A Framework for Sustainability Science: A Renovated IPAT Identity

Citation: Proceedings of the National Academy of Sciences U S A 99 (12): 7860–7865 2002

PDF Full Text: A Framework for Sustainability Science: A Renovated IPAT Identity

Link: https://www.pnas.org/doi/full/10.1073/pnas.122235999 [external link]

Supplements to the ImPACT Identity

From time to time updates and additional supplements to the ImPACT
paper will be provided by the authors in response to questions and new

Supplement 1: Do consumers’ behavior and producers’
efficiency move in consistent patterns? View the
PowerPoint presentation

Supplement 2: Air Travel — the example of Materialization. View the PowerPoint presentation.

Supplement 3: New ways to visualize the ImPACT identity and its
forces. View the PowerPoint presentation.

Supplement 4: The Sustainability Plane — sustainability as a journey on
a plane to richer & cleaner coordinates in a short text and six slides.
View the PowerPoint presentation or
Word document.

Supplement 5: With a victory over trash,
New York City traced an environmental Kuznets Curve on the sustainability
plane during the 20th Century.
View the article (PDF).

Supplement 6: DynaCad, a simulator of cadmium flow from zinc processing
and cadmium recovery through the manufacturing, use, and exhaustion of products.
Download the model (Excel spreadsheet).


Learning actors’ leverage for change along the journey to sustainability requires quantifying the component forces of environmental impact and integrating them. Population, income, consumers behavior, and producers efficiency jointly force impact. Here, we renovate the IPAT Identity to identify actors with the forces. Forcing impact I are P for population, A for income as gross domestic product (GDP) per capita, C for intensity of use as a good per GDP, and T for efficiency ratios as impact per good. In the ImPACT Identity, parents modify P, workers modify A, consumers modify C, and producers modify T. Because annual percentage changes in component forces add to a change in national impact, actors leverage is reflected transparently in consistent units of annual percentage changes that can be compared from force to force. Examples from energy and food, farming and manufacturing, and steel and water show that declining C, called dematerialization, can temper the sustainability challenge of growth (P × A), and that innovation or efficient technology that lowers T can counter rising consumption (P × A × C). Income elasticity can accommodate connections between income and other forces. From rates of change of forces, the identity can forecast impacts. Alternatively, by identifying the necessary change in forces to cause a projected impact, ImPACT can assay the likelihood and practicability of environmental targets and timetables. An annual 2-3% progress in consumption and technology over many decades and sectors provides a benchmark for sustainability.

Keywords: environmental Impact identity, population, affluence, impact identity

Areas of Research: The ImPACT Identity