Demographers aren't known for their sense of humor, but the ones who work for the United Nations recently announced that the world's human population will hit 7 billion on Halloween this year. Since censuses and other surveys can scarcely justify such a precise calculation, it's tempting to imagine that the UN Population Division, the data shop that pinpointed the Day of 7 Billion, is hinting that we should all be afraid, be very afraid.
We have reason to be. The 21st century is not yet a dozen years old, and there are already 1 billion more people than in October 1999 — with the outlook for future energy and food supplies looking bleaker than it has for decades. It took humanity until the early 19th century to gain its first billion people; then another 1.5 billion followed over the next century and a half. In just the last 60 years the world’s population has gained yet another 4.5 billion. Never before have so many animals of one species anything like our size inhabited the planet.
And this species interacts with its surroundings far more intensely than any other ever has. Planet Earth has become Planet Humanity, as we co-opt its carbon, water, and nitrogen cycles so completely that no other force can compare. For the first time in life's 3-billion-plus-year history, one form of life — ours — condemns to extinction significant proportions of the plants and animals that are our only known companions in the universe.
Did someone just remark that these impacts don't stem from our population, but from our consumption? Probably, as this assertion emerges often from journals, books, and the blogosphere. It's as though a geometry text were to propound the axiom that it is not length that determines the area of a rectangle, but width. Would we worry about our individual consumption of energy and natural resources if humanity still had the stable population of roughly 300 million people — less than today’s U.S. number — that the species maintained throughout the first millennium of the current era?
Article continues at Yale Environment 360: http://e360.yale.edu/feature/the_world_at_7_billion_can_we_stop_growing_now/2426/