Case study 2: Hawaii and the northern Line Islands, central Pacific
Our understanding of what is natural in the marine environment is becoming increasingly compromised by the absence of locations that are not impacted by human activities and nowhere is this more acute than on coral reefs, where overexploitation and severe depletion have occurred on a global scale (Bellwood et al. 2004; Pandolfi et al. 2005). Although numerous factors have contributed to the decline in coral reefs worldwide, fishing has historically exerted the most direct and pervasive influence through the disproportionate removal of large-bodied top-level predators that exert strong control over the productivity of the entire ecosystem (Pauly et al. 1998; Jackson et al. 2001). Protected, remote locations are some of the few remaining examples of coral reefs without major anthropogenic influence and these 'ecological baselines' provide fundamental insights into natural patterns and processes in these high biodiversity ecosystems and allow for comparisons with more impacted human-dominated coral reefs (Knowlton and Jackson 2008; Sandin et al.
2008). This type of 'space-for-time' substitution is an alternative to long-term studies to assess the impact of human-induced changes where pre-impact records are sparse or non-existent.