The examples discussed here show how closely connected are purely natural biogeochemical processes with the consequences of Man's impact on Nature in the present-day biosphere—especially if this impact takes the form of deforestation, largearea irrigation without drainage, or massive introduction into the biosphere of complex compounds utilized in industry, farming, and other branches of economy and life. Reconstruction of Man's economic activities on a planned scientific basis is becoming imperative now. We need implementation of the principles of science-based, waste-free technology, maximum reutilization and recycling of the rejects and by-products, and adoption of an extremely delicate approach to Nature and its links. Regular observations of the status of Nature (monitoring) at suitable biospheric stations are necessary. This means that a lot of various technological, field, and laboratory studies, with experiments and modelling, have to be done. They will help us to unravel further the mysteries of the biosphere-man system, and to use with greater effect all available mineral wealth, energy, soils, water, plants, and other natural resources. Then we shall better understand the aridization and other depletion phenomena with which we are confronted, and be able to devise methods of fighting them and of multiplying the productivity of land and water.

Our environment and natural resources should be used and controlled in such a way as to maintain normal biospheric functions and efficiently prevent cases of functional disorganization of this complicated system. We must also try to reduce the possible negative after-effects of any disruptive processes in order to protect Man and his health and also Nature.

We have to preserve the biosphere of our beautiful and unique planet Earth for ourselves and for future generations.

Taiwan has the highest population density in the world today. The population growth-rate has been decreasing linearly since 1951, but the present growthrate of 2% is still much too high to lessen the population pressure. With the area of agricultural land severly limited, the agricultural sector of Taiwan can no longer absorb extra farm labourers without sacrificing the productivity of each farm labourer.

In order to feed the growing population, the high productivity of a rice paddy has been maintained by applying ever-increasing amounts of chemical fertilizers and pesticides, which in turn cause many pollution problems. Moreover the rapid growth of industries, which are mainly financed by outside capital, causes the expansion and congestion of the cities along with all sorts of pollution problems (air pollution of cities, water pollution of rivers, harbours, coastal waters, etc.)

The heavy dependence on imported energy (70% of the total energy consumption) and on trade with Japan and the United States, puts Taiwan in a vulnerable position with regard to fluctuations in the world economy. The ever-increasing population density, and the demands of a higher per caput consumption on the limited natural resources, risk leading to economic inadequacy and ecological degradation. Such a situation could endanger our industrial civilization more widely.

Biophysical and other ‘outer limits’ of food, land, water, climatic change, stratospheric chemistry, energy, hazardous substances, non-fuel minerals, human stress, and social and ecological stability, raise fundamental questions about present trends in management methods and in global organization. The diverse outer limits surveyed in this paper reflect complex, poorly perceived, and often unsuspected, interconnections between numerous biological and geophysical processes, many of which are obscure or still unknown. Our lack of predictive power, let alone of quantitative understanding, implies a need to treat essential life-support systems with great caution and forbearance, lest we erode safety margins whose importance we do not yet appreciate.

Even those outer limits which now seem remote are relevant to present policy, as their timely avoidance may require us to discard otherwise attractive short-term policies in favour of others that offer less immediate advantage but that retain options which may be needed later. Such alternative policies may have to rely more on social than on technical innovation in order to address underlying disequilibria rather than merely palliating their symptoms. Moreover, some outer limits are sufficiently imminent, or require such long lead-times to avoid, that fundamental changes in policy, in institutions, and in the degree of global interdependence, seem necessary if we are to live to enjoy some of the later and more interesting limits to human activity.

Hong Kong comprises an area of some 400 square miles (1,036 km2) and a population of 4.5 million people largely living in an urban and city complex centred around a magnificent natural harbour. Such an urbanized community, hemmed in by mountains, is separate from the hitherto rural remainder of Hong Kong.

The geographical position of Hong Kong, lying as it does on the borders of the temperate and tropical zoogeographic regions, when correlated with a local diversity of geomorphological and hydrological eccentricities, creates a fascinating assemblage of littoral biotic communities within a small area. The expanding urban area, however, resulting from a population growth that is confidently expected to reach 5.5–6.5 millions by 1991, is encroaching into the rural and coastal areas.

The demand for low-lying flat land has resulted in official and unofficial reclamations, initially of soft shores which are of significant archaeological and ethnological interest. The same shores constitute Hong Kong's countryside, but people bathe in waters that are grossly polluted by human and agricultural effluents, so that coliform bacterial counts in excess of 106 per 100 ml have been recorded. Squatter huts still dot Hong Kong's coastline despite massive rehousing projects, and shellfish are widely collected. Moreover, oysters are cultivated and not cleansed prior to resale.

No coastal parks, conservation areas, reserves, or even a coastal code, actually exists. The sea-shore is not used as an ‘open-air laboratory’, nor as an educational tool except at the tertiary level.

In such a community the sea-shore demands special attention, and in a world that is approaching urbanization as a way of life, Hong Kong, as a microcosm of south-east Asia, offers a case in point and a lesson in survival.

Roles or expressions of attitude which scientists should play or display in achieving a better environment for Man and Nature need to include (1) a positive and optimistic viewpoint, (2) a proper perspective in time-dimensions, (3) identification of major developments that have profoundly influenced our view of ourselves as humans, (4) development of a rational conceptual framework within which to arrange the activities required to influence the human environment (involving the four basic processes of energy provision, materials-cycling, life-cycling, and information leading to decision-making), (5) relating of these four basic processes to linking Man far more propitiously than latterly to his environment, (6) effective interaction among disciplines and concomitant advising of decision-makers, (7) developing sophisticated insight into the array of societal issues that confront mankind, and (8) tackling the set of environmental hazards that are particularly critical in developing countries.

The paper ends with an appeal to all ‘to reaffirm a robust faith in the destiny of Man.’

The exclusion of fire from the low-elevation foothills of the southern Sierra Nevada of California over the past century has resulted in large expanses of over-mature, senescent chaparral. The fuel buildup associated with this situation poses a threat, in that any fire which gets started has the potential of becoming a major holocaust.

A detailed analysis is made of the vegetational succession following fire in four different-aged stands of Chamise chaparral in the southern Sierra Nevada. Progression from a diverse multi-species herb and shrub community towards a dense, structurally uniform, low-diversity stand dominated by a single woody species, Adenostoma fasciculatum (Chamise), is demonstrated. An increase in shrub cover and height along with the amount of dead material found laddered through the canopy, create optimal conditions for combustion within some 35 years following the last fire. The herbaceous vegetation shows a high diversity and cover in the first few years after burning, but rapidly decreases thereafter. Evidence is presented that frequent fires are required to maintain the chaparral community in a vigorous and healthy state. The need to institute progressive fuel-management programmes which recognize the natural role of fire in the evolution of the chaparral type wherever it is found, is discussed and advocated. Attempts are also made to relate these findings to the preservation of other fire-adapted vegetation types of the world.

Solar energy could be a major resource for the semiarid regions of the United States and the world. This source of energy is a popular topic in the media at this time, but is it really the option which many would like to see or is it more likely to remain the illusion it has been up to now? Many ways of using solar energy have been proposed, and each appears to have a good technological basis. The additional factors that will see many solar schemes fall by the wayside are the hard facts of economics and the realities of social assimilation of technological advances.

The major options of house-heating and cooling and electrical power production need to be examined. Home uses depend upon the degree to which people are willing to put up with the inconveniences associated with bulky roof-top units. It is more likely that solar energy will subsequently find wider acceptance when it can be converted into power and transportable fuels at remote solar power-farms located in the arid regions of the United States and other lands that are fortunate enough to have these sunny regions. The savings to the environment could be very considerable.