New Zealand’s marine area
New Zealand administers the sixth largest marine area in the world. At more than 4.4 million square kilometres, it is about 14 times larger than our land area (Organisation for Economic Co-operation and Development, 2007).
New Zealand contains an archipelago of more than 330 islands with 18,218 kilometres of coastline (Department of Conservation, 2007) extending from subtropical to subantarctic waters7 over 30 degrees of latitude (see Figure 11.1).
New Zealand’s marine area has three key jurisdictional zones, each of which has a different legal regime. The territorial sea extends seaward from the coast to 12 nautical miles offshore. The Exclusive Economic Zone (EEZ) is the area of sea and seabed that extends from 12 to 200 nautical miles offshore. New Zealand has formally lodged the outer limits of its extended continental shelf – the 1.7 million square kilometres of seabed outside New Zealand’s EEZ – with the United Nations Commission on the Limits of the Continental Shelf.8 The commission is considering the submission. Once confirmed, the extended continental shelf boundary will be binding on other countries.
Biodiversity in the marine environment
New Zealand’s vast marine area contains a diverse range of marine ecosystems, providing habitats for many species. Scientists have formally identified almost 16,000 marine species in New Zealand waters, although it is estimated that tens of thousands of species may still be undiscovered (Gordon, 2007). According to some estimates, the possible number of species in New Zealand waters could be as high as 65,000 (MacDiarmid, 2007). It is estimated that as much as 80 per cent of New Zealand’s biodiversity occurs in the marine environment (Ministry for the Environment, 2006).
Because of New Zealand’s geographical isolation, our marine area, by international standards, has a comparatively high level of endemism (species that do not occur elsewhere), particularly in isolated areas such as Three Kings Islands and our subantarctic islands (Gordon, 2007). Forty-four per cent of our known marine species are endemic (MacDiarmid, 2006). For example, over half of the 24 species of albatross breed in New Zealand and, of those, nine species breed only in New Zealand (MacDiarmid, 2007).
As a result, New Zealand is considered internationally to be an important contributor to global marine diversity. For example, endemic species include:
about 95 per cent of the 733 known sponge species
84 per cent of bivalves and gastropods (types of marine molluscs)
75 per cent of ascidians (commonly known as sea squirts).
In addition, a comparatively high proportion of our seabirds (including half of our albatrosses) and a third of our seaweeds are endemic.
See Chapter 12, ‘Biodiversity’ for information on land-based and freshwater biodiversity.
Importance of our oceans
Most New Zealanders (90 per cent) live within 50 kilometres of the coastline. We use our marine area for many purposes, including transportation, fisheries, recreation, and tourism, and value it for its cultural and spiritual significance. Māori regard the ocean as a taonga (treasure) integral to their culture and identity. Many coastal areas contain culturally significant sites such as urupā (burial grounds) and tauranga waka (canoe landing sites). The ocean is also an important source of food to many New Zealanders.
Healthy oceans deliver a range of important environmental benefits: they absorb and transfer nutrients and sediments from the land, absorb carbon, and regulate heat transfer from the atmosphere. These functions are critical to sustaining life.
Many of New Zealand’s economic activities are dependent on the sea. In 2006, 99.5 per cent of our exports (by weight) were transported by sea (Statistics New Zealand, 2006b). In 2002, the estimated economic value of marine industries was about $3.3 billion (about 3 per cent of gross domestic product), including earnings from shipping, fisheries and aquaculture, offshore minerals, and government and defence.
Considerable value is also generated from other marine activities, such as tourism, research and education, and marine construction (Statistics New Zealand, 2006a).
Fisheries and aquaculture
Export earnings for fisheries in 2006 were worth $1.34 billion, including $187 million in earnings from salmon and mussel aquaculture (Statistics New Zealand, 2007b). Fisheries and aquaculture employ more than 26,000 people, both directly and indirectly (Organisation for Economic Co-operation and Development, 2007).
In 2006, the asset value of fish species managed under New Zealand’s quota management system was estimated to be $3.8 billion, a 40 per cent increase from 1996 (Statistics New Zealand, 2007a). However, New Zealand produces less than 1 per cent of global fisheries output, as much of our EEZ is commercially barren (Organisation for Economic Co-operation and Development, 2007).
Natural factors that affect the marine environment
New Zealand’s marine environment is influenced by its geological history, its isolation, and the action of major ocean currents. Marine life in New Zealand waters is influenced by the range and complexity of our marine habitats.
Longer-term weather cycles also affect New Zealand’s oceans. Together, the atmosphere and the rotation of the earth drive major ocean circulation patterns and climate systems across the world, affecting deepwater and surface currents, sea temperature, sea levels, the productivity9 of our oceans, and seawater chemistry.
Natural inflows of nutrients and sediments into coastal ecosystems are an important part of biological, physical, and chemical cycles in New Zealand’s inshore area. Such cycles are the basis for productivity in these areas. The offshore ocean area is primarily influenced by major oceanic currents.
