ABSTRACT
This chapter considers the problem of biodiversity conservation in the high seas. It starts from the assumption that the aim of conservation is the sustainable use of marine resources, and that this implies maintenance of the resilience of large marine ecosystems (LMEs). There are many threats to the resilience of such systems, including the effects of pollution on marine environments, the transmission of pests and pathogens in ballast water, bottom trawling that harms biodiversity in the substrate, seamounts and deep-water corals and the habitat disruption caused by the mining of seamounts for ferromanganese crusts, or hydrothermal vents for polymetallic sulphides (Pew Oceans Commission, 2003a; FAO, 2004; UN, 2004a). Of all threats, however, the greatest relate to the commercial exploitation of fish and other marine animals. This is the most frequently cited source of stress in marine systems (Jackson et al, 2001; Pauly et al, 2002; Myers and Worm, 2003; Hughes et al, 2005), with bycatch (Lewison et al, 2004), loss of habitat (Pandolfi et al, 2003; Pyke, 2004), climate change (Hughes et al, 2003) and the spread of pathogens (Harvell et al, 2004) being contributory factors. The linkage between changes in the relative abundance of species due to overexploitation and the resilience of marine ecosystems is often indirect, but has been shown for particular systems, for example coral reefs (Bellwood et al, 2004; McManus and Polsenberg, 2004; Hughes et al, 2005) and kelp systems (Stenek et al, 2002). Indeed, there appears to be a consensus among marine biologists that overexploitation of fisheries is significantly more important as an explanation of biodiversity loss than all other factors (Dulvy et al, 2003; Tittensor et al, 2006).
