The widespread fear that the Earth's deserts are spreading was reawakened by the major 1968–73 drought in Sahelian West Africa, Sudan, Ethiopia, and parts of Kenya. There appears, however, to be no firm evidence that a permanent desiccation of the arid zone is in progress. Instead, the evidence suggests that ‘desertification’—defined as the spread of desert surfaces, regardless of cause—results more immediately from faulty land-use practices and their interaction with prolonged natural drought episodes.

Desertification appears to be a process of degradation of grassland, scrub, or savanna, ecosystems under the impact of overstocking or excessive cultivation. During periods of desiccation there is widespread destruction of perennial vegetation, compaction of soil (especially near watering places), and deflation of fine materials (wind erosion).

Such surfaces are lighter-coloured than native vegetation, and reflect more sunlight. This may enhance atmospheric subsidence, and hence intensify drought. Loss of surface organic litter may also act as a positive feedback for drought.

Prediction of such episodes is at least some years away, but three possibilities exist for such prediction: use of cyclical variations, where present; time-lagged teleconnections; and general circulation modelling.

Reduced infiltration in some arid areas, combined with excessive withdrawals in others, have lowered both shallow alluvial and deep fossil ground-water tables—in some areas to the point at which stock water-supply can no longer be maintained.

The present global economic order is one which fails to recognize the finiteness of global resources and the finiteness of the global ecosystem to absorb wastes. Indeed, there may be a great deal of lip-service paid to these truths; but nevertheless the global economic system, as it is functioning today, exhibits little or no awareness that they are at all important to a stable world economy. Superimposed upon this condition is the ‘Autophage Effect’, which points to a continuing acceleration in depletion of raw resources even though the net resource-demands of the world's populations may stabilize.

This is a human predicament which cannot and will not continue indefinitely. The key question is, ‘Will Earth's societies acknowledge the situation early enough to choose alternatives?’ There appear to be only two fundamental alternatives: either the present level of population and material abundance (imperfect as it may be) will crash, or it will be replaced by a world economic order which attends to the finiteness of this planet. Should we be fortunate enough or quick enough to realize the second alternative, I suggest that the basic structure of the new economic order may rather closely resemble the ecologists' ‘trophic’ divisions in natural ecosystems (e.g. Lindeman, 1942). If this comes to pass, conservation of energy and order (negentropy) will very likely emerge as the prime forcing functions in the resulting world socio-economic order.

This exploration has progressed from logical derivation into imagination, but still leaves a plethora of unanswered questions. If one does admit that industrial civilizations must eventually face resource limitations and thereby be driven towards the patterns exposed by the hypothetical society that has been sketched here, how do we get there from our present predicament? Can such a society be capitalistic, with grossly or moderately unequal distribution of resources among its citizens? Or must it be a form of socialistic idealism; and, if so, should it be democratic or autocratic? Can the present momentum of the highconsumption Keynesian theology be redirected? And if so, how—and will there be time? If the seeds offered here have any credibility, they should be nurtured further.

Natural and semi-natural ecosystems in many parts of the world are in the most serious danger of being degraded or lost through Man's mistaking short-term economic gains under temporarily favourable conditions for long-term stability. This is particularly obvious in arid and semi-arid regions where ill-advised land-use methods have led to profound and often irreversible changes. Under the austere conditions prevailing in such regions, the dynamic ecological equilibrium is fragile: minor changes in the physical environment entail dramatic changes in plant and animal life. These circumstances lead easily to desertification. Due to overexploitation of natural resources by Man (especially overgrazing, and overcutting of shrubs) in North Africa, desertification has proceeded at a rate of more than 100 square kilometres per year. There is a great need to establish scientific bases for the conservation and rational use of the resources of natural and semi-natural ecosystems, especially in regions fringing the deserts where these resources continue to disappear regularly and all too rapidly.

The western Mediterranean desert of Egypt provides clear examples of such losses. As a result of the misuse of its resources, the region is producing at a rate that is probably far below its real potential. Agriculture (mainly barley cultivation) provides the livelihood for 74% of the population between Alexandria and Daba'a; this agriculture is either rain-fed (along most of the coastal strip), supplied by Nile and drainage-water mixed (Mariut Project, 500,000 feddan = 210,000 ha), or fed by irrigation and rainfall where Nile water is used as a supplementary source (Mariut Extension Project, 18,000 feddan). The most important land-use in terms of area, however, is animal husbandry (very largely sheep and goats, whose herding becomes more important and farming less important passing from the sea towards the interior). Actually there is overstocking, so that range vegetation is seriously depleted due to overgrazing and poor management.

Various land-use policies have been tried in the past decades with varying degrees of success, though fig and olive cultivations, which act within the framework of the natural ecosystem and with minimum human intervention, have a remarkable record of viability.

The Samdene Project (Systems Analysis of Mediterranean Desert Ecosystems of Northern Egypt) was conceived to bring together information on the Mediterranean desert ecosystems of northern Egypt. The Project involves the construction of predictive models simulating the major ecosystems of the region interms of energy flow and circulation of matter, and of spatial and temporal changes in plants and animals aswell as in soil features in relation to environmental variations.

So he preliminary results are already offered on soil moisture, vegetation, effects of fencing, phenology, litter production, and soil fauna.

It is a signal honour to have been asked to deliver this lecture to commemorate the outstanding contributions of Jean Baer and Julian Huxley to the cause of conservation. Both of these great men devoted their genius as scientists to helping us to broaden our perceptions of the human condition and their talents as leaders to establishing the institutions needed to safeguard and to improve the conditions of life on this planet. No two individuals did more to establish the foundations on which environmental conservation can now be seen and dealt with as a critical global issue.

Knowledge of the present status and future potential of the world's marine food resources is a key prerequisite to their ecological exploitation. Rationales for the exploitation of these resources are twofold. Most important is the expectation that more time to reduce human population growth—the ultimate goal—could be made available. Secondly, because fish and shellfish are typically high in their content of protein and low in fat, nutritional quality in the human diet can be improved through their increased use.

Fundamental to marine biological production are the phytoplankton populations which comprise the basis of the oceanic food-structure. This production involves the photosynthesis of organic matter by phytoplankton and the subsequent flow of this matter through the food-web. Spatial and temporal discontinuities in marine production are related to the patchy distributional pattern of phytoplankton and to natural fluctuations in oceanic populations due to geographically and temporally varying conditions. A review of past estimates of the potential marine yield suggests that there has been significant variation in the methodology employed to arrive at these estimates.

Much-improved management of the oceanic food resources is urgently needed. Present mismanagement of these resources includes chemical pollution and the overexploitation of several important fish-stocks, which together threaten the viability of marine life. On the positive side, the future potential of the overall marine food-resources appears to be considerably larger than the present yield. The current harvest can be augmented by further development of aquaculture and by the exploitation of unconventional species, both of which could offer a relatively untapped source of valuable protein. Thus, Man must quickly establish and implement a rational, global management plan for the world's oceans and control his own population numbers to ensure conservation of the marine food-resources.

Disposal of municipal solid wastes may result in needless environmental damage and loss or degradation of land. In addition, the material and fuel resources contained in the wastes remain unused. The extents of these latter in the entire United States are estimated in this paper.

New terms are introduced to aid more precise estimation than hitherto of the amount of energy which can be conserved through processing and recovering the resources in municipal solid waste. Further, the likely rate of implementation of resource recovery in the U.S. is predicted on the basis of a simple model which relies on the assumption that the rate of implementation is proportional to the number of plants that are or will be actually on-line.

There is a great temptation to combine the rate of implementation with the sum of the energy potentially recoverable from the various sources of wastes, and to convert the answer to, for example, so many barrels of oil per day. As is indicated in the discussion, this exercise in not technically justified. Nonetheless, the energy that is potentially recoverable from solid wastes has an arithmetic equivalence of the order of magnitude of 1 million barrels of oil per day (1.6 × 106 m3, or 158 × 106 litres) in the United States alone, and even more if a generous fraction of agricultural and crop residues could be garnered for processing. This order of magnitude, perhaps as much as substitution equivalence, should be compared with the stated U.S. goal of conservation of 2 million barrels of oil per day (presumably also an arithmetic equivalence) from all sources by the end of 1977—not just from solid wastes (Ford, 1975).

The analogy of solid waste as an ‘urban ore’ has been used to the point of almost becoming trite. Nevertheless it may well be timely to extend the analogy to waste as an urban oil-well or coal-mine.

A research project in freshwater ecology is described whose main intentions are: 1) to increase the contact between the University of Oslo and a local community; 2) to solve actual problems for the local community by prosecuting applied research without interfering with the researchers' demand for free choice of research items; and 3) to allow for a larger student population without increasing the supervisory staff (compatible with steadily falling grants).

The Voss Project is a cooperative project between the Zoological Institute of the University of Oslo and the Voss District Council, western Norway. It was initiated to analyse the Voss River system, which is threatened by eutrophication and water-power development.

The research is mainly carried out by Cand.Real. students, who live for 1–2 years in the local community. During the work, an intensive exchange of information about biological and social items, and about municipal politics, naturally takes place.

Large natural preserves, known as zapovedniki, represent the main territorial entities employed in biosphere preservation in the Soviet Union. In the past decade, a large expansion of the zapovedniki system has taken place, 35 new preserves totalling 4,477,000 ha having been created. In all, the system totalled (in 1976) 107 preserves covering about nine million hectares. The period since 1970 has also seen the creation of the U.S.S.R.'s first three national parks, one in each of the three Baltic republics.

Both zapovedniki and national parks in the Soviet Union are still in the process of having uniform administrative policies formulated for their management, which represents a difficult task in view of the fact that they have traditionally been managed by a wide variety of concerned agencies.

The zapovedniki network represents one of the great biosphere preservation systems of the world, and remaining problems associated with ecosystem management, tourism, economic uses, and administrative coordination, are being given thoughtful attention.