EMERGY ANALYSIS OF HUMAN CARRYING-CAPACITY AND REGIONAL SUSTAINABILITY - AN EXAMPLE USING THE STATE OF MAINE

The human carrying capacity for a region at a specified standard of li ving depends on the economic and environmental resources of the region and the exchange of resources across regional boundaries. The length of time that a human population living at a given standard can be sust ained depends on the rates of use and renewal of the resource base. Al l environmental, economic, and social resources are produced as a resu lt of energy transformations; therefore, the energy required for their production can be specified and evaluated in common terms by converti ng their energy values into emergy. Emergy is defined as the available energy of one kind, previously used up directly and indirectly to mak e a product or service. Its unit is the emjoule. Emergy values and ind ices are used to evaluate the resource base for Maine, a politically d efined region, and to estimate its human carrying capacity at the 1980 standard of living and for possible future resource bases. Emergy ind icts for Maine are compared with similar indices for Florida, Texas, a nd the United States to demonstrate variations in human carrying capac ity and sustainability among different regions. The 1980 standard of l iving for Maine, Florida, Texas, and the Nation as measured by emergy use per person fell within a relatively narrow range of 3.4E16 to 4.3E 16 solar emjoules y(-1). The human carrying capacity for a region is c onsidered within a pulsing paradigm for sustainabilty and within the c onstraints provided by a renewable resource base. For example, in the short-term the developed human carrying capacity for Maine is largely determined by the fuel emergy inflow relative to renewable emergy reso urces. If purchased emergy inflows relative to Maine's renewable emerg y increase to the average ratio for a developed country around 1980, t he population living in Maine at 1980 standards could increase to 2.9 million or 2.6 times Maine's 1980 population. In contrast, the human c arrying capacity based on Maine's renewable resources alone was 0.37 m illion people at the 1980 standard of living or 33% of the 1980 popula tion.