Seven troubling trends: A checkup on the condition of the world's oceans
1. Two-thirds of the major marine fisheries are fully exploited, over exploited or depleted. Just over 40 years ago, this figure stood at less than 5 percent.
2. The concentration of carbon dioxide in the atmosphere has increased by 30 percent since the beginning of the Industrial Revolution. The best (and cautious) predictions forecast a global temperature increase of between 2 and 6 degrees F, and a rise in sea level of 6 inches to 3 feet over the next century.
3. The explosively growing human population currently utilizes over half the available surface freshwater of the planet. About 70 percent of that amount is used in agriculture. Above and beyond the ramifications of these numbers for population, this figure has critical implications for water flow through estuaries and bays, and therefore habitat quality, e.g., for salmon.
4. Between one-third and one-half of the land surface of Earth has now been transformed by human action. Examples include the conversion of wetlands and forests to urban and industrial areas or of grasslands to pastures and agricultural fields. The recent listing of nine salmon and steelhead populations in the Pacific Northwest highlight some of the consequences to marine species of land transformation due to logging, grazing, hydroelectric power generation, agriculture and urbanization. Habitat transformation is more difficult to quantify in oceans.
5. The amount of nitrogen that enters the nitrogen cycle each year has more than doubled over the past century as a result of human activities. The making of fertilizers and burning of fossil fuels account for the bulk of this newly "fixed" nitrogen. Additional wasted nitrogen is carried into the air and transported elsewhere on land or into oceans. This excess nitrogen can disrupt downstream ecological systems. The chemistry of coastal areas around the world is changing, in part because of this influx of nitrogen into previously nitrogen-poor systems. The growth of many (though not all) species that cause red tides and other harmful algal blooms is often triggered by an influx of nitrogen and other nutrients.
6. A number of scientific experts have stated that Earth is in the early states of the sixth mass extinction event in the history of the planet. This is the first mass extinction that is due directly to human activities. Major drivers include habitat destruction or alteration, introduced and invasive species, and overfishing.
7. There are now some fifty "dead zones" or areas with low to no oxygen, in the coastal areas around the world, most of which have appeared within the last fifty years. Globally, dead zones have tripled in number in the last thirty years. The dead zone in the Gulf of Mexico, for example, has doubled in size since 1993, and at 1600 square miles is the largest in the Western Hemisphere. Excessive nutrient influx, especially nitrogen and phosphorus compounds from agricultural, livestock and poultry enterprises in upstream watersheds, are the suspected causal agents.
Source: Jane Lubchenco, distinguished professor of zoology at Oregon State University, in comments to the House Subcommittee on Fisheries Conservation and Oceans on May 6. Lubchenco, past president of the American Association for the Advancement of Science, has done extensive research on the ecology of rocky shores of Oregon, Washington and California for over three decades.