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Appendix 2

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History and Rationale for a Summary of Biodiversity in the New Zealand Marine Ecoregion

Franz Smith

Introduction

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. As previous efforts were generally focused on restricted geographic extents and for a subset of ecosystem components, the broader-scale processes which are responsible for maintaining populations and whole ecosystem functioning were largely outside of the scope of conservation biology. Emergent themes in conservation biology, such as the importance of metapopulation dynamics for maintaining populations and communities, have further demonstrated the limitations of previous conservation efforts to preserve biological diversity (eg, Tilman et al. 1994) and protect representative areas (eg, Pressey et al. 1993). One advancement towards achieving a more comprehensive representation of ecosystem components involves the development of an ecoregion-based strategy, whereby species assemblages, dynamics and environmental conditions are considered as a unit for conservation action. The assessment of ecoregions based on their representativeness and endemic features on a global scale can be used as criteria for identifying priorities for conservation efforts and the analysis of threats and risks.

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 (Olson et al. 2000). Ecoregions were stratified among three realms, including terrestrial, freshwater and marine, and divided among Major Habitat Types (MHTs), describing different areas around the world that share similar environmental conditions, habitat structure, and patterns of biological complexity. The MHTs were then further subdivided among major biogeographic realms (eg, Nearctic, Indian Ocean), to address global representation of biological assemblages within a habitat type. The identification and evaluation of each ecoregion was based on extensive literature analyses and consultation with experts working in each region. Ecoregion boundaries were intended to roughly coincide with the area over which key ecological processes strongly interact.

Once identified, ecoregions were evaluated in terms of their biological distinctiveness, relating to rarity and the relative importance of different levels of biodiversity (Olson et al. 2000). Biological distinctiveness was based on aspects of species richness, endemism, taxonomic uniqueness, unusual ecological or evolutionary phenomena, and the global rarity of MHTs. These criteria were then used to estimate the 'urgency of action' according to opportunities for conserving distinct units around the world.

As a tool for guiding conservation action on a global scale, the Global 200 was designed to target distinctive biogeographic units and an ecosystem-level representation of biodiversity. The use of additional criteria to delineate ecoregion boundaries, incorporating aspects of habitat diversity, ecological and evolutionary phenomena, and the relative intactness of ecosystems, was used to highlight the best opportunities for long-term conservation (Olson et al. 2000). It was acknowledged during the development of the Global 200 that linkages among terrestrial, freshwater, and marine systems are often overlooked. It was noted that 34 (ie, 23%) of the terrestrial ecoregions shared at least 50% of their coastline with a marine ecoregion. Also, the Global 200 does not specifically address aspects of large-scale ecological phenomena, such as migrations, hydrothermal vent communities, cave and groundwater systems, and aspects of global ecosystem dynamics, such as carbon sequestration. Ecoregions that are able to incorporate these aspects could thus be considered to be making an additional contribution to global conservation of habitat and biological diversity.

For the identification and characterisation of marine ecoregions within the Global 200, nine different MHTs were identified, such as polar, temperate shelf and seas, and tropical upwelling areas (Olson et al. 2000). Four of these MHTs were beyond the scope of the Global 200, including pelagic trades, pelagic westerlies, abyssal and hadal environments. The identification and assessment of marine ecoregions contrasted with those of the terrestrial realm, as the spatial and dynamic processes between these ecosystem types were considered to be different (Olson et al. 2000). For example, it was recognised that relative to most terrestrial ecoregions, the marine ecoregions represent more spatially and temporally dynamic units of ecological and biogeographic character. Also, species endemism tends to be less pronounced in marine ecosystems, although several centres of regional endemism of marine taxa have been recognised (eg, Roberts et al. 2002). It was also acknowledged that information pertaining to the biodiversity and the ability to delineate biogeographic boundaries is limited for some of the marine habitat types recognised in the Global 200. Therefore, it was considered that comparative analyses of the conservation status of marine ecoregions could not be done with confidence (Olson et al. 2000).

