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Effects of human impacts

Because we need the ocean for food, jobs, transportation, fun, recreation and other resources. Kiwis need to take care of the health and future of the oceans. Human activity can affect the ocean and the creatures that live in it in many different ways.

Our activities can affect our oceans in many ways but the three main ways are:

  1. Harvesting sea foods
  2. The impacts from our activities on land
  3. The introduction of marine pests.

Harvesting sea foods

Food from the sea is not unlimited. We have to be careful about how much we catch or we may not leave enough fish for others. This is true for the big fishing boats as well as people who go fishing with just a fishing rod. It is not just people who would miss out on eating fish. Lots of animals that feed in the sea only eat fish and they couldn’t survive without them. That is why there are rules about how many fish we can take.

Fishing boats can impact the oceans in other ways – fishing techniques, such as dredging or trawling, could damage seascapes and habitats and sometimes fisheries catch species that they do not want or need. This is called ‘by-catch’: This could be other fish species, sea mammals and/or seabirds. There are ideas being tried to reduce the amount of by-catch. Some of them include:

  • Fishing at night so seabirds won’t be caught.
  • Using devices to scare seabirds and mammals away from fishing lines and nets so they won’t get hurt.
  • Making some marine areas ‘off limits’ at certain times of the year. For example, popular breeding grounds are ‘off limits’ to help protect a particular species.

The impacts from our activities on land

It’s not just activities that we do in the sea that effects the marine environment – it is also things we do on the land.

It is natural for things to be washed out to sea by rivers and by heavy rain. But some land uses also increase the amount of soil (or run off) washed out to sea. It has been estimated that 390 million tonnes of run-off enters our marine environment each year. Run-off can include chemicals such as pesticides and herbicides that are harmful to our marine environment and creatures.

Waste water and sewage can also impact the marine environment. Sewage must be treated properly to reduce the impact it has on the environment, but even individual actions can pollute the ocean.

Most storm-water drains found on our streets run straight out to sea. This means that any chemicals and rubbish that flow down the drains when people wash their cars or paintbrushes on the street, or dump, goes straight out to sea.

The coastal environment can also be modified by building ports, roads, communication lines and sewage systems. which are important for our communities to grow and prosper. These manmade changes to the coastal environment can affect the habitats of the creatures living there. Coastal habitats including mangroves, sand dunes and estuaries are important for many marine and coastal species life-cycle. New Zealand needs to manage these different uses of the coastal environment and to balance the need to protect it and use it safely.

The introduction of marine pests

Another way that our marine environment can be affected is by the introduction of marine species from other parts of the world. These species often arrive without us even knowing. Because we have lots of ships visiting our seas, it is easy for marine species from the other places in the world to hitch a ride and try to make New Zealand its new home. These new species may be a threat to the species that are already here. This can result in smaller populations of native species

All of these things listed can impact on the marine environment. Individually the impact may not be huge but together they add up) and can become too much for our oceans to cope with. We need to manage the risks to our ocean environment.

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Got a question about marine issues? Email oceans@mfe.govt.nz

Last updated: 17 September 2007