Living Sanibel: The sixth extinction
Coined by the Kenyan paleo-anthropologist Richard Leakey in the 1990s, the phrase “the Sixth Extinction” aptly describes the desolate state of the world’s bio-diversity today. The last dying event of this magnitude occurred 65 million years ago when a massive meteor decimated the dinosaurs.
Under natural conditions, the “background” rate of extinction is estimated to be between one and five species per year. Today, we are losing species at 1,000 to 10,000 times the background rate, which translates to approximately 200 species a day. By mid-century many biologists calculate that 30 to 50 percent of all remaining species on earth will be extinct. Unlike past extinction events due to volcanism, abrupt climatic shifts or meteor impacts, this time we are the cause.
Exactly when this sixth extinction began is open to debate. While some scientists focus on the Holocene epoch (about 12,000 years ago), others contend that the event started in the late Pleistocene, some 6,000 years earlier near the end of the last glacial maximum. The first wave of Asiatic peoples migrated across the Bering land bridge during the late Pleistocene to reach the New World. The fact that almost all megafauna in North America vanished within several thousand years of their arrival indicates that the sixth extinction may be an extension of what is commonly called the “Pleistocene Overkill.”
North and South America were not the only continents to experience dramatic losses of indigenous megafauna during this time. Australia, New Zealand, Eurasia and Africa also lost countless species. These included the 6,000-pound, hippo-sized marsupial diprotodon of Australia, a dozen giant Moa species from New Zealand, and the colossal Irish elk of northern Asia and Africa. Historically, most of these extinctions were blamed on the changing climate but more recent evidence points to the killing skills of a tool-making ape.
These primal humans cannot be blamed for their lack of foresight. The average life expectancy of a Paleolithic male was 35 years; females could expect to live to just 30. Life before the advent of agriculture was brutal. Diseases, starvation, predators and tribal warfare all took a heavy toll on early humankind. Clever apes with sticks found it easy to hunt and kill giant ground sloths, woolly mammoths and other species with little innate fear of humans. These early peoples had no way of understanding they were exterminating species after species to survive. Indeed, most megafauna vanished before written language was invented.
That is clearly not the case today. Half the world’s population has access to the Internet, putting people a few clicks away from knowing how close any given species is to the bitter rollcall of extinction. The International Union for Conservation of Nature (IUCN) maintains a Red List of threatened species that is updated annually. Every known species is given a rating, from LC (Least Concern) to CR (Critically Endangered). EW denotes a category that will likely grow in coming decades: Extinct in the Wild.
For some animals, such as the Yangtze dolphin, the infamous dodo and the Steller’s sea cow (a 30-foot-long manatee), this rating system doesn’t matter. All of them are now outright EX (Extinct). Others cling to remnant habitats increasingly encroached upon by a tsunami of humans, touting declining numbers that foreshadow their demise. The Amur leopards of Russia’s southeast amount to just 40 individual cats. The Javan rhino’s entire population is 60. The North Atlantic right whale boasts 350 members, while the lemurs of Madagascar, the Chinese giant salamander, and the Siberian tiger all teeter on the brink of obliteration.
As horrific as this is, we must wonder how those species with a “bounty” on their heads will fare over the next 50 years. A 488-pound bluefin tuna recently sold for $1.76 million dollars, or $3,600 per pound, in Tokyo. Each rhinoceros has a bounty of up to $500,000 on its head because of demand for the purported medicinal and aphrodisiac qualities of rhino horns, one of which, the aphrodisiac properties, has been universally debunked by scientists.
In Africa and Asia, elephants are slaughtered for their tusks at a rate approaching 100 animals per day. For an impoverished sub-Saharan African, where per-capita income averages $762 per year, the lure of making $3,000 per kilogram for ivory is a difficult temptation to resist. Even park rangers have been caught poaching.
Despite the international community’s best efforts, the slaughter of these and many more species continues unabated. Add to this the perils of climate change and escalating birth rates in third world countries, and it’s not hard to see the impetus behind this mass extinction.
In my next segment in this series, I will examine what can be done to save what’s left. Preservation is not easy. Owing to the thriving international black market for many of these endangered species, treaties will need have the backing of each of the various governments involved. If the status quo continues unabated, most, if not all, of the remaining megafauna in the wild will not live to see the year 2100. This is the tragic reality of the Sixth Extinction. We cannot say we didn’t know this time, because we do.
-Charles Sobczak lives and writes on Sanibel Island. He is the author of several books including “Living Sanibel” and “The Living Gulf Coast.” He will be doing a power point presentation titled, “The Human Footprint” at the Bailey Matthews National Shell Museum on Jan. 7, 2015 at 2 p.m. if you are interested in learning more about our impact on the planet.