The framework consists of three parts:

• the Four System Conditions
• the Funnel
• Strategies for Action

The Four System Conditions

Four System Conditions for Sustainability 1. Substances from the earth's crust--fossil fuels and mined minerals--must not systematically increase in nature. 2. Substances produced by society must not systematically increase in nature. 3. The physical basis for the productivity and diversity of nature must not be systematically deteriorated. 4. Human society must be fair and efficient in meeting basic human needs.

Through his work with child leukemia patients, Dr. Robert began to look at the sources of cancer that he found in the environment. However, Dr. Robert noticed that discussions of the links between the environment and health continually bogged down. This led him to engage in an extensive consensus process with 50 other scientists to find a set of irrefutable scientific principles on which to base his work. It is from those principles that Dr. Robert developed what are known as the Four System Conditions for sustainability.

In short, TNS addresses what we take, what we make, what we maintain, and how and what we share.

System condition one addresses what we take from the Earth's crust. It says that if we take metals, minerals and fossil fuels from the Earth faster than they can be recycled back into nature, these substances will build-up in the environment in problematic ways. We experience those problems in the form of smog, ozone depletion, global warming and poisoning from heavy metals like lead and mercury. Burning oil and coal faster than the trees can absorb the carbon is an example of violating the first system condition.

System condition two looks at the things we make and how well and quickly they can be reintegrated into the natural environment. Too much of anything, like garbage in land fills or sewage compromises the health of the natural system. There are also problems when we create synthetic chemicals nature can't break down quickly, like Styrofoam and plastics. Creating nuclear waste is an example of violating system condition number two.

System condition three is about maintaining the natural systems that support life. Everything comes from and goes back to the natural environment. All life, including humans, depend on these natural services: clean water and air, building materials and food. So system condition three says we need to restore and maintain these natural life support systems for our long term well-being.

System condition four is about fairness and meeting the needs of all people and all species by using the most resource-efficient methods possible. If we don't meet the basic needs of everyone, through fair and efficient use of resources, it will be difficult or impossible to meet the other three conditions. Bananas and coffee grown on tropical plantations for sale in rich countries reflects problems with local food systems, loss of habitat and exploitation of cheap labor and so is an example of violating number four.

The Funnel

The downward sloping line describes the decline in the life support systems of the world. This would include the loss of species, the decline of many natural systems such as forests, coral reefs, soil, etc. as well as the build up of toxins that increasingly make resources unavailable to us like the pollution of fresh water.

The other, upward sloping side of the funnel represents the increasing demands of human activity. This is driven by increasing numbers of people consuming greater amounts of resources such as food, forests, land as well as minerals, metals, fossil fuels, etc.

Together these two trends show that human demand is outstripping (and many would say has already outstripped) our supply of natural resources. In order to be sustainable, we must change the shape of this funnel. We need to both decrease our impacts and restore the life support systems.

Strategies for Action

TNS's Strategies for Action includes four elements referred to as ABCD:

• Awareness--Developing a common understanding of the situation within an organization

• Base-line mapping--Mapping current operations of an organization in terms of the four system conditions.

• Clear vision--Creating a vision and identifying measures that take an organization from where it is now to where it can be in a sustainable future

• Down to Earth action--Prioritizing measures for achieving the organization's vision that move it toward sustainability.

To assist with this last step, TNS uses a technique called "backcasting". Unlike forecasting, where one looks forward with projections, backcasting starts with one's goal or vision and looks back at how one might get there.

TNS also recommends that initial steps toward sustainability address the "low hanging fruit", meaning "do the easy things first". In this way people are encouraged to get started and make progress where they can. The first step is often the most important.

Some of the companies that have embarked on this journey toward sustainability using TNS include Interface Carpets, McDonalds Sweden, Nike, Ikea, and Scandic Hotels. You can read the stories of these companies in The Natural Step for Businesses by Brian Nattrass and Mary Altomare.

To learn more, visit The Natural Step.

More info about ways you may apply TNS to your life.