Ocean degradation accelerated by global warming
The research analyzes data collected by oceanographers at Germany’s Helmholtz Center for Research over the past 50 years, which show that ocean oxygen levels have fallen an average of 2 percent worldwide and up to 40 percent in certain regions, such as the tropics.
This, the scientists note, “is the most pressing issue facing sea animals today.” They specifically compare it to ocean acidification, the increase in ocean water acidity caused by global warming. It has been shown to wipe out coral reefs and
Oxygen is essential for the survival of all aquatic animals, just as it is for those on land. A human in an environment with 2 percent less oxygen than their body is used to might become light-headed or suffer altitude sickness. In an environment with 40 percent less oxygen, they will likely suffer hypoxia and possibly die.
While the changes in oceanic oxygen content have not been instant, and so the problems are not as immediately drastic, they have been rapid enough to force species to migrate to more oxygen-rich areas, exposing them to new predators while disrupting the already existing ecosystem. Polar regions in recent years, for example, have suffered an invasion of species from lower latitudes seeking to escape increasingly inhospitable areas.
Oxygen-poor waters make it difficult
Earlier research also revealed that oxygen-poor waters make it more difficult for male fish to produce sperm and for
Another effect of oxygen deficiency includes impairing animals’ ability to see and hear, impeding their ability to find food and escape from predators.
One of the causes of oxygen depletion is the use of fertilizers that end up in the rivers like the Mississippi. The river carries these nutrients into the Gulf of Mexico where they fuel the growth of algae which, in turn, deplete the level of oxygen in the waters. This creates regions known as “dead zones” in which marine plants and animals cannot live, let alone reproduce.
The more important cause of oxygen depletion, however, is the ongoing warming of the world’s oceans. Warm water is unable to hold as much dissolved gas. Global warming also melts ice, which releases fresh water that rests on the surface of the
The studies also indicate that oxygen deprivation is now moving into areas previously believed to be less vulnerable, the open oceans and at the poles, showing that current ocean models need to be more carefully crafted to account for the effects of climate change.
One of the major consequences of oxygen depletion is falling fish populations. The habitat of the tropical Atlantic tuna, for example, has declined by 15 percent between the years 1960 to 2010. As fish move into more oxygen-rich areas, they concentrate in these areas where fishermen find them. This has led to the illusion of abundance and to even more fish being harvested.
There has, as a result, been an overall decline in fish populations of 4.1 percent in the 38 different regions around the world studied by scientists at the University of California Santa Barbara. Their research, published in the March 1 issue of Science, titled, “Impacts of historical warming on marine fisheries production,” details this population loss in 124 species between 1930 and 2010. The areas most impacted by climate change and overfishing, they wrote, have lost up to 35 percent compared to their early 20th century levels. If this trend continues, the hundreds of millions of human beings who use fish as a primary source of food and make their livelihood from fishing will suffer.
As has been demonstrated in the aftermath of the Monaco Declaration, however, appeals to the various nation-states of the world solve nothing. Global warming and the