The Anthropocene Extinction

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While on the subject of moving species, the unnatural movement of organisms from their native lands to other regions of the world has also been causing significant species extinction. While fragmentation has been isolating species, translocation of non-native species has been doing the opposite. Global trade and travel have been causing an unprecedented “mass invasion event.” This began as soon as humans started migrating across the Earth and has rapidly intensified in recent decades, to a point where some parts of the world have more non-native plant species than native ones. One shocking figure is that on any given day, around ten thousand different species are being transported around the world in the ballasts of ships alone (Kolbert 198).

This reshuffling of Earth’s wildlife is causing major disruption of food webs and imbalances in local ecosystems. An example of this is the introduction of the brown tree snake into Guam. Native to Papua New Guinea and Northern Australia, this serpent was brought to Guam in the 1940’s, most likely on a military ship. It voraciously chomped its way through almost all of Guam’s native birds, and reduced the country’s number of native bat species from three to one. The snake proliferated throughout the island and its population density at its peak was forty snakes per acre (Kolbert 203). While this snake sounds like a terror to Guam’s native wildlife, author David Quammen cautions us against demonizing it, because what it has done in Guam, he writes, “is precisely what Homo sapiens has done all over the planet: succeeded extravagantly at the expense of other species” (Kolbert 204).

What are some consequences of these human-caused processes of climate change, ocean acidification, deforestation, and species invasion for the world? The examples of coral extinction and biodiversity problems in Guam have been mentioned, but these alone do not constitute a mass extinction. What does constitute a mass extinction is the current overarching rate of loss of animal species that we are experiencing. In the history of Earth, there is a normal, cyclical “background” extinction rate for all animals. For mammals, background extinction rate is one species every seven hundred years. For amphibians, the normal extinction rate is one every thousand years, but the extinction rate that amphibians are currently experiencing is 45,000 times faster than this. This is due to an invasive species of chytrid fungus that has been plaguing frog populations in recent years (Kolbert 17). While other animals’ extinction rates are not as dramatic as the amphibians’, the extinction rate on average across all species is still about 1,000 times faster than normal background extinction rates (Kolbert 18).

In terrestrial vertebrates, a 25-28% loss in abundance has been observed since 1500. As far as specific species extinctions go, there have been at least 322 recorded terrestrial vertebrate species that have vanished from the planet since that time. In invertebrate species that have been studied, there has been a 45% mean abundance decline, but less than 1% of the invertebrate species have been assessed. It is estimated that there are currently between 5 and 9 million species on this planet, and as each year passes, we are losing between 11,000 and 58,000 species. This “defaunation” that the world has been experiencing, must be taken just as seriously as deforestation, because its consequences bear the same level of gravity (Dirzo et al 401). Elizabeth Kolbert’s studies have shown that within the next few hundred years, one third of all corals, one third of all fresh water mollusks, one thirds of sharks and rays, one fifth of all reptiles and a sixth of all birds will be extinct, all due to “one weedy species” (Kolbert 18).

This one weedy species, is of course, our own species, and the ironic part of all of this is that we are not only the cause of the Anthropocene Extinction, we may also be one of its victims; we will likely be the agents of our own demise. Ecologist Paul Elrich put it eloquently: “In pushing other species to extinction, humanity is busy sawing off the limb on which it perches.” This extinction may have dire consequences for the human race, yet so many people do not even recognize it. “One fewer bat species? I’ve got my mortgage to pay! Another frog extinct? There are plenty more!” (Worrall). This reaction is probably not because people do not care, but because they are genuinely unaware of the intensity of the extinction rates. They do not know that this extinction is even happening, or that it will effect humans, too (Worrall).

Humans will lose many of the services that animals give to us for free. For example, we are currently seeing great declines in pollinator abundance and diversity, which is definitely worrisome, considering that insect pollination is necessary for 75% of all the world’s food crops. This service is estimated to be worth about 10% of the economic value of the world’s food supply (Dirzo et al. 403). Another service we will lose is pest control, since bats and other small vertebrates are losing numbers. In the U.S. alone, pest control by native predators saves us 4.5 billion dollars each year. We do not want to lose these species. Extinction will also affect our water quality, as many freshwater mussels and amphibians provide natural water filtration. Loss of large animals such as crocodiles and hippos will also negatively affect our waters, because their movement keeps oxygen in the water, and without this, anoxic zones will be formed that cannot support life. Finally, human health will be affected in that we will lose so many organisms that produce pharmaceutical compounds, provide food resources and regulate disease. Somewhere between 23 and 36% of all amphibians, birds, and mammals currently used for medicine or food are under threat of extinction. There will be more widespread malnourishment and starvation as the organisms that provide seed dispersal and pollination die off (Dirzo et al.). Clearly, humans need to care about this serious issue.

We are currently at a crossroads in the geologic timescale. Whether we are conscious of it or not, we humans are deciding which evolutionary paths will continue on, and which will forever end. No other species has ever affected the world in this way, and we need to deal with it properly, as it will be our enduring legacy (Kolbert 269). The “planetary scale of human impact is unquestionable” and we need to be considerate of this (Potts). All creatures are interdependent, and even the loss of just a few species can have an enormous effect. The fragile web of life is like a tapestry—if you pull one thread out the whole thing will fall apart. If we annihilate the living things on our planet, we end the narrative