The last three decades of the Author's research work were devoted to the Earth's soil cover both on dry land and under shallow waters. That soil cover could emerge on the Earth only after life had appeared, even though only in primitive forms. The soil cover is a product of organisms' activities and their interaction with mineral surroundings; therefore it could not appear on the Earth in the absence of living matter. If it was not for life, the soil cover would not have existed. V.I. Vernadsky always considered terrestrial soils as ‘bioinert bodies’ formed as a result of the long-term interaction of living matter and rocks (Vernadsky, 1940). According to modern theories, the Earth, like other planets of the Solar System, was formed 4–5 thousand million years ago from a thickened mass of different lifeless minerals. It could include huge asteroids and fragments of mineral rocks, big and small meteorites, and cosmic dust. Up to the present, the Earth's surface has accepted annually some 5–6 million tons of diverse cosmic dust and many meteorites of different sizes.

We face major and intimately interlinked problems of population, environment, and development. They are so profound and pervasive that they surely represent a uniquescale challenge for Humankind. The issues and policy responses will preoccupy the best understanding on the part of political leaders and scientists alike during the planning process leading up to the United Nations Conference on Population and Development which is to be held in Cairo from 5–13 September 1994.

Scientific aspects are to be addressed at an earlier conference that is to be attended by representatives of some 80 of the world's academies in New Delhi in late October 1993. The present paper reviews the principal factors and analyses relating to the three problems, with emphasis upon their interactive relationships. It concludes with an extended list of strategies to reduce both population growth and environmental degradation—twin challenges to be tackled within a framework of sustainable development, to which both will make critical contributions.

Issues of environment and development are increasingly being analysed within the framework offered by sustainability and sustainable development. This article explores a number of deep-seated contradictions and tensions that exist within these concepts at least as they are currently construed. It is noted that these contradictions are often glossed over in intellectual and policy debates, but are nonetheless profound and should be made explicit.

The contradictions identified and discussed in the paper are as follows:

–the paradox of technology (cause or cure?);

–uncertainty and decision-making (humility or arrogance in the face of ignorance?);

–intergenerational and intragenerational equity (a politically impossible trade-off?);

–economic growth versus ecological limits (is ‘sustainable development’ an oxymoron?);

–the reconciliation of individual and collective interests, applying both to individuals in their society, and nation states in the international community;

–the potential conflict between the diversity of democracy and purposeful action;

–differing kinds of resilience in the face of change (resistance, marginal change, and adaptability); and

–the question of whether or not optimization is anti-sustainability.

In conclusion we ask what the implications of this labyrinth of contradictions are for moving towards a sustainable state. Are these contradictions too profound and thus insurmountable, or does Homo sapiens' apparently innate ability to live with contradiction and logical inconsistency offer a way out?

Within the past few years, interest in climate change has increased dramatically in the face of the many apocalyptic predictions associated with the highly-popularized ‘greenhouse’ effect. Accordingly, scientists have produced many studies based on global, hemispheric, and regional, climatic data-bases. While most of the regional studies have been based on data from North America, Europe, and Australia, little research has been conducted in other areas of the world that have an equal (or greater) economic and climatic stake in the ‘greenhouse’ debate. In this investigation, we analyse the climatic records of the Arabian Gulf area in an attempt to identify recent changes that may or may not be related to any ‘greenhouse’ effects.

The observed climate changes over the past century in the Arabian Gulf area include (a) an increase in temperature of 0.65°C, (b) warming in summer and little or no warming in winter, (c) no warming in the first 60 years of record but accelerated warming in the most recent 40 years, and (d) a small decline in precipitation. In many cases, the results are unlike those found in the analysis of Northern Hemispheric and/or global climate records. However, many of these observed climate changes in the Arabian Gulf area are broadly consistent with 2×CO2 predictions from various numerical climate models. We hope that the analyses presented in this investigation will aid decisionmakers in their difficult policymaking activities.

The climatic similarity of desert environments everywhere has engendered parallelism and the evolution of ecological analogues in different regions of the world. This tends to mask the actual diversity of their inhabitants. Although biodiversity may be poor in the desert, at least compared with most other terrestrial ecobiomes, deserts are extremely vulnerable to degradation and therefore deserve as much as, or even more, consideration than many biologically richer habitats.

Interpretation is most effective when its form and content are adapted to the situations in which it will be presented. Although many developed countries have a long and rich tradition of interpretation, the physical, financial, and socio-economic, differences among and within developing nations suggest that this tradition will not always apply there. As our colleagues in developing countries look for interchange and suggestions, the temptation to impose our model—and the difficulty for them to accept it—will be great.

