|Fisheries managed to rebuild ecosystems? Reconstructing the past to salvage the future|
Pitcher, T.J. (2001). Fisheries managed to rebuild ecosystems? Reconstructing the past to salvage the future. Ecol. Appl. 11(2): 601-617
In: Ecological Applications. Ecological Society of America: Tempe, AZ. ISSN 1051-0761, more
Ecological disturbance; Fisheries management; Overfishing; Marine
biodiversity, ecosystem rebuilding, fisheries management and sustainability, fisheries policy, harvest refugia, history of fisheries, mass–balance models, restoration ecology
This paper presents the case for adopting ecosystem rebuilding as the goal of fisheries management. Movement toward this goal may represent the only hope for fisheries, as we know them, to exist 50 years in the future alongside essential services provided by marine ecosystems. First, I review archaeological, historical, and recent evidence that bears witness to a long, dismal record of overexploitation. Second, I examine the ecological effects of overfishing on aquatic ecosystems. Fish with life histories and spatial behavior inimical to harvesting are selectively removed, both within and among species. The loss of keystone species and the replacement of high-value, demersal resources with pelagic, rapid-turnover, low-value species shifts the nature of ecosystems, evidenced by accelerating local extinctions and a worldwide decline in trophic level. Disconcertingly, harvest limits that appear safe by single species evaluation can engender ecosystem changes that are hard to reverse. Driven by a progression of clever human harvest technologies, three ratchet-like processes have brought about episodes of depletion. "Odum's ratchet" is ecological in nature, comprising depletion and local extinction. "Ludwig's ratchet," economic in nature, is a positive feedback loop between increased catching power and serial depletion, driven by the need to repay borrowed money. "Pauly's ratchet" is cognitive, shifting the baseline of what each generation regards as primal abundance and diversity. Third, a rebuilding policy goal is distinguished from that of sustaining current catches and biomass, since the baseline can refer to present misery. In this sense, present policies can inadvertently foreclose future options for the generation of food, wealth, and services from ocean resources. A policy to rebuild ecosystems can reverse this trend and maximize economic value in tomorrow's markets, where supply will vastly outstrip demand for high-quality fish products. Fourth, I outline a novel methodology, termed "Back to the Future," that can implement a goal of ecosystem rebuilding. Models of past ecosystems are reconstructed using information about the presence and abundance of species from historical documents, archaeology, and local and traditional environmental knowledge (LEK and TEK). Economic evaluation compares past with present and alternative ecosystems. "Back to the Future" gives the TEK of aboriginal and indigenous peoples a valuable, direct function in resource management. Finally, I discuss two practical management measures, paralleling recent developments in terrestrial reconstruction ecology, the implementation of large no-take marine reserves, and the reintroduction of high-value species that were formerly endemic.