[Opinion] A Sixth Mass Extinction Has Begun

How many species would have existed since the creation of life? Estimates range from 30 billion to 4 trillion species. With this huge number of species, the number of individual creatures must have been far greater.

What is clear is that 99.99 percent of the life that existed on our planet went extinct, and that people live on, consuming the vestiges of those creatures, oil and coal.

A higher organism’s average life span is 4 million years. Human beings, which currently rule the world because of their intelligence, are no exception, scientists say.

In most cases, the history of life is the history of extinction. In the history of the earth, there have been five mass extinction periods we know of, in the Ordovician, Devonian, Permian, Triassic, and Cretaceous periods. 80 to 85 percent of species including trilobites, perished with the extinction of the later half of the Devonian period in the Paleozoic period, 365 million years ago. The biggest extinction occurred in the Permian period, 250 million years ago. Some 96 percent of living creatures, including oceanic life, disappeared at the time.

Reasons for the mass extinction of life included cooling temperatures, methane gas emitted from the ocean floor, the depletion of oxygen in the ocean, infectious diseases, earthquakes and sea level changes caused by volcanic eruptions.

Recently, ultraviolet light and solar X-rays are said to be culprits for extinction. The mass extinction in the Cretaceous period, 65 million years ago is when the dinosaurs were gone. The causes of the extinction were brought to light. Iridium, a rare element, was discovered in concentrations 300 to 500 times higher than normal in that period, indicating that the earth might have collided with a meteorite or comet.

The United Nations Environment Program (UNEP) announced an environment report warning that the earth’s sixth mass extinction is underway, the other day. The report said that more than 30 percent of amphibians, more than 23 percent of mammals and more than 12 percent of birds are on the brink of extinction, due to the destruction of habitats caused by indiscriminate development. The report concluded that extinction in the past was caused by natural disasters, but that humans are responsible for the current extinction. Species are intertwined with one another. If one species vanishes, other species are immediately in danger. Humanity could be the next on the line for extinction, if we keep ignoring the extinction crisis around us.

Chung Sung-hee, Editorial Writer, shchung@donga.com