Coastal communities, including those on the Vineyard, are struggling with plastics on the beach. Animals are killed, which is visually unpleasant and bad for tourism. But while a clean environment is important, it’s also important to make prudent decisions on how we tackle a problem. There are some surprises in what we know and don’t know about plastics, and many unanswered questions about their true impact on our environment.
Recent studies on plastics by local scientists and those from around the world are beginning to shed light on the behavior of plastics in the coastal and open ocean. I was involved with a study of plastics with the Sea Education Association in Woods Hole, investigating 22 years of sampling plastics in the top few feet of the Atlantic Ocean. Over 64,000 individual samples were collected and analyzed from 6,000 net tows. We found that even though plastic production had risen over that time frame, the number of plastic pieces collected did not. It’s hard to find the smoking gun on why we found a trend out of sync with the manufacturing of plastics.
What we saw in the Atlantic Ocean could be a result of better at-sea policies on plastic dumping or the fact that some of the plastics transported from land to the ocean may sink. In fact, when we look at the types of plastics found on Falmouth beaches versus the open ocean, they differ in the distribution of the numerous types of plastics. Plastics denser than water, such as those used to make soda bottles, were found on beaches but were nearly absent in the open ocean. This would point to plastics sinking. But we don’t know where they sink, perhaps within a few miles of the coast or not until they travel hundreds of miles. There is also evidence of biological growth on the small pieces of plastic in the ocean. But we don’t know what actually lives on every piece and the extent to which the ocean moves this small life around the ocean.
Recently, the emotion around this issue has fallen on plastic grocery bags, with many towns and counties currently battling to ban them in favor of cotton or other reusable bags (with the exception of some next-generation products, plastics are made from fossil fuels). But in a recent study of supermarket carrier bags by the Environmental Agency in the United Kingdom, plastic bags fared surprisingly better than cotton bags. In its life-cycle assessment, the environmental agency took a comprehensive approach involving a cradle-to-grave view of producing a bag, including the resources, the fossil fuels used to make the bags and power the plants where they’re made and transporting them to the eventual users. This report estimated that when you compare plastic bags to cotton bags, the conventional, high-density polyethylene bag actually had a smaller global warming potential by a factor of over 100. Global warming potentials consider all the knowledge of a product or chemical and determines its impact on global warming.
What these U.K. scientists did was take a broader view on plastics, not just on beaches, but how they affect global climate. Compared to burning fossil fuels, this finding is not so big, but nevertheless suggests that environmental decisions on the town level have to be global as well. The study was also produced for the U.K. from data based on 2006. It is quite possible in the U.S., a different outcome could happen. Production costs may be cheaper, based on transpor t of raw materials and products. The study did not consider how a tax can affect usage but did evaluate many other environmental impacts such as the production of smog. The UK study is intriguing and it paves the way for more like it, but it may not reflect what the state of knowledge is in the U.S.
Science is complicated, and our actions can reverberate beyond our town limits. For example, we know that excess carbon dioxide in the atmosphere from burning fossil fuels is acidifying our coastline and open ocean, putting shell-building marine organisms at risk as well as the marine life that depends on them. While less visible than plastic on the beach or in the water, this is a global issue that threatens entire species and economies. So when making decisions, the total impact of our choices needs to be considered.
Scientists are being presented with an excellent opportunity to study plastics along the West Coast of the United States from the debris of the 2011 tsunami that devastated Japan. Over the next two years, tons of plastics will come ashore and allow us to study what types of plastics made it across the Pacific and how they changed in their several-year ride.
Like any form of pollution, local or global, diminishing the inputs is important. No one likes to have plastic littering our environment, whether on the side of the road, on the beach or in the open ocean, and we should all do what we can to minimize the impact of plastics on our environment. As the bumper sticker says, Think Globally, Act Locally.
Chris Reddy is a senior scientist and director of the Coastal Ocean Institute at the Woods Hole Oceanographic Institution, where he studies marine pollution.