This paper outlines the concept of environmental sustain-ability (ES), shows why it is important to make it a top-priority goal, and why that will be difficult to attain but essential. The ES equation of impact = population × affluence × technology, is outlined. When the world approaches stability in both population size and the throughput of energy and materials per unit of production, we may indeed be approaching sustainability. As the world's population is apt to double every 40 years, and as only a few countries (e.g. Japan and Sweden) have managed so far to reduce the energy intensity of production, we are hurtling away from sustainability rather than even approaching it. Environmental sustainability can be approached by implementing four priorities: first, by using sound microeconomic means; second, by using sound macroeconomics to differentiate between use and liquidation of natural capital by means of environmental accounting; third, by using environmental assessment to incorporate environmental costs into project appraisal; and fourth—until the first three become fully achieved—by following operational guidelines for sustainability. Thus:

1) Sound Microeconomic Means involve: (1) Getting the prices right: to reflect full social marginal opportunity cost; use the ‘full cost’ principle, or the ‘cradle-to-grave’ approach. (2) Repealing perverse fiscal incentives. (3) Strengthening the ‘polluter pays’ principles. (4) Including non-monetary values in project justification. (5) Adopting the transparency principle that markets can function efficiently only if relevant information is available at low cost. This involves the participation of people in decisions affecting them, and advertising who is polluting what and by how much.

2) Sound Macroeconomics by Environmental Accounting is essential to discern decapitalization and to shift to using income rather than drawing down capital assets. Environmental accounting clarifies what is liquidation of natural capital from what is income. This is essential because decapitalization is frequently confused as income. Environmental accounting warns us when liquidation of potentially renewable resources exceeds their regeneration rates, such as in many forests.

3) Environmental Assessment is part of the project selection process. The purpose of EA is to ensure that the development options under consideration are environmentally sustainable. Any environmental consequences should be addressed in project selection, planning, siting, and design. EAs identify ways of preventing, minimizing, mitigating, or compensating for, adverse impacts.

4) Sustainability Guidelines: Until the first three rules are heeded and duly acted on, the following guidelines will be necessary: 1, Output Rule:—waste emissions from a project should be within the assimilative capacity of the local environment to absorb without unacceptable de-gradation of its future waste-absorptive capacity; and 2, Input Guide:—harvest rates or renewable resource inputs should be within regenerative capacity of the natural system that generates them. Depletion rates of non-renewable resource inputs should not exceed the rate at which renewable substitutes are developed by human invention and investment.

Of the renewable resources of The Biosphere, agricultural land, including its water resources, is very high among the most important, because it is elemental for human and domestic-animal life. The stability and sustained fertility of the soil largely depend on both prevailing soil–climate conditions and on anthropogenic influences.

There are strict limits to the human interference which soil substrates, ground, soil, and surface water, flora, fauna, and microorganisms, can tolerate under moderate, let alone subtropical and tropical, soil–climate conditions. Economic, social, and aesthetic, yield of agricultural resources is limited even where economically and technically optimal use is made of capital and labour. A ‘maximum sustainable yield’ varies as a function of the soil–climate location, the established land-use system, and the technology applied, but only as long as this yield is not exceeded is the enduring availability of the resource ensured.

With the demand for land and energy to produce food and agricultural raw materials rising throughout the world, per caput food production continuing to fall (especially in Africa), and the cultivated area per caput declining worldwide, the urgent question for the long term is how to preserve the natural resources of water, soil, and vegetation cover, and how to arrest desertification, deforestation, salinization, soil degradation, and soil erosion.

These reflections centre on the call for farming systems which are suited to given locations and do no harm to the environment, and also for sustainability of agricultural production—two aspects which have been badly neglected in the past. The necessary simultaneous tasks of developing farming systems and preserving resources, can be tackled only in relation to specific locations and in a conducive development ‘climate’, where appropriate general conditions prevail. As a rule, the microeconomic development options for coping with these tasks can be improved only at a supra-farm and community level, and require new, environmentally oriented national agricultural and rural development policies.

The decline and subsequent above-replacement plateau in Costa Rican fertility rates illustrates a demographic pattern that is apparent in other developing countries. This paper discusses the complexity of factors that contribute to the fertility plateau in Costa Rica. These contributory factors include the social and economic status of women, socio-economic conditions in general, lack of government commitment to and supply of family planning services relative to demand, deficient sex and family-planning education, and the powerful institutional influence of the Catholic Church.

We then discuss possible strategies, for developing and developed nations alike, to slow and eventually halt the exponential growth of the global human population. For this quintessential need the most important strategies, we suggest, are targeted education for both sexes and provision of comprehensive contraceptive and abortion services.

Representatives of national academies of science from throughout the world met in New Delhi, India, from 24 to 27 October 1993, in a ‘Science Summit’ on World Population. The conference grew out of two earlier meetings—one of the Royal Society of London and the United States National Academy of Sciences, and the other being an international conference organized by the Royal Swedish Academy of Sciences. Statements published by both groups expressed a sense of urgent concern about the expansion of the world's population and concluded that if current predictions of population growth prove accurate and patterns of human activity on the planet remain unchanged, science and technology may not be able to prevent irreversible degradation of the natural environment and continued poverty for much of the world.

