Strategic marine ecosystem restoration in northern British Columbia.

摘要

Innovative methodology is developed for Back to the Future (BTF) restoration policy analysis to aid long-term strategic planning of ecosystem-based restoration in marine ecosystems. Mass-balance and dynamic ecosystem simulation models (Ecopath with Ecosim: EwE) are developed to represent the marine system of northern British Columbia as it appeared in 1750, 1900, 1950 and 2000 AD. Time series statistics are assembled for biomass and catch, incorporating local ecological knowledge (LEK) from community interviews and new estimates of illegal, unreported and unregulated (IUU) fishery catch. The dynamic behaviour of the historic models is fitted to agree with this time series information, when driven by historic catch rates and climate anomalies. Each historic period is evaluated in an optimal policy analysis for its potential to supply sustainable harvest benefits. Harvest benefits are quantified using socioeconomic and ecological indicators, including novel measures such as the Q-90 biodiversity statistic. Candidate goals for restoration are drafted based on these historic ecosystems. A new conceptual goal for ecosystem-based restoration is introduced, the optimal restorable biomass (ORB) that represents an optimized form of the historic ecosystems. It is structured to maximize sustainable harvest benefits, and to achieve a compromise between exploitation and the maintenance of historic abundance and biodiversity. Finally, restoration plans are drafted using a novel addition to Ecosim's policy search routine, the specific biomass objective function, which determines the pattern of fishing effort required to restore the depleted present-day ecosystem into one resembling a more productive ORB state. Cost-benefit analysis indicates that northern BC ecosystem restoration to an ORB state based on the 1950 ecosystem can deliver a rate of economic return, in terms of increased fisheries yields, that is superior to bank interest. The effect of fleet structure is paramount; reducing bycatch will greatly enhance the effectiveness of the fleet as a restoration tool. Restoration plans that sacrifice immediate fisheries profits tend to restore more biodiversity in a given amount of time, but a convex relationship between profit and biodiversity suggests there is an optimal rate of restoration.