16: Impacts of Humans on the Oceans

By far the most important human pollution of the oceans is the release of carbon dioxide and methane to the atmosphere. The adverse effects on the oceans that are predicted to occur as a result of carbon dioxide releases since the industrial revolution far transcend all other human impacts on the oceans combined. Massive disruption of marine ecosystems and likely numerous marine species extinctions are anticipated to result from the changing temperatures, current patterns, sea level rise, and especially from the deoxygenation and increased acidity of the oceans that has already occurred, or will occur. These already unavoidable adverse effects will become more severe if carbon dioxide releases are not drastically reduced. This issue is so important that it was discussed in some detail in Chapter 1 and referenced in many other chapters. This chapter explores the range of ways in which humans can, and do, adversely affect the oceans and examines the concept of pollution and of toxicity both of which are widely misunderstood. It then examines the wide range of human activities, such as sewage waste disposal, industrial waste discharges, and oil spills that have been the focus of most public concern and debate with regard to ocean pollution. Finally, the chapter examines the human activities that have caused significant harm, or pose a much larger threat to ocean ecosystems, most of which receive little or no public recognition or debate. These include, fishing, the introduction of nonindigenous species, habitat alteration, and finally the most important and greatest threats of climate change, deoxygenation and acidification caused by anthropogenic releases of carbon dioxide releases to the atmosphere and anthropogenic nutrient inputs to the oceans.

Chapter 2 reviewed the historical importance of the ocean and the growing use of ocean resources for fisheries; transportation; trade; extraction of offshore oil, gas, and other minerals; pharmaceuticals; energy; and recreational and aesthetic opportunities. Each use potentially can or actually does have deleterious effects on ocean ecosystems and on the other uses of the ocean. Such deleterious effects are encompassed by the term pollution, which can be characterized as “the addition of substances to, or alteration of, the ocean ecosystem in a manner that is deleterious to the ocean ecosystem or its resources.” This definition, or a similar one, is generally accepted by many national and international organizations that have responsibilities for managing and protecting the oceans and ocean resources. For example, the formal definition accepted by the premier world scientific body in this area, the United Nations Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection (GESAMP), is as follows:

Pollution means the introduction by humans, directly or indirectly, of substances or energy into the marine environment (including estuaries) resulting in such deleterious effects as harm to living resources, hazards to human health, hindrance to maritime activities including fishing, impairment of quality for use of sea water and reduction of amenities.

Notice that, according to the generally accepted official definition, the term pollution includes not only the discharge of harmful wastes, but also activities such as overfishing, construction of structures, and other human activities that adversely affect ocean ecosystems by changing currents, distributions of dissolved substances or heat, or sediment transport patterns. The definition also includes adverse impacts of one ocean use on another, such as the degradation of recreational and aesthetic value caused by trash on ocean beaches or offshore oil rigs “spoiling” the ocean view. Ocean pollution also includes harmful effects on ocean ecosystems of the anthropogenic release of carbon dioxide and other greenhouse gases to the atmosphere, as these releases indirectly add carbon dioxide, a “waste” material and heat energy to the oceans. Thus, ocean pollution is a very broad term that includes any anthropogenic activity that causes directly or indirectly harm to ocean ecosystems or resources. Notice also that there must be harmful (“deleterious”) effects before any activity can be considered pollution. By contrast, the popular definition of pollution continues to be restricted to the addition of substances (chemicals, materials, or organisms) to the environment, and the term often is misused to include any such contamination, whether “deleterious” or not.