A PLANET OF 3 BILLION

Tucker argues for the benefits of decreasing Earth’s population in this debut work on sustainability.

Earth has a carrying capacity, according to the author, and it’s less than half the number of human beings that it currently has: “In effect, humanity has been on a century-long binge,” he says, “featuring exponential population growth, continuous growth in industrial output and individual consumption, and the ecological devastation that goes with it.” He argues that the ideal population is 3 billion people—approximately the number that were alive on Earth in the mid-20th century. This may sound like a low number, but Tucker’s method of calculating it sounds quite reasonable. The population is not only growing, but becoming increasingly “middle class,” he asserts, meaning that each person is able to consume more things and generate more waste. Even if the population were to stabilize and humanity found new, hyperefficient ways to recycle its trash, the author argues that we’ve already passed the point of sustainability given the size of the planet and its amount of resources. The author presents and analyzes many different population-sustainability hypotheses and also examines historical trends from humanity’s first 200,000 years, which had relatively minuscule population growth. Tucker then lays out his case for why estimates above 3 billion are, in his opinion, starry-eyed. So what, then, do we do with all the extra people? The author has a long-term plan—and it’s actually much simpler, and less sinister, than one might think. In the second half of the book, the author provides a strategy for getting back to a sustainable civilization—an act that he characterizes not as a retreat or decline but as a chance for a new beginning. This book has a premise that’s likely to alarm the vast majority of readers at first glance, but Tucker executes his argument in a tone that’s calm and even cordial. Although he admits that his target number might be wrong—and encourages others to attempt to raise it, based on the available data—he shows a deep familiarity with the issue of overpopulation and comes to his argument armed with information. Indeed, many readers may find themselves marveling at the complexity of Earth’s resource cycle, as he lays it out. Even those who finish the book unconvinced of the necessity of curbing Earth’s population will get a better understanding of the factors that go into human sustainability—and of how easily they can become imbalanced. In the end, Tucker’s primary theme seems to be that humankind needs to start thinking about its problems in a geographic framework: “Without a shared geographical understanding of our planet, our species, and the civilizations we have created, we will soon find ourselves unable to deal with the unfortunate consequences of ignoring certain realities about our planet.” This is a book that may initially inspire fear, but ideally, it will also be one that engenders discussion.

A book that offers an engaging and sometimes-frightening dose of overpopulation reality.