This chapter explains why the condition of our marine environment is important. It presents information about the pressures and state of New Zealand’s marine environment, and how its state is changing over time.
Our marine environment – a summary
The marine domain extends from the coast to the outer limits of New Zealand’s exclusive economic zone (EEZ, the 200 nautical mile limit) and includes the extended continental shelf (see figure 37). Together, our territorial sea (extending to the 12 nautical mile limit) and our EEZ cover 4 million square kilometres, which is 15 times bigger than our land area. When the extended continental shelf is included, our marine environment is 21 times larger than our land area.
New Zealand has one of the world’s most diverse marine environments because it encompasses sub-antarctic and subtropical waters. Our marine environment supports a wide range of habitats and sea life.
The oceans have played an important part in the lives of New Zealanders and our economy since Polynesian settlers arrived 700–800 years ago. Hunting and harvesting depleted some sea life, particularly larger animals such as seals, sea lions, and whales. Commercial harvesting is carefully managed now to ensure it is economically sustainable, but fishing methods such as trawling that damage the marine environment, as well as overfishing and bycatch (when fish and other animals are unintentionally caught in fishing gear) are ongoing pressures on sea life. While overfishing and trawling have decreased, many of our marine species and seabirds are still at risk from fishing activities. Aquaculture, the extraction of oil and minerals, waste, exotic species, and run-off from urban and agricultural land are also pressures on our marine environment, but we have little information on their impact on New Zealand’s marine environment.
The most serious long-term pressures on our marine environment are likely to be caused by climate change. Coastal sea levels and long-term sea-surface temperatures around New Zealand have risen over the last century, and our oceans are more acidic than when measurements were first taken in 1998.
More than one-quarter of our indigenous marine mammal species are threatened with extinction, and the extinction risk of one mammal species, the New Zealand sea lion, has increased since 2005. Māui’s dolphin is now one of the rarest marine mammals in the world, with an estimated 55 individuals more than a year old remaining. Ninety percent of indigenous seabird species and subspecies that breed in New Zealand are threatened or at risk of extinction. The risk of extinction has increased for seven of the 92 seabird species since 2005.
Note: Data from the satellite ocean colour sensors SeaWiFS and MODIS-Aqua.EEZ – exclusive economic zone; NM – nautical miles.
This map illustrates the extent of New Zealand’s marine environment, outlining the boundaries of New Zealand’s territorial sea, exclusive economic zone, and extended continental shelf.
How our marine environment is monitored
From economic and ecological perspectives, the health of our fisheries (fish stocks that are harvested) and marine ecosystems is critical. Three government agencies monitor aspects of our marine environment. The Ministry for Primary Industries monitors fish stocks to ensure fishing is kept within sustainable limits under the quota management system for commercial catch. The Environmental Protection Authority is responsible for monitoring economic activities in our marine environment, such as aquaculture and exploration for oil and gas. The Department of Conservation monitors the marine environment to understand the state of its biodiversity and ecosystems.
Satellites now allow us to remotely monitor aspects of the marine environment such as sea-surface temperature, sea levels, and primary productivity (the amount of organic matter produced by plants and some microorganisms).
Regional councils monitor the quality of coastal water to check whether it is suitable for swimming and other recreational activities. Some iwi and hapū also monitor the health of the coastal marine environment in their rohe (area), using both scientific methods and mātauranga Māori (traditional knowledge).
The Government has designated marine reserves to help protect areas of the marine environment from fishing and disturbance from other activities. There are 44 marine reserves around our coast, all within the territorial sea. Collectively, these reserves cover 17,430 square kilometres, or about 10 percent of our territorial sea. They cover 0.4 percent of the territorial sea and EEZ combined. The Convention on Biological Diversity, of which we are a signatory, has a target of 10 percent of territorial sea and EEZ combined for marine conservation areas (Secretariat of the Convention on Biological Diversity, 2015).