One of the biggest threats to our oceans is man-made pollution. Discarded plastics and other residential waste, discharge from pesticides and industrial chemicals eventually find their way into the sea with devastating consequences for marine life and the habitats they depend on. Shipping accidents and oil spills add additional toxins to the mix.
It is estimated that a staggering 80 per cent of marine pollution originates on land. Land-based pollutants – such as agricultural run-off and nutrients from sewage outflows - are contributing to ocean ‘dead zones’ – areas which can no longer sustain life because they have low or zero oxygen. There are now some 500 of these dead zones around the world.
In addition, rapid urbanisation along the world’s coastlines has seen the growth of coastal ‘megacities’ (cities with a population of 10 million or more). In 2012, thirteen of the world’s 20 megacities were situated along coasts. Many of these populations put pressure on infrastructure where urban waste and sewage management is poor. In such areas, implementing effective waste reduction initiatives, recycling and effective waste and sewage management is key to improving the healthy longevity of our oceans.
Plastics are one of the biggest man-made pollutants in the marine environment, with an estimated eight million tonnes of plastic waste finding its way into our oceans each year. The build-up of plastic litter - bottles and cups, plastics found in cigarette filters, straws and other ‘macroplastics’ (those which are larger than 5mm) – in these urban coastal areas washes out to sea in heavy rain, polluting coastal waters and eventually drifting out to sea, where it breaks down into ever smaller pieces, eventually becoming microplastics.
The harm caused by plastic pollution is wide ranging. It chokes wildlife above and below the waterline. An estimated one million sea birds and an unknown number of sea turtles die each year as a result of plastic debris clogging their digestive tracts, and marine animals of all sorts can become tangled and incapacitated by discarded fishing lines and plastic bags. Fish and other marine life ingest microplastics which in turn can find their way into the human food chain.
There are small but significant changes we can all make to help reduce the plastics threatening to engulf our oceans, for example reducing our dependency on single-use items such as thin plastic bags, plastic water bottles, straws and cutlery, or taking part in local beach clearing initiatives. It’s a small price to pay towards achieving SDG 14 and preserving our greatest resource.