The discussion above sought to clarify some of the key aspects of the relationships among impoverishment, population, and environmental degradation, and to pose a conceptual framework for addressing the issue. At various times, impoverishment has been identified: as a root cause of environmental degradation; as a proximate cause; and as a contributing factor, merely reinforcing the linkage between environmental degradation and poverty often caused by wealth and greed. Despite an abundance of recent literature on the topic, it is not clear how environmental degradation and impoverishment are linked. What is apparent is that the relationship amongst these elements is complex, multidimensional, conditional and, at present, indeterminate. Although much of the evidence linking impoverishment and environmental degradation is anecdotal, it appears that the key issue is one of equity. Considerations of international equity, national equity, and intergenerational equity, must form the cornerstone of any strategy to confront the joint issues of environmental degradation and impoverishment.

Promoting equity as a key principle or strategy, however, does not reduce the complexity of the issue; equity has an economic dimension, a political dimension, and a social dimension; numerous case-studies can be found to illustrate these dimensions, and a few are noted in our above discussion. This framework is also tied to the goal of sustainable livelihood security, which recognizes that security has both political and environmental components. Despite the complexity of these issues, it is still possible to develop general recommendations to be used as a guide to the design of intervention strategies by agencies providing development assistance. Accordingly, five such recommendations are noted last above.

The conceptual framework developed in this paper sought to extend the work on the impoverishment, population, and environment, issue begun by Leonard (1989), Holmberg (1991), and others. It is clear, however, that much more study of these complex interrelationships is needed before the linkages amongst them are well identified and understood. In addition, it is not enough to accept the importance of equity as a key principle of sustainable livelihood security; development agencies must be willing to act on this principle, and to design intervention strategies which aim at reducing and eliminating the inequities which are a major cause of environmental degradation.

Long-term climatic variations over the past 400,000 years, disclose a cyclical alternation of cold or glacial phases. At the present time, the world is experiencing one of its warmer climatic periods. Nevertheless, summer insolation has decreased sharply during the last 9,000 years and, apart from human influences, a gradual reduction in temperature might well be expected to occur during the next 50,000 years. On the other hand, if the human-induced ‘greenhouse effect’ manifests itself as is sometimes forecast, climatic changes will take place much faster, and temperatures could reach higher levels than in any of the post-Pleistocene interglacial phases. The future of the Sahara depends to a considerable extent upon which of these trends actually manifests itself.

Climatic change is not a new phenomenon, nor is it random, as most of the variation can be explained in terms of variations in the sunlight reaching the surface of the Earth. The solar energy reaching the surface is modified by the aerosols in the atmosphere, however, and that means primarily aerosols of volcanic origin.

The climatic history of the Earth is divided up into episodes with abrupt beginnings and ends. Rapid changes from one climatic state to another are normal. The fluctuations within this century do not appear to be unusual in any respect.

To the Author's knowledge there is no evidence that past climatic changes, including those of the last decades, are related to changes in carbon dioxide in the atmosphere—except perhaps for warmer nights in the North American mid-west. It is not possible to simulate past climates using carbon dioxide content as the main variable, but it is possible to do so using calculated solar radiation as modified by volcanic aerosols. This strongly suggests that forecasts of the climatic future based on carbon dioxide increases are suspect.

Computerized models of the climate that can simulate decadal and century-long variations of climate as well as variations on the millennium scale, suggest that the climate will not warm dramatically in the next fifty years, but will, rather soon after that, begin a rather rapid change towards the next glacial climate.

Changes in our global array of cultures, sufficient to affect the global climate in a way which we perceive as beneficial, probably are not possible within centuries without massive physical conflict. There are both winners and losers when the climate changes in a non-uniform pattern, as it always does. It is a well-known fact that a global change of 0.5°C in mean temperature, such as has happened in recent years, might produce some regions of 10°C change in either direction and some regions with no change at all, and additionally an array of rainfall changes of various magnitudes. Russians would welcome warming of their climate!

The problems with attempting to modify the global climate in a particular direction are enormous and would be incredibly costly. This is compounded by our not knowing what the climate would do without intervention. Only one thing is truly clear, and it is that the present knowledge of the climatic effect of changing carbon dioxide content of the atmosphere is totally inadequate as a basis for initiating any global attempt to change the climate.

The indicated action would appear to be to engage in some high-quality climatic research based on sound science before taking global risks greater than those that might arise from the putative ‘global warming’.

Significant differences in embryonic mortality and occurrence of structural developmental defects between three separated populations of the Black-headed Gull were examined. Growth retardation was not studied.

Population ‘C’ (average 2.78 eggs per nest), living in Western Slovakia, exhibits in three-egg clutches relatively low mortality (7%) as well as a low occurrence of developmental defects (2.8%). In population ‘B’ (2.6 eggs per nest, living in Southern Moravia), breeding in a region that is intensively exploited for agriculture, the mortality is still very low (3%) but the proportion of malformed embryos increases to 15%. In population ‘A’ (2.6 eggs per nest, living in Southern Bohemia) the highest mortality was found (13%) but only 4.3% of embryos were malformed, though there was a broader spectrum of developmental defects. In this population the eggs were significantly smaller and had thinner shells.

In all the populations which were examined, the mortality and occurrence of developmental defects were higher in one-egg clutches, which were more frequent in populations ‘B’ and ‘A’ than in ‘C’.

Except for mercury, it does not seem that concentration of toxic substances in eggs could be responsible for the observed differences in reproductive success. An increase in embryonic mortality at locality ‘C’ is probably evoked by malnutrition in garbage specialists.