Carnegie Mellon University

US Environmental Carrying Capacity

In collaboration with the Colcom Foundation, the Steinbrenner Institute has been exploring the dimensions of environmental carrying capacity with a focus on the United States.  Environmental carrying capacity is an ecological concept defined generally as the population of organisms that can be sustained at a steady state considering the resources available in the ecosystem in which they reside.  This concept and the set of ecological assessment tools that have been applied to the to evaluate sustainable levels of human population for the earth as a whole and for partciular regions.  Such evaluations are difficult, except for isolated populations at small scales, because of uncerainty with some important processes in the analyses - such as technical adaptation - and with assumptions needed for such analyses. Some may discount the analyses for these reasons, but nonetheless, the earth clearly has physical limits, and the concept of carrying capacity has been well docuement in ecology for ecosystems of certain scales and particular organisms.

The Colcom Foundation has provided the opportunity to engage in scholarly exploration of the ways in which changes in the population might impact the availabilty of natural resources; and how those natural resources might be limiting factors to quality of life standards.  The question of what is a maximum number of people that can be supported by U.S. natural resources is one that can only be answered by construction of a model with assumptions for many of the diverse factors related to this question, including the core factor of the average desired standard of living. If such a model were to be produced, the submodels and assumptions could be immediately challenged, making it difficult to convince others of the value of the results. 

An Engineering and Public Policy project course (Spring '09) focused on the challenge of trying to identify the limiting resources for U.S. population growth.  An important finding from this effort was that we don’t seem to encountering resource limits except with respect to energy and some minerals.

In an open, democratic society, decision-making that affects population will occur in a highly distributed and decentralized manner.  These decisions will be made by individuals, groups, companies, local communities, regional groups of communities, states, groups of states, and the federal government.  The decision making will be driven by incentives.   The role of government will be primarily to inform people and to provide incentives to nudge the plethora of decisions that affect population in the direction of higher standard of living.

In this context, we proposed that the most useful research pertaining to defining and managing the environmental carrying capacity of the U.S. will be to develop broadly useful aggregate measures and indices of resource consumption and quality of life, to link these measures to population growth, and to make the data and measures widely available for the purpose of informing the distributed decision making that influences population growth.