosing chemicals were employed within the hatchery. Fish tissue and blood samples were collected for histological and chemical analysis, respectively.

It was concluded that a combination of manganese and organic material (probably humic in nature) in reduced chemical states in discharges of bottom (hypolimnetic) waters of the impoundment during periods of minimum power-generation was responsible for the mortality. Parallels between the fish-kill under investigation and other reported causes of hypolimnetic water toxicity were also drawn. It would appear that the redox state and nature of organic materials present may control the mechanisms in the various fish-kill situations. Implications for other users of the water are currently under investigation in an expanded programme.

During the winter of 1974–75, both tar and aromatic hydrocarbons were sampled in the Mediterranean Sea. A detailed report of the tar findings were given in a previous paper (Morris et al., 1975). Aromatic hydrocarbon concentrations at a depth of 1 m averaged 167 ng/1 (expressed as phenanthrene equivalents). This is only about 60% as great as the average aromatic hydrocarbon concentration found in the Baltic Sea, but is 5 times greater than what was found in the north-west Atlantic—including the Sargasso Sea (Zsolnay, 1977).

No relationship was found between tar and aromatic hydrocarbon concentrations. This would indicate that the concentration of the latter is dependent upon other factors—such as the presence of other organic compounds that are capable of keeping the hydrophobic hydrocarbons in the water column by ‘solubilization.’

In urban areas, continuing fragmentation of natural habitat, disturbance, and increasing isolation of individual ‘habitat islands’, has brought on almost general reduction in species richness. Sensitive species are being replaced by aggressive synanthropic ones. Continued loss seems inevitable, but reducing the rate of that loss is a worthwhile conservation goal. It is imperative that the numerous and varied habitats within each urban area be considered as interrelated and not as separate units. Island biogeography models supply the means for unifying the disparate elements in urban ecological studies and can provide a useful strategy for conservation.

It is difficult to define colonization, extinction, and equilibrium, in disturbed, often transient, urban habitats. Pseudo- and successional turnover dominate. The occupation of each ‘habitat island’ is a function of its own geography and of its position relative to other ‘islands’. Each habitat may serve as isolated ‘island’, ‘stepping-stone’, or ‘corridor’, depending on its spatial relationships with other ‘habitat islands’ and with the nature of each organism present.

‘Habitat islands’ in small cities appear to function like large or near oceanic islands, while those in large cities seem to respond like small or distant oceanic islands. In all cases, the analogy with land-bridge islands is appropriate. Continuing urbanization is leading to reduced ‘habitat island’ size, and increasing the isolation of units from one another and from the surrounding rural ‘reservoir’.