Sustainability means long-term cultural, ecologic and economic health and vitality. Or put another way, sustainability is about actions which are ecologically sound, economically viable, and socially just and humane.

It has also been defined as meeting our needs today while ensuring that future generations can continue to meet their own needs. Sustainability involves preserving the natural environment upon which people and economies depend.

In 1996 the Minnesota Legislature defined sustainable development -- the process of moving toward the state of sustainability -- as "development that maintains or enhances economic opportunity and community well-being while protecting and restoring the natural environment upon which people and economies depend. Sustainable development meets the needs of the present without compromising the ability of future generations to meet their own needs."

Sustainability is different from environmentalism. To elaborate on what Alan AtKisson wrote in his 1999 book "Believing Cassandra: An Optimist Looks at a Pessimist's World" (see http://www.atkisson.com/pubs/cassandra.html): Activism to protect Nature from the ravages of the economy and from the typical American lifestyle (traditional environmentalism: the stick) is different than redesigning industry and lifestyles to fit benignly into the natural world (sustainable development: the carrot). Working toward sustainability necessarily engages disparate groups -- labor unions, industry leaders, Wall Street, citizen groups, government, academia and others -- as well as environmentalists. It offers people a bold, inspiring, very long-term vision.

Two well-accepted sets of sustainability principles - the Natural Step and Cradle-to-Cradle frameworks - establish conditions for how we can develop our products, services, our individual lives, our economy, and our society in a truly sustainable manner.

• What we take, make and waste: The inputs, products, pollution and wastes of our industrial society - originating with fossil and radioactive fuels, mined metals and minerals, synthetic chemicals, pesticides, plastics,etc. - must not accumulate long-term in the environment as wastes. "Wastes" must ultimately be compostable or remain in closed-loop reuse cycles that don't contaminate compostables. All energy must eventually come directly and indirectly from the earth's one perpetual source of energy: the sun.

• What we do to the Earth: Biodiversity and natural systems - soils, forests, water, air, genetic material - must not be irreversibly degraded by human activities. Healthy natural systems allow us to eat, drink, and breathe safely.

• What we need: The bounty of the Earth - food, raw materials, natural systems - must be used equitably, fairly and efficiently so that the basic needs of all humans are met locally and globally. Social, economic, and ecologic diversity that builds off the uniqueness of each specific place builds resiliency into geographic regions.

According to Minnesota Planning's 1998 publication Sustainable Development: The Very Idea (available at http://www.mnplan.state.mn.us/pdf/sdiprim3.pdf), for human activities to be sustainable over time, they should:

• Meet people's economic and social needs

• Use renewable resources, such as timber and fish, at a rate that can be maintained over time

• Gradually reduce reliance on nonrenewable natural resources, such as coal and oil

• Reduce reliance on and limit the release of toxic substances that do not readily break down in nature

• Use all resources as efficiently and fairly as possible so that present and future generations can meet their needs

• Use land in ways that meet diverse needs, conserve financial and natural resources, and preserve its ability to meet future needs

• Reflect the interdependence of social, economic and environmental conditions

• Preserve the integrity of ecological processes and biological diversity

Another way of thinking about sustainability is to note how communities often work toward becoming more sustainable. These actions often involve each of the following five characteristics (as modified from a discussion in The Eagle Bird: Mapping a New West by Charles F. Wilkinson, 1999, p. 108):

- holistic (combining environmental, social and economic considerations

- place-based (rooted in a specific geographic location

- long-term in focus (looking decades or more ahead)

- collaborative and inclusive (welcoming the involvement of a wide range of stakeholders)

- practical and results-oriented (seeking to make a visible and concrete difference)

For a checklist that details over two dozen specific criteria for evaluating the sustainability of proposed community projects, see http://www.pca.state.mn.us/oea/sc/criteria.cfm

For more information about the definition of sustainability, the following web sites are recommended:

Smart Communities Network: http://www.smartcommunities.ncat.org/overview/ovintro.shtml

Sustainable Measures: http://www.sustainablemeasures.com/Sustainability/index.html

For an article that summarizes nine well-used frameworks of sustainable development, visit http://www.nextstep.state.mn.us/res_detail.cfm?id=217

And finally, to convey the essence of sustainability in a few sketched lines, skim through over 175 images - diagrams, graphics, scematics, charts - at http://computingforsustainability.wordpress.com/2009/03/15/visualising-sustainability/