1. Substances from the earth's crust can not systematically increase in the biosphere.
    
   
2. Substances produced by society can not systematically increase in the biosphere.
    
   
3. The physical basis for the productivity and diversity of nature must not be systematically deteriorated.
    
   
4. There must be fair and efficient use of resources to meet human needs.
   

Robert, Daly, Hawken and Holmberg

• Nothing disappears--matter and energy are constants
   
  
• Ability of ecosystem services to handle results of human activity, including waste
   
  
• Carrying capacity
   
  
• Equity
   
  
• Developing a language and process for businesses to see how they fit into the larger world

The Natural Step was developed in Sweden in 1989 by Dr. Karl-Henrik Robert. Robert used a consensus process involving the country's top scientists to define principles of a sustainable society. The principles look at the earth as a complex system of which humans are an integral part.

The four systems conditions listed form the basis of the Natural Step. The four conditions mean

• 1. Material that humans take out of the earth such as lead and mercury can't be allowed to accumulate in the environment. The environment and health-related issues due to lead and mercury are probably the most well known problems the first condition addresses.
   
  
• 2. Material that are created by humans can't build up faster then the ecosystem can break them down. Examples of this range from materials which are harmful in relatively small doses such as DDT, PCBs and ozone-depleting chemicals, to materials which are less harmful but are being produced in very large quantities, such as CO2.
   
  
• 3. Human activity cannot destroy the ability of the earth to provide the services we need. Examples include farming practices that cause erosion or land use practices that destroy the flood calming and water filtering abilities of wetlands.
   
  
• 4. Resources need to be used equitably and efficiently. Equitable distribution means that poor people will not have to destroy their natural resources just to survive in the short term. The Natural Step process helps companies to understand the connections between their business and the earth's ecological and social processes. The Natural Step in many ways is a continuation of other efforts by business to improve their processes and reduce their impact on the world. These other efforts have included Total Quality Management, Total Quality Environmental Management, pollution prevention, toxics use reduction, design for the environment, ISO 9000, and ISO 14000. The Natural Step moves beyond these to focus on how businesses will work in a sustainable society. The Natural Step U.S. web site is: http://www.ccnet.com/~emis/tns/.