The Anthropocene Extinction

Rachel Neff

Dr. Sniegocki

Theology 345

16 December 2016

The Anthropocene Extinction

        In the long narrative that describes our world’s history, it is an undisputed fact that Homo sapiens created the biggest plot twist of all time. No species has shaken up the natural order of things like we humans have. Our species really changed the game. Regrettably, this change was not necessarily a positive one. While many children have still been lucky enough to grow up seeing bunnies frolicking through the fields, deer leaping across the meadows, and squirrels scampering up the trees, the future youth of our world may not be so fortunate. They may never know the resounding noise of bullfrogs on a spring evening, or feel the excitement at the sight of a fluttering bat on a summer night. This is because our world is currently undergoing a mass extinction. Poignantly named the “Anthropocene Extinction,” this human-caused event may have the power to destroy life on our planet, unless we begin acting as responsible citizens of Earth now.

        While minor extinction events have occurred many times throughout the history of Earth, there have been only five previous mass extinctions on our planet (Kolbert 3). Dubbed “the Big Five,” these events constituted the loss of at least 75% of the life present on Earth at that time (Sutter). Another way to define mass extinction is as follows: the elimination of a significant portion of the world’s living creatures in a geologically insignificant amount of time. The first mass extinction event occurred 450 million years ago, the most devastating happened 250 million years ago, and the most recent happened 66 million years ago when a giant asteroid collided with Earth and wiped out the dinosaurs. The current extinction we are experiencing, the “Anthropocene”, meaning “age of humans” (Kolbert 108), has been characterized by rapid disappearance of countless irreplaceable wildlife species, all at the hands of Homo sapiens (Kolbert 17).

The exact time the Anthropocene Extinction began is heavily debated among scientists. Some define its beginning as the start of the industrial revolution, in the early 1800’s. Others claim its beginning was in 1945, right after World War II, when Earth’s human population began to explode exponentially (Kolbert 235). The author of The Sixth Extinction, Elizabeth Kolbert, claims that the Anthropocene began millennia before, about 11,700 years ago, around the time of the conclusion of the last ice age (107).

        She cites this time as the beginning of the extinction because it was the point when the human species began noticeably altering Earth’s biota, its animal and plant life. It was the time of the decimation of the megafauna—the “jumbo-sized” animals that used to roam around most parts of the world. This category of animals included the woolly mammoth, the mastodon, the ground sloth, the saber-toothed tiger, and other strange behemoths like beavers the size of grizzly bears and armadillos the size of cars (Kolbert 225). These animals were Earth’s top predators until humans came along and learned how to hunt them. Because these animals’ reproductive strategy was to have a long gestation period and only give birth to a single offspring at a time, they could not replenish their numbers fast enough to keep up with the humans’ overhunting (Dirzo et al. 403).

        Since that time, there has been an observable pattern of humans literally transforming the face of the Earth. The biggest change has been how we have altered the composition of the atmosphere (Kolbert 108). Since the beginning of the industrial revolution, we have been burning up fossil fuels so persistently that we have added a whopping 365 billion metric tons of carbon to the atmosphere. Every year we add about nine million tons more to this number, an amount that has increased by about six percent each year. Carbon dioxide levels are currently greater than 400 parts per million, which is higher than any time in the last 800,000 years. If we continue at this rate, CO2 levels will reach over 500 parts per million by 2050, a tipping point that will cause the vanishing of glaciers, inundation of the coasts, and the disappearance of the arctic ice cap (Kolbert 113).

        One of the most problematic effects of this increasing level of carbon dioxide is ocean acidification. In a very short amount of time, the ocean has absorbed about 1/3 of all human carbon emissions. This has caused the ocean’s pH to drop to 8.1 and become 30 percent more acidic than the 8.2 pH pre-industrial-age ocean. It has been predicted that the ocean will be 150 percent more acidic, with a pH of 7.8, by the middle of this century if current rates continue (Kolbert 114). This is quite alarming, because in an ocean this acidic, many marine animals cannot perform even the most basic metabolic functions. In lab experiments using seawater with this pH level, it was found that hard-shelled “calcifiers” like starfish, sea urchins, clams, oysters, and barnacles were hit the hardest, making up 75% of the species that could did not survive (Kolbert 121). Corals are another group of calcifiers, and scientists have dubbed them the second most endangered group of animals, behind amphibians. Some scientists give corals until the end of the century, others say they will be virtually extinct even before then (Kolbert 130). In the case of corals, this species’ endangerment is not only from ocean acidification, but also algae blooms, and siltation of water from a menacing culprit—deforestation (Kolbert 141).

        Deforestation is another major driver of species extinction. In addition to the carbon emissions from fossil fuels, deforestation has added another 180 billion tons of carbon dioxide to the atmosphere (Kolbert 113). The purposes for deforestation have historically been logging, development of agricultural pasture, along with commercial and residential development (Kolbert 176), and these purposes have led to nearly half of the rainforests in Central America and nearly a fifth of the Amazon rainforest being cut down (Kolbert 186). All of this deforestation has caused widespread fragmentation, where sections of forest are fragmented into “islands,” being separated from each other by roads, villages, and cities (Kolbert 179). As shown in the Biological Dynamics of Forest Fragments Project, this causes huge declines in species biodiversity (Kolbert 174). It is especially disastrous, because in order to keep up with rising temperatures from climate change, animals need to be moving about 30 feet northward every day. If they cannot move because a highway or a town is in the way, their species is not likely to survive (Kolbert 189).