Let us return to people and food, and another simple equation. The number of people per hectare of arable land, calculated over large regions, looks like a climatic distribution. I guessed at the form of the equation, calculated what the population per arable hectare was on the basis of climate, and compared it with the situation as observed. The correlation between them is 0.998. (See Fig. 8.) It is an almost perfect relationship. The equation relates population per arable hectare to rainfall and temperature, and ultimately to sunlight and water. If one enters Fig. 9, which is a graph of the equation, with the temperature, and finds the intersection with the appropriate rainfall curve, one can see how many people are currently fed from an arable hectare.

This explanatory note is intended to accompany the map included in this issue. The map is on a scale of 1:30,000,000 (1 cm = 300 km) and shows regional-scale ‘ecosystem’ units, or ecoregions, differentiated according to a scheme modified from J.M. Crowley (1967), and using climate and vegetation as indicators of the extent of each unit. The units are similar in concept to ‘ecobiomes’ as proposed by Polunin (1984). The map was developed following a proposal by Bailey & Hogg (1986) to supplement the Udvardy (1975) system of biogeographical provinces with a treatment of higher resolution. Three levels or categories of this hierarchy are shown. Of these the broadest, domains, and within them divisions, are based largely on the broad ecological climate zones following the Koppen system as modified by Trewartha (1968), and summarized in our Tables I and II. Climate is emphasized at the broadest levels because of its overriding effect on the composition and productivity of ecosystems etc. from region to region.

Plant genetic resources are vital in safeguarding and increasing crop production and enhancing human nutrition, particularly in a Man-dominated world. Crop genetic resources are currently under threat of loss for various reasons. Conservation as seed is the most common and practicable method of preserving plant genetic resources. The International Board for Plant Genetic Resources (IBPGR), in cooperation with gene-banks around the world, has created a global network of base-collections. In order to minimize losses of stock in the gene-banks, standards were developed in 1985 and base-collections were assessed against them.

Military destruction by conventional arms of both terrestrial and freshwater ecosystems is described, with emphasis placed on the effects of World Wars I and II on the territory of the USSR (especially of Russia, Byelorussia, and Ukraine). It is shown that a wide range of serious damage is done in terrestrial natural areas: to forests which may be decimated, to mammals which are commonly killed, and to the land which is extensively disturbed and rendered infertile or even uncultivable. Inland waters, too, are widely disturbed, though numerous new bodies of water may be formed in various ways, while fisheries are commonly disturbed, though ‘Wartime military activities can greatly reduce fish catches, to the benefit of fish populations.’

This paper examines the level of environmental security in the Danube River drainage basin: an ecogeographical region covering 800 thousand square kilometres, supporting some 86 million inhabitants, and occupying greater or lesser portions of 12 nations—especially of the 8 riparian nations. The waters of the basin are important, if not indispensable, to the basin inhabitants for various purposes, among them: household, municipal, agricultural, industrial, waste disposal, transportation, power generation, fishing, and aesthetic.

Despite a flow at the mouth of some 6,500 cubic metres per second, the Danube basin waters do not suffice for all of these diverse and sometimes conflicting demands that are placed upon them, this paper outlines the resulting environmental problems—especially those associated with Danubian pollution, habitat disruption, and the generation of hydropower. It refers to the existing legal instruments that address environmental vandalism (especially in time of war), pollution (of both air and water), habitat disruption, and resource utilization (both non-extractive and extractive), noting their levels of acceptance and their lacunae.

Because fish populations are the classical examples of common-property resources, Garrett Hardin's ‘tragedy of the commons’ is frequently cited as the cause of their decline. However, it has now been shown that many small community fisheries, as well as a number of larger commercial fisheries, are not managed according to the ‘commons’ model but rather are subject to internal limitedentry restrictions which prevent resource overexploitation. Further, Hardin's model ignores critical relationships which exist between common-property and private resources in many Third World rural societies. Changes in these relationships have significant implications for sustained yield management of common-property resources, such as fisheries, in these societies.

In Amazonia, the current changing relationship between common-property and private resources on the terra firme uplands profoundly affects the degree of exploitation that is experienced by the region's fisheries. It also has important implications for the survival of Amazonia's flood-forests which play a critical role in the region's fisheries ecology.

Forested areas of Kanching Recreation Forest exposed to concentrated recreational use tend to show signs of deterioration as indicated by soil parameters related to soil compaction. The results of the present study clearly indicate that such a deterioration of soil conditions has already occurred, though not on an alarming scale. Indeed the status of these soils remains favourable, as the figures for saturated hydraulic conductivity and plant-available water are still ‘satisfactory’, or at least were so during the period of study (1989). Surface runoff and sheet-erosion in intensively-used recreational sites must not, however, be looked upon in isolation when advising on recreational forest land-management.

A recent study in Kanching Forest Reserve, Malaysia, showed that recreational use of forested areas could adversely affect soil conditions. Soil bulk density and micropore space were significantly increased, but total porespace and macropore space were significantly decreased. Available water-holding capacity, saturated hydraulic conductivity, and particle-size distribution, were not significantly affected by recreational use on such sites, indicating that the status of Kanching Recreation Forest soil is still favourable for plant growth, or at least it was during the period of this study.

To embody the concept of sustainability in environmental management and development planning has latterly become recognized internationally as a priority for the future. Governments in many countries have consequently dedicated substantial funds to the task of defining planning and management strategies that are sustainable. Somewhat surprisingly, however, there has been very little attention given so far to establishing appropriate frameworks within which to evaluate the implications of planning and policy alternatives for sustainability.

One of the most important questions to be addressed in evaluation exercises relates to the conflicts among different systems – economic, social, and biophysical – that may be realized in pursuing development options that may be sustainable. It is also important to establish whether the pursuit of sustainability may compromise the capability to fulfil other important societal goals and objectives. If the potential for these various conflicts can be discerned, then it may also be possible to identify development strategies that minimize conflict, while simultaneously achieving sustainability.