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Context for the New Zealand Marine Ecoregion Assessment

Within the scheme of the Global 200, the New Zealand Marine Ecoregion was considered to represent the MHT of Temperate Shelf and Seas, within the major biogeographic realm of the Southern Ocean (Olson et al. 2000). 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 (Olson and Dinerstein 1998). Selected species included several species of penguins (including some endemic species), albatross and petrels (with some endemic breeding colonies), and marine mammals, including seals, sea lions, dolphins, sperm whales and southern right whales. General threats to the biodiversity of the region that were identified included fishing effects and environmental degradation in coastal areas, due to sedimentation, sewage discharge and agricultural runoff. Additionally, it was noted that for some areas, seabird species are under threat by introduced species (eg, cats and rats).

In terms of building a framework for this summary of the biodiversity in the New Zealand marine ecoregion, it was desirable to provide additional information on the setting and characterisation of the region in the context of the Global 200. Geographically, the New Zealand Ecoregion is located between several other ecoregions of the Global 200, including tropical and subtropical ecoregions of the South Pacific, and the south temperate marine ecosystem of Southern Australia, and the Antarctic ecoregion (represented by the area surrounding the Antarctica Peninsula and Weddell Sea) (Figure 1a). Because the region consists of elements of subtropical, temperate, subpolar and polar ecosystems, regionally, this makes the New Zealand Marine Ecoregion a significant representation of the biota in the South Pacific region. In addition, as there is a limited representation of 'subpolar' marine ecosystems in the southern hemisphere, making the New Zealand Marine Ecoregion significant on a Global scale. Identified in the Global 200, the only recognition of large deltas, mangroves, or estuaries in the Australasian region was for the New Guinea mangroves, and because these systems have been recognised in other biogeographic realms, it was thought pertinent to try to assess their significance for the region. In addition, two other MHTs that were identified can be found within the New Zealand ecoregion. One of these MHTs, 'coral reefs and associated organisms' can be found along the Kermadec Islands in the far north of the New Zealand region, which are thought to be similar to that of Lord Howe and Norfolk Island, but span approximately two degrees of latitude (Schiel et al. 1986, Francis 1993). For the MHT 'coastal marine ecosystems', areas around mainland New Zealand could also share elements with areas of South Australia, of which protection of these elements could be potentially achieved through management of complimentary areas between these regions. As the Antarctic marine ecoregion in the Global 200 was identified as the region surrounding the Antarctic Peninsula and Weddell Sea, the proximity of New Zealand to the Ross Sea and overlap number of Antarctic elements in the New Zealand flora and fauna was considered to be an important attribute for the conservation on Antarctic ecosystems.

For small rivers and streams of freshwater ecosystems, it was noted that in the Australasian region, only New Guinea, New Caledonia and Eastern Australian systems were formally recognised as part of the Global 200. However, as New Zealand streams contain a number of diadromous fishes (ie, that spend a part of their life-history in coastal marine systems) including several endemic species, the inclusion of these fishes seemed to be warranted.

Although the Global 200 was not specifically designed to target migratory species or widespread pelagic ecosystems, hydrothermal vent or abyssal systems, the New Zealand marine ecoregion contains several of these ecosystem components in close proximity to land and forms an integral part of the dynamics of the region, such as sites of active volcanism in the Bay of Plenty and extensions along the Kermadec Ridge and depths of over 1000 m in close proximity to the landmass (eg, Kaikoura Canyon and Fiordland Coast). Several of the species found in these habitats are endemic to the New Zealand region, underscoring their importance for both regional and global representation of biodiversity (Lewis and Marshall 1996).

These attributes of the New Zealand marine ecoregion thus have a significant contribution to the overall Global 200, by covering a broad range of habitat types, ecological conditions and endemic character, of which some elements were not formally incorporated into the Global 200.

Although there were several examples of large marine ecosystems that have been characterised as part of the Global 200 (eg, East African, Sulu-Sulawasei), the relevant spatial scale of an ecoregion was not specifically defined. As the measure of species diversity, rarity and endemism are dependent on spatial scale, information on statistics for the New Zealand marine ecoregion would need to be converted to a similar spatial scale in order to make meaningful comparisons between other marine ecoregions.

There was difficulty in evaluating temporal trends and risks for the majority of taxonomic/functional entries due to the lack of information. In instances where populations have become drastically reduced and/or the contraction of distributional ranges has occurred, assessments were made with knowledge of the temporal component of species distribution and abundance. In cases where major habitat types have been impacted or severely altered through human activities, consideration was given to taxonomic/functional groups likely to be effected.

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