Terrestrial reserves and national parks have taken many forms and they continue to be directed toward variable and often imprecisely defined outcomes. A prominent contemporary focus is to pursue the continuance of biodiversity. To this aim the concept of protecting comprehensive, effectively managed and representative areas from overt development, such as urban sprawl and agriculture, has been globally adopted. Within Australia ‘effectively managed’, has been replaced by ‘adequate’, a poorly defined term which is interpreted optimistically and combined with ‘comprehensive’ and ‘representative’ to create the CAR principle. This principle was first developed within the Australian forestry sector to guide management in addressing a very specific threat to a clearly identified component of biodiversity in limited and well defined areas; the preservation of declining stands of some tree species within limited old growth forests. Eventhough the CAR principle is central to Australia’s process of developing a network of marine protected areas (MPAs) its relevance to marine systems has not been demonstrated. Its efficacy for the conservation of marine environments is questioned. The uncritical transposition of terrestrial management paradigms, including the CAR principle, to the marine realm has misled marine management. It is argued that disproportionate commitment to terrestrial principles, including CAR, and unjustified advocacy for MPAs generally have biased public perception and management efforts to the detriment of effective marine conservation and sustainable use of marine resources.