Interpreters in developing countries need to pursue a different model—one which gives relative emphasis to interpretation's role in strategic environmental education for target audiences. Though not altogether excluding the visitor service function that is frequently emphasized in US protected areas, interpretive programmes in many developing countries are often included as just one component of country-wide environmental education master-plans aimed at establishing sustainable development as a national ideology.

Host countries sometimes accept the conventional model too readily, often because the only available training materials are translated from these sources. When application falls short of expectations, in-country interpreters usually blame themselves or conclude that interpretation ‘just isn't for us—rather than questioning the model they have been handed. Universities must also share some of the responsibility for this sorry state of affairs. International students studying at US or European institutions sometimes return home better prepared to work as interpreters in those countries’ protected areas than in those in their own countries. Trainers and teachers, whether working at home or elsewhere, need to do a better job of listening to their students. They need to learn what it is like to be an interpreter in that student's country, and they need to learn what it is like to be part of the audience. Would we accept anything less of our own mentors and interpretive trainers?

Clearly, a superior strategy to exporting our model of interpretation is to assist developing countries in arriving at their own. Over many decades, interpreters in the US and other developed countries have developed a profound knowledge about their craft. Although much of it will not apply everywhere, some of our ideas may have widespread application. The key will be to determine which ones these are. Working with our developed country colleagues, learning with them and through them, we can explore together a range of possibilities that neither of us is able to envision alone. Filtered through our cultures and individual realities, the ideas which have merit will be identified and put to test. Others will be rejected. In the very best scenario, both parties will learn, and sustainable environmental quality will be the result.

The River Yamuna, originating in the Himalayas, is the largest tributary of the River Ganga (Ganges) into which it flows at Allahabad. Its drainage basin covers about 42% of the Ganga River basin and about 11% of India's total land area. The area of the Yamuna drainage basin is densely populated and under intensive agriculture, while industrial activity is also rapidly growing in it. Climatically, a large part of the basin is semi-arid, and the river-flow depends upon highly erratic monsoonal rains. Therefore, the River and its tributaries have been regulated for over a century by dams and barrages for domestic water-supply and irrigation.

Besides increased flow-regulation, the River's system has been under increasing anthropogenic stress from discharge of—mostly untreated—domestic and industrial wastewaters, and from other activities in the basin. River Yamuna is severely polluted by domestic and industrial effluents especially from Delhi down to Agra. Water extraction and consequently low flow has affected the selfpurification capacity of the River. The greater inflow of River Chambal helps River Yamuna to recover to some extent after their confluence near Etawah.

Studies of water quality and biota of the River Yamuna along its course during the past 30 years show rapid deterioration of water-quality, loss of fisheries, and significant changes in the biotic communities. In the manner of River Yamuna, its tributaries have also become increasingly polluted during the same period. There has, however, been little attention paid to the management of the River system and conservation of its resources, except for some efforts at the treatment of sewage effluents but emphasizing only water-quality. Ignoring the river-flood-plain interactions which play significant roles in the ecology of a river, most of the floodplain has been reclaimed by constructing high levees.

We emphasize that the Yamuna River basin should be treated as one ecocomplex in developing appropriate management strategies, and that the conservation of waterquality and biota can be achieved through protection and better management of floodplains than has been practised to date.

Increasingly, seabirds nesting on islands are exposed to tourists who view, photograph, and study, them for variable periods of time. The escalating frequency of human-seabird contacts on heretofore undisturbed nesting islands raises questions and concerns about the effects of human disturbance, and of the continued preservation of nesting colonies of marine birds. We examined short-term changes in behaviour of Masked (Sula dactylagra), Redfooted (S. sula), and Blue-footed (S. nebouxii), boobies when tourists walked by, and examined display station and nest placement as a function of distance from a regularlytraversed tourist path on Tower (Genovesa), Hood (Espanola), and North Seymour, Islands, Galápagos.

Whether displaying boobies walked, flew, or remained on their station, when tourists passed, was related to their distance from the trail. Boobies displaying at stations on or up to 2 m from the trail, walked or flew from their station 62 to 95% of the time, depending on the species. All species of boobies performed more head and body turns, and gave-out more calls, after tourists passed than before, while the rate of preening did not differ. All three species of boobies avoided nesting right along the trail, despite similarities of habitat.

These data suggest that boobies respond to tourists in subtle ways often related to their species, and that further studies should delineate impacts operating over longer periods—including reproductive success variation as a function of disturbance.