More than 70% of our planet's surface is covered by oceans that support a wide variety of habitats and great biodiversity. Unfortunately, the marine environment is used extensively as a dumping site for domestic and industrial waste, directly or via rivers, leading to potential negative impacts on ecosystems and the economy.

Marine litter is any durable, manufactured or processed material that is discarded, disposed of or abandoned on shore or at sea.  It is a growing global problem and a direct threat to the marine environment that has attracted the world's attention especially after the discovery of the large “garbage patch” in the North Pacific Gyre.

The rubbish we see on our beaches is only a small percentage of all the rubbish that exists in the oceans (15%). According to the United Nations Environment Program (UNEP), 15% of marine litter  floats to the surface or is  in the water column (more than 40 centimeters deep). The remaining 70% are on the sea floor, out of sight.

Marine litter consists of a wide range of materials, especially materials that degrade slowly, which makes the situation increasingly serious. Even if we stopped producing litter today, the problems associated with marine litter would remain for many years.

About 70% of all marine litter is made up of plastics. The remaining 30% correspond to other materials such as glass, paper, metal, textiles, among others. There are, however, significant differences between regions in the type and amount of waste that enters the sea, which are usually associated with socioeconomic factors such as urbanism, tourism and fishing activities.

When does plastic become a problem?

Most of the products we consume or use on a daily basis are wrapped in plastic, a material designed to last forever, yet used in products that we quickly dispose of. This throwaway mentality is a recent global phenomenon, as only a few generations ago we packaged products in reusable packaging or using recyclable materials – glass, metal and paper. Glass containers, for example, were used several times to store products (vegetables, sweets, etc). The need to transport a greater quantity of products for the same tare in trucks, has led the industry to opt for plastic packaging that is lighter than glass packaging, thus bringing an economic advantage to transporters. As a result, consumption of this type of product has increased. Today, landfills and beaches are full of plastic packaging waste and expendable products that are not valued in their short life cycle. The short term effects of our daily actions are becoming a long term problem. Plastic that is not recycled or landfilled ends up in the ocean through extreme events such as floods or through river currents.

How much plastic is there in the oceans?

Although there is a lot of research to be carried out in this regard, it is not possible to estimate the amount of plastic existing in the ocean today, since during degradation processes the plastic can reach microscopic dimensions, and although invisible it is still present.

Marine litter - global problem

The oceans are dynamic systems of complex networks of currents that circulate water around the world. Ocean currents are influenced by the Earth's rotational motion, winds and density differences. Temperature is yet another important factor as currents are divided into hot and cold currents. In the areas of convergence of ocean currents, due to the effect of the Coriolis force, ocean gyres (or vortices) are usually formed, which are large systems of rotating marine currents. The following figure shows ocean currents and gyres. Once the currents start to have circular movements, it is quite common to find organic (seeds) and inorganic (plastic) residues in the gyres. One of the most studied cases is the North Pacific Gyre, where Captain Charles Moore presents impressive results of the amount of plastic compared to plankton (microscopic organisms that are the basis of the marine food chain) collected in an area thousands of kilometers from the area nearest coastline. The “plastic soup” as he called it shows how marine pollution is strongly affected by coastal uses.

Marine waste is a complex problem, where responsibilities are unclear and costs are unevenly divided. This is clearly an example of a problem that does not have a one-size-fits-all solution, but that requires an integrated approach and concerted efforts. As it is a global problem and without borders, solutions must involve international partnerships.

Pressures on the marine environment are increasing in parallel with economic growth and population growth and are likely to continue to increase if society takes an approach.  business-as-usual . There is an urgent need to more sustainably regulate and manage the marine environment in order to safeguard it for future generations.