Although ecosystems provide myriad services to economies, only one service is considered in most renewable-resource models. The general equilibrium bioeconomic model introduced here admits a second service, and more importantly it accounts for how the two services are impacted by interactions within an eight-species ecosystem and interactions within a regional economy. Endangered Steller sea lion recovery measures via alternative pollock quotas change all ecosystem populations and all economic variables. While non-use values associated with the ecosystem (e.g., existence values) are not considered, all species matter for the economy because they are all used indirectly as support for ecosystem services. Regional welfare changes from reduced quotas show the tradeoff between consumptive and non-consumptive uses of the ecosystem.
To summarize, the CGE/GEEM approach yields the following outputs:
(1)
a simulation of how human responses to changing prices of goods and factors causes changing energy prices in the ecosystem to which plants and animals respond;
(2)
economic welfare changes and ecological population changes attributable to alternative harvesting quotas;
(3)
measures of how the ecosystem externality generated by harvesting (an ecosystem service) impacts tourism (another ecosystem service);
(4)
welfare measures associated with changes in charismatic marine mammal populations;
(5)
introduction of a renewable resource into a CGE framework.
Output (1) refers to the joint dependence between the economy and ecosystem as a result of the linkages, both consumptive (through pollock harvests) and non-consumptive (through tourism). Economic prices in any period are a function of species populations in that period, and populations in any period are a function of ecosystem prices in preceding periods, making economic prices a function of lagged ecosystem prices. Conversely, ecosystem prices in any period are a function of pollock harvests in preceding periods, thus ecosystem prices are dependent in a lagged fashion upon the regulator's quotas. To the extent that quotas respond to economic prices, ecosystem prices are a lagged function of economic prices. For example, with reduced harvesting, the price humans pay for pollock increases and the energy price marine mammals pay for pollock decreases, while the price humans pay for viewing marine mammals decreases.
The CGE/GEEM linked modeling approach can be applied to numerous conflicts that arise when economic activities and environmental conservation appear at odds. For example, in a terrestrial economy/ecosystem there may be the same consumptive and non-consumptive links used here in addition to pollution that can interfere with species respiration patterns, habitat loss that would reduce space available for plants and, therefore, food for animals, and introduced exotic species that compete with native species. Another marine example is provided by Larson et al. (1998) who examine bycatch in multispecies fisheries. Although their approach is very different than that presented here, CGE/GEEM can address multispecies harvests (Gong, 2007) and could be extended to include in the ecosystem the important non-fished species that comprise the bycatch.
The application to marine ecosystems may be particularly appropriate at this time. Recent reports on the state of the U.S. and world marine ecosystems paint a discouraging picture. According to the Pew Oceans Commission (p. v, 2003):
We have reached a crossroads where the cumulative effect of what we take from, and put into, the ocean substantially reduces the ability of marine ecosystems to produce the economic and ecological goods and services that we desire and need.
In a high profile piece, Worm et al. (2006) report that current trends in overfishing and biodiversity loss project a global collapse of all commercial fishes by the middle of this century. To reverse these trends, both reports recommend changing fishery policies to protect the ecosystems and biodiversity on which the fisheries depend. There are positive signs in the U.S. that policies are changing. In 2002 the National Marine Fisheries Service (NMFS) began including ecosystem effects on stocks and fishery effects on ecosystems in its individual groundfish stock assessment reports to the North Pacific Fisheries Management Council. As part of its strategic goals, the NMFS has replaced single-species management with ecosystem based management that balances ecological and social influences (NOAA, 2004).
Integrated economic and ecological GE models offer one approach to broadening fishery policies, because they can capture the interactions within and between the systems. We have developed a methodology that integrates simple economic and ecological GE models, and may provide a prototype for more detailed models that would be fitting for ecosystem based management.
