Uncertainty in Marine Management

Abstract

Introduction.- Uncertainty is likely a greater impediment to sustainable resource management in marine systems than in their terrestrial counterparts for several reasons. Terrestrial populations can be directly observed, while the estimation of population abundance in the marine environment depends on indirect observations. Also, marine plants and animals exist in a complex, energetic, and fluid medium, and most life histories involve an early larval (or spore) stage that is subject to the vagaries of the planktonic environment. Another unusual aspect of marine resources is the recently recognized existence of population change on long time scales, synchronous over global spatial scales (Schwartzlose et al. 1999).Though uncertainty has a similar deleterious effect on management of many marine systems, its general impacts are most visible in the management of fisheries. Data from world fisheries indicate approximately 30 percent of them are overfished (Garcia and Newton 1997).1 While details vary, a general explanation for the relatively high number of overfished stocks is the ratchet effect: the unidirectional increase in fishing rates due to constant economic and social pressure for higher catches, which remains unchecked because of the large uncertainty in potential negative effects of fishing (Table 22.1, left column). This effect was originally defined as increasing effort only during times of high abundance (Caddy and Gulland 1983). Ludwig et al. (1993) emphasized the role of uncertainty in this process, and here we consider uncertainty an intrinsic part of the ratchet effect (Botsford et al. 1997). In the typical scenario, fishery biologists project the potentially deleterious biological effects of continued or increased fishing, but those responsible for the ultimate management decision must take into account social and economic considerations. In weighing the tradeoff between certainly losing jobs and other tangible short-term, negative economic impacts, against the uncertain possibility of the fishery collapsing, managers opt for continued or increased fishing. For a variety of reasons, often involving a lack of insulation of the management process from political pressure, the infrastructure of fisheries management is ill equipped to deal adequately with uncertainty.Even in marine management problems other than fisheries, there is a general tendency to favor actions that appear economically advantageous in the short term because their deleterious effects on the environment are uncertain. Here we describe the relative roles of methods for dealing with the uncertainty in marine systems by characterizing them in terms of their effects on different aspects of this general ratchet effect. To describe the effects of uncertainty in management of marine systems, we focus in this chapter on management of single populations, the most common concern of management.