Human factors that affect the marine environment
By international standards, New Zealand enjoys abundant marine resources and healthy marine environments (Organisation for Economic Co-operation and Development, 2007). This is particularly so for our deepwater environments which are not readily accessible. It is estimated that about 30 per cent of New Zealand’s marine environment experiences some degree of disturbance from human activities.
New Zealand’s inshore and offshore marine areas are generally subject to different human pressures. The largest single pressure on the marine environment in New Zealand is fishing.
In particular, large-scale commercial fishing can have a range of ecological effects, such as destroying habitats and removing large numbers of organisms from the area. Both of these effects have long-term impacts on marine ecosystems, including on the marine food chain. Bycatch (the unintended catch of species other than the target fish) also puts pressure on marine species in some fisheries.
Other pressures result from the increasing levels of shipping in New Zealand waters. Shipping can bring new marine species into New Zealand waters. While most introduced species (see box ‘More about introduced marine species’) are harmless, some have had localised but significant effects on marine biodiversity (Dodgshun et al, 2007). For example, the sea squirt Styela clava is expected to have a significant negative impact on aquaculture around the Hauraki Gulf and Lyttelton areas unless it is controlled (Biosecurity New Zealand, 2006).
More about introduced marine species
By 1998, more than 140 introduced marine species had been recorded in New Zealand waters. Since 1998, surveys have confirmed at least 18 new species at 16 of New Zealand’s high-risk ports and marinas (Biosecurity New Zealand, 2007). Most of these probably arrived as a result of shipping activity rather than by natural processes.
Changes to climate and ocean current patterns may bring more new species to New Zealand naturally. For example, rare tropical species are more likely to be observed (and survive) on offshore islands during warmer La Niña years (Evans, 2007). These changes may also allow a greater proportion of the new species that arrive as a result of shipping activity to survive.
The past 60 years have seen increasing levels of pollutants, nutrients, and sediments in the inshore marine environment. This increase is the result of urban and agricultural run-off, road run-off, industrial discharges, and air pollution. Estuaries situated in heavily urbanised catchments often have high levels of chemical pollutants (Auckland Regional Council, 2004). Excessive nutrients, particularly nitrogen, from sewage and land run-off have also caused increased algae growth in many of our coastal areas (Robertson and Stevens, 2007). Litter and debris, both from vessels and land-based activities, can also affect marine organisms and pollute waters and coastlines.
Because of land clearance in catchments, wetland drainage, and land development, average sedimentation rates in estuaries are typically at least 10 times higher than they were before Europeans arrived in New Zealand (Robertson and Stevens, 2007).
The mining of fossil fuels such as oil and gas from under the sea floor can put considerable pressure on marine ecosystems. Oil and gas have been produced from New Zealand’s EEZ since the 1960s, from the oilfields in Taranaki, and new fields in the Great South Basin (Associate Minister of Energy, 2007; Ministry for the Environment, 2005).
To date, the extraction of minerals from the sea floor has not been a large pressure on the marine environment because such exploration has not been consistently economically viable. However, several prospecting licences to mining companies have recently been granted areas on the Kermadec Ridge. These areas are now being explored (Ministry of Economic Development, 2007).
Habitat degradation or loss due to intensive coastal development is a pressure on the inshore marine area. Vulnerable coastal ecosystems including wetlands, mangroves, and coastal lagoons are most at risk from such habitat changes (United Nations Environment Programme, 2006). Many New Zealanders already live on the coastal margin, but previously undeveloped coastal areas have experienced significant development in the last decade.
More about climate change and the oceans
Climate change may significantly affect the marine environment. Increasing levels of atmospheric carbon dioxide are expected to have major implications for the distribution and health of marine biodiversity, because the absorption of carbon dioxide into the ocean increases the acidity of seawater. Organisms such as marine plankton, corals, and shellfish are particularly vulnerable to such a change because it may reduce their ability to form calcium-based shells and skeletons (Hays et al, 2005).
New Zealand waters have shown a small decrease in productivity of about 1 per cent each year in recent years (Pinkerton, 2007). Large-scale changes in productivity resulting from climate change would negatively affect New Zealand’s marine ecosystems and fisheries.
In addition, the sea level has risen an average 0.16 metres in the last century at all four main ports in New Zealand (Hannah, 2004). The rate at which the sea level will rise is predicted to nearly double in the next century (Intergovernmental Panel on Climate Change, 2007).
Changes in sea level are likely to cause complex readjustments in coastal marine habitats and in the physical structure of beaches, estuaries, and sheltered foreshores. Changes to surface and subsurface temperatures could also affect how oceans circulate and the distribution of marine organisms.
7 This chapter does not discuss marine areas in New Zealand’s Antarctic territory.
8 The outer limits of New Zealand’s extended continental shelf remain subject to the delimitation of boundaries with Fiji, Tonga, and possibly France (in respect of New Caledonia).
9 Productivity is a measure of the amount of life that can be supported in an area. It is driven by the availability of nutrients and light (Pinkerton, 2007).