Left to its own devices, the earth is a sustainable system. As we continue to learn, however, the accumulated impacts of human activity over the past two centuries are now threatening our continued well-being. An international network of scientists have unanimously and publically concluded that human society is damaging nature and altering life-supporting natural structures and functions in three fundamental ways. Consequently, they were able to define three basic conditions that must be met if we want to maintain the essential natural resources, structures and functions that sustain human society. Further, acknowledging that human action is the primary cause of the rapid change we see in nature today, they included a fourth system condition that focuses on the social and economic considerations that drive those actions and the capacity of human beings to meet their basic needs.

While written to be clear scientifically, the specific wording of the four system conditions can be confusing to non-scientists who try to put them to work. Fortunately, the system conditions can be reworded as basic sustainability principles that provide explicit guidance for any individual or any organization interested in moving towards sustainability. The table below contains the four system conditions on the left and the reworded the basic sustainability principles on the right. In most instances, we refer to the basic sustainability principles.

At first reading, the system conditions and basic principles might seem to imply that we must rid society of all materials extracted from the earth and all substances produced by society and that, further, we must never disturb a natural landscape. But that’s not what they mean. The problem is not that we mine and use heavy metals, or use chemicals and compounds produced by society, or disrupt natural processes, or even temporarily interfere with people’s capacity to meet their basic needs. It is, rather, that our industrial system has developed so that substances extracted from the earth and produced by society will continue to build up indefinitely in natural systems. That means a systematically increasing concentrationa of pollutants and substances that not only harm us directly but damage natural processes that have taken billions of years to develop.

With respect to the fourth sustainability principle, The Natural Step’s understanding of human needs is based on the work of the Chilean economist Manfred Max-Neef. Max-Neef identifies nine fundamental human needs that are consistent across time and cultures: subsistence, protection, affection, understanding, participation, leisure, creation, identity and freedom. Max-Neef points out that these fundamental human needs cannot be substituted one for another and that a lack of any of them represents a poverty of some kind.

Next: Backcasting from Principles