What we need now is to find the balance required between all types of space from the ecological point of view. A great danger for food production is being created by the expanding human settlements. As soon as commercial forms of energy and machines enter our settlements, they start to expand at a much greater rate than does the growth of the settlement's propulation and economy. As the growing settlements need to add a lot of industry and many big buildings, their expansion is not directed towards mountainous areas but occurs chiefly on the plains. It is here that the best soils usually lie: thus urban growth means profligate elimination of agricultural land.

This is not an immediate problem for tomorrow, in terms of days; but it is a very big problem in terms of years and decades, as agricultural land covers a very small percentage of the total global surface and we cannot afford to lose it. The danger is very great and we must act quickly if we are to avoid it.

This need for action has led me to classify twelve zones of land-use with the ultimate goal of reaching a Global Ecological Balance (G.E.B.) and the immediate goals of saving land for agriculture and food production, of conserving the environment, and of giving a boost to the dying flora and fauna.

Nations face three challenges in the modern world: to ensure the greatest welfare for their people; to make wise use of natural resources; and to do these things in such a way that they contribute to a solution that makes sense for the whole world. To face these challenges requires a high degree of international cooperation and a clear-thinking, unemotional approach.

Hitherto the bank of natural capital has been treated as though it were income; this is the antithesis of wisdom. In the future, natural resources should be used so as to get the greatest immediate benefit that is consistent with keeping open a range of choices and maintaining natural capital intact.

To be successful in this endeavour, ecological guidelines must be applied in the planning and use of natural resources. The depletion, or restoration, of natural capital, should be fully represented in calculations of costs and benefits, in order that what is good land-use is also seen to be profitable. Where the link between these two qualities is not evident, great political skill may be necessary in presenting proposals for the use or rehabilitation of natural resources. The final challenge is to reassess the values of societies and not to accept blindly those which have become customary—particularly if this has happened through their provision of short-term benefits.

It is my intention, in the following remarks, first to review briefly the present state of the environment as a world issue in relation to the other major issues which, today, bear upon the prospects for the human future. Secondly, I would like to advance the premise that it is possible to think positively about the human future and to point up some of the principal elements which I believe will be necessary to make that positive vision of the future a reality.

The environmental issue has evolved rapidly in the less-than-three years since the United Nations Conference on the Human Environment, which was held in Stockholm, Sweden, in June 1972. Most notably—and largely as a result of what we nowadays commonly refer to simply as ‘Stockholm’—it has become a truly global issue in the sense that virtually all governments and peoples throughout the world have now acknowledged it as an issue of importance to themselves, and have taken at least the first steps to establish national environmental policies and machinery to carry them out. In the developing countries in particular, there has been a literal explosion of interest based primarily on the larger concept of environment and its relationship to development which emerged from the Stockholm Conference.

Studies of past climates show unequivocally what can happen to our atmospheric environment. From climatic history we can learn several very specific lessons.

The climate can change rapidly. Major climatic changes, such as the change from glacial to non-glacial conditions, can occur in a few centuries, even though the adjustment of biota and the wasting of continental ice-sheets may take longer. Smaller changes may take only decades.

Changed climatic states may persist for centuries or millennia. While the climatic excursion of this century appears to have lasted half-a-century or so, the ‘little ice-age’ was at least three centuries long (roughly 1550–1850 A.D.), a North American drought period lasted two centuries, and there was a monsoon failure of seven centuries. These have all been recorded in the evidence of Nature.

Climatic changes may occur in different senses in different parts of the world. This paper has outlined several cases where cooling in the sub-Arctic was associated with reduced rainfall or increased frequency of failure of the monsoon, and a case in which drought in North America was concomitant with wet weather in western Europe.

The climate we think of as normal is quite abnormal by the standards of the past few centuries, and the magnitude of the change since 1945 is significant by comparison with similar changes in the past.

Combining the nature of the recent climatic change with the present narrow margin of world food-grain reserves, an urgent need to consider and react to the possibility of continued climatic variation is indicated.

Pacem in Maribus once again stressed that an ocean regime must encompass the oceans as a whole and be considered as a sub-system of the entire global system. Jurisdictional decisions, including those affecting the Exclusive Economic Zone (EEZ), must reflect that paramount concern. It is not a matter of geographical realignment or of partition; marine ecosystem do not correspond to political demarcations. Nor is mankind, for which the concept of the common heritage is prescribed, confined to coastal states or to the present generation.

