7.1 Introduction

Marine environments provide significant benefits to man, for example through the provision of seafood and other resources worth trillions of dollars per annum, regulation of the Earth's climate, and the modulation of global biogeochemical cycles (Holmlund and Hammer, 1999), water quality maintenance (Worm et al., 2006), and also cultural and aesthetic benefits (Lewis, 2012). In spite of its clear importance, the marine environment is subject to huge pressure from anthropogenic sources. These pressures arise from inter alia the overexploitation of marine species, nutrient loading from land-based agriculture, underwater noise, the introduction of invasive species, and increasing oceanic acidification and habitat degradation. The threats are frequently interlinked. Further, in terms of biodiversity loss, Lotze et al. (2006) estimate that the human exploitation of marine species is responsible for 96% of species extinctions.

The ecosystem based approach (EBA) is a managed response to these anthropogenic impacts on marine ecosystems. The aim of the EBA is to facilitate the protection, recovery, and sustainable use of marine ecosystems, applying a multisector approach. Any management approach is likely to entail trade-offs, in the sense that there are some stakeholders who will realize net benefits from the management intervention and others that will incur net losses. There are winners and losers even within a body of stakeholders (e.g. fishermen). Further, one significant broad stakeholder group is ‘wider society’, and it is important to capture broader social welfare changes arising from any management intervention.

There is considerable variability in the extent to which the benefits and costs arising from applying the EBA are measurable, and also the extent to which they can be valued in monetary terms. For instance, changes in fish stocks have a relatively direct market value, whereas other benefits (such as a feeling of wellbeing arising from the aesthetics of the marine landscape) are much less tangible.