Oil and plastic pollution and sewage can come from both marine- and land-based activities. Large amounts of waste, mainly from urban centres, are carried along waterways and washed out to sea. Other waste can come from recreational boating, fishing boats, shipping, and oil and gas operations.
Habitats in coastal waters, and harbours, estuaries, and reefs along exposed coasts, are particularly vulnerable to the effects of plastic pollution (MacDiarmid et al, 2012a). While some waste collects on beaches, most remains in the ocean.
Some of the effects of build-up of debris in the marine environment include:
- marine animals and seabirds can become entangled in it and be injured or killed
- fish, seabirds, and turtles can swallow plastic debris they mistake for food
- debris drifting in the ocean can damage fragile marine habitats
- plastics can remain in the ocean for hundreds of years
- when plastics eventually break down into small particles they can enter the food chain (Derraik, 2002; World Economic Forum, 2016).
The data on marine waste in New Zealand’s marine environment are limited. One New Zealand study identified that between 1995 and 2005, the incidence of fur seals and sea lions being entangled in plastic and other debris in Kaikoura was one of the highest rates reported in the world (Boren et al, 2006).
Globally, it is estimated that at least 8 million tonnes of plastic waste enters the ocean each year (Jambeck et al, 2015), with packaging comprising more than half this waste (World Economic Forum, 2016). Some of this waste forms huge drifting patches, such as the Great Pacific garbage patch in the North Pacific Ocean (Turgeon, 2014).
By 2050, there may be more plastic than fish in the ocean, by weight, based on the current estimated rate of global plastic entering the ocean (World Economic Forum, 2016).
For more detail see Environmental indicators Te taiao Aotearoa: Effects of marine debris on marine life.