The Tragedy of the Free Seas: How Human Impact is Degrading the World's Oceans

The scale of the human footprint on the world’s oceans is enormous, far-reaching, and yet, for the most part, overlooked. In addition to providing protein, the primary producers of the oceans supply about one-half of our atmospheric oxygen, and the deep oceans are a major sink for the sequestration of atmospheric carbon.

For centuries, the oceans were envisaged as immutable and immune to human activities, and thus regulation of their use was unnecessary. Fish were plentiful, and the capacity of the oceans to absorb human wastes was believed to be unlimited. Hugo Grotius, a Dutch jurist who authored the 1608 tome Mare Liberum (Free Sea), perpetuated this worldview, which continues to underpin the actions of many nations to this day. The unregulated environment created by the free seas doctrine predictably led to the rapid degradation and exploitation of resources, as well as the annexation of coastal seas by adjacent nations.

The “free seas” doctrine resulted in four centuries of neglect and non- as well as mismanagement. Many stocks of once globally abundant fish, such as cod, herring, and tuna, have since become ecologically and commercially extinct. Over one million whales were harvested during the past century, and to date, only the eastern Pacific gray whale has recovered to near pre-exploitation levels. Elevated levels of pollutants are found in most marine species, even those living in polar regions. Ocean temperatures are rising— aggravated by the addition of greenhouse gases from the combustion of fossil fuels— with many deleterious effects. Tens of thousands of square kilometers of coral reefs have bleached (lost their photosynthetic symbionts), with large associated die-offs in recent years. Important breeding, feeding, mating, and resting areas for migratory species have been affected by human activities. This is merely a brief summary of the continuing degradation of marine systems.

Although the knowledge that humans have the capacity to massively disturb marine environments has been known at least since the extinction of the Steller’s sea cow in 1868, the plight of the oceans did not become a public concern until the appeals in the 1950s and 1960s by authors such as Rachel Carson (1962) and Jacques Cousteau. The prolific output of books, films, and television series, along with the establishment of organizations such as Greenpeace, has resulted in raising public awareness and concern. Efforts to better manage the marine environment began in earnest with international conventions and programs such as the London Dumping Convention, the International Convention for the Prevention of Pollution from Ships, the United Nations Convention on the Law of the Sea, and the International Whaling Commission.

However, human uses and impacts on the ocean continue unabated, and the diversity of life in our oceans is now being dramatically altered by rapidly increasing and potentially irreversible human activities. Approximately 40 percent of the world’s population and 60 percent of the world’s economic production are concentrated in a 100-kilometer swath along the world’s coasts. Twenty-one of the world’s thirty-three megacities are coastal, and it is estimated that by 2020 up to 75 percent of the world’s 7.5 billion people may be living within 60 kilometer of the coastal zone. The global seabird population has declined by 69.7 percent between 1950 and 2010, and over the past forty years, the abundance of marine vertebrates (fish, seabirds, sea turtles, and marine mammals) has declined by an average of 22 percent.

Human impacts on the oceans can be broadly categorized as a result of overharvesting, pollution, habitat loss, introduced species, and global climate change/ocean acidification. The following sections provide a brief discussion of these impacts on the marine environment. It should be noted, however, that these impacts do interact, often in ways detrimental to ocean health. These negative interactions are termed cumulative effects, whereby the seemingly rational regulation and management of individual sectors fail to consider the collective impacts of these activities on the environment, public health, or human use of the resource. This results in unintended consequences to ecological systems and human well-being. Cumulative effects may be localized (e.g., pollution discharge) or global (e.g., climate change) and may be acute (e.g., overharvesting a fishery) or enduring (e.g., disposed radionuclides).