As the Earth’s population surges toward the 7 billion mark, the following twist on an old maxim perhaps best applies: A single birth is a joyous occasion. A billion births is a tragedy.
When the planet’s human head count topped the 6 billion threshold in 1999, few pundits seemed to grasp the catastrophic ecological implications. Rush Limbaugh weighed in with frequent assurances that the entire global population could fit comfortably in the state of Texas. But as the planet endures an alarming net gain of more than 73 million a year, or some 200,000 people a day, it would be naïve to think that this explosion can occur without grave environmental repercussions.
Until now, there has been a dearth of literature linking human population growth and biodiversity loss. However, Jeffrey K. McKee’s stunning, albeit flawed, new book Sparing Nature pinpoints the precise moment (in geological terms) when our early ancestors’ success resulted in the death of neighboring species–roughly 1.8 million years ago, with the arrival of Homo erectus. Around that time, African mammals began to disappear at an unparalleled pace. But the biodiversity crisis really accelerated, McKee establishes, at the onset of the agriculture age, some 10,000 years ago, when humans enjoyed unprecedented growth. The book then takes the cause-effect model one step further and assesses what the mass decline of species diversification means for the continuity of the human race.
McKee, an anthropology professor at Ohio State University and co-author of The Riddled Chain: Chance, Coincidence, and Chaos in Human Evolution, offers several theses in Sparing Nature. He argues that preserving biodiversity is essential to the health of the planet, and consequently the long-term survival of the human species. On this point, he offers incontrovertible evidence. Mining the fossil record, McKee demonstrates that it is no coincidence that our impressive proliferation also corresponds with what many scientists believe is the planet’s sixth major period of mass extinction. And as history reveals, mass extinctions don’t bode well for the top of the food chain (just ask the victims of Mass Extinction No. 5–the dinosaurs).
Humans, McKee notes, have a long and troubling history of muscling out other species through a myriad of practices, including agriculture, irrigation, habitat destruction, pollution, the introduction of invasive species and our latest contribution–the dramatic and irresponsible overproduction of greenhouse gases. While tropical rainforests are cleared in order to make room for farms, McKee ruefully observes, the constant felling has generated a mere 13 percent of the world’s cropland, yet it has spelled disaster for disproportionately high numbers of flora and fauna. For example, of the known plant species worldwide, at least one in eight is threatened or hovers near the brink of extinction. To date, human activity has put 40-50 percent of the Earth’s available land out of commission to a vast number of species, which are critical to eco-stability. Furthermore, these lands have now been rendered worthless even to humans because of overfarming and excessive development.