How do we understand the term "sustainability"? The task is not to provide a theological undergirding of the current use of the term. Rather we must interpret, in the light of the Scriptures, the challenge posed by the ecological crisis and identify the criteria which must guide our response. What, then, is a correct reading of the signs of times?

For the churches it is essential to recognize the magnitude and complexity of the challenge and to resist any temptation to discount the problem by excluding certain aspects from consideration. The ecological responsibility of human beings is inseparably linked to a strong commitment to justice and peace in a sustainable society. A focus on ecological aspects must not ignore this wider context.

It has become more and more clear that there are limits to human expansion on planet Earth. There is mounting evidence that some human activities already exceed the limits of the carrying capacity of parts of the environment, the damage to the stratospheric ozone layer for example. In many other areas, limits are likely to be reached in the foreseeable future. In general, we are now coming to realise that, for many human activities, there is a scale which should not be exceeded. We are therefore faced with the daunting task of establishing indicators of permitted human expansion. The concept of environmental space has recently gained ground: it points to the limited carrying capacity of the Earth and establishes that all people must be given the right to equitable shares of these limited resources.

Although we still need to understand much more about the effects of human activity on the environment, this does not mean that we can delay our response. We underline the importance of the "pre-cautionary principle". This means that where there is a serious risk of harm to the environment we cannot afford to wait for a high degree of scientific proof before acting to prevent damage. We also need to remember that sustainability is a "moving target": limits to human expansion cannot be fixed once for all. We may be led in the future to new and serious risks, with both positive and negative consequences. We must leave room for what is yet unknown.

For the churches, sustainability is inseparably linked with a renewed call to justice. Threats to the environment must not be used as a pretext for maintaining the present unjust distribution of the goods of the Earth. Sustainability presupposes willingness to share the gifts of creation within the limits imposed on humanity. The fundamental needs of all must be met.

The calling of the churches includes responsibilities towards and advocacy on behalf of those suffering today from exploitation and poverty. It also includes concern for the life of future generations: they should inherit a planet whose resources allow them to develop and enjoy life with dignity.

Realizing a sustainable society, then, requires a radical change of direction. When terms like "sustainable growth" or "sustainable development" are used, often the assumption is made that the present course of society can essentially be maintained. We understand sustainable growth to be a contradiction in terms, in the long run, especially with the rapid increase of the world's population; human demands on creation must not grow, but be reduced. Human life in ecological balance is only possible if the rich are prepared to accept for themselves a new quality of life.

For the richer industrialized countries the challenge is particularly demanding in view of the need for economically weaker nations to improve their situation. They must be given the opportunity of pursuing economic growth.

Among the issues which most challenge our present patterns of life we mention our energy consumption as an example. The emissions of greenhouse gases, especially through the combustion of fossil fuels, exposes us to the risk of far-reaching changes in the climatic conditions of our planet. In order to mitigate the effects of global warming, drastic reductions of our energy consumption are required. In 1990 the Second World Climate Conference declared that in order to stabilize atmospheric CO₂ concentrations at about 50% above pre-industrial concentrations by the middle of the next century, a continuous world wide reduction of net CO₂ emissions by one or two percent a year starting from now would be required. As the responsibility for these dangerous emissions at present lies mainly with the industrialized nations, their reductions must be even higher. At present, the industrialised nations are causing the majority of these emissions, and have the resources and technology to curb them. Meanwhile, given their legitimate desire for development, developing nations are expected to significantly increase over the next decades their emissions. Together, these factors place a responsibility on industrialised nations to reduce their emissions more than the average. Population growth will further increase the pressure. In the light of these prospects, it is clear that many activities now taken for granted in industrialized countries are, in fact, not sustainable. This is particularly true for present patterns of mobility in Europe, especially the steady expansion of road and air transport.

Sustainability presupposes peace and at the same time conditions it. Conflicts and wars represent an acute danger not only to human life but also to the integrity of the environment; they therefore must be avoided on this ground as well. The over-exploitation of our planet's resources is itself likely to lead to conflict. The 1995 dispute between Spain and Canada over fishing rights was an example of this kind of tension. In several regions, the scarcity of water supply has been a cause of hostility. Such disputes may eventually escalate into armed conflicts. Sustainability therefore requires a commitment to both justice and peace-making.

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