In its discussions and studies, Pacem in Maribus has consistently stressed the significance of rapid scientific and technological developments which have radically changed the nature of many conventional uses of the sea and call for management as the only alternative to conflict and possible disasters. In its commitment to an Ocean Space Authority rather than to an International Sea-bed Authority, Pacem in Maribus contends that activities on the sea-bed cannot be dissociated from activities in the water-column, at the surface, and at the atmospheric interface; that the sea-bed must become part of an integrated management system for ocean space; and that claims to national jurisdiction carry a surrogate responsibility in that management.

Pacem in Maribus contends that any Law of the Sea which does not respect and embody these overriding considerations will prove to be ineffective if not inoperable.

Population explosions of the Crown-of-thorns Starfish, Acanthaster planci, first reported on reefs of the Great Barrier Reef in the Cairns region near lat. 17° S during the early 1960s, have since spread to numerous other reefs. The spread has been predominantly southwards, the principal region of infestation currently lying between lat. 19° S and lat. 19°20' S. South of this region, scattered infestations of reefs have recently been reported. Available data indicate that most reefs in the middle third of the Great Barrier Reef were infested during the last decade, and it is postulated that most reefs in the southernmost third will be infested during the next decade.

The bulk of the hard-coral cover of most of the inner platform reefs infested, and a lower but significant percentage of the hard-coral cover of the outer platform reefs affected by the infestations, have been devastated. Recovery of devastated reefs is in progress but is slow.

The A. planci infestations appear to the authors to be man-induced, and it is suggested that international action be taken to assess the magnitude of the A. planci problem and to coordinate possible control activities in the Indo-West Pacific region.

Inland waterways provide more opportunities for the conservation and improvement of the environment and the provision of amenity, sports, and recreation, facilities than do any other means of transport. The demand for more space for leisure pursuits is world-wide, and is accompanied by a growing appreciation of the need for environmental quality and conservation of Nature in catering for this demand. Thus in seeking solutions to related leisure, environmental, energy, and transport problems, authorities everywhere are coming to recognize the unique potential of inland water in meeting the concerns and wishes of modern society.

Britain, with an unparalleled exclusively amenity waterways network, leads the world in the amenity development and utilization of inland waterways. The United States is broadening its objectives to encompass amenity development within the framework of traditional commercial-priority development of its waterways. Canada has launched the most sweeping and spectacular amenity waterway corridor development in history. France has begun actively to promote ‘tourisme fluvial’, while the Netherlands is progressing with integrated planning to harmonize the interests of commercial navigation with recreation and Nature conservation. The projected waterways link between the North and Black Seas has fostered amenity waterway development by all states along the Danube. Russia, too, is beginning to cater to the requirements of increasing numbers of water-oriented leisure seekers. Many other countries, including Portugal, are looking to the development of navigable waterways for leisure pursuits to help solve mounting national problems.

Plagues of caterpillars and other plant-feeding insects tend to occur where trees and other plants grow as man-made monocultures. Herbivorous insects rarely cause extensive damage to mature trees in tropical forests; but even in the tropics, outbreaks are frequent wherever trees of the same species are grown together—as for example along roadways and in built-up areas. In Africa, in particular, peasant cultivators growing their own food tend to plant a variety of species in the same plot, and it is suggested that these people have found by trial and error that polycultures are more resistant to insect damage than are monocultures. English flower-gardeners maintain polycultures in their herbaceous borders and are rarely troubled by insects, but vegetables are now grown as pure stands. This probably leads to a build-up of pests and a need to use pesticides, which of course is encouraged by the gardening and pesticide industries.

Although there remains considerable controversy over the precise relationship between species diversity and population stability, there is much circumstantial and some direct evidence that plagues of plant-feeding insects are much more likely in pure stands of vegetation than in diverse communities. What might be called the community ecology of peasant cultivation is little understood, and there is an urgent need for research before more and more land is converted to monocultures.

The purpose of this study was to learn how ozone might affect the growth and reproduction of understorey species of the aspen community, and thereby influence its stability and composition. Plants of 14 species belonging to the aspen community were grown in greenhouse chambers and fumigated with ozone for 3 hours each day, 5 day per week, throughout their growing-seasons. The plants were exposed to 30 pphm (parts of ozone per hundred million parts of air), 15 pphm, ambient air reaching 5–7 pphm during about 2 hours each day, and filtered air.

Exposure to ambient air did not appear to cause a significant reduction of total plant-weight in any of the species investigated, while plant-weight of Achillea millefolium and Isatis tinctoria grown under such conditions was significantly greater than that of control plants grown in filtered air. At 15 pphm, growth of Isatis tinctoria, Madia glomerata, and Viola italica, was significantly reduced; on the other hand, growth of Ligusticum porteri and Polygonum aviculare was increased. At 30 pphm, growth was substantially suppressed in all plants except Chenopodium album and Phacelia heterophylla.