*The Connecticut Agricultural Experiment Station, New Haven,
CT 06504-1106; and
**Program for the Human Environment, The Rockefeller University, New York, NY 10021-6399
Contributed by P. E. Waggoner, April 19, 2002.
Citation: Proceedings of the National Academy of Sciences 99(12):7860-7865,2002.
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.
Last updated: Thursday, 29-Jul-2004 10:48:57 EDT