The Treasures of the Sea:
Ngā Taonga a Tangaroa
A Summary of Biodiversity in the New Zealand Marine Ecoregion.
Alison MacDiarmid (editor)
Photo: Malcolm Francis
New Zealand has a unique and particularly rich marine flora and fauna. There are an estimated 65,000 known and unknown species and the level of endemism-species not occurring elsewhere-at 44% is particularly high, making the New Zealand marine region a hotspot of marine diversity worldwide. This richness in New Zealand's marine biodiversity has been caused by two forces: isolation and physiographical complexity. The New Zealand continent and its submerged margins have been largely isolated in the southwest Pacific for many millions of years, thus reducing the potential for transport of larvae or adults into the region. Isolated New Zealand populations were thus likely to evolve into new species. New Zealand's isolation, moreover, has been coupled with a particularly rich and complex seascape; a consequence of its extension over 30 degrees of latitude, position on an active plate boundary with all the consequent folding, faulting, and volcanism, and its positioning in relation to major subtropical and subantarctic water masses and surface and deep-water current systems. This wide variety in marine seascapes means that New Zealand has a great diversity of different marine habitats that are occupied by an enormous variety of organisms.
A global trend in habitat modification and the loss of biodiversity has called for the development of conservation efforts that protect ecosystem components at a scale that enables relevant ecological processes to maintain them. The Global 200, developed by WWF, established a network of 238 ecoregions based on a hierarchy of biogeographic regions and habitat types used to identify representative areas on a global scale. Within the scheme of the Global 200, the New Zealand Marine Ecoregion was considered to represent the Major Habitat Type (MHT) of Temperate Shelf and Seas, within the major biogeographic realm of the Southern Ocean. The biodiversity features of the region were characterised as being "one of the most diverse and productive Pacific south temperate and polar ecosystems" and recognised for supporting a diversity of algae, fish, bivalves, seabirds, and marine mammals.
In support of the New Zealand marine ecoregion in the Global 200, this resource reviews and summarises the number of living species across all the major groups of organisms in New Zealand's marine environment, apart from the nemertean and functional decomposers including fungi and bacteria. Taxonomic and functional groups covered in this summary were selected based on a number of criteria, including the threatened status or vulnerability of the taxa and/or functional group, taxonomic knowledge, and information on the geographical distribution of species, including the level of endemicity or range restriction. In some cases, the functional or life-history characteristics of a group of taxa allowed for a more reasonable assessment of the biodiversity and status within that group.
Although this work was not conducted as an exercise for setting priorities, several themes with implications for management of New Zealand's marine biodiversity emerge from it. Although these themes are not wholly new they are worth emphasising in this context. First, the large number of species within the New Zealand marine ecoregion indicates that the management responsibilities for New Zealand's marine conservation and management departments and agencies are also great. Second, the large percentage of still-undescribed species in many groups, and the rate of new discovery in others, underscores the need for increased effort to fully document New Zealand's biodiversity. Third, the high level of endemism means that New Zealand cannot be reliant upon the good stewardship of marine biodiversity in neighbouring countries or areas to maintain many of the species present in the New Zealand marine ecoregion. This need for self-reliance needs to be translated into policies and strategies that maintain the integrity and long-term sustainability of the environments and habitats in which New Zealand's marine species occur. Lastly, it is apparent that there are a significant number of highly migratory species within New Zealand waters that are dependent on safe access to either breeding or feeding grounds in environments and habitats well beyond New Zealand's exclusive economic zone; in some cases in the northern hemisphere. For these species, New Zealand's management policies and actions must include close and continued dialogue with the countries and agencies responsible for management and conservation of these species.