A world without plastic is almost impossible to imagine, yet large-scale plastic production only started in the 1950s. Since then global production of plastics has increased from two metric tons in 1950, to 380 metric tons in 2015. The rapid expansion of plastic into everyday life poses a clear environmental issue since most plastic is not biodegradable, leaving nearly all plastic waste to accumulate in the natural environment.

Sadly, plastic has been found in all major ocean basins around the world, contaminating the environment permanently due to the difficulties associated with waste extraction.

Early estimates concluded that 80% of all current marine plastic debris ultimately came from land-based sources, though more recent estimates report that number may be much higher. If nearly all plastic is produced in factories on land, this begs some questions:

How does our plastic make it to the ocean?

What routes does it take?

Are there certain types of plastic that are more likely to end up in the ocean than others?

A quick Google search will provide some answers: beach litter, flushing plastics like cotton balls and q-tips down the toilet, and plastics carried into waterways by rain or wind are some ways plastics end up in our oceans. These assumptions stem from the belief that plastic waste is generally buoyant and can be seen floating across the sea surface.

But if we look closer, we’ll see that only a fraction of marine plastic is actually visible—the majority of plastic ends up buried in sediment on the seafloor—and that poorly designed waste management systems substantially contribute to ocean plastic, not just the litter we see on a beach.

How does it get there?

A 2015 report by the Ocean Conservancy found that eight million metric tons of plastic leak into the ocean every year, in addition to the approximately 150 million metric tons of plastic that’s already there. This analysis, based on data from China and the Philippines, found that uncollected waste tends to be abandoned in public places near marine ecosystems, creating a clear pathway for waste to enter the ocean due to the proximity of high population areas to the coast. Waste leakage, therefore, is a function of both waste density and population density, creating clear categories of concern when it comes to waste in high-polluting countries.

Rural areas

Low-waste-density rural areas don’t tend to have waste collection services. In rural areas, waste collection rates are typically lower than in urban areas. This is particularly true in low to middle-income countries where sometimes less than 10% of all waste is collected within individual districts.

Assuming general rates across nations around the world, researchers estimated that these types of areas account for 1.7 to 2.1 million metric tons of plastic to the ocean per year.

Urban areas

Medium-waste-density urban areas tend to have waste-management systems, but they haven’t been able to keep up with the rapid pace of urbanization. Without proper infrastructure or support, researchers estimate that between 1.9 and 2.4 million metric tons of plastic enter the ocean per year from these common areas.

High-waste-density urban areas with inadequate waste management services are the third general area for concern. Collection rates in these areas tend to be the highest compared to suburban and rural areas, matching the high generation of plastic waste.

Given their high population and waste density, waste management systems can become overburdened, especially in low to middle-income countries where infrastructure might be lacking or outdated. Cities also commonly impose fees for the collection and disposal of waste, which can discourage proper waste management and increase illegal dumping. These urban areas add between 1.6 to 1.9 million metric tons of plastic to the ocean per year.

Collection systems and illegal dumping

Collected plastic waste is much less likely to leak into the ocean, but no collection system is perfect. Waste management systems handle large quantities of waste, so a few weak points in the system can result in substantial post-collection waste leakage into the ocean and waterways. This can be especially true for dump sites that are located on or near marine environments.

Many collection systems in low income countries still heavily rely on informal dumping sites that possess little or no infrastructure to control leakage. And when waste-transport systems are poorly regulated, trash haulers utilize either informal or illegal dumping areas to avoid travel expenses and save on time. Local rivers and tributaries are frequently used as illegal dumping sites, exacerbating the situation and contributing to over 1.1 to 1.3 million metric tons of plastic into the ocean per year.

The findings from the Ocean Conservatory report conclude that waste leakage is dependent on waste density as it relates to population density, where different factors contribute to uncollected waste. Collected waste is less likely to end up in the ocean, but waste management systems are not airtight. Leakage tends to stem from the waste-transport system and/or the end disposal sites.

What plastic gets collected and what doesn’t?

Within the collection system itself, researchers have determined that low-residual-value plastics are typically collected at a much lower rate than high-value plastics. That’s because high-residual-value plastics are collected from disposal sites to be resold and turned into something else, while low-residual-value plastics, such as shopping bags, have no resale value and cannot be turned into another product.

Since there’s no incentive to collect low-residual-value plastics, they are much more likely to end up at a disposal site, adding to the large percentage of total waste that ultimately gets transported to the ocean.

The future of our ocean and plastics

Plastic is a versatile and durable product, which is great for consumers but damaging when it ends up in our oceans or on our land. As plastic waste becomes more abundant in the natural environment, we are theoretically conducting an experiment on every living thing on this planet at the global scale: What effect will hundreds of millions of pounds of plastic waste have on our oceans and land?

How will the toxic chemicals leached from them affect our food, water, and air?

There are advantages and disadvantages to any solution, but any course of action must consider the enormous growth of plastic waste since its initial production—and the continued trajectory of plastic waste in the future.

+4 References

Buranyi, S. (2019). The missing 99%: why can’t we find the vast majority of ocean plastic?The Guardian. https://www.theguardian.com/us-news/2019/dec/31/ocean-plastic-we-cant-see
Greyer, R., Jambeck, J. R., & Law, K. L. (2017). Production, use, and fate of all plastics ever made. Science Advances, 3(1700782), 1-5.
Jambeck, J. R., Geyer, R., Wilcox, C., Siegler, T. R., Perryman, M., Andady, A., Narayan, R., and Law, K. L. (2015). Plastic waste inputs from land into the ocean. Science, 347(6223), 768-771.
Ocean Conservatory. (2015). Stemming the Tide: Land-based strategies for a plastic-free ocean. https://oceanconservancy.org/wp-content/uploads/2017/04/full-report-stemming-the.pdf