Last Tuesday morning, the U.S. population officially reached 300 million. Some may praise this growth, but if you ever have had to sit in traffic or wait in line at the Department of Motor Vehicles, you realize that population growth causes serious growing pains for our nation. When we were just 200 million people in 1967, reaching that number was a celebrated milestone. But at 300 million, the challenges our growing numbers bring are daunting. For the environment, growing population translates into more resource consumption, more pollution, and more demands on our ecosystems. Now with 300 million and approaching 400 million by 2043, can we plan our growth in sustainable ways to minimize the impact of our growing numbers?

We add another person to our ranks every 11 seconds. In the U.S., our population growth is due more to longer life expectancies and immigration than fertility rates. In fact, the fertility rate in the United States is about 2.1 children per woman – that is, the average American woman is expected to have 2.1 children in her lifetime. This number is also known as the replacement rate or the needed number of children to replace their parents. The United States is the only industrialized nation that is actually experiencing substantial population growth; by 2050, the countries of the European Union are expected to actually lose population.

But many developing countries have much higher fertility rates. The United Nations projects that by the year 2050 we will have a human population of 9.4 billion. That’s assuming that fertility rates globally fall to 2.1 children per woman by 2050. If this projection is off in its assumptions, we could be facing a much larger growth.

Currently, the world fertility rate is 2.65 children per woman. To lower this rate to 2.1 and thus lower the world population growth, the status of women around the world needs to improve. The more education a woman is afforded, the fewer number of children she is likely to have. Investing in girls at a young age will reduce our future population by many millions and improve the lives of these women at the same time.

With nations like China and India – whose populations combined make up over a third of all of the world’s population – gaining in wealth and beginning to mimic our affluence levels, resource competition is rapidly growing. The United States comprises about 5 percent of the world’s population, but consumes over a quarter of the earth’s resources. Using these numbers, it’s easy to see that earth simply does not have enough resources to support another two billion people in China and India who want to consume like Americans.

Environmentalists are sometimes charged with the crime of valuing the intrinsic value of the environment over the needs of humans. But you cannot fault individuals in these nations to strive for a better life. The challenge for the world is how to improve the lives of millions without producing the environmental degradation associated with the industrialized nations’ expansions.

We do need to slow down the growth of population internationally, but that does not change the fact that the United States is now at 300 million and will likely reach 400 million in 40 years. We need smart growth development models to accommodate another 100 million people.

Not only is our population growing, our affluence level is, too. As a nation we consume 40 percent more energy than we did when we were just 200 million. Since 1967, we’ve added more cars to the road than people, with over 130 million new automobiles added to our roadways in the last 40 years.

With growing demand for energy, we need to deliver more energy without adding to our global warming problems. Ensuring water in both quantity and quality is another challenge we will face with another 100 million people.

In many parts of the country the rate of land development is double the growth rate of population. Cities should encourage developers through new zoning codes and incentives to build along transit ways. Here in Minneapolis, new smart development is growing along the Hiawatha light rail corridor. Suburban communities need to develop their land to allow the growing population to break free of their cars and be accessible for all their residents.

When our nation reaches 400 million, what will our country look like? When many of us students reach our late 50s, the United States will reach 400 million. What will our environment look like with that many people? If we do not start now on building transit projects, clean energy, and efficient new technologies for our future, our population crunch will feel even heavier. Let’s not wait until we reach 400 million to plan for the future.

Holly Lahd welcomes comments at [email protected].