At the first Earth Day, our campus slogan was, “Whatever your cause, it’s a lost cause unless we control population.”  Those words are as true today as they were in 1970.

In 1970, the U.S. population was 200 million folks.

Sometime during 2015, the population of the United States will top 320 million, and the Earth seems destined to harbor at least 10 billion humans by the middle of this century.

Daily I hear descriptions of environmental degradation across our country, including urban sprawl, traffic congestion, and air pollution. All these problems, and rising carbon dioxide from fossil energy, are exacerbated by rising numbers of people, each demanding their portion of the global resource pie. Our politicians should realize that an emphasis on growth is short-sighted; it offers economic benefits today at the cost of a sustainable environment and economy for tomorrow.

It is easy to develop a notion of inevitability about the problem of human population growth. The high proportion of young people alive today creates what is known as demographic momentum—making it inevitable that the world’s population will continue to grow substantially in the coming decades.

I’ve also heard it said that the rate of population growth will naturally decline as standards of living increase. Studies have shown this to be true. But the slope of the line is not nearly steep enough. Multiplying the human numbers by resource use shows that by the time global reproduction reaches the replacement level (i.e., one birth for each death), we’ll be using more than six times the energy resources than we do today (Moses and Brown 2003). Ditto for our harvest from the oceans. Ditto for developed and agricultural land. Only slowing the rate of population growth will reduce our total resource consumption and our impact on the environment. One only needs to look at the direct correlation between rising human population and rising atmospheric CO₂ to realize that human numbers are causing the ongoing climate disruption (Hofmann et al. 2008).

The newest predictions of future population are lower than they were a few years ago, when the United Nations anticipated 12 billion global citizens for 2050. Funding for family planning, education, and economic empowerment have made a difference, and further progress is possible. One can envision the benefits of a world in which every child is a wanted child; any reduction in births would reduce future resource demand upon our planet.

In the U.S., about half of the population growth is driven by immigration from outside our borders. The rate of population growth in the U.S. rivals that of many third-world countries. Do we close the borders of our country and preserve our lifestyle, or do we continue to absorb the overflow of rapid population growth elsewhere in the world?  Given the immigrant heritage of nearly all U.S. citizens, this is a tough question. Several have made the analogy to the early passengers in a lifeboat, who face the choice of pulling in more passengers to join them, perhaps swamping the boat, or passing by those who flounder in the water.

Global environmental issues make this analogy too simple, for we are all in the same boat. There are no national boundaries on a map of earth system function. Climate changes wrought by actions of the industrialized world are likely to have a disproportional impact on the developing world, leading to a greater immigration pressure. Economic empowerment of the developing world will help lead to lower birth rates in those regions, but direct aid to enhance family planning is essential. We should take the lead.

Can we foster conditions around the world that offer a better life and a better environment for all of Earth’s peoples? Yes, and the first step will be to have fewer new mouths to feed.

Hofmann, D.J., J.H. Butler, and P.P. Tans. 2008. A new look at atmospheric carbon dioxide. Atmospheric Environment 43: 2084-2086.

Moses, M.E. and J.H. Brown. 2003.  Allometry of human fertility and energy use.  Ecology Letters 6: